Thermoforming & Die Cutting of Recycled/Virgin PET Sheet

Thermoforming & Die Cutting of Recycled/Virgin PET Sheet (PETCO of Lavergne Group) 

Thermoforming & Die Cutting 

of 

Recycled/Virgin PET Sheet 

by Larry Koester, Sheila Nemeth, & Mark Koester of Lavergne Group 

Contents 

Section Page(s) 

Introduction 2-3 

What is PET sheet? 3-6 

Intro: PET in relation to other resins 3-4 

PET vs. PVC 4-5 

PET Sheet Properties 5-6 

Extruding PET Sheet 6 

Thermoforming PET Sheet 7-9 

Heating PET Sheet 7-8 

Forming PET sheet 8 

General Do’s and Don’ts of Thermoforming PET Sheet 9 

Die Cutting PET Sheet 10-14 

Kiss Cut Dies (Steel Rule and Forged Dies) 10-11 

Scissor-type Dies (Matched Metal Dies) 12-13 

General Do’s and Don’ts of Die Cutting PET Sheet 14 

Conclusions 14-16 

Summary Checklist 15-16 

Appendixes 17-27 

I. Glossary 17-20 

II. Transition Temperatures of Thermoformable Polymers 20 

IIIA. 2000 Gross Recycling Rate 20 

IIIB. RPET End Use Products 2000 21 

IV. Plastic Bottles by Resin Type 21 

V. Comparison of Thermal Conductivity and Thermal Diffusivity for Several Polymer 

22 

and Mold Materials 

VI. Shrinkage Values 22 

VII. Inflation Pressure Ranges 22 

VIII. Drying Conditions 23 

IX. Coefficients of Thermal Expansion for Thermoformable Polymers 23 

X. Make-Ready Procedure for “Kiss Cut” Dies 24 

XI. Physical Properties of Film Extruded of PETG and APET 25 

XII. Technical Data and Property Comparison: RPET vs. PVC 26 

XIII. Rockwell Hardness Scale of Abbreviations 26 

XIV. Application Pictures 

27 

Sources, Thanks and Contact Information 28 

Lavergne Group Inc. 8800, 1er Croissant, Ville d’Anjou, Quebec, Canada H1J 1C8 

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~ Introduction ~ 

Over the years, a steady increase in the use of PET has triggered a decrease in the use 

of aluminum, glass, and other conventional packaging materials. Convenience stores are now 

stocked with chilled rows of PET bottles of soda, water, milk, and juice, and finding a glass 

bottle has become a rarity. Even beer bottles have seen a recent shift to plastic at sporting 

events. The upward trend and usage of PET bottles has trickled down to increased use of PET 

in other applications including thermoformed PET sheet. Local groceries and hardware stores 

are a gallery to the multiple uses of PET sheet from fruit containers to plastic trays to nut and 

bolt packages. With this perspective in mind, it is crucial to evaluate the current uses, 

techniques, properties, and characteristics in thermoforming and die cutting recycled and virgin 

PET sheet. 

When a polymer is heated from a low temperature, it transforms from a glassy state to a 

rubbery state. The temperature in which this transition occurs is generally termed “glass 

transition temperature” (abbreviated Tg), and the temperature range over which the polymer is 

sufficiently pliable for stretching and shaping to a desirable shape is called “thermoforming 

window.” Thermoforming is the general category of processes heating a polymer sheet to this 

rubbery state and then using one of several methods to shape the heated sheet into the desired 

form. After cooling and hardening, the edges are cut away through a procedure called die 

cutting leaving the completed product. While the process may seem simple, numerous factors 

dictate and manipulate the slim degree of perfection needed to create a perfect product. Not 

only must the physical properties of the cooled substance be considered, but the properties of 

the polymer when it is heated must also be calculated. 

Polyethylene terephthalate or more commonly PET is a polymer made by combining 

either terephthalic acid or dimethyl terephthalate acid with ethylene glycol. From this 

chemical combination, a vast range of thermoplastic applications and uses arise for PET and its 

additive offshoots. PET is an extremely versatile substance, because its properties and 

characteristics provide relatively easy usability and versatility. Virgin PET sheet’s compliance 

with Food and Drug Administration (FDA) regulations has allowed a diversity of food 

applications including such packaging staples as clamshells, trays, containers, and fruit and 

vegetable baskets. And recycled PET (RPET) through regrind and addition with virgin has 

allowed companies to create their needed product along with allaying many environmental 

concerns of tomorrow. 

The industry has coined several acronyms to specify PET’s specific end use 

capabilities. For example, when used in the crystalline state for ovenable trays, PET is referred 

to as CPET; when used as oriented film to utilize its toughness, high-temperature and chemical 

resistance properties, it is termed OPET; when used for the extrusion blow-molding of 

containers, it is called EPET; and when glycol modifiers are added to minimize brittleness and 

premature aging, it is called PETG. The acronym APET describes PET when it is in the form 

of clear, amorphous sheet for thermoformed packaging and related products. And RPET 

signifies recycled PET sheet, which displays similar properties as virgin PET or APET. PETE 

is utilized on the bottoms of bottles because of copyright infringement of “PET Carnation 

Milk” products. For all intense and purposes, APET, PET, RPET, Polyester and PETE are the 

same thing, polyethylene terephthalate. 

- 2 -


Thermoforming is heating the sheet, to a temperature below its melting point, to a 

glassy or soft state, and then stretching it to contours of a mold. The characteristics of PET 

sheet are similar to other amorphous sheet, and thus the thermoforming methods are 

comparable as well, especially with PVC. The key considerations to remember with PET sheet 

are to keep it very dry and to not overheat; otherwise significant changes occur in the PET 

weakening its properties. PET is a tough substance, which leads to the biggest challenge 

facing thermoformers: die cutting. Although other substances break after only cutting part way 

through, PET sheet has to be cut completely through for it to fracture. This puts a tremendous 

strain on equipment and laborers. The two techniques for die cutting are clamp cut or kiss cut, 

which includes steel rule and forged die, and scissor type, which includes matched-metal 

cutting. This will provide the basics to cutting, but if a few guidelines are followed, then your 

efforts will improve and benefit as well. 

~ What is PET sheet? ~ 

As previously mentioned in the introduction, PET (also known as APET, RPET, PETE 

or polyester) is a plastic resin chemically constructed by combining terephthalic acid with 

ethylene glycol. Plastics consist of hydrocarbons, basic building blocks typically derived from 

natural gas or petroleum. These hydrocarbon monomers are bonded into long chains called 

polymers or plastic resins. Different combinations of monomers will result in resins with 

specialized characteristics and properties. Much like different metals like copper, silver, and 

aluminum displaying unique properties, which result in varying uses, plastics, are very 

versatile and display varying properties and characteristics resulting in a wide range of 

applications. No single polymer is perfect for every application. Cost as well as an individual 

polymer’s benefits must be considered. 

The resins that constitute nearly all the plastics used in thermoforming (See Appendix 

IV for percentage breakdown of top 6 resins used in plastic bottles): 

• Polyesters or PET (polyethylene terephthalate) is a clear, tough, stable polymer with 

exceptional gas and moisture barrier properties. It is often used to contain carbon 

dioxide (alias carbonation) in soft drinks bottles. Its applications also include film, 

sheet, fiber, trays, displays, clothing, and wire insulation. 

• Acrylic or PMMA (polymethyl methacrylate) is a tough polymer with good optical 

clarity, weatherability, and resistance to sunlight, which make it great for outdoor 

items like sky domes, signs, light fixtures, and bathtubs. 

• PC (polycarbonate) is a tough, high temperature transparent plastic but is difficult to 

thermoform and is very susceptible to moisture. It is used in windows, helmets, cases, 

and glasses. 

• PE (polyethylene) is the most used polymer in thermoforming with an array of 

applications. It is a durable, tough, inexpensive plastic with excellent impact, moisture 

and chemical resistance. 

- 3 -


• PP (polypropylene) has great high-temperature chemical resistance and is used in 

manufacturing industrial parts, automotive and electrical hardware, stadium seats, and 

battery cases. 

• PS (polystyrene) was the dominating thermoforming material 20 years ago. It has 

excellent processability and good dimensional stability but limited solvent resistance. 

Its uses today include food and medical packaging, housewares, toys, furniture, 

advertising displays, and refrigerator liners. 

- HIPS (high impact polystyrene) 

• Vinyl or PVC (polyvinyl chloride) has very similar properties as PET displaying 

excellent clarity, puncture resistance, and cling. As a film, vinyl breathes the right 

amount making it ideal for packaging fresh meats. 

