Plastics News correspondent Michael Lauzon reported the following news briefs from the International Conference on Biocomposites, held May 2-4 in Toronto.
Researcher finding ABS scrap is useful
Scrap ABS can produce stronger wood-plastic composites than polyolefins, according to Rakesh Gupta, a researcher with West Virginia University in Morgantown, W.Va.
Plastics from scrap electronics have found few uses, but ABS sourced that way can be used to make composites, said Gupta. Scrap ABS has variations in quality, but when used with wood filler, the variations are smoothed out.
The problem with polyolefins is low stiffness, Gupta said, adding that with ABS, composites have twice the stiffness and good impact strength.
Gupta said his group used maple fiber with 80 mesh, typical of that for wood-plastic composites. In addition to ABS, a coupling agent, lubricant, wood flour and flame retardant were added. Ingredients were mixed in a Leistritz co-rotating compounder.
Nanofibers suitable for transparent sheet
Cellulose nanofibers are transparent when wetted out in a polymer, making them suited to reinforced transparent sheet, said Hiroyuki Yano, a researcher with Kyoto University in Kyoto, Japan.
Optically transparent substrates could find uses in displays, solar panels and flexible computers, the speaker said.
Nanofibers are small enough to be transparent, Yano told delegates. He and his colleagues worked with bacterial cellulose fibers impregnated with acrylic and epoxy resins. Compositions with up to 60 percent fibers were still transparent. But bacterial cellulose is expensive so they made wood cellulose nanofibers by grinding pine.
Cellulose nanofiber-reinforced acrylic sheet has low thermal expansion, making it suited to flexible displays. Straight plastic sheet has high thermal expansion, precluding its use for displays and related panels, according to Yano.
Yano laminated pure nanocellulose sheet to plastics to make transparent sheets with low thermal expansion for polylactides, PET, high-impact polystyrene, PS and polycarbonate.
Composites can be injection molded
GreenCore Composites Inc. has developed composites based on wood fiber and polypropylene that can be injection molded.
NCell pellets contain 40 percent wood fiber and are designed to compete with glass-reinforced polypropylene, said Vince Yan, technical development manager for the Toronto firm. The pellets are stronger than natural PP and have mechanical values comparable to glass fiber-reinforced PP, Yan said.
Compared with glass-reinforced PP, NCell has lower weight, is non-abrasive, requires lower processing temperatures and can claim to have renewable, sustainable content, he said.
His firm is developing uses in automotive, furniture, lawn and garden, sports and industrial markets. One project GreenCore is working on is a food tray that will be launched by an undisclosed customer in September.
Injection processes suited to NCell include gas assist, coinjection and hot runners.
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