New Bioplastic Features Higher HDT, Impact

A RhodeIsland compounder says it has improved impact strength and heat deflectiontemperatures 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 suitedfor high-end disposable food service items such as cutlery, coffee lids andcontainers for microwavable products.

Teknor Apex says it has overcome an inverse relationship between heatdistortion temperature (HDT) and Izod impact strength in PLA, creating a newseries of compounds, Terraloy BP-34001, that provide up to two times the HDTand up to six times the impact strength of standard PLA resins.

Previous workto enhance PLA performance beyond standard levels had generated resins witheither higher HDT or greater impact strength - but not both in the same grade,according to the Bioplastics Div. of Teknor Apex.

There are otherbenefits to the newly developed PLA compound.

Incomparison with previous enhanced-performance PLA resins, the new Terraloy compoundsprocess faster - cycle times are 28 to 30 percent shorter.

Anotherbenefit: The compounds incorporate a larger percentage of renewably resourcedcontent, about 10 to 30 percent more. Nearly all of the new Terraloy compounds aresaid to comply with FDA requirements for food-contact applications.

"TerraloyBP-34001 Series compounds dramatically improve the heat and impact resistanceof PLA while largely retaining the environmental benefit of this polymer as abioplastic," says Edwin Tam, manager of new strategic initiatives. "Theseinnovative formulations promise to expand the applicability of PLA, makingpossible new uses in higher-heat food service items as well as consumer goods."

In propertytests, a typical grade in the new series, Terraloy BP-34001D, exhibits a heatdistortion temperature of 112C and Izod impact strength of 135 J/m. Bycomparison, approximate values for standard PLA are 65C and 33 J/m. The newcompound complies with FDA 21 CFR requirements and has a renewablecontent of 78 percent.

The basepolymers for Terraloy BP-34001 products are Ingeo resins supplied by NatureWorks.

"Teknor Apex built upon research by NatureWorksto develop higher-performance PLA compounds," says Gregory J. Anderson, TeknorApex technical manager. "By discovering alternative formulations andcompounding techniques, we succeeded in eliminating a chronic property trade-offbetween heat resistance and impact resistance, while improving processabilityand reducing the petrochemical content."

Tam saysthat the price for the PLA compound will be greater than for standard PLA. Nospecific data was available.

TheBioplastics Div. of Teknor Apex is a custom compounder of plastics derived fromrenewable resources. Product families include: hybrids that combinethermoplastic starch (TPS) with standard petrochemical-based polymers such aspolyolefins or polystyrene; biodegradable or compostable blends of bioplastics;recycled-content hybrids that combine post-industrial or post-consumer polyolefinswith TPS; and PLA-based masterbatches that incorporate additives such as impactmodifier or melt strength enhancers.