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Bioplastics | materials feature


Raising the performance of PLA bioplastics


Progress continues to be made in improving the properties of bio-based polylactides through the judicious addition of complementary polymers and addi- tives. As a result, polylactides (better, if erroneously known as polylactic acid or PLA) are moving into applications beyond their initial target market of packaging products. PLA compounds are now being increasingly used in the automotive, electrical & electronics, and building & construction sectors. In particular, several developments are targeting applica- tions traditionally catered for by ABS. The leading producer of PLA polymers NatureWorks


is working hard to expand the property and applications envelope for the polymer, which it markets as Ingeo. In late April, it unveiled new ABS replacement formula- tions, saying that these clearly demonstrate that the resins “have evolved into a practical and safe alternative for a broad range of styrenics in terms of performance, price, and eco profi le.” The three new formulations, which are based on the


company’s heat-stable technology, are said to offer improved impact resistance, stiffness and chemical resistance. Two of them provide medium and high impact performance for injection moulding applications, while a high modulus formulation (50% higher fl exural modulus than a standard ABS) is optimised for profi le extrusion. These levels of performance have previously been


achieved by blending PLA with petroleum-based polymers. However, Frank Diodato, who leads Nature- Works’ Durables Business platform, says that the new Ingeo formulations derive their functionality from the crystallization enabled by combining the company’s newly commercialized polymer chemistries. This means


www.compoundingworld.com


Peter Mapleston examines how compounders are improving the properties of PLA bioplastics, delivering higher temperature resistance, shorter cycle times and increased mechanical performance


that they have a higher renewably sourced carbon content of approximately 90%. The rapid crystallization rate of the new grades leads


to defl ection temperatures under load of up to 92°C. It also cuts cycle times. “An important step in development of the new


formulations was to begin to understand how Ingeo components used for consumer products would perform when exposed to common household chemi- cals,” says Diodato. NatureWorks carried out a series of environmental stress crack resistance (ESCR) tests comparing Ingeo to ABS. Rather than using standard industrial solvents, which he says are irrelevant for the non-industrial markets targeted by these grades, the company used common household chemicals typically of interest to brands in its targeted markets. Test parts were put under a strain of 1% and exposed to products such as vinegar, Ajax cleaner, a liquid soap, extra virgin olive oil, and butter.


Both Ingeo and ABS had excellent resistance to


distilled vinegar. For Ajax spray, Ingeo was rated excellent at all-time intervals, while ABS was rated as


June 2015 | COMPOUNDING WORLD 31


Polylactides require a


helping hand to compete for


more demand- ing applications


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