bioplasticsMAGAZINE_0905
bioplasticsMAGAZINE_0905
bioplasticsMAGAZINE_0905
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Basics<br />
arable land<br />
biopolymers<br />
by weight is required. This means that under<br />
certain circumstances up to 60 % of the material<br />
is not cellulose at all but is based on acetic acid<br />
(largely produced under pressure by catalytic<br />
conversion of petrochemical methanol with carbon<br />
monoxide), and other petrochemical softeners.<br />
With an assumed minimum degree of substitution<br />
of 2 the acetate content alone represents 30 and<br />
the plasticizer 20 % by weight.<br />
2: Cellulose regenerate: Percentage<br />
of cellulose based material 90 - 99 percent<br />
by weight<br />
Cellulose regenerates are used in the biopolymer<br />
sector mainly as coated film (e.g. with a barrier<br />
coating or sealing layer). From the point of view<br />
of the weight of the dominant material a cellulose<br />
percentage of near enough 100 % can be assumed.<br />
For the coating, a percentage by weight of at the<br />
most 10 % is assumed. Normally the coating will<br />
account for a much smaller percenatge.<br />
3: Thermoplastic starch (TPS): Starch based<br />
percentage of the material 70 - 80 percent<br />
by weight<br />
To optimise the performance of thermoplastic<br />
starch in processing and use, native starches must<br />
be modified and/or in particular be added with a<br />
softener such as glycerine or sorbitol (for details<br />
please see the respective section in the book).<br />
To calculate the average starch content, a total<br />
conversion of 100 % of the unmodified starch to a<br />
biopolymer was assumed. For starch acetate on<br />
the other hand, similar to cellulose acetate with a<br />
high degree of substitution, a starch requirement<br />
of only 600 kg per tonne is required. For the<br />
remaining additives or softeners raw materials<br />
of petrochemical origin were assumed. We can<br />
therefore assume on average that thermoplastic<br />
starch materials require an input of 70 to 80 % by<br />
weight of starch itself.<br />
4: Starch blends: Starch-based percentage<br />
25 - 70 percent by weight<br />
To optimise the properties in the processing and<br />
use of thermoplastic processable starch polymers<br />
it is necessary for native starch - as already<br />
Raw material yield [t/(hectare*annum)]<br />
The percentage of material in biopolymers<br />
that is biobased, i.e. obtained from<br />
renewable resources (% by weight)<br />
Output: tonnes of biopolymer or bioethanol /<br />
Input: tonnes of regenerating raw materials<br />
25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
100%<br />
80%<br />
60%<br />
40%<br />
20%<br />
0%<br />
6<br />
5<br />
4<br />
3<br />
2<br />
1<br />
0<br />
Sugars Starches Plant oils Cellulose (fibres)<br />
Sugar (cane)<br />
Sugar (beet)<br />
Maize starch<br />
Potato starch<br />
Wheat starch<br />
Rice starch<br />
Palm oil<br />
Jatropha oil<br />
Cocoa oil<br />
Castor oil<br />
Rapeseed oil<br />
Sunflower oil<br />
Soy oil<br />
Wood fibres<br />
Wheat straw<br />
Hemp<br />
Flax<br />
Cotton<br />
Fig 1: Absolute yield of various renewable raw materials<br />
per hectare per annum<br />
Cellulose regenerates 2<br />
Cellulose acetates 1<br />
Thermoplastic starches (TPS) 3<br />
Starch blends 4<br />
Polylactides (PLA) 5<br />
Polylactide blends 6<br />
Polyhydroxyalkcanoates (PHA) 7<br />
Fig 2: Percentage of renewable raw materials<br />
by weight in various biopolymers<br />
Cellulose regenerates 2<br />
Cellulose acetates 1<br />
Thermoplastic starches (TPS) 3<br />
Starch blends 4<br />
Polylacticdes (PLA) 5<br />
Polylactide blends 6<br />
Polyhydroxyalkcanoates (PHA) 7<br />
Bioenthanol 8<br />
Bioenthanol 8<br />
Fig 3: Total Biopolymer output in relation to the<br />
input of renewable raw materials<br />
Biopolyesters 9<br />
Biopolyesters 9<br />
Biopolyethylene (BIO-PE) 10<br />
Biopolyethylene (BIO-PE) 10<br />
bioplastics MAGAZINE [05/09] Vol. 4 35