Compounding bioplastics | materials development
Peter Mapleston reviews the latest developments in polymers and additives that can lift the performance levels of bio-based plastics
Options increase for improving bioplastics performance
Biodegradable polymers are set to further develop into markets traditionally dominated by conventional thermoplastics. Today, polylactic acid (PLA) is the dominant resin in the fi eld. However, it still requires some modifi cation to overcome technical issues, such as brittleness and poor melt strength, in order to further expand its use. Leading biopolymer supplier NatureWorks says the
durable products market for its Ingeo PLA, although still much smaller than that for biodegradable/ compostable packaging, is currently growing much faster. One of the reasons is that its partners are learning fast how to round-out its property profi le. NatureWorks sells its resins neat, saying “the
formulator or compounder will need to add nucleating agents, impact modifi ers, reinforcing agents, etc. as needed.” Compounders of the material include PolyOne, RTP, Tecnaro, Teknor Apex, Toray and Unitika. At the “Innovation takes Root” conference organized by NatureWorks in February in Orlando, Florida, several
additives producers working on products that enhance PLA properties presented their latest developments. They included Metabolix, Proviron, Takemoto Oil & Fat, and Wacker. Metabolix offers PHA (polyhydroxyalkanoate)
biopolymers as modifi ers for PLA (and also as moulding grades in their own right). Bob Engle, vice president, biopolymers at Metabolix, introduced Mirel rubber modifi ers, new amorphous PHA copolymers with the physical characteristics of a rubber with a low glass transition temperature (Tg). They have been shown to improve the ductility and fl exibility of PLA, while also retaining clarity and compostability. Metabolix is currently prototyping these modifi ers in a range of PLA applications. The Mirel grades have molecular weights ranging
from 200,000 to 700,000, and their crystallinity can be varied by changing the level of comonomer. At comono- mer levels from just under 40% to around 65%, crystallinity is zero, and glass transition temperature is
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June 2014 | COMPOUNDING WORLD 21
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