PET vs. PVC 

As Table 1 shows, PET displays physical similarities as PVC. The comparable nature 

of their density, thermal conductivity, thermal expansion, rigidity, and shrinkage allows for 

machines designed and used for thermoforming PVC to be slightly altered in order to 

thermoform PET. As Table 1 points out key similarities, Table 2 (on the top of the next page) 

shows several key differences. The advantages of PET over PVC is its faster cycle times and 

lower oven temperatures, which leads to less energy used and economic savings. PET’s 

toughness of cutting and wearing out of dies gives PVC a slight advantage. But with their 

similar price, PET displays it’s environmental edge over PVC with its ease of recycling and 

regrinding. PET regrind can easily be used to return to sheet while PVC regrind is much more 

difficult and expensive to reuse. 

Table 1: Physical Properties of Thermoformable Polymers 

Polymer Density 

[lb/ft 3 Density 

] [kg/m 3 Thermal 

Conductivity 

] [Btu/] 

[x 10 -3 

Thermal Heat Thermal 

Conductivity Capacity Expansion 

Coefficient 

[Btu/lb. [°F or [x10 

ft.hr.°F kW/ m. °C] cal/g°C] 

-6 

°F -1 Thermal 

Expansion 

[x10 

] 

-6 

°C -1 ] 

Polystyrene 65.5 1050 0.105 0.18 0.54 40 70 

ABS 65.5 1050 0.07 0.12 0.4 50 90 

Polycarbonate 74.9 1200 0.121 0.207 0.49 40 70 

LDPE 57.4 920 0.23 0.39 0.95 140 250 

HDPE 59.9 960 0.29 0.50 1.05 110 200 

PP Homo. 56.2 900 0.11 0.19 0.83 85 150 

Low-density 

PS foam 

4.0 64 0.016 0.027 0.5 110 200 

Rigid PVC 84.2 1350 0.100 0.171 0.365 45 80 

PET 85.5 1370 0.138 0.236 0.44 40 70 

from Understanding Thermoforming by Throne, pg. 13 Table 2.2 

- 4 -


Table 2: Technical Comparison of PET and PVC 

PET Comparison PVC 

Faster 

Cycle Times 

Slower 

Lower (450°F, 230°C) Oven Temps. Higher (600°F, 315°C) 

Lower 

Energy 

Higher 

= 

Rigidity 

= 

= 

Shrinkage 

= 

= 

Molds 

= 

Stronger 

Steel for Cutting Not needed to be as strong 

Wears out faster 

Wear of Die 

Better wear 

More pressure needed Pressure for Cutting 

Less 

= 

Price 

= 

+ 

Environmental 

- 

Recyclable 

Regrind Reuse Difficult to Reuse 

PET Sheet Properties 

While PET packaging is predominately familiar in its application in carbonated 

beverage bottles, under proper conditions, PET slowly crystallizes to give a high-temperature, 

semi-crystalline plastic. With certain extrusion machines and equipment, extruded PET can be 

cooled quickly enough to prevent substantial crystallization, and the result is clear sheet used in 

thermoforming. 

The PET properties that make it desirable include: 

• Clarity and Sparkle 

• Toughness 

• Light Weight 

• Good Gas Barrier 

• Solvent/Corrosion Resistance 

• Good Cost/Performance Ratio 

• Durable, difficult to break 

• Durable hinge properties 

• Recyclable and Regrindable 

While these advantageous qualities do stand out, there are disadvantages and difficulties that 

must also be considered. 

PET is very moisture-sensitive. In other polymers the moisture emerges as bubbles, but 

moisture in PET directly attacks its chemical backbone, breaking it down. This is called 

hydrolytic degradation (or intrinsic viscosity breakdown) and tends to result in excessive sag 

while heating and hard-to-detect loss in properties. PET flake or resin must be dried to a 

“moisture level of 0.005% or less” (TRS-106B) before extrusion of sheet or injection molding 

of bottles, otherwise there will be a reduction in physical properties including impact strength. 

Impact strength is the sheet’s ability to withstand puncture. While PET can be properly dried 

in several ways, it is worth repeating that PET flake must not be moist before processes 

including extrusion and injection molding. PET sheet does not need any special drying prior to 

thermoforming, but should not be exposed to rain or water. See Appendix VIII for Dry 

Conditions of other polymers. 

- 5 - 

Roll of PET Sheet 

Courtesy of the Lavergne Group


PET is tougher than other plastic polymers. This toughness is one of the positive 

reasons for the growth of PET sheet applications. In particular PET sheet exhibits outstanding 

durable hinge properties making longer life packages like PET egg cartons and nut and bolt 

packages possible. Polystyrene (OPS or HIPS) packages are suitable for short life packages 

like bakery packages, but do not have the toughness or durable hinge properties for longer life 

packages. Even PVC sheet do not have the durable hinge properties of PET sheet. This 

toughness of PET sheet allows for very durable, longer-life packages, but also creates more 

difficulty for cutting and trimming. 

The toughness of PET requires very sharp and often heated dies, yet improper trimming 

can occur resulting in fuzz, angel hair, and trim dust. Trim dust sometimes dirties the 

remaining trim or scrap and consequently ruins PET sheet reclaim or regrind. In order for 

reclaim and regrind to function appropriately, the regrind must be kept clean, free from 

contamination, and dry. 

This paper focuses on amorphous PET sheet or simply APET, but it is worth noting this 

distinction between CPET (crystallized PET) and APET. CPET is allowed during processing 

to form very quick crystals. These crystals allow it to withstand higher heats that normal 

APET cannot. While this makes thermoforming more difficult, CPET’s heat resistance enables 

usage in microwaves and ovens. 

A special characteristic of APET is ease in recycling. Recycled PET or RPET, which 

comes from reground trim or scrap of APET as well as recycling of PET beverage bottles, 

enables prolonged use without sapping resources or increasing waste. Recycled material is 

often combined with virgin PET when it is re-extruded creating a stable, usable blend. RPET’s 

only real restriction is usage in food packaging, but it is still highly usable in other industrial 

packaging applications displaying very similar properties as virgin APET sheet. 

Extruding PET Sheet 

In extrusion as opposed to thermoforming, raw PET must 

be heated past its glass transition temperature of 70 °C (158°F) to 

above its melting temperature of 255°C (490°F). At this 

temperature this PET is in a liquid state where extrusion 

continues. (For a basic comparison of transition temperatures of 

thermoformable polymers, see Appendix II.) 

The extrusion basic process is as follows: 

1. PET pellets or flake are dried in a desiccant dryer, fed 

into a hopper, and placed on top of the barrel. 

2. The barrel of the extruder contains a rotating screw, 

which conveys, melts, and pumps the melted resin into a 

flat sheet. 

3. Calender rolls adjust the sheet thickness. 

4. The extruded PET sheet is wound into a clear roll or 

stock and cut to the appropriate width. 

This finish sheet can be used in various thermoform operations to 

create the desired product. 

- 6 - 

PET Sheet Extruder 

Courtesy of the Lavergne Group 

PET Sheet Extruder 

Courtesy of the Lavergne Group


~ Thermoforming PET sheet ~ 

After examining and comparing PET’s various properties and characteristics against 

other plastics, it is apparent that, for all practical purposes, PET sheet’s viscoelastic properties 

are similar to other amorphous polymers such as PVC (polyvinyl chloride) and HIPS (high 

impact polystyrene). And consequently, most thermoforming equipment can be adapted to 

properly handle PET sheet. There are only slight changes needed in the thermoforming 

conditions of PET as opposed to PVC or HIPS. 

Basically, thermoforming uses heat, vacuum, pressure, and/or mechanical means to 

force the plastic sheet against contours of a mold (or molds). The PET sheet is heated to a 

temperature above the glass transition but far below the melting temperature where it softens. It 

is stretched over the shape of its mold. Once cooled and removed from the mold, secondary 

actions occur on the plastic like trimming, labeling, printing, and cutting. 

Heating PET Sheet 

When thermoforming PET sheet and most thermoformed polymers, one of the most 

important considerations is heating. Heating contributes a significant percentage to the final 

cost of a formed product. Under-heating will result in failing to forming to the contours of the 

mold. Overheating leads to numerous problems including poor quality and weak end products. 

Overheating will crystallize the PET sheet and result in excessive sag and visible haze. This 

increases brittleness and hinders thermoformability. With thicker sheet and its longer heating 

cycles, crystallinity and haze become greater concerns. Once crystalline haze appears, it can 

only be eliminated by re-extrusion of that material. Simply, it is crucial to maintain the PET’s 

proper forming temperatures (300°F or 149°C). 

