materials feature | Bioplastics
Tensile strength (in black) and elongation at break (in red) as a function of the amount of Capa 6500 (left plot) and Capa 6800 (right plot) in Ingeo PLA 2003D blends
maintain the fl exibility where for example PLA and starch-based material would suffer from their brittle- ness,” Zellner notes.
Biodegradation data for Perstorp Capa 6800, compared to PBAT and PLA according to EN 13432 – tests performed at the Swedish SP test institute
improving its mechanical properties while maintaining biodegradability. Although it is fossil-based, polycaprolactone is
readily biodegradable, under both aerobic and anaero- bic conditions. PCL is initially degraded enzymatically by the microorganisms followed by a hydrolysis process converting the polymer chains into smaller fragments such as oligomers and monomers. Although it is highly biodegradable, PCL is stable in
abiotic conditions against hydrolysis, Zellner says. Its hydrolytical stability, evaluated according to an OECD standard in a wide range of pH values, is superior to PLA and a rival biopolymer, polybutylene adipate terephthalate (PBAT). Polycaprolactone can be used in applications such as bags and fi lms to improve the tear resistance and elongation properties. It can also be applied in paper coatings as a barrier for moisture and grease, while also maintaining the fl exibility of the material as well as its compostability. In rigid packaging and service ware applications, it can improve the fl exibility to reduce brittleness and cracking in the material. “Thanks to the low glass transition temperature, PCL is suitable for packaging and articles used in cold environments to
38 COMPOUNDING WORLD | June 2015
Perstorp has recently synthesized new copolymers of caprolactone with lactides and evaluated them on a lab-scale. “Already in an early phase of the develop- ment, there was a perfect match between caprolactone and lactides,” Zellner says. “It was possible to increase the melting point which [can be] a limitation for PCL. The copolymers will be more amorphous, which opens up new alternatives of use.” The translucency of polycaprolactone makes it unsuitable in blends for applications which require transparency, but the copoly- mers can have high clarity.
Bio-based and fl ame retardant Clariant says that demand for plastics derived from renewables is rising in technical applications beyond the automotive sector, in areas such as the electrical and electronic (E&E), and the building and construction markets. “Of potential relevance to these industries, research groups are focusing on halogen-free fl ame retardants (HFFRs), often in combination with renew- able fi llers such as wood, lignin, starch and oyster shell, for the bio-based plastics and composites of interest,” the company says. “It is being shown that non-halogen- ated fl ame retardants have proven effi ciency in bio-based polymer matrices, providing mechanical properties fi t to use for certain applications.” The company says its Exolit HFFRs can ensure
effective fl ame retardancy in key bio-based polymers and composites used in building and construction and E&E applications. It cites one laptop computer manu- facturer that developed a model with a cover made from a fl ame-retardant blend of PLA and polycarbonate. Similar blends are under development for other offi ce equipment, Clariant notes. Fujitsu introduced a laptop with a PLA cover 10 years ago. Kimura Koichi, who was involved in the develop-
www.compoundingworld.com
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