Materials | bioplastics
Purac claims its new lactide monomers can lift HDT performance of bio-based PLA resins to match PS, PP and even ABS
New monomers lift PLA limits
Injection moulders around the world are keeping a very close eye on sustainability shifts and bioplastic developments. Concerns over future fossil fuel availability, along with increasing pressure from sustainability-minded customers and consumers, are forcing many to re-evaluate their products and processes. From making real
reductions in water use and CO2 emissions, to reduced packaging and waste, companies are tackling this shift in a multitude of ways.
In the plastics industry, perhaps the most signifi cant sustainability shift is the move from fossil fuel-based plastics to bio- based polymers (those made from annually renewable resources). The sustainability benefi ts of biobased plastics over oil based plastics may be plentiful, yet the key hurdle for bioplastics has been to match the performance levels of their oil-based predecessors. Heat resistance, for instance, is a major requirement in a number of applications. Bioplastics cannot truly compete with oil-based plastics until their performance is on a par.
Monomer innovation Now, the Netherlands-based lactides producer Purac Bioplastics, which has some 80 years’ experience in lactic acid production, claims to have successfully developed high heat resistant lactide monomer technol- ogy that makes the resultant polylactic acid (PLA) polymer suitable as a direct bio-based replacement for traditional polymers such as PS and PP. Its new monomer technology is said to yield PLA polymers that can withstand temperatures in the range of 80°C up to 120°C HDT B (Figure 1). With careful product design, the service temperature can be even higher, says the company.
“The biggest challenge has been to overthrow the
existing impression that people have of PLA as being low performance and only suitable for packaging or cold-application disposable serviceware. With this next
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generation PLA, we are now approaching new indus- tries and product segments to reposition PLA as a serious bio-based contender in the replacement race,” says François de Bie, global marketing director for bioplastics at Purac. The key to achieving these new performance levels is in the base ingredients, according to Purac. The company commenced commercial production of its Puralact L and D lactide monomers last year at its 75,000 tonne/year plant in Thailand. The monomers, which form the basis of these new PLLA and PDLA homopolymers, offer a claimed stereochemical purity of more than 99% (Figure 2). Under the right conditions, PLLA and PDLA homopolymers are able to crystallise faster than current PLA offerings, resulting in a signifi cantly higher melting point and higher service temperature. The fi nal application retains its bio-based status, says de Bie, yet with the right compounding can exhibit properties similar to oil-based PP, PS and ABS (Figure 3). PLA also offers the benefi t of food contact approval within both the US and European regulatory regimes, and the polymer can be readily recycled. Purac also says its monomers are produced from GMO-free feedstocks, which is still a consumer concern in Europe.
Main image:
Puralact-based PLA tableware produced by New Sunrise Plastics in
Singapore for the Giant
Hypermarket retail group
April 2013 | INJECTION WORLD 37
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