vor 7 Jahren

02 | 2008

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  • Bioplastics
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  • Automotive
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Natural Fibres

Natural Fibres Automotive door in-liner, instrument panel made from bio-fibre reinforced composites (Photo: Dräxlmaier Group) Natural Fibre/PP (LoPreFin, Fibroflax) Natural fibre/PP is made of two different types of fibres. These are natural fibres (flax, sisal or similar) on the one hand and thermoplastic fibres (PP or similar) on the other hand. The two types of fibre are mixed in a closed tank to a homogeneous mixture. The non-woven mat obtained can be formed by placing in a heated mould and forming under pressure. The synthetic fibres are melted and given the shape of the finished part. Fibropur A needle-punched vegetable fibre mat is sprayed into a mould together with a two component PU system. The sprayed mat is then heated to 125°C and compression moulded to realize a light structural carrier. COIXIL Fibre Resources The principal fibres being used for automotive components come from flax and hemp, grown in the temperate climates of Western Europe, the sub-tropical fibres, jute and kenaf, mainly imported from Bangladesh and India, banana fibre from the Philippines, sisal from the USA (Florida), South Africa and Brazil, and wood fibre from all over the world. The table shows the commercially important fibre sources of agricultural bio-fibres that could be utilized for composites. The traditional source of agro-based composites has been wood, and for many countries this will continue to be the major source. Commercially important fibre sources [Suddell, Evans, 2005] Fibre Species World production [10 3 t] Origin Wood >10,000 species 1,750,000 Stem Bamboo >1,250 species 10,000 Stem Cotton lint Gossypium sp 18,450 Fruit Jute Corchorus sp 2,300 Stem Kenaf Hibiscus cannadbinus 970 Stem Flax Linum usitatissimum 830 Stem Sisal Agave sisilana 378 Leaf Hemp Cannabis sativa 214 Stem Coir Cocos nucifera 100 Fruit Ramie Boehmeria nivea 100 Stem Abaca Musa textiles 70 Leaf COIXIL is a Johnson Controls Automotive co-injection technology with sequential injection of two different materials in the melted state from the same point - first a soft TPO skin (A) and then a more rigid core material (B) which is a short bio-fibre reinforced polyolefin to give shape and resistance to the component. The final structure is a sandwich (A-B-A). Exterior parts are on the way The automotive industry requires composite materials that meet performance criteria as determined in a wide range of tests. A typical market specification includes criteria such as ultimate breaking force and elongation, flexural properties, impact strength, flammability and fogging characteristics, acoustic absorption, processing characteristics, dimensional stability, water absorption or crash behaviour. Most of the composites currently used are designed with long-term durability in mind. Generally, bio-fibres can be used as both filler and reinforcement for interior components and are now generally accepted for those applications. Furthermore they can be expected to increase steadily with increased model penetration. But today more and more bio-fibre composites are also used in the exterior components of an automobile. DaimlerChrysler‘s innovative application of abaca fibre (banana) in exterior underfloor protection for passenger cars has been recently recognized. Exterior parts such as front bumpers or under-floor trim for buses made from flax fibre reinforced composites are other examples. A full list of references for further reading can be obtained from the publisher. 20 bioplastics MAGAZINE [02/08] Vol. 3

Materials Improving heat-resistance of PLA using poly(D-lactide) by Sicco de Vos Sr. Polymer Product Development Engineer PURAC Innovation Center Market Unit Chemical & Pharma Introduction In 1987, Tsuji & Ikada were the first to publish about the handshake of mirrored polylactides: the stereocomplexation between poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) that produces crystals with a melting temperature beyond 200°C. Many scientific papers on stereocomplex-PLA followed, but its commercial utilization had to wait until the 21st century. A decisive development for commercialization of PDLA is the start-up of a dedicated plant for D-lactic acid in 2008 by Purac. In addition, Purac plans to expand its product portfolio with L- and D-Lactide. These cyclic monomers can be polymerized in one-step to PLA, thereby eliminating several time- and cost-intensive technologies for the PLA producer. Purac PDLA is a bio-based additive for blending with PLA with the following benefits: • More efficient nucleating agent in injection molded PLA than talc at lower loading • Semi-crystalline PLA plastics with HDT B values of 100 - 150°C possible • PLA plastics with better heat resistance enable new applications, e.g. automotive parts • Reduced shrinkage of film and fiber • Bulk density of PLA unchanged Purac’s roots in PLA PLA was already developed in the 1960s for use in medical applications. Purac is a significant player in that market with its medicalgrade lactides, PLLA, and other resorbable lactide copolyesters. Fermentation is the core expertise of Purac and is used to produce lactic acid, the key ingredient for lactide. Lactide is the cyclic dimer of lactic acid that is basically obtained by dewatering lactic acid. Subsequent ring-opening polymerization of lactide is the simplest route to PLA. PLA Material Properties: Strengths and Weaknesses PLA for technical applications has conquered a promising market volume and is the strongest growing bioplastic with a favorable environmental footprint. The added value of PLA originates primarily from its unique combination of properties, such as high optical clarity, rigidity and strength, and favorable gas and water barrier properties for food packaging. These properties can be modified by value added bioplastics MAGAZINE [02/08] Vol. 3 21

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