Fibre reinforced plastics (FRP) have been a standard in lightweight construction for a while now. One alternative trend in manufacturing, however, has turned to natural materials, which can be produced with lower energy costs and are biodegradable. The thermoset specialists at Lorenz Kunststofftechnik, for example, have developed a Bulk Moulding Compound (BMC) with jute, cotton or sisal fibre, that exhibits, depending on the composition, similar properties to traditional FRP. The fibre’s length can be selected according to the requirements of the intended use and the material can accordingly be produced through compression or injection moulding. In addition, the different natural materials open up new possibilities of use; the cotton thermoset, for example, is easy to paint, laminate or finish and can thus also be used for design objects.
This new development is based on the tried and tested BMC 0204, which already contained two eco-friendly materials with calcium-carbonate as a bulking agent and ATH as a flame retardant. The new natural fibres also replace the glass fibres, which leads to lower energy consumption during production, which in turn leads to an improved carbon footprint. The type and length of the fibre to be used can be chosen according to the intended use; for instance, compounds with sisal are characterised by a very low degree of processing shrinkage of -0.1 to -0.3 percent, while cotton-reinforced thermosets have a high elasticity modulus of over 8,000 MPa and a low abrasion. They all have a very low density of 1.65 to 1.7 g/cm3, which leads to lower weights, even in comparison with FRP. This makes the produced parts ideal for lightweight construction.
Flame retardant, moisture resistant and flexibly processable
Natural fibre-reinforced plastics (biocomposites) generally offer good thermal and acoustic insulation. By changing the actual composition of the BMC, the specific properties can also be adjusted individually. This allows giving the normally highly flammable natural fibres excellent fire resistant properties. In UL94 flammability tests, a 1.5 mm thick sample could be put out within ten seconds. This result corresponds to the best classification, V0. The problem of moisture absorption, very common in biocomposites, could also be solved through the right material composition so that, measure according to ISO 62, it is only at ≤ 0,5% for the eco-friendly BMC with cotton,
≤ 1,3 % with jute and ≤ 1,8 % with sisal.
Unlike the traditional, often thermoplastic biocomposite panels, the production as BMC also opens up different processing options. It allows for parts to be produced not only in compression moulding processes, but also in injection moulding. This means that more complex and delicate parts, which up until now could only be produced from FRP, can be produced from biocomposites as well. The required moulding temperature in the cylinder is 20 to 40 °C and, in the mould itself, 140 to 170 °C. This means that the material is suitable for various fields of application; from large parts, for instance in car interiors, to tiny components, for example in electronics.
Eco-friendly and recyclable
All Lorenz natural fibre thermosets can be recycled; 100 percent of cutting and punching waste can be reused, in accordance with their material composition. Energy recovery of the fibres is carbon-neutral and they burn without residue. Since the RoHS conforming composites also contain neither halogens nor any heavy-metal compounds, they are overall highly ecologically friendly and harmless to humans and the ecosystem. To further enhance this, the experts at Lorenz are already at work on an organic resin matrix which is to replace the polyester resin currently used. With this, a composite material made entirely of natural substances is achieved.
Companies: Lorenz Kunststofftechnik GmbH