materials development | Compounding bioplastics
Dow’s Paraloid BPM 520 improves the impact strength of PLA
result of their moisture sensitivity. Moisture and processing heat trigger the start of the degradation process, leading to a molecular weight (MW) reduction. This reduction in MW can negatively impact the platics’ mechanical properties and aesthetics. Drying the materials before processing is recommended for optimum performance. Some biopolymers, especially some grades of PHA, can exhibit a rather sharp increase in viscosity, which makes this polymer diffi cult to process.
geometric articles, she explains.
Licomont CaV 102 causes almost no mould deposits and is more effective at improving fl ow than amide waxes, according to Treffl er. It has no negative effect on transparency and mechanical properties, but it provides better surface post-treatment and outstanding thermal stability. Injection moulding trials with Licomont CaV 102 calcium soap indicated that it is possible to reduce cooling times by 25% and cycle times by 20%, thanks to better nucleating behaviour, which causes the PLA to crystallize much earlier than neat PLA. In the end this provides customers with productivity increases of as much as 25%, Treffl er says.
Preventing biodegradation in the extruder Marcel Dartée, global marketing director for sustain- able solutions & biomaterials at PolyOne, points out that biodegradation of biopolymers can begin sooner than you might think: right there in the extruder as a
Another typical characteristic is the tendency of biopolymers to stick to a mould or winding rolls, or to itself when rolled or otherwise wound. Some biopoly- mers readily charge with static electricity (PLA) whereas others are naturally static dissipating (starch blends) PolyOne has developed a range of additive concen- trates that contribute to stabilizing biodegradable polymers. These formulations delay the molecular weight reduction that occurs at the molecular level. Another type of additive concentrate increases the molecular weight of biopolymers. To overcome the sticky nature of these biopolymers, PolyOne has developed a full range of slip and antiblock additive solutions as well as antistatic ones.
Teknor Apex is another compounder that is active in the bioplastics market. Last month it was awarded the SPI’s second annual “Innovation in Bioplastics Award” for its development of Terraloy high-impact, heat- resistant PLA compounds.
Edwin Tam, manager of new strategic initiatives at the company, says: “The work of our Terraloy technical team, headed by technical manager Greg Anderson, along with our research partner Cerestech, has enabled us to enhance polylactic acid in areas such as heat resistance, impact resistance and processability while retaining key bioplastics values such as FDA compli-
The effect on fl ow properties of PLA by the addition of 0.5% of lubricants, showing how Clariant’s soaps of montanic acid perform in comparison with amide wax
26 COMPOUNDING WORLD | June 2014
The effect on the transparency of PLA by the addition of 0.5% of lubricants, comparing Clariant’s soaps of montanic acid with amide wax
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