Composite fibres – natural and synthetic blends
Composite fibre products are not new. The first composite material known was made in Egypt around 3,000 years ago when clay was reinforced with straw to build walls. With the advent of metals, the use of natural fibre for reinforcing declined. The rise of composite materials began during the 1960s when glass fibres in combination with tough rigid resins could be produced on a large scale. The advantages of using plant fibre include weight saving, a lower raw material price, caloric recycling or saving of non-renewable resources.
In the last couple of decades, natural fibre composites of thermoplastics and thermosets have found their way into the European car manufacturers for door panels, seat backs, headliners, package trays, dashboards, and trunk/boot liners.
Most of the developmental work for natural fibre composites in interior trim is focused on polypropylene (PP) based composites produced by compression moulding or thermoforming extruded sheet or commingled mats of PP and plant fibres.
Some automotive industries are cautious of applying natural composites in structural components or where requirements, like surface quality or moisture resistance are very critical. Natural fibres do not confer nearly as much impact resistance as glass fibre, except at very low temperatures. However natural fibres have specific gravities of 1.25 g/cc as compared to glass at 2.6 g/cc. This gives them a higher strength-to-weight ratio for reinforcing plastics.
Low cost is one of the main attractions of natural fibre reinforcements.
There are a range of companies successfully exploring natural fibre composites. For example;
- Kafus Bio-Composites make a kenaf-based Flexform nonwoven mat, plus LoPreFin kenaf-based composites, as part of a strategic alliance with R&S Stanztechnik.
- Astechnologies has three mat-making lines at its plant in Belgium using hemp, kenaf, flax, sisal and abaca.
- Cargill Ltd makes Durafibre from the bast of flax. They also make Durafill from the inner core of flax.
- Dexter Corporation's Nonwoven Materials Division makes sisal-based nonwoven mats in roll form for compression moulding or thermoforming.
- Georgia Composites' developmental product is made of partially consolidated recycled PP reinforced with sisal.
- Global Resource Technologies has compounded virgin and recycled PP and HDPE with kenaf, jute, hemp, sisal, flax, coconut fibre and wood pulp.
- Kenex Hemp Ltd produces a mat from hemp or blends of hemp with flax or jute and virgin or recycled PE or PP.