Table 4: Normal Forming Temperatures 

Polymer 

Temperature 

°F °C 

Polystyrene [GPPS] 300 149 

ABS 330 166 

Rigid PVC 280 138 

PMMA [Acrylic] 350 177 

Polycarbonate [PC] 375 191 

HDPE 295 146 

Polypropylene 310 154 

40% GR PP 400 204 

APET 300 149 


There are three basic methods of heating sheet: conduction, conventions, and radiation. 

Conduction is heat transfer via direct contact between the sheet and the heated area. No matter 

what method of actual heating is used, conduction is the primary way energy moves through 

the plastic sheet. The speed and heat needed to transfer heat from the surface to the entire 

sheet is a controlling factor especially in thicker sheet. Convection is heat transfer by contact 

between a fluid medium and a solid. For example, the cooler sheet will meet warmer air, and 

an energy and heat exchange will warm the sheet. Faster and more efficient transfer also 

occurs in moving air compared to still or stagnant air. Radiation is heat transfer via an 

interchange of electromagnetic energy between cold and hot surfaces. 

- 7 -


Conduction is much more energy effective than convection heating, but PET’s 

tendency to adhere to hot metal requires Teflon-coated heating plates. Often, hybrid methods 

with combination of each are employed. No matter which heating method used, it is critical to 

maintain a uniform temperature across the sheet. Air currents and sudden shifts in surrounding 

temperatures should be kept to a minimum. A temperature sensing device will also vastly 

improve results when thermoforming. 

Along with temperature, time should also be considered when heating. “To prevent 

excessive sag and possible crystallization of the sheet, the heating cycle should be as short as 

possible, provided the proper sheet temperature is reached.” (TRS-111). Time to heat the sheet 

will control the machine-cycle and also dictate overall time needed to thermoform. One benefit 

of PET over PVC is its faster cycle time, but it should still be noted the importance of 

consistency with thermoforming. Each and every cycle should have the same time and 

temperatures. 

Forming PET Sheet 

One of the main advantages of thermoforming PET sheet is its versatility along with its 

toughness, durable hinge properties, and reasonable cost. There are numerous options for 

thermoforming; one could use plug assist or drape forming; one could use vacuum or pressure 

forming; one could use matched mold; the options and adaptations are numerous. This paper 

will not go into specific procedures and techniques for thermoforming, but provide only some 

general considerations when working with PET sheet. 

If one wants information on specifics of thermoforming procedures, see Eastman’s 

TRS-194A (available by request from Eastman) or “Thermoforming in a Nutshell” by Empire 

West Inc.’s Thermoforming Tech Academy (available at www.empirewest.com/academy/) 

The following chart will provide a good starting point for forming sheet, particularly if the 

sheet thickness is 1,250 microns (50 mils) or less: 

Eastar PETG 6763 APET 

Mold Temperature, °C (°F) 40-60 (100-140) 25-50 (80-120) 

Sheet Temperature, °C (°F) 140-150 (280-300) 140-165 (280-330) 

Plug Temperature, °C (°F) 120-135 (250-275) 125-155 (260-310) 

Cycle, seconds 3-10 2.5-6 

Forming Pressure, MPa (psi) 0.21-0.28 (30-40) 0.10-0.28 (15-40) 

Vacuum, mm (in.) of Mercury 508-660 (20-26) 508-660 (20-26) 

The following criteria should also be noted (from Eastman’s TRS-111, pg. 15): 

1. Mold temperatures below 27 ο C (80 ο F) may cause “freezing” of the sheet, non-uniform 

drawing, and stressed parts; however, mold temperature is the key to faster cycles. 

Above 60 ο C (140 ο F), a longer production cycle could be required, and distortion of the 

part may occur. 

2. At temperatures slightly above the Tg of 80 ο C (176 ο F), PET can be oriented, but it takes 

forming forces much greater than those available in vacuum forming to do so. As the 

APET sheet temperature approaches 149 ο C (300 ο F), its viscosity is reduced to the point 

where it is very formable by pressure and vacuum forces. It should be emphasized 

again that stressed and brittle parts can result from sheet that is too cold. 

- 8 -


General Do’s and Don’ts of Thermoforming PET Sheet (from DDS-3C) 

To achieve controlled, consistent, and reliable results when thermoforming PET sheet, a few 

basic guidelines should be considered: 

Do 

1. Use moderate heat settings on thermoforming equipment to give a sheet temperature 

between 140 ο C to 165 ο C (280 ο F to 325 ο F). 

2. Use mold temperatures that range from 40 ο C to 60 ο C (100 ο F to 140 ο F). 

3. Monitor temperatures 

4. Use shorter forming cycles and lower temperatures than those used in thermoforming 

other sheet such as PVC. 

5. Use silicone-coated sheet for optimum denesting of blisters. 

Don’t 

1. Overheat sheet. Crystallization will occur if sheet is overheated, resulting in whitening 

and embrittlement of the sheet. Excessive sag with resultant webbing can also occur. 

2. Use cold molds. Mold temperatures as low as 20 ο C to 25 ο C (70 ο F to 80 ο F) can cause 

“freezing” of the film and non-uniform drawing, especially with male molds. 

3. Use sheet temperatures below 140 ο C (280 ο F). Due to freezing internal stresses in the 

part, cold forming can cause embrittlement. 

- 9 -


As a recent study by Moskla and 

Barr so appropriate stated, “thermoplastic 

sheet such as oriented polystyrene (OPS) 

and polyvinyl chloride (PVC) are 

generally easy to cut, producing minimal 

wear on the die and few defects on the cut 

edge of the plastic,” but “amorphous 

polyethylene terephthalate (APET)…is 

notoriously difficult to cut.” Although 

PVC or HIPS break or facture after being 

cut only “approximately 75 percent 

through the thickness” (TRS-1111B 16), 

PET sheet must be cut completely through in 

order to separate cleanly. This puts a 

tremendous strain on cutting materials, time, 

and laborers. 

~ Die Cutting ~ 

While there are several ways to cut thermoformed PET sheet, this paper will cover only 

the three major ones: steel rule, matched-metal, and forged dies. The steel rule die and forged 

die have the same principle of cutting which is a “clamp cut” or “kiss cut”, where as the 

matched-metal die cutting principle is more of a “scissor” type cutting action. 

I. “Kiss Cut” Dies (Steel Rule and Forged Dies) 

Most of the concepts and principles in steel rule dies apply 

to forged dies. 

Steel rule dies offer the least expensive option for limited 

volume cutting. This method of cutting is simply a sharpened, 

metal cutting edge or knife mounted on a laminated birch or maple 

die board. Steel rule dies can function as cut-in-place, and cut-in- 

Steel Rule Die 

line trimming, but often is best used cut-in-place because that way the PET sheet is still warm 

and easing wear on the cutting surface. (For Stanley Rosen’s make-ready procedure for 

accurately and effectively setting up steel rule dies, see Appendix X.) For cutting simple 

designs with a steel rule die, use a long central bevel or a double bevel die with a hardness of 

50-55 Rockwell C, especially if the sheet is thicker than 0.25 mm (0.010 in.). Although harder 

dies wear better, softer dies of 45-50 Rockwell C may have to be used to prevent breakage 

during die fabrication when complex shapes and sharp bends are used. (For information on 

meanings of Rockwell Hardness scale, see Appendix XIII.) 

Forged die can be used instead of a steel rule die in a cut-in-place trimming procedure, 

or also known as a “contact heat pressure forming and cutting” procedure. The forged die 

method is excellent for middle of the road volume applications, and has an advantage in cutting 

PET sheet, because the forged die is cutting hot PET sheet. In a forged die, the PET sheet is 

heated and thermoformed by vacuum or pressure forming to the contours of the mold. While 

the thermoformed part is still in the mold, the heated forged die is pressed down further 

- 10 - 

Cutting performance of PET (circles), PETG (squares) an OPS 

(triangles). Solid symbols are for the sheet. Open symbols for 

the baseline. (from Moskla-Barr Study)


through the PET sheet. The die edge makes “kiss cut” contact on the base plate cutting the hot 

PET sheet. 

Kiss Cut Die Diagram 

An important factor to consider is the 

material’s shrinkage from forming to the time 

it gets to cutting. Although it would be best to 

measure shrinkage from an actual cavity, 

“0.005 mm per mm (.005 in per in.)” (TRS- 

111) or 0.3-0.6 percent is a good rule of 

thumb to use with PET sheet. (For 

comparison of shrinkage values of other 

thermoformable polymers, see Appendix VI.) 

Dies should be installed in a press that 

has enough force so that it can close smoothly 

as and cut completely through the sheet. As 

the cut progresses, the press should be capable 

of consistently bringing the die to the same 

line on the backing plate. Eastman’s rule of 

thumb for clamp requirements is 70 kg. per 

lineal cm (400 lbs. per lineal in.) of rule die. 

Pressing too hard will bend the cutting edge 

removing its edge and only pressing with its 

bent side. Pressing too softly will fail to cut 

the part at all. 

The preferred material for the backing 

plate is stainless steel. Aluminum is not 

recommended for backing plates because it 

tends to have a short life and often splinters 

contaminating parts. No matter what material 

is used, the backing plate should have a 

hardness less than that of the die. That way 

the backing plate will take the wear and the 

die will dull less. (There is disagreement on 

this point.) 

Cutting hot PET sheet is easier than 

cutting cold PET sheet. Heating the PET 

sheet by applying heat to the die and/or the 

backing plate will improve cutting, but 

temperatures should not exceed the Tg of the PET sheet or 71°C (160°F). One method of 

heating the PET sheet only at the cutting area can be termed “Heat Assisted Die Cutting.” The 

first step of this die cutting method involves the die touching the PET sheet with low pressure, 

so that the sheet contacts the base plate and heat transfers from the base plate to the PET sheet 

cutting area via conduction. 

- 11 -


The base plate temperature should be controlled just below the point where the PET 

sheet sticks to the base plate (PET sheet at 71 ο C (160 ο F)). The base plate should be insulated 

in order to maintain temperature and to prevent heat loss. Only the spot where the die touches 

the sheet is heated. The rest of the PET part is not distorted. After a short time delay and heat 

transfer, the PET sheet in contact with the die becomes softer. The hot PET sheet has reduced 

shear strength, which requires less cutting force. The final step is high pressure cutting, which 

finishes with “kiss” cut contact. 

Since the dies must evenly contact the backing plate during cutting to insure the PET is 

cutting, one must accurately “make-ready” the die to the backing plate to avoid damaging the 

die as well as properly cutting the PET. This “make-ready” procedure is critical to correctly 

cutting PET sheet and not damaging the dies. See Appendix X. for Stanley Rosen’s Make- 

Ready Procedure for “Kiss Cut” Dies. 

It may seem obvious, but it is worth reiterating: Cut in the same place every time and 

keep dies as sharp as possible to insure the best and most reliable cutting. 

II. Scissor-type Dies (Matched Metal Dies) 

- 12 - 

Matched Metal Die 

diagrams from 

Thermoforming: 

Improving Process 

Performance by 

Stanley R. Rosen, 

copyright 2002



A Matched Metal Die, also called a 

punch and die, is recommended for large 

volume applications. This in-line trimming 

method is mounted in a separate cutting press 

through which the continuously formed sheet 

passes. 

The basic concept and functionality of 

the matched metal die works with hardness or 

more specifically the contrasting hardness. A 

harder punch is used with a softer die (typical 

hardness is 43 Rockwell C for the die and 55 

for the punch). Minimum die clearance must 

be maintained, and as it wears, the die can be 

peened (A process used on a die to recover 

minimum clearance by spreading the edge of 

the die back to its original size. Peening is 

done with an air-operated hammer. Any 

excessive spreading is sheared off by the 

punch on the first cycle.) to recover the proper 

clearance. 

An alternative to contrasting hardness 

is equal hardness for both the die and punch 

(at roughly 62 Rockwell C). Minimum 

clearance is maintained by resurfacing the die 

and punch, which takes more time due to 

resurfacing of both. There is less downtime 

with only one tool, the die, to fix. 

Coining may be used in order to 

extend die life. Coining is a process that 

occurs during thermoforming whereby the 

areas to be cut are thinned by as much as 50% 

by ridges located on the pressure box. 

Coining occurs as the pressure box is clamped 

to the mold. Coining seals the cavity, locks 

the sheet in place, reduces cutting tonnage, 

and extends cutter life. Shrinkage of the 

formed part must be considered when locating 

the area to be coined so that it will properly 

match the cutting die. 

With matched metal dies, the key concept to remember is maintaining minimum 

clearance; otherwise, a clean and efficient cut will not occur. 

- 13 - 

#2 

#1 

#3 

Matched Metal Die Diagram


General Do’s and Don’ts of Die Cutting (from DDS-3C) 

To achieve controlled, consistent, and reliable results when die cutting PET sheet, a few basic 

guidelines should be considered: 

Do 

Don’t 

1. Use properly guarded roller-die, matched-die, slitters, or guillotine cutters for 

maximum tool life. 

2. Use sharp and well-maintained cutters. 

3. “Make Ready” Procedure is critical 

4. Make sure that proper clearance is maintained between punch and die when matcheddie 

cutters are used. 

5. Cut completely through the sheet to cleanly separate the parts. 

6. Use a stainless surface with a hardness less than that of the die for the backing plate 

when using steel-rule dies. (There is disagreement on this point.) 

1. Trim formed blisters if the temperature of the sheet is above 71 ο C (160 ο F). 

2. Attempt to trim formed blisters unless the equipment and die perimeter are such that 

the available cutting force is at least 400 pounds per linear inch. 

~ Conclusions ~ 

While this paper presents numerous aspects, considerations, and suggestions for 

thermoforming and die cutting PET sheet, the true functionality of any idea or thought is 

results. This paper is intended as merely a stepping-stone into greater consideration of PET as 

an option when thermoforming. PET has definite advantages including toughness, hingeability, 

ease of recycling, and environmentally. PET also has challenges including difficulty 

cutting and increased wear of dies resulting from its generally advantageous toughness. Its 

clarity and sparkle make it great for applications in packaging from clamshells to nut and bolt 

containers. The possibility for applications is vast. See Appendix XV “Application Pictures” 

to explore the current offerings in PET. 

No guide, paper, book, or suggestion provides the exact solution to any problem. As 

any engineer knows, a perfect plan may not create a functional solution. Trial-and-error is a 

must when thermoforming and die cutting any polymer especially PET and recycled PET, but 

if the few suggestion is this paper are followed then experimentation will quickly provide the 

desired results. 

- 14 -


The following should provide a general overview when thermoforming PET sheet: 

Summary Checklist for Thermoforming and Die Cutting PET Sheet 

• Keep PET sheet dry. 

• Don’t assume that APET sheet will process that same as PETG sheet. 

• Use suggested sheet-forming temperatures of 140 ο C to 165 ο C (280 ο F to 325 ο F). 

• Do not overheat the PET sheet, which will cause crystallinity and brittleness in the PET 

sheet. (If the PET sheet turns white and crystallizes, then it is overheated.) 

• Maintain uniform and consistent sheet temperature 

• Choice of PET sheet dies: 

o Steel rule dies are the least expensive, and are for small volume applications 

o Forged dies are best for middle of the road volume applications 

o “Kiss” cut contact for steel rule and forged dies is required for PET sheet 

o Match-mold dies are the most expensive, are the surest with regard to cutting, 

and are preferred for fast, high volume applications 

• The recommended cutting force for PET sheet is at least 400 pounds per linear inch of 

“kiss” cut die. The force required on the corners of the part are probably 2X the linear 

sections. These cutting force requirements can be reduced if the PET sheet is hot. 

• Hot PET sheet is easier for cutting than cold PET sheet. 

o Control the base plate temperature just below the point where the PET sheet 

sticks to the base plate (PET sheet at 71 ο C (160 ο F)). Insulate the base plate in 

order to maintain temperature and to prevent heat loss. 

o Steel rule dies are the most difficult to maintain heat, and forged dies are the 

easiest to maintain heat. (Some people feel that die temperature are not that 

important.) 

• Heat Assisted Die Cutting: Low Pressure / Time Delay / Heat Transfer / High Pressure 

o The first step of die cutting involves the die touching the PET sheet with low 

pressure, so that the sheet contacts the base plate and heat transfers from the 

base plate to the PET sheet via conduction. 

o The base plate temperature is just below the PET sticking point, and only the 

spot where the die touches the sheet is heated. The rest of the PET part is not 

distorted. 

o After a short time delay and heat transfer, the PET sheet in contact with the die 

becomes softer. The hot PET sheet has reduced shear strength, which requires 

less cutting force. 

o The final step is high pressure cutting, which finishes with “kiss” cut contact. 

- 15 -


Summary Checklist for Thermoforming and Die Cutting PET Sheet (cont.) 

• Precision of the cutting tools and dies is critical for proper cutting of PET sheet 

o HIPS, OPS, and PVC sheet will fracture or break when the die is 50-70% 

through the sheet; (Some of the PVC sheet is hard and the sheet will fracture. 

Some of the PVC sheet is soft and the sheet will distort, which will cause the 

thermoformed part to break easily from the sheet.) 

o The “kiss” cut die must be 90-100% of the way through the PET sheet before 

the thermoformed part is separated from the PET sheet; 

o With matched metal dies, the key concept to remember is maintaining tolerance; 

otherwise, a clean and efficient cut will not occur. 

