Issue 03/2016
bioplasticsMAGAZINE_1603
bioplasticsMAGAZINE_1603
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Injection moulding<br />
By:<br />
Marco Neudecker<br />
Hans-Josef Endres<br />
Institute for Bioplastics & Biocomposites (IfBB)<br />
Hanover, Germany<br />
characteristics. Due to its filler content,<br />
however, it has the highest viscosity<br />
among all PLA materials in the tests.<br />
The highest flowability is indicated, as<br />
expected, for the PLA optimised for<br />
injection moulding applications.<br />
Variety of bioplastics<br />
Considering the variety of bioplastic<br />
materials, it is evident that they cover<br />
a range comparable to conventional<br />
plastics.<br />
PBS, Bio-PA, and Bio-PE are bioplastic<br />
materials with a flow behaviour similar<br />
to that of HDPE. Low viscosity and,<br />
thus, high flowability is shown for PHB,<br />
which is a good condition for molding<br />
even large components with a low wall<br />
thickness. Bio-PE, which is combined<br />
with 50 wt% natural fibres, shows low<br />
flowability and, just like the PLA filled<br />
with natural fibres, settles at the lower<br />
end of the parameters of comparison.<br />
The fibre-filled bioplastics are therefore<br />
not recommended for use in cases<br />
where low wall thickness is desired.<br />
Another point against it is that natural<br />
fibres tend to react to high shear forces<br />
by darkening or even by denaturation.<br />
Overall, the tests have revealed<br />
that bioplastics, with respect to their<br />
flow properties, already cover quite a<br />
broad range and possess attributes<br />
comparable to those of conventional<br />
plastics. Apart from the exceptions<br />
mentioned, they are suited for use in<br />
thin-wall components. Based on the<br />
findings from these tests, it will also<br />
be possible in the future to use specific<br />
bioplastics available as a substitute<br />
for conventional plastics, selected by<br />
their wall thickness dependent flow<br />
characteristics.<br />
Acknowledgement<br />
The authors express their gratitude<br />
to the German Federal Ministry of Food<br />
and Agriculture (BMEL) for funding this<br />
project.<br />
http://ifbb.wp.hs-hannover.de/<br />
verarbeitungsprojekt/<br />
Flow length [mm]<br />
900<br />
800<br />
700<br />
600<br />
500<br />
400<br />
300<br />
200<br />
100<br />
0<br />
0 0.5 1 1.5 2 2.5 3 3.5<br />
Wall thickness [mm]<br />
Fig. 1 Wall thickness dependent flow behaviour of conventional plastics<br />
Fig.2 Wall thickness dependent flow behaviour of PLA-based bioplastics<br />
Flow length [mm]<br />
Flow behaviour of conventional plastics<br />
Fig. 3 Wall thickness dependent flow behaviour of various bioplastics<br />
Flow length [mm]<br />
900<br />
800<br />
700<br />
600<br />
500<br />
400<br />
300<br />
200<br />
100<br />
Area of flow behaviour<br />
of conventional plastics<br />
0<br />
0 0.5 1 1.5 2 2.5 3 3.5<br />
Wall thickness [mm]<br />
900<br />
800<br />
700<br />
600<br />
500<br />
400<br />
300<br />
200<br />
100<br />
Flow behaviour of PLA-based bioplastics<br />
Area of flow behaviour<br />
of conventional plastics<br />
Area of flow behaviour<br />
of conventional PA<br />
Flow behaviour of various bioplastics<br />
Area of flow behaviour<br />
of conventional plastics<br />
Area of flow behaviour<br />
of conventional HDPE<br />
Area of flow behaviour<br />
of conventional PP nv<br />
0<br />
0 0.5 1 1.5 2 2.5 3 3.5<br />
Wall thickness [mm]<br />
Injection pressure = 645 bar<br />
PP nv<br />
T m<br />
= 200 °C<br />
T W<br />
= 30 °C<br />
PS<br />
T m<br />
= 260 °C<br />
T W<br />
= 30 °C<br />
HDPE<br />
T m<br />
= 180 °C<br />
T W<br />
= 30 °C<br />
PP hv<br />
T m<br />
= 200 °C<br />
T W<br />
= 30 °C<br />
PA<br />
T m<br />
= 260 °C<br />
T W<br />
= 80 °C<br />
Theoretical<br />
computing values<br />
In cooperation with UL TTC<br />
Injection pressure = 645 bar<br />
PLA injection moulding grade<br />
T m<br />
= 200 °C<br />
T W<br />
= 30 °C<br />
PLA fibre spinning grade<br />
T m<br />
= 200 °C<br />
T W<br />
= 30 °C<br />
PLA injection moulding grade 2<br />
T m<br />
= 200 °C<br />
T W<br />
= 30 °C<br />
PLLA<br />
T m<br />
= 200 °C<br />
T W<br />
= 30 °C<br />
PLA + 60 wt% NF<br />
T m<br />
= 200 °C<br />
T W<br />
= 30 °C<br />
Theoretical<br />
computing values<br />
In cooperation with UL TTC<br />
Injection pressure = 645 bar<br />
PHB<br />
T m<br />
= 210 °C<br />
T W<br />
= 30 °C<br />
Bio PE<br />
T m<br />
= 180 °C<br />
T W<br />
= 30 °C<br />
Bio PA<br />
T m<br />
= 250 °C<br />
T W<br />
= 90 °C<br />
PBS<br />
T m<br />
= 190 °C<br />
T W<br />
= 30 °C<br />
Bio PE + 50 wt% NF<br />
T m<br />
= 200 °C<br />
T W<br />
= 30 °C<br />
Theoretical<br />
computing values<br />
In cooperation with UL TTC<br />
bioplastics MAGAZINE [<strong>03</strong>/16] Vol. 11 23