Biocomposites Green
Biocomposites Green composites: The coming New Age www.human.cornell.edu/bio.cfm?netid=ann2 John Deere 6M Series Tractors (Photo: Courtesy John Deere) Past few decades have seen significant growth in the use of high strength fiber reinforced composites fabricated using carbon, aramid and glass fibers and reins such as expoxy, unsaturated polyester or polyurethanes. However, both fibers and resins used in these composites are made using petroleum, a non-sustainable raw material. In addition, most commercial composites are also non-degradable. This poses a serious disposal problem. While there are some efforts to solve the disposability issues through incineration (to recover energy), recycling (grinding into powder for use as filler) or reclaiming fibers (for secondary applications), we are still far away from having an eco-friendly end-of-life solution. Over 90% of the composites, at present, end up in landfills after their intended life. With ever-growing use of composites the end-of-life issue is only expected to get bigger and increasingly difficult and expensive. Greener Composites Significant research conducted in greening of plastics and composites has led to the development of new generations of plastics and composites that are not only derived from sustainable plant-based resources but are fully biodegradable. As a result, many plant-based fibers such as ramie, sisal, hemp, flax, jute, bamboo, sugarcane bagasse and others are increasingly being used with non-degradable resins such as polypropylene (PP), nylons, polyesters, etc., to form composites that may be called greener composites. Green Composites Research is also being conducted to develop fully green composites that combine biodegradable fibers and sustainably derived resins such as polylactic acid (PLA), polyhydroxyalkanoates (PHAs) and their copolymers, polybutylene succinate (PBS), etc., as well as those derived from plant-based starches, proteins and lipids or oils. Composites based on crosslinked oils (non-degradable), being inexpensive, have hit the markets, e.g. for parts of John Deere tractors. Advanced Green Composites A new process to produce high strength liquid crystalline cellulose (LCC) fibers developed at the Groningen University (The Netherlands) has opened up the possibility to make high strength green composites by combining them with biodegradable resins. The LCC fibers have high stiffness (over 40 GPa) and strength (over 1.7 GPa). Being in continuous form conventional fiber placing machines can be easily used for these fibers. Composites made using the LCC fibers and soy protein based resins have been shown to possess excellent strength and toughness to be termed as ‘Advanced Green Composites’. LCC fibers treated by KOH (potassium hydroxide) solution, a process similar to mercerization used for cotton fibers, under tension have shown to significantly improve their strength and modulus by increasing fiber molecular orientation and crystallinity and thus increasing the composite properties further. For example, composites of LCC fibers (41.5% by wt) made with soy protein based resins resulted in strength of over 625 MPa. With fiber volume of 65%, which is common for most composites, the estimated strength of these advanced green composites was over 1 GPa. Interestingly the toughness of such composites was comparable to those based on Kevlar ® fibers which are commonly used for ballistic applications. We can expect many such new developments which are at the research stage to come to market in the near future. These fully sustainable green composites, while easily protected during their use, can be biodegraded or composted at the end of their life and hence nothing has to go to the landfills. In fact, when composted, these composites can complete the nature’s intended carbon cycle. Sustainability, green chemistry, cradle-to-cradle design, industrial ecology, etc. are not just newly coined words but have become the guiding principles for the development of new generation of green materials. Composites are no exception to this new paradigm. As major manufacturers embrace these developments, the green composites can only be expected to play a major role in greening the future products. MT 14 bioplastics MAGAZINE [04/14] Vol. 9
Biocomposites Natural fibre composites for injection moulding Next to their standard material classes ARBOFORM ® and ARBOBLEND ® , Tecnaro have managed to develop natural fibre composites optimized for processing by injection moulding – ARBOFILL ® . In the meantime further production processes such as extrusion blow moulding and thermoforming were successfully carried out with grades of this material class. These materials are especially interesting for applications where good heat resistance, scratch and creep resistance are required, while an economical substitution of fossil resources is desired. Additionally they offer an appealing appearance, often intuitively understood as natural by the end consumer, without any further explanation. While compounds of natural fibres and polymers are already fairly common in applications such as decking, fencing and fascias, produced by the extrusion processes, injection moulded parts are still a rather rare sight, although very interesting for a large number of uses. Assuming proper pre-drying (which is necessary for many standard polymers, such as ABS and polyesters) the material can be easily processed with comparable processing properties to standard polyolefins, gaining a smooth surface at moderate mould temperatures of 30°- 40°C. As the material can be processed at slightly lower temperatures, additional energy savings in the production can be achieved. That of course comes on top of the replacement of fossil resources, which can be as high as almost 100% when the matrix material is also adjusted (at Tecnaro found among the Arboform and Arboblend grades). The performance and processing properties described above have already led to several products made of Arbofill In series production they are mainly household articles (photo) and stationery, but the material is also found in applications such as furniture. Before a major player in the food preparation and storage business accepted a special series made of Arbofill, the material was (literally) put to the acid test. Starting with food contact conformity, through thousands of cycles in the dish washer and completed by the above mentioned tests on resistance to several aggressive chemicals. The Brazilian household goods company Coza have used Arbofill materials in their portfolio for several years now, and it has properly withstood the tropical climate since 2009. The compost bin introduced by Rotho (photo) is a very nice example of a coloured natural fibre composite, which allows for an even broader aesthetic appearances than the application of different fibre grades. The compatibility of Arbofill with standard polyolefins enables the use of common master batches and leading to easy colouring. Good scratch and especially creep resistance could be proven in the application of a backrest for an office chair (photo). Compared to unreinforced and unfilled polyolefin the low warpage and shrinkage are also crucial in this part. Aesthetic aspects played a major role when one famous Italian fashion brand introduced this material for their hangers - Benetton. This underlines the innovative and appealing character that natural fibre reinforced composites can show, with a premium touch compared to conventional plastics. Through several national and international R&D projects as well as in-house development, Tecnaro is continuously working (among many others) on the improvement of natural fibre reinforced materials, one of which is Arbofill. The company is testing various newly available fibres and fibre qualities for their addition to the property portfolio, and also investigating improvements in the compounding process. www.tecnaro.de (Photo: Samas) (Photo: Rotho) (Photo: Coza) bioplastics MAGAZINE [04/14] Vol. 9 15
