Natural Fibre Composites
Natural Fibre Composites By Jim Preston Vice President Strategic Growth RheTech, Inc. Whitmore Lake Michigan, USA www.rhetech.com New biofibers for PP-NF-compounds In 2009 RheTech Inc. (Whitmore Lake, Michigan, USA) started to develop its biocomposites product line RheVision ® . At that time the market was buzzing with the potential of bio fibers being incorporated into plastic compounds. Knowing that bio fibers are extremely temperature sensitive, the company developed a machine and compounding design that allowed the processing of bio fibers without causing them to burn. With their own custom compounding line RheTech initially developed pine wood and maple wood compounds based around copolymer polypropylene. Wood was chosen because it was readily available locally and there was information available about the compounding of this type of product. RheTech equipment produced a dry (less than 1% moisture) compound that exhibited properties similar to that of mineral-filled polypropylene. Following market demands, RheTech added ground rice hulls (husks) and flax fiber to the RheVision portfolio. Rice hulls provided a unique aesthetic appeal that gives polypropylene compound a ‘granite’ look while achieving properties similar to mineral filled polypropylene. Flax fiber gave an entirely new property set which allowed marketing into applications that were traditionally made from glass reinforced polypropylene. RheVision products are in use for bird feeders, pet dishes, fence post caps, board game pieces, soap dishes and many other consumer applications. RheTech recently attained its first automotive approvals for wood and rice hull compounds for automotive interior and under-the-hood applications. This will allow progress into the automotive marketplace. Once RheTech began to actively market these compounds, other bio fiber manufacturers suggested to use of their particular grade in RheTech compounds. However, not every bio fiber can be added to the RheVision line, but if a bio fiber offered a unique aesthetic quality or a physical property benefit, the material was developed for commercial sale. After an extensive vetting process, RheTech added ground coconut shell and agave fiber to its product line in 2012. Agave fiber gave another alternative to glass fiber compounds with unique fibrous aesthetic qualities and good impact / flexural properties. Ground coconut shell provided a compound that has good surface hardness to compete with talc filled polypropylene. These products are under consideration for a wide range of consumer applications and automotive parts. All of the bio fibers used are true waste products that are not grown for polypropylene compounds and are available in commercial quantities; thus, commercial supply is not a concern. RheTech has also developed grades that incorporate certifiable post-consumer waste in compounds. This creates a product that is over 50% waste product. To date, RheTech offers compounds that range in filler content from 10 – 51% depending on the type of filler. 38 bioplastics MAGAZINE [03/12] Vol. 7
Natural Fibre Composites Improved extruder technology for WPC Cincinnati Milacron is gearing up for an expected growth in the European Wood Plastic Composite (WPC) market of around 20% during 2012. This expected growth will come from a mix of new business and the pushing out of existing imported products from the Far East and the USA. “We are seeing more customers coming to us looking for higher output machines after realising that their existing plant is just ‘not up to the job”, reports Steve Jones, European Business Manager and WPC processing specialist! “It is now becoming increasingly apparent that running a basic extruder with WPC is just not a viable option for successful and profitable production of WPC’s”. Many WPC manufacturers entered the sector with a basic entry-level extruder and little or no technology know-how. “They really had to learn about WPC the hard way”, says Jones. At the same time as production quantities and sales have increased, so has the requirement for more tailed expertise applied to the issues of wear resistant materials in extruder construction, and processing expertise from the extruder supplier. Cincinnati Milacron has been the world leader in WPC production across a broad spectrum of polymer types and niche markets for co-extruded products for a number of years. As the production rates are increased on standard extruders of different brands, more and more of these extruders are failing. Cincinnati Milacron supply replacement extruder screws and barrels to all brands of extruders as well as their own. “The company is seeing a significant rise in enquiries for replacement screws and barrels for competitive machines due to screw breakage and excessive barrel wear”, reports Jones. “It is frightening just how many other screws are breaking out there in the market. As the need for more output increases producers are finding their standard extruders and barrel coating technology are not surviving.” Cincinnati Milacron has only ever supplied tungstencoated screws and barrels for WPC production. This was based on many years’ experience of supplying high output WPC lines throughout the USA WPC market. Now this strategy is proves its advantages as producers using Cincinnati Milacron WPC extruders are realising the true benefit of the superior quality of high resistant tungstencoated screws and barrels. Tungsten out performs other more basic screw and barrel coatings by nearly 50% in some cases. “It’s not just wear rate we are fighting here but corrosion resistance as well”, Jones continues. “It is universally accepted that for the best quality extruded product your need to have low moisture content ingredients in your formulation. If you try to process moisture within your formulation then as it enters the extruder barrel and heats up the moisture turns to steam and forms an insulated blanket at the barrel wall and restricts the heating process from the extruder barrel heaters.” “High wood loadings have been popular and fashionable in Europe in the past, but as these products are starting to suffer and fail under outside conditions, the need for formulation expertise and wood fibre encapsulation is now much more evident. CM has been able to extrude high wood loaded products which are popular for internal applications. But for external applications most of the large successful WPC producers choose a formulation that contains below 65% wood flour to enable a completely encapsulated product”, Jones explains. This is the basic key to outside stability and longevity when linked with the correct processing aids and stabilisation additives. Cincinnati Milacron has long been associated with key suppliers and technology partners that can supply a viable total solution for stable and successful WPC extruded products suitable for external applications like decking, fencing and railing. www.milacron.com bioplastics MAGAZINE [03/12] Vol. 7 39