• No matter what material is used, the backing plate should have hardness less than that 

of the die. That way the backing plate will take the wear and the die will dull less. 

(There is disagreement on this point.) 

• “Make Ready” Procedure is critical for proper “kiss” cutting of PET sheet 

o A flat base plate, which is parallel to the die is critical. If the base plate is worn 

out and cannot be repaired, then the base plate must be replaced. 

o Doing the proper “make ready” procedure takes time and patience. (This job 

should be assigned to the person with the most patience in the work force.) 

o If the die cutting edge contacts the base metal too much, then the die edge will 

mushroom. The die edge will not be able to cut the PET sheet cleanly, and will 

create angel hair and fines. 

o See Appendix X. for Stanley Rosen’s Make-Ready Procedure for “Kiss Cut” 

Dies. 

www.lavergne.ca 

This paper is part of a research and marketing project by the Lavergne Group. For more 

information about PET Sheet, its PET sheet extruding line, thermoforming and die cutting PET 

sheet or about the company and its writers, please contact us: 

Lavergne Group 

PETCO Division 

8800, 1er Croissant 

Ville d’Anjou 

(Quebec) Canada H1J 1C8 

To contact any of the presenters or writers of this paper: 

Larry Koester, VP Marketing & Sales, tel. 402-861-9524, 

fax 402-861-9527, Lkoester@lavergne.ca 

Sheila Nemeth, Marketing & Sales, tel. 514-354-5757 ext. 116, 

fax 514-354-3087, snemeth@lavergne.ca 

- 16 -


Appendix I. Glossary of Terms 

Acrylic Polymethyl methacrylate. It is a tough polymer with good optical clarity, weatherability, and 

resistance to sunlight, which make it great for outdoor items like sky domes, signs, light fixtures, 

and bathtubs. Also known as PMMA. 

Amorphous Refers to the physical arrangement of PET molecules. In amorphous PET, the molecules have 

had no interaction with each other, and remain independent and randomly oriented. The term 

“amorphous” implies that no crystalline structures have developed and that end uses will be 

limited to temperatures reasonably below the Tg. All polymers are essentially amorphous when 

molten. Clarity is a characteristic of amorphous polymers. 

Angel Hair Fine fibers caused by improper trimming technique 

APET Acronym that refers to an end use of PET that utilizes its amorphous state. Thermoforming is a 

prime example. Also known as PET, PETE, or Polyester. 

Backing Plate The mild or stainless plate against which steel rule dies cut out the APET sheet. 

Bearers Spacers placed outside the sheet area to ensure that press platens do not over-close on steel rule 

dies during cutting. Two to four long bears are used, usually 12 mm (½ in.) wide by the height 

of the die. 

CPET Acronym that refers to an end use of PET that utilizes its unoriented crystalline state. Dual 

ovenable trays are an example of this end use. 

Coining A process that occurs during thermoforming whereby the areas to be cut are thinned by as much 

as 50% by ridges located on the pressure box. Coining occurs as the pressure box is clamped to 

the mold. Coining seals the cavity, locks the sheet in place, reduces cutting tonnage, and extends 

cutter life. Shrinkage of the formed part must be considered when locating the area to be coined 

so that it will properly match the cutting die. 

Conduction Heat transfer via direct contact between the sheet and the heated area. It is also the primary way 

energy moves through the plastic sheet 

Convention Heat transfer by contact between a fluid medium and a solid. For example, the cooler sheet will 

meet warmer air, and an energy and heat exchange will warm the sheet. 

Co-polyester Polyester modified with additional component(s) to achieve specific properties. 

Copolymer A polymer modified with additional component(s) to achieve specific properties. 

Crystalline Refers to the physical arrangement of molecules in a crystallizable polymer. Molecules align 

themselves into dense, highly ordered crystals when subjected to either a thermal treatment 

above their Tg or to an orientation process. The percent crystallinity can range from 0% up to 

approximately 50%, depending on the thermal and mechanical history of that sample. A 

polymer that is 50% crystalline, for example, will be made up of 50% crystals by weight, all 

uniformity dispersed throughout the remaining 50%, which is still amorphous. 

Crystallizable Refers to any polymer capable of being crystallized with a thermal or mechanical treatment. 

Crystallization Half- 

Time 

The time required for a sample of PET to crystallize to 50% of the maximum crystallinity that 

could occur at a given temperature. 

Denest Lugs Shapes thermoformed into a part that controls the depth to which parts will nest 

Drape Forming Thermoforming in which a male mold is pushed into a hot plastic sheet or the plastic sheet is 

pulled over the male mold. It is similar to straight forming except that after the PET sheet is 

framed and heated, it is mechanically stretched, and a pressure differential is then applied to 

form the sheet over the male mold. 

EPET Acronym that refers to the use of PET in the extrusion blow-molding process. 

- 17 -

Glass Transition 

Temperature (Tg) 


The temperature at which APET sheet transitions from a glassy state to a rubbery state. As the 

temperature of APET sheet rises from room temperature, an abrupt softening occurs as the 

temperature passes through the Tg. During cooling, the formed APET part will return to its 

glassy state as it cools below the Tg. 

HDPE High density polyethylene. It is used in milk, juice, and water containers. Its chemical 

resistance properties also suit it for use in containers for household chemicals and detergents. 

Heat Setting A process wherein oriented PET is subjected to an additional heat treatment to increase percent 

crystallinity. 

Heavy-gauge Commonly, a sheet with thickness greater than 120 mils (03120 in. or 3 mm) 

HIPS High impact polystyrene plastic. 

I.V. Intrinsic viscosity is a number obtained from a solution viscosity test that represents the average 

molecular weight of PET. The value is calculated by extrapolating the concentration of PET in 

solution back to zero. The industry commonly uses I.V. as a specification. 

In-line Trimming In thin gauge, roll-fed forming, trimming that takes place in a separate machine after the 

thermoforming machine. 

In-machine 

Trimming 

Trimming that takes place while the formed sheet is still within the thermoforming machine 

In-place Trimming Trimming that takes place while the formed sheet is still on the mold surface. 

LDPE Low density polyethylene. It offers clarity and flexibility, and is used to make bottles that 

require flexibility. To take advantage of its strength and toughness in film form, it is used to 

produce grocery bags and garbage bags, shrink and stretch film, and coating for milk containers. 

Make-Ready The process of setting up a steel rule die cutting operation. The prime objective of this process is 

to obtain clean cutting without incurring damage to the rule dies. 

Matched-Mold 

Forming 

Thermoforming technique in which the heated sheet is trapped between the male and female 

dies, and the male form rams the sheet so that it forms appropriately. 

OPET Acronym that refers to an end use of PET that utilizes its oriented state. PET fibers and biaxially 

oriented film are examples. 

Orientation The process of imparting a degree of molecular alignment by stretching at a temperature above 

its Tg. If stretching is in the machine direction only, it is considered uniaxial, whereas biaxial 

orientation implies stretching in the machine and transverse directions. Orientation of PET 

creates internal stress and rapid crystallization that work together to enhance strength properties 

and chemical resistance. Crystals generated by orientation (with or without heat setting) are too 

small to refract light and will not influence optical properties. 

PC Polycarbonate. A tough, high temperature transparent plastic, which is difficult to thermoform 

and is very susceptible to moisture, used in windows, helmets, cases, glasses, and compact discs. 

PE Polyethylene. The most used polymer in thermoforming with an array of applications. It is a 

durable, tough, inexpensive plastic with excellent impact, moisture and chemical resistance. See 

also HDPE and LDPE. 

Peening A process used on a die to recover zero clearance by spreading the edge of the die back to its 

original size. Peening is done with an air-operated hammer. Any excessive spreading is sheared 

off by the punch on the first cycle. 

PET Polyethylene terephthalate. A polyester homopolymer made by reacting either terephthalic acid 

or dimethyl terephthalate with ethylene glycol. It is a clear, tough, stable polymer with 

exceptional gas and moisture barrier properties, and often used to contain carbon dioxide (alias 

carbonation) in soft drinks bottles. Its applications also include film, fiber, trays, displays, 

clothing, and wire insulation. Also known as APET, PETE, or Polyester. 

- 18 -


Polyester A polymer made by reacting dibasic acid with glycol. These monomers are polymerized to a 

molecular weight suitable for a specific end use. See PET. 

Polymer A generic term used to describe any plastic, usually a homopolymer. 

PP Polypropylene. It has great high-temperature chemical resistance and is used in manufacturing 

industrial parts, automotive and electrical hardware, stadium seats, and battery cases. 

Pressure Box A chamber that is clamped to the mold(s) during thermoforming to supply air pressure to the 

exposed surface of the forming sheet. This air pressure, added to that from the applied vacuum, 

provides faster forming with improved cycles and better definition. Coining ridges can be added 

to the pressure box. 

PVC Polyvinyl chloride plastic. It has very similar properties as PET displaying excellent clarity, 

puncture resistance, and cling. As a film, vinyl can breathe just the right amount, making it ideal 

for packaging fresh meats. Also categorized by Vinyl. 

PS Polystyrene. It was the dominating thermoforming material 20 years ago. It has excellent 

processability and good dimensional stability but limited solvent resistance. Its uses today 

include food and medical packaging, housewares, toys, furniture, advertising displays, and 

refrigerator liners. 

Radiation Heat transfer via an interchange of electromagnetic energy between cold and hot surfaces 

Re-crystallization A process whereby the initial crystallization in a polymer is destroyed through melting and then 

allowed to reform when the product is held at a temperature above its Tg. 

Rockwell C Category on Rockwell Hardness Scale includes steel, hard cast irons, pearlitic malleable iron, 

titanium, deep case hardened steel, and other materials. It is harder than B. See also “Rockwell 

Hardness Test” and Appendix XIII. 

Rockwell Hardness 

Test 

A hardness measurement based on the net increase in depth of impression as a load is applied. 

Hardness numbers have no units and are commonly given in the R, L, M, E and K scales. The 

higher the number in each of the scales means the harder the material. Hardness has been 

variously defined as resistance to local penetration, scratching, machining, wear or abrasion, and 

yielding. 

RPET Recycled PET. 

Shear Point Cutting Refers to the crowning of a matched metal die so that the punch first contacts the centerline and 

proceeds to cut with a shearing action as it enters the die. 

Shrinkage Refers to the unit difference in dimension of a thermoformed APET part with respect to the mold 

dimension. An APET part will always be smaller than the mold. A typical shrinkage value for 

APET is 0.005 mm per mm (.005 in. per in.) of mold dimension. 

Snap-Back Refers to the tendency of an APET sheet to try to shrink and remain horizontal, rather than sag, 

when being heated during thermoforming. The degree of snap-back depends on the amount of 

internal stress imparted to the sheet by nip polishing during extrusion. 

Spherulites PET crystals whose major dimension is greater than one half the wavelength of visible light. 

They form when an un-oriented, crystallizable polymer is held at a temperature above its Tg. 

Spherulites will refract light to create haze from slight to complete opacity depending on 

temperature and time of exposure. 

Stability PET is very stable with respect to heat and oxygen at processing temperatures. However, it is 

hydrolytically unstable and must be thoroughly dried before melting processing. 

Thermoforming temperatures are not high enough to effect hydrolytic stability. 

Stripping Rubber Foamed, compressible rubber placed adjacent to a steel rule cutting die that expands after cutting 

to force the cut APET part off the die. 

Tg See Glass Transition Temperature 

- 19 -


Thermal Diffusivity Ratio of thermal conductivity to the product of density and specific heat. It is important in timedependent 

heat conduction 

Thermoplastic Any plastic material that can be repeatedly subjected to a thermal cycling history without 

incurring an increase in molecular weight. This is in contrast to a thermosetting material, which 

polymerizes with heat and/or catalyst to achieve its final and permanent state. 

Thin-gauge Commonly, sheet thickness less than 60 mils (0.060 in. or 1.5 mm) 

Trim That portion of the formed sheet that is not part of the final product 

Vinyl See PVC. 

Appendix II. Transition Temperatures of Thermoformable Polymers 

Glass Transition Melting Heat Distortion Temperature 

Temperature Temperature 66 lb/in 2 or 0.46 N/mm 2 

Polymer 

°F °C °F °C °F °C 

Polystyrene 200 94 - - 155-204 68-96 

PMMA 212 100 - - 165-235 74-113 

PMMA/PVC 221 105 - - 177 81 

ABS 190 248 88-120 - - 170-235 77-113 

Polycarbonate 300 150 - - 280 138 

Rigid PVC 170 77 - - 135-180 57-82 

LDPE -13 -25 239 115 104-112 40-44 

HDPE -166 -100 273 134 175-196 79-91 

Cellulose acetate 158,212 70,100 445 230 125-200 52-93 

Homopolymer Polypropylene 41 5 334 168 225-250 107-121 

Copolymer Polypropylene -4 -20 302-347 150-175 185-220 85-104 

PETG 180 82 - - 158 70 

PET 158 70 490 255 


120 49 

Appendix IIIA. 2000 Gross Recycling Rate (NAPCOR 2000 Final Report) 

Total U.S. Bottles Collected and Sold for Recycling 769 million lbs 

÷ 

Total U.S. Bottles Available for Recycling 

3,445 million 

lbs 

Year 

Total U.S. Bottles 

Collected (MM lbs.) 

Bottles on U.S. Shelves Gross Recycling Rate 

1995 775 1,950 39.7% 

1996 697 2,198 31.7% 

1997 691 2,551 27.1% 

1998 745 3,006 24.8% 

1999 771 3,250 23.7% 

2000 769 3,445 22.3% 

http://www.napcor.com/rate00.html 

- 20 - 

= 

22.3%


Appendix IIIB. RPET End Use Products 2000 (NAPCOR 2000 Final Report) 

Appendix IV. Plastic Bottles by Resin Type 

http://www.napcor.com/rate00.html 

from http://www.plasticsresource.com/resource_conservation/plastics_in_perspective/plastics.html 

- 21 -


Appendix V. Comparison of Thermal Conductivity and Thermal Diffusivity 

for Several Polymer and Mold Materials 

Material Thermal Thermal 

Conductivity Conductivity 

{Btu/ft.hr.°F] [x10 -3 Thermal 

Diffusivity 

kW/m°C] [x10 -4 ft 2 Thermal 

Diffusivity 

/hr] [x10 -4 cm 2 Thermal 

Conductivity 

/s] Relative to 

PS 

Polystyrene 0.105 0.180 29.7 7.66 1 

ABS 0.07 0.12 25 6.45 0.67 

Polycarbonate 0.121 0.207 33.0 8.51 1.15 

Rigid PVC 0.100 0.171 32.5 8.39 0.95 

LDPE 0.23 0.39 46 11.9 2.2 

HDPE 0.29 0.50 55 14.2 2.75 

PP homopolymer 0.11 0.19 25 6.45 0.67 

PET 0.138 0.236 36.8 9.49 1.3 

Low density PS foam 0.016 0.027 80 20.6 0.15 

Aluminum 72.5 124 18,850 4860 690 

Steel 21.3 36.4 3,930 1010 200 

Maple 0.073 0.125 104 26.8 0.7 

Plaster 0.174 0.298 120 31.0 1.66 

Syntactic foam 0.07 0.12 40 10.3 


0.67 

Appendix VI. Shrinkage Values 

Polymer Shrinkage 

Range (%) 

- 22 - 

Recommended 

Value (%) 

ABS 0.5-0.9 0.7 

EVA 0.3-0.8 0.6 

FEP fluoropolymer 1.5-4.5 3.0 

Polycarbonate 0.5-0.7 0.6 

LDPE 1.5-4.5 3.0 

HDPE 2.0-4.5 2.5 

PMMA 0.2-0.8 0.6 

PP 1.0-2.5 2.0 

PS 0.5-0.8 0.6 

Rigid PVC 0.1-0.5 0.3 

K-Resin 0.4-0.8 0.6 

APET 0.3-0.6 0.5 

CPET 10-18 12 


Appendix VII. Inflation Pressure Ranges 

Polymer Inflation Pressure 

Range [lb/in 2 Inflation Pressure Inflation Temperature Inflation Temperature 

] Range [kPa] Range [°F] 

Range [°C] 

PS 2-4 14-28 275-300 135-150 

ABS 1.5-4 10-28 285-300 140-150 

PMMA 7-10 48-70 320-355 160-180 

Rigid PVC 1.5-3 10-21 240-285 110-140 

Flexible PVC 1-3 7-21 240-285 110-140 

PC 6-10 41-70 350-375 170-190 

PET 2-4 14-28 275-320 135-160 

LDPE 1-3 7-21 255-290 125-145 

HDPE 1-3 7-21 265-300 130-150 

PP 1-2 7-14 300-330 150-165 

from Understanding Thermoforming by Throne, pg. 84 Table 6.1


Appendix VIII. Drying Conditions 

Polymer Typical Drying Temperature Typical Drying Time [hr] 

[°F] [°C] 

APET 150 65 3-4 

CPET 320 160 4 

ABS 175 80 2 

PBT 320 160 4 

PMMA 175 80 3 

PC 300 150 4 


Appendix IX. Coefficients of Thermal Expansion for Thermoformable Polymers 

Polymer Range (10 -6 / ο F) Range (10 -6 / ο C) 

ABS 60-130 35-70 

EVA 80-200 45-110 

FEP fluoropolymer 35-70 20-40 

Polycarbonate 70 40 

LDPE 100-220 55-120 

HDPE 60-110 35-60 

PMMA 50-90 30-50 

PP 80-100 45-55 

PS 50-80 30-45 

Rigid PVC 70 40 

K-Resin 65-70 35-40 

APET 65 35 


- 23 -


Appendix X. Stanley Rosen, Author: Make-Ready Procedure for “Kiss Cut” Dies 

Since the dies must contact the backing plate to get complete cut-through, great care must be 

taken during make-ready to ensure that the dies are not damaged. The following is an example 

of a make-ready procedure for a “kiss” cut die in an on-line trim press: 

1. Reduce hydraulic press cutting pressure to the minimum level that will allow actuation 

of the lower platen. 

2. Prepare a heavy Kraft paper sheet to the exact size of the platen and mark the outgoing 

edge as “front”. Tape the paper facing the front to the face of the base plate, allow the 

press and die to close, and strike the paper, leaving a cut impression on what is now the 

“master sheet”. Usually 75% of the die will either cut or mark the paper. Remove the 

master sheet and base plate; use a pencil to complete the cut impression of cavities that 

are incomplete. 

3. Obtain 0.002-in. thick x 0.250-in. wide (0.05-mm x 6.35-mm) stainless make-ready 

shim tapes with adhesive backing from a die-maker supply house. Study the die 

impression on the master and apply one layer of shim tape only on the very light or 

penciled-in die impressions. Trim the shim tape so it never extends closer than 0.250 

in. (6.35 mm) to a neighboring heavy die impression. The objective is to build up the 

shim pack so it never disturbs an existing cut section. Avoid installing loose shims. 

They may shift and disrupt the process. 

4. Place the master sheet on the lower buildup in the same orientation marked “front” as 

the die. Install the base plate on top of the master sheet and replace the mounting 

screws. 

5. Tape a clean Kraft paper cut to the exact size of the striker plate on top. Mark it “No. 1 

front” on the appropriate edge. Die cut the No. 1 sheet and compare the results to the 

master sheet under the base plate. If the die impression still is not uniform, add one 

thickness of shim to the master sheet on any faint cuts, including those on the top of 

earlier shims. When building upon an earlier shim, cut the length shorter by 0.250 in. 

(6.35 mm) from each end so the shimming is feathered and not abrupt at its edges. 

6. Save sheet No. 1. Then cut sheet No. 2 and continue the process until the die 

impression becomes uniform. Save all the trial-cutting Kraft sheets to keep a record of 

progress and as a guide to avoid disturbing sections that were previously cutting. If 

previously cutting segments stop cutting, remove the last shims placed on the adjoining 

segments and start the process anew. 

7. When satisfied that make-ready is complete, insert a flat sheet of the same plastic to be 

thermoformed and attempt to trim it at low pressure. If it appears to be a uniform 

impression, raise the hydraulic pressure until the die cuts through. Lock the hydraulic 

pressure regulator at that point and shim-up area of the impression that may not have 

cut through. Judgment and experience will indicate when the die impression is uniform 

and when additional hydraulic pressure is needed to cut through a plastic sheet without 

dulling the die. 

Ref. Thermoforming: Improving Process Performance by Stanley R. Rosen, copyright 2002 

- 24 -


Appendix XI: Physical Properties of Film Extruded of PETG and APET (Eastman's Laboratories) 

Property Units Test Method 

(ASTM) 

PETG APET 

Inherent Viscosity 

Thickness of Film Tested 

D 3763 0.70 0.74 

Microns 

D374 

250 

250 

Mils 

10 

10 

Density, kg/m 3 (g/cm 3 ) D 1505 1,270 (1.27) (1.33) 

Haze, % D 1003 0.8 0.8 

Gloss @ 45° D 2457 108 108 

Transparency, % 

Transmittance, % 

D 1746 85 85 

Regular (Specular) 

D 1003 89 

89 

Total 

Water Vapor Transmission Rate 

91 

91 

g/m 2 ּ 24h 

g/100 in. 2 F 372 

6 

6 

ּ 24h 

Gas Permeability 

cm 

0.4 

0.4 

3 ּmm/m 2 ּ24hּatm 

(cm 3 ּmil/100 in. 2 ּ24hּatm) 

CO2 

D 1434 49 (125) 28 (70) 

O2 

Elmendorf Tear Strength, N (gf) 

D 3985 10 (25) 5.1 (13) 

M.D. 

D 1922 13.7 (1,400) 9.8 (1,000) 

T.D. 

PPT Tear Strength, N (lb-ft) 

16.7 (1,700) 12.7 (1,300) 

M.D. 

D 2582 93 (21) 102 (23) 

T.D. 

Tear Propagation Resistance 

Split-Tear Method @ 254 mm/min (10 in./min) 

M.D., N (lb-ft) 

93 (21) 120 (27) 

N/mm (lb-ft/in.) 

D 1938 9.1 (2.1) 15 (3.3) 

T.D., N (lb-ft/in.) 

36 (205) 58 (330) 


9.1 (2.1) 16 (3.6) 

Tear Resistance, Trouser @ 200 mm/min speed, 

36 (205) 63 (360) 


M.D. 

D 882 

36 (205) 54 (310) 

T.D. 

Tensile Strength @ Yield, MPa (psi) 

36 (205) 59 (340) 

M.D. 

D 882 

52 (7,500) 59 (8,500) 

T.D. 

Tensile Strength@ Break. MPa (psi) 

52(7,500) 57 (8,300) 

M.D. 

D 882 

59 (8,600) 58 (8,400) 

T.D. 

Elongation @ Yield, % 

55 (8,000) 39 (5,600) 

M.D. 

D 882 

4 

4 

T.D. 

Elongation @ Break, % 

4 

4 

M.D. 

D 882 

400 

300 

T.D. 

Tensile Modulus of Elasticity 

400 

200 

Mpa (10 5 psi) 

M.D. 

D 882 

1,900 (2.8) 2,200 (3.2) 

T.D. 

Dart Impact, 12.7-mm (½-in.) dia. head, 127-mm 

1,900 (2.8) 2,200 (3.2) 

(5-in.) dia.clamp, 660-mm (26-in.) drop, g 

@ 23°C (73°F) 

D 1709A 

400 

400 

@ -18°C (0°F) 

500 

500 

- 25 -


Appendix XII. Technical Data and Property Comparison: RPET vs. PVC 

Material RPET PVC 

Gauge, Mils 10 10 

Density, g/cm 3 1.33 1.35 

Haze, % 0.5 1.2 

Gloss at 45 deg. (Gardner) 110 93 

Transparency, % 85 36 

Tensile strength, psi 7,100 7,100 

Tensile Modulus of Elasticity, psi 280,000 325,000 

Oxygen Transmission Rate 

109 174 

cc/sq.meter/24 hr/mil 

HVTR.g/100 sq.in. /24 hr 0.40 0.19 

Vicat Softening Point (°C) 80 82 

Blushing No Yes 

Dart, Impact, ½ in. 

Dart, g@ 26 in. drop 

At 73 °F (23 °C) 

At -20 °F (-29 °C) 

- 26 - 

425 

300 

415 

345 

Heat Deflection (°F at 264 psi) 145 167 

Sealing Temperature (°F) 275-400 315-360 

Sheet Temperature (°F) 250-300 275-350 

Courtesy of the Lavergne Group 

Appendix XIII. Rockwell Hardness Scale of Abbreviations 

The ASTM (American Society for Testing & Materials) has standardized a set of scales (ranges) for Rockwell 

hardness testing. Each scale is designated by a letter. 

• A Cemented carbides, thin steel and shallow case hardened steel 

• B Copper alloys, soft steels, aluminum alloys, malleable iron, etc. 

• C Steel, hard cast irons, pearlitic malleable iron, titanium, deep case hardened steel and other materials 

harder than B 100 

• D Thin steel and medium case hardened steel and pearlitic malleable iron 

• E Cast iron, aluminum and magnesium alloys, bearing metals 

• F Annealed copper alloys, thin soft sheet metals 

• G Phosphor bronze, beryllium copper, malleable irons 

• H Aluminum, zinc, lead 

• K, L, M, P, R, S, V Bearing metals and other very soft or thin materials, including plastics.


Appendix XIV. Application Pictures 

PET Clamshells 

PET Packaging 

PET Snap 

- 27 - 

PET Hinge 

PET Sheet


Sources 

• Eastman Publications: DDS-3C, TRS-65L, TRS-106B, TRS- 111B, and TRS-194A. 

• Empire West Inc.’s “Thermoforming in a Nutshell” available at www.empirewest.com 

• Thermoforming: A Practical Guide by Adolf Illig, copyright 2001 

• Understanding Thermoforming by James L. Throne, copyright 1999 

• “Evaluating the Cutting Behavior of Amorphous PET Sheet Using Steel Rule Dies” by 

Moskala-Barr from ANTEC 2000 

• Thermoforming: Improving Process Performance by Stanley R. Rosen, copyright 2002 

Special Thanks to: 

• G.N. Plastics Ltd. 

• Ontario Die Company 

• American Tool & Engineering Inc. 

• C.R. Clarke & Co. 

• Future Mold Corp. 

• Sherwood Technologies, Inc., James L. Throne 

• Mold Systems Corporation, Stanley R. Rosen 

• Selected PETCO customers, who have reviewed this paper. 

www.lavergne.ca 

This paper is part of a research and marketing project by the Lavergne Group. For more 

information about PET Sheet, its PET sheet extruding line, thermoforming and die cutting PET 

sheet or about the company and its writers, please contact us: 

Lavergne Group 

PETCO Division 



(Quebec) Canada H1J 1C8 

To contact any of the presenters or writers of this paper: 


fax 402-861-9527, lkoester@phonet.com 

Sheila Nemeth, Marketing & Sales, tel. 514-354-5757 ext. 116, 

fax 514-354-3087, snemeth@lavergne.ca 

- 28 -

PET Sheet 

Thermoforming & Die Cutting 

Presented by Larry Koester and Sheila Nemeth 

from the PETCO Division of Lavergne Group 

What is PET Sheet? 

PET is a plastic resin chemically constructed by 

combining terephthalatic acid with ethylene 

glycol. It has a wide-range of applications. 

Its other names include APET, RPET, PETE or polyester 

Thermoforming & Die Cutting PET Sheet 

Challenges of PET Sheet 

Moisture Sensitive 

Toughness resulting 

in difficulty cutting 

and trimming 

Patience & Precision for “Make-Ready” 


Introduction 


What is PET Sheet? 

PET Sheet Properties 

Applications 

PET vs. PVC 


Thermoforming PET Sheet 

Heating & Forming PET Sheet 

General Considerations 

Die Cutting PET Sheet 

Kiss Dies 

including Steel Rule Dies and Forged Dies 

Scissor-type / Matched-Metal Dies 

General Considerations 

Advantageous Properties 

Clarity and Sparkle 

Toughness 

Durable Hinges & Closures 

Light Weight 

Good Gas Barrier 

Solvent/Corrosion Resistance 

Good Cost/Performance Ratio 

Durable, difficult to break 

Recyclable and Regrindable 


Applications 

PET Sheet


Applications 

Packaging 


Applications 

PET Hinge 


PET 

Faster 

Lower (450ºF, 230ºC) 

Lower 

= 

= 

= 

= 

More Difficult 

+ 

Recyclable 

PET Sheet vs. PVC 

Comparison 

Cycle Times 

Oven Temps. 

Energy 

Rigidity 

Shrinkage 

Tooling 

Price 

Die Cutting 

Environmental 

Regrind Reuse 

PVC 

Slower 

Higher (600ºF, 315ºC) 

Higher 

= 

= 

= 

= 

Less Difficult 

- 

Difficult to Reuse 


Applications 

Applications 

Clamshells 


Snap Closure 

Thermoforming & Die Cutting PET Sheet (a Lavergne Group presentation) 


In extrusion as opposed to 

thermoforming, raw PET must 

be heated past its glass 

transition temperature of 70°C 

(158°F) to above its melting 

temperature of 255°C (490°F). 

At this temperature the PET 

changes to a liquid state where 

extrusion continues.

Thermoforming & Die Cutting PET Sheet (a Lavergne Group presentation) 


PET pellets or flake are dried in a desiccant dryer, 

fed into a hopper, and placed on top of the barrel. 

The barrel of the extruder contains a rotating 

screw, which conveys, melts, and pumps the 

melted resin into a flat sheet. 

Calendar rolls adjust the sheet thickness. 

The extruded PET sheet is wound 

into a clear roll or stock and cut to 

the appropriate width. 


Thanks to… 

G.N. Plastics Ltd. 

Ontario Die Company 

American Tool & Engineering Inc. 

C.R. Clarke & Co. 

Future Mold Corp. 

Eastman Chemicals 

James L. Throne 

Stanley R. Rosen 

Selected PETCO Customers 

…for their help and improvement of this presentation 



Moderate heat settings 

between 140 ο C to 165 ο C (280 ο F to 325 ο F). 

Mold temperatures ranging from 

40 ο C to 60 ο C (100 ο F to 140 ο F). 

Monitor temperatures 

DO NOT: 

Overheat sheet 

Use cold molds 

Use sheet temperatures below 140οC (280οF) ***These can result in embrittlement, excessive sag, 

non-uniform drawing, and “freezing” of the sheet*** 

“ 


Methodology of This Paper 

PETCO/Lavergne Group is PET Bottle Recycler & 

PET Sheet Producer 

Review of Existing Literature & Publications on TF 

& Die Cutting of PET Sheet 

Focused on Die Cutting (most challenging aspect) 

Reviewed by Equipment Mfg., PETCO Customers, 

& TF Consultants (not necessarily endorsed) 



Similarity with other amorphous polymers allows 

thermoforming equipment to be adapted to 

properly handle PET sheet. 

Cycle Times and Forming Temperatures must be 

adjusted to appropriately suit PET. 

PET typically has shorter forming cycles and lower 

temperatures than those used in thermoforming 

other sheet such as PVC. 

Don’t Assume PET & PETG are the Same 



As a Moskla and Barr study stated… 

APET is notoriously difficult to cut. 

”


I. Kiss Cut Dies (Steel Rule & Forged Dies) 

General Procedure: 

PET sheet is heated and thermoformed by vacuum or 

pressure to the contours of the mold. 

While still in the mold, the heated forged die is pressed 

down further through the PET sheet. 

The die edge makes “kiss cut” contact on the base 

cutting the hot PET sheet. 


I. Kiss Cut Dies (Steel Rule & Forged Dies) 

Forged die… (a.k.a “form and cut” procedure) 

Cost Value: Excellent for middle of the road volume 

applications 

Usable: In-place trimming procedure 

Main Advantage: Easiest die to heat 

Main Disadvantage: Its attachment to the mold requires 

a completely new mold if die ever breaks. 



Hot PET sheet is easier to cut than cold sheet (reduced 

shear strength requires less force) 

Control Base Plate Temperature Just Below PET 

Sheet Sticking Point (Sheet

Thermoforming & Die Cutting PET Sheet Thermoforming & Die Cutting PET Sheet 


I. Kiss Cut Dies (Steel Rule and Forge Dies) 



Matched Metal Die… (a.k.a a punch and die) 

Procedure: 

Mounted in a separate cutting press through which the 

continuously formed sheet passes… 

The matched metal die works with hardness. 

A harder punch is used with a softer die (typical hardness is 43 

Rockwell C for the die and 55 for the punch). 

Minimum clearance is maintained as it wears. 

The die may be peened – a process used on a die to recover 

proper clearance by spreading the edge of the die back to its 

original size. 



Matched Metal Die… (a.k.a a punch and die) 

Cost Value: recommended for large applications 

Usable: in-line trimming method 

Main Advantage: easiest to repair as die wears 

Main Disadvantage: inflexibility in adjusting to different 

cutting specs 


II. Scissor-type Dies (Matched Metal Dies)


Conclusions: 

PET Sheet offers clarity, toughness, durable 

hinges, good cost/performance ratio & ease of 

recycling 

Die Cutting requires precision & patience (Make- 

Ready Procedure) 

Heat Assist to Reduce Shear Strength 

PET Sheet is a packaging opportunity that is 

worth the investment 


Contact Us… 

For more information about PET Sheet, its PET sheet 

extruding line, thermoforming and die cutting PET sheet 

or about the company and its writers, please contact us: 

PETCO, Division of Lavergne Group 



(Quebec) Canada H1J1C8 


fax 402-861-9527, lkoester@phonet.com 

Sheila Nemeth, Marketing & Sales, tel. 514-354-5757 

ext. 116, fax 514-354-3087, snemeth@lavergne.ca

Thermoforming & Die Cutting of Recycled/Virgin PET Sheet

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