MATERIALS | NATURAL FIBRES AND FILLERS
applications, from disposable PLA-based cutlery to automotive interior components. The custom compounder has worked with many types of fillers and fibres in multiple resin types. “The biggest challenges with [many] natural
fibres are moisture, odour, and colour,” says Pasquale. “These materials typically must be dried prior to compounding, but even then can have residual moisture content up to 1%. Pulling a vacuum on the compounding extruder can help to reduce this moisture, as well as reducing the volatile components that cause odour and even colour in some cases.”
Additives can also be used to mitigate negative
Above: As part of the COMPOlive research project, a compound made from 40% olive tree fibres and 60% recycled PP was used to injection mould a footrest for the Ford Focus
and Illinois). “We are planning for additional processing to manufacture our hemp masterbatch from the harvested material,” says John Ely, Heart- land’s Chief Marketing Officer. “Our goal is to have all hemp locally sourced (within 150 miles) of any of our processing facilities to streamline logistics.” While the company was initially producing the additive in powder form, Imperium is now provid- ed primarily as a functionalised, highly loaded (approximately 98% hemp fibre) masterbatch pellet that is much easier to handle in plastics part processing. Ely says that the fibre has successfully completed trials in PP and HDPE, and testing is underway in other polymers such as PVC and polyamides, which could go into automotive or building and construction applications. Initial results in higher temperature polymers (such as polyamides), have been very promising. A common challenge with natural products is that they tend to be less consistent than synthetic ones; Heartland, however, has successfully developed proprietary methods to ensure what the company says is absolute consistency in their additives.
Challenges Heartland’s initial focus was automotive suppliers. “Vehicles use many different polymers with different requirements, such as conductivity or heat or chemical resistance, so we researched many different formulations that met those needs,” says Ely. “Today, in addition to developing compounds for automotive components, we’ve found that our materials work well in things like industrial packag- ing, which will open up even more markets for lower carbon polymers.” AJ Pasquale, Co-founder and Director of
Operations at Tennessee-based Insight Polymers & Compounding, sees growing interest in natural fibres and fillers as a means of increasing bio- based content in plastic parts for a wide range of
16 COMPOUNDING WORLD | May 2024
effects. For example, odours can be trapped with additives designed for that purpose or masked with scents such as vanillin. Impact modifiers can counteract the property degradation that can result from residual moisture in compounds made with moisture-sensitive polymers such as PLA. Bleaching additives can whiten the typically brown colour of natural fibres and fillers. The ideal end-use, how- ever, is one that can tolerate some odour or brown colour, rather than spending the energy and cost to make them odourless and clear, suggests Pasquale. Another challenge with most natural materials is
an inherent degree of variability in properties and composition. “Added to this natural variability in raw material is variation between different vendors,” says Jeremy Lizotte, Co-founder and Director of Innova- tion at Insight Polymers. “Many biomaterials are new to the market and there is a lack of consistency even in one type of material. If you develop a product and process around a specific vendor, it might not translate to another vendor’s biomaterial.” Some of these issues are part of the “growing
pains” of a new industry, which may normalise as the industry matures and develops more standardi- sation and economies of scale, adds Pasquale. Meanwhile, variability can be recognised as a risk that compounding and formulation techniques can attempt to mitigate.
Cellulose nanofibres Norwegian research organisation RISE PFI has been working to improve the reinforcement of polyolefins with nanocellulose to make biocompos- ites, particularly for 3D-printed and injection moulded products. Nanocellulose – also called cellulose nanofibres (CNFs) – is produced from pulps with varying lignin content, utilising refining, grinding and high-pressure homogenisation processes. Notably, the lignin content in the pulp fibres significantly influences the morphology of the resulting fibrillated materials, says Gary Chinga
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IMAGE: FORD
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