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Bioplastics are developing significantly today. Natural wood (Lignocel) and cellulose (Arbocel) fibres are used for mechanical reinforcement, economic improvement, better processability, and as a solution to raw-material shortage and shelf-life variation.
(Published on December 2007 – JEC Magazine #37)
STÉPHANE LAURENT, TECHNICAL SALES MANAGER RETTENMAIER FRANCE (JRS)
Following the presentation “New applications in the woodplastics composites sector: the French example” by the author at the Biocomposites Forum of the JEC Composites Show 2007, new developments, applications and products are now available. Apollor and Rettenmaier have been partnering to develop starch-wood fibre composites (Figure 1). Rettenmaier is also working with FuturaMat to propose a PLA-wood fibre compound, and carrying out joint research with the Ecole des Mines de Douai on injection moulding of PLA-cellulose fibre composites.
Starch-wood fibre composites
Apollor is a technological resource centre that specializes in polymer and composite materials. The centre carries on research to industrialize new material, product or process concepts, and one of its objectives is to foster the creation of new activities and support companies in their innovation approach. To this end, Apollor develops new materials, such as composites using natural fibres or biodegradable polymers. The centre can test and research customised formulations meeting the needs of a specific company. In co-operation with Rettenmaier, the centre developed several combinations of starch and wood fibres, preparing three different grades:
With a wood-fibre reinforcement, the Young’s modulus of the mix containing 40% wood fibres is multiplied by 6.5 (Figure 2).
These compounds (starch + wood fibres) remain 100% compostable and are derived from natural resources. Multiple applications are possible: replacing existing products, developing new “green” product lines, or expanding existing product lines.
Plant-based polyester-wood fibre compound
Using agricultural and forest resources to create bioproducts offers significant environmental advantages. Contrary to their fossil counterparts, renewable materials and energies derived from biomass make it possible to reduce energy consumption and gas (CO2) emissions, or to decrease the impacts on air, water or ground. FuturaMat produces and sells sophisticated thermoplastic products based on wood flours whose formulations were patented by the researchers of the Valagro R&D platform. These compounds (pellets) are used as new raw materials by plastic processors in injection moulding, extrusion, and calendering.
The BioFibra® range, based on vegetable and compostable raw materials, is currently under development. Two grades are already available: PL30E11 and PL30E26. Entirely produced from renewable carbon (plant-based polyesters, wood and plant additives), BioFibra® products are compostable in a few weeks. The bio-assimilation results in water, CO2 (aerobic) or CH4 (anaerobic), heat and reorganized biomass.
These materials are perfectly suitable for injection moulding processes (Figure 3).
They are used in applications such as horticulture, packaging and, more generally, single-use technical parts. The formulations can be customised according to the customer’s requests, thanks to FuturaMat’s expertise in the bioplastics field and Rettenmaier’s expertise in the woodfibre field.
PLA-cellulose fibre composites
The Polymers and Composites Technology & Mechanical Engineering Department (TPCIM) of the Ecole des Mines de Douai worked with manufacturers to launch a project which aims at producing injection-moulded parts made of a PLA matrix with cellulose fibres (Figure 4).
The cellulose fibres, provided by JRS, have the advantage of being easier to use than hemp or flax in the extrusion phases (mixture) and then in injection.
The structure of these wood-derived white cellulose fibres is more flexible and elastic than that of wood fibres. The elimination of lignin after wood extraction improves compatibility with PLA and avoids premature UV ageing. Various mixtures using different cellulose grades and contents were formulated to study the effect of the length and amount of fibres in the composite (Figure 5).
The following effects were highlighted: