Issue 03/2016

Injection moulding
By:
Marco Neudecker
Hans-Josef Endres
Institute for Bioplastics & Biocomposites (IfBB)
Hanover, Germany
characteristics. Due to its filler content,
however, it has the highest viscosity
among all PLA materials in the tests.
The highest flowability is indicated, as
expected, for the PLA optimised for
injection moulding applications.
Variety of bioplastics
Considering the variety of bioplastic
materials, it is evident that they cover
a range comparable to conventional
plastics.
PBS, Bio-PA, and Bio-PE are bioplastic
materials with a flow behaviour similar
to that of HDPE. Low viscosity and,
thus, high flowability is shown for PHB,
which is a good condition for molding
even large components with a low wall
thickness. Bio-PE, which is combined
with 50 wt% natural fibres, shows low
flowability and, just like the PLA filled
with natural fibres, settles at the lower
end of the parameters of comparison.
The fibre-filled bioplastics are therefore
not recommended for use in cases
where low wall thickness is desired.
Another point against it is that natural
fibres tend to react to high shear forces
by darkening or even by denaturation.
Overall, the tests have revealed
that bioplastics, with respect to their
flow properties, already cover quite a
broad range and possess attributes
comparable to those of conventional
plastics. Apart from the exceptions
mentioned, they are suited for use in
thin-wall components. Based on the
findings from these tests, it will also
be possible in the future to use specific
bioplastics available as a substitute
for conventional plastics, selected by
their wall thickness dependent flow
characteristics.
Acknowledgement
The authors express their gratitude
to the German Federal Ministry of Food
and Agriculture (BMEL) for funding this
project.
http://ifbb.wp.hs-hannover.de/
verarbeitungsprojekt/
Flow length [mm]
900
800
700
600
500
400
300
200
100
0
0 0.5 1 1.5 2 2.5 3 3.5
Wall thickness [mm]
Fig. 1 Wall thickness dependent flow behaviour of conventional plastics
Fig.2 Wall thickness dependent flow behaviour of PLA-based bioplastics
Flow length [mm]
Flow behaviour of conventional plastics
Fig. 3 Wall thickness dependent flow behaviour of various bioplastics
Flow length [mm]
900
800
700
600
500
400
300
200
100
Area of flow behaviour
of conventional plastics
0
0 0.5 1 1.5 2 2.5 3 3.5
Wall thickness [mm]
900
800
700
600
500
400
300
200
100
Flow behaviour of PLA-based bioplastics
Area of flow behaviour
of conventional plastics
Area of flow behaviour
of conventional PA
Flow behaviour of various bioplastics
Area of flow behaviour
of conventional plastics
Area of flow behaviour
of conventional HDPE
Area of flow behaviour
of conventional PP nv
0
0 0.5 1 1.5 2 2.5 3 3.5
Wall thickness [mm]
Injection pressure = 645 bar
PP nv
T m
= 200 °C
T W
= 30 °C
PS
T m
= 260 °C
T W
= 30 °C
HDPE
T m
= 180 °C
T W
= 30 °C
PP hv
T m
= 200 °C
T W
= 30 °C
PA
T m
= 260 °C
T W
= 80 °C
Theoretical
computing values
In cooperation with UL TTC
Injection pressure = 645 bar
PLA injection moulding grade
T m
= 200 °C
T W
= 30 °C
PLA fibre spinning grade
T m
= 200 °C
T W
= 30 °C
PLA injection moulding grade 2
T m
= 200 °C
T W
= 30 °C
PLLA
T m
= 200 °C
T W
= 30 °C
PLA + 60 wt% NF
T m
= 200 °C
T W
= 30 °C
Theoretical
computing values
In cooperation with UL TTC
Injection pressure = 645 bar
PHB
T m
= 210 °C
T W
= 30 °C
Bio PE
T m
= 180 °C
T W
= 30 °C
Bio PA
T m
= 250 °C
T W
= 90 °C
PBS
T m
= 190 °C
T W
= 30 °C
Bio PE + 50 wt% NF
T m
= 200 °C
T W
= 30 °C
Theoretical
computing values
In cooperation with UL TTC
bioplastics MAGAZINE [03/16] Vol. 11 23