FORMULATION | FRICTION AND WEAR
Right: Granules of millimetre- long recycled para-aramid fibres for use in thermoplastics compounding
Aramid solutions Short aramid fibres can be used in a variety of polymers in sealing and friction and wear applica- tions. “The use of primary aramid fibre, however, also comes with a number of key challenges,” says Dr Hans Miltner, who provides technical market and business development services for Procotex, a supplier of recycled fibres. “First, primary aramid fibre is an expensive
material, comparable to carbon fibre, which restricts its use mainly to high-performance application domains,” he says. “Secondly, even though aramid fibre can be beneficial from a sustainability standpