New technology from Teknor Apex Company eliminates a property tradeoff that has prevented polylactic acid (PLA) from serving as a
“green” alternative to polystyrene (PS) and polypropylene (PP) in high-heat thermoformed sheet for microwavable frozen food trays, lids for hot beverage cups, and carry-out containers such as those for restaurant food, the US-headquartered company said in its new release.
As introduced, the new Terraloy BP-39070 series of enhanced-PLA compounds for extrusion and thermoforming have a bio-based content level of around 90% and are biodegradable. They meet the FDA requirement for food-contact applications and Teknor Apex expects them to meet ASTM specification D-6400 and qualify for Biodegradable Products Institute certification for composting as well, according to Edwin Tam, manager of new strategic initiatives for the Bioplastics Division of Teknor Apex.
Terraloy BP-39070 compounds are based on innovations by Teknor Apex that have overcome an inverse relationship in standard PLA between Heat Distortion Temperature (HDT) and Izod impact strength. The new products exhibit up to two times the HDT and more than four 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.
The formulations on which the new compounds are based differ from those of Terraloy enhanced-PLA products recently introduced for injection molding. “Teknor Apex has optimized Terraloy BP-39070 for extrusion and thermoforming, building in greater melt strength than is available with standard PLA and providing for a faster crystallization rate,” Mr Tam said. “As a result, we expect users of these compounds to achieve higher throughputs in extrusion and benefit from a broader processing window in thermoforming than standard PLA.”
According to Teknor Apex, in microwavable carry-out containers such as those used for leftover restaurant foods, Terraloy BP-39070 compounds would replace pulped fiber as well as polypropylene. As a replacement for PS in lids for hot beverage containers such as those for coffee, the compounds would be used with cups that typically are themselves compostable.
In property tests, a typical grade in the new series, Terraloy 39070A, exhibits HDT of 100°C and Izod impact strength of 69J/m. By comparison, approximate values for standard extrusion-grade PLA are 55°C and 16J/m.
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