PLA | sustainability
Manufacturers of PLA bioplastics are working hard to improve toughness, temperature resistance, and processibility. Peter Mapleston reports*
Injecting durability into PLA
Progress continues in improving the properties of bio-based polylactides through the judicious addition of complementary polymers and additives. As a result, polylactides (better known as polylactic acid or PLA) are moving into applications beyond packaging and are now being used in the automotive, electrical & electronics, and building & construction sectors, where developers are targeting applications traditionally catered for by ABS. Leading PLA polymer producer NatureWorks, which has some 140,000 tpa of PLA capacity at its plant in Nebraska in the US and is currently planning a second unit in Asia, is working hard to expand the property and applications envelope for the resin, which it markets as Ingeo. In late April, it unveiled a number of new ABS replacement formulations, saying that they clearly demonstrate that Ingeo 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 the new Ingeo formulations derive their functionality from the crystal-
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lisation enabled by combining the company’s newly commercialised polymer chemistries. This means the new grades have a higher renewably sourced carbon content of approximately 90%. The rapid crystallisation 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 chemicals,” says Diodato. So 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 target markets. Test parts were put under a strain of 1% and exposed to products including vinegar, Ajax spray cleaner, a liquid soap, extra virgin olive oil, isopro- panol 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 poor after 96 hours. For olive oil and butter,
July/August 2015 | INJECTION WORLD 47 Main image:
New blend and additive
technologies
are improving the durability and perfor-
mance of PLA in applications ranging from housewares to automotive and electronics
Below: Smartphones
are a key target market for
Natureworks
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