For many converters, bio-based plastics are materials they have little experience with. How different are they from conventional materials and what adjustments - if any - need to be made when using these resins?
To gain a better understanding of aspects such as the extent to which the processing and cavity parameters required differ from conventional injection moulding machine manufacturer Arburg regularly carries out processing tests on bio-based plastics at its Customer Center in Lossburg, Germany.
"There is a growing interest in alternative plastics among our customers," explained Bertram Stern, Sustainability Manager at Arburg. "Depending on the application, bio-based plastics offer advantages in terms of resource efficiency and disposal.
The company recently tested the Inzea range of PLA-based products, produced by Nurel Biopolymers and distributed by Biesterfeld since 2016.
“As a distributor, we bridge the gap between the plastics producer and the processing industry. We're very proud to be actively supporting our customers as they move towards greater sustainability," said Philip Malke, Product Manager Sustainable Polymer Solutions at Biesterfeld. "The Inzea product family is an integral part of our range of solutions.”
Inzea is an EN13432-compliant bio-based and fully biodegradable and compostable polymer based on polylactic acid from renewable and non-genetically modified sources, which does not compete with the food chain. Some types also contain a proportion of starch. Inzea offers grades that are suitable for injection moulding, extrusion and thermoforming.
Food-contact approved, Inzea’s main applications are in the household segment, catering, packaging and agriculture, typically in plastic bags, coffee capsules, bottles and boxes. The product family can also be used in many other short-lifespan applications, as well as in 3D printing.
The processing test at Arburg was performed according to the processing parameters specified in the product data sheet. During the test the screw geometry and process parameters were varied and the resulting effects on the quality of the parts were analysed. Parameters such as the cylinder and hot-runner temperature, dosing speed, back pressure and injection speed were assessed.
The tests showed problem-free conventional production on the basis of the parameters in the product data sheet resulting in moulded parts with a high degree of process reliability, with no need of additional machine equipment. “We've demonstrated that our ALLROUNDER machines can be optimally adjusted to the required material-specific process parameters,” said Stern.
Also, during the test, the effect of moisture content was looked out. It was found that although the datasheet did not specify the need for additional drying, ample drying with a vacuum dryer resulted in even better part quality. The tests also demonstrated - as expected - that extreme stresses such as hot runners with long flow channels had a negative impact on part quality due to thermal damage.
Additional comparisons with an oil-based ABS confirmed that Inzea offers an excellent alternative to fossil-derived materials.
“It's great news that the tests performed by ARBURG confirm the positive feedback we receive from our customers,” said Malke.