A Rhode
Island compounder says it has improved impact strength and heat deflection
temperatures for a major bioplastic.
As a result,
the material, polylactic acid (PLA), may become a candidate for injection-molded,
semi-durable and durable applications. The bioplastic is also now better suited
for high-end disposable food service items such as cutlery, coffee lids and
containers for microwavable products.
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Teknor Apex says it has overcome an inverse relationship between heat distortion temperature (HDT) and Izod impact strength in PLA, creating a new series of compounds, Terraloy BP-34001, that provide up to two times the HDT and up to six times the impact strength of standard PLA resins.
Previous work to enhance PLA performance beyond standard levels had generated resins with either higher HDT or greater impact strength - but not both in the same grade, according to the Bioplastics Div. of Teknor Apex.
There are other benefits to the newly developed PLA compound.
In comparison with previous enhanced-performance PLA resins, the new Terraloy compounds process faster - cycle times are 28 to 30 percent shorter.
Another benefit: The compounds incorporate a larger percentage of renewably resourced content, about 10 to 30 percent more. Nearly all of the new Terraloy compounds are said to comply with FDA requirements for food-contact applications.
"Terraloy BP-34001 Series compounds dramatically improve the heat and impact resistance of PLA while largely retaining the environmental benefit of this polymer as a bioplastic," says Edwin Tam, manager of new strategic initiatives. "These innovative formulations promise to expand the applicability of PLA, making possible new uses in higher-heat food service items as well as consumer goods."
In property tests, a typical grade in the new series, Terraloy BP-34001D, exhibits a heat distortion temperature of 112C and Izod impact strength of 135 J/m. By comparison, approximate values for standard PLA are 65C and 33 J/m. The new compound complies with FDA 21 CFR requirements and has a renewable content of 78 percent.
The base polymers for Terraloy BP-34001 products are Ingeo resins supplied by NatureWorks.
"Teknor Apex built upon research by NatureWorks to develop higher-performance PLA compounds," says Gregory J. Anderson, Teknor Apex technical manager. "By discovering alternative formulations and compounding techniques, we succeeded in eliminating a chronic property trade-off between heat resistance and impact resistance, while improving processability and reducing the petrochemical content."
Tam says that the price for the PLA compound will be greater than for standard PLA. No specific data was available.
The Bioplastics Div. of Teknor Apex is a custom compounder of plastics derived from renewable resources. Product families include: hybrids that combine thermoplastic starch (TPS) with standard petrochemical-based polymers such as polyolefins or polystyrene; biodegradable or compostable blends of bioplastics; recycled-content hybrids that combine post-industrial or post-consumer polyolefins with TPS; and PLA-based masterbatches that incorporate additives such as impact modifier or melt strength enhancers.
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