REINFORCING FIBRES | MATERIALS
Carbon fibre: preparing for the middle ground
The benefits of carbon fibre have long come at too high a price for most plastics compounders but that situation may be changing. Peter Mapleston reviews developments in carbon and glass reinforcements
Carbon fibre has been waiting in the wings for thermoplastic compounders for a long time. Its ability to substantially improve mechanical properties has never been in doubt, but its cost has generally been considered prohibitive for all but very high-end applications. While its area of application has gradually been expanding from aerospace into automo- tive and sports markets, even here we have for the most part been talking about continu- ously reinforced composites. However, the market is chang-
ing. Numerous efforts are ongoing to bring down costs along the carbon fibre production chain, from the manufacture of precursors of polyacrylonitrile (by far the most common feedstock) through to ovens for carbonising the PAN. At the same time, some producers of glass fibres are developing products that extend the property envelope upwards for these more traditional reinforcing materials. And additive suppliers are playing their part too, with coupling agents that create better bonds between fibres of all types and the polymer matrix. Looking first at the carbon fibre sector, develop-
ers of production technologies are creating routes to bring down the price of these fibres to levels not so far above those of glass. Demand for carbon fibres could grow at more than 15%/yr in the near future, according to some estimates, largely as a result of the need for lightweight composites for more fuel-efficient cars. As already noted, carbon fibres are mostly derived from polyacrylonitrile (PAN) fibres
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and the acrylonitrile (ACN) monomer for this is currently obtained from ammoxidation of propylene. Prices of propylene have been high and volatile
in the recent past - in July, according to Platts, propylene cost 20% more than it did a year earlier. Independent US-based research organisation Southern Research (SR) is aiming to develop a cost-effective, low environmental impact catalytic process for production of a drop-in ACN utilising sugars derived from non-food biomass. The process is said to result in greenhouse gas emissions of up to 37% less than the conventional ACN process, while costs are down by 15-22%. Resulting carbon fibres could be as much as 10% less expensive than current commercial types, it is claimed. SR has demonstrated the full process and the
Main image: Efforts to cut the cost of carbon fibre are leading to strong interest from com- pounders
October 2017 | COMPOUNDING WORLD 37
PHOTO: SHUTTERSTOCK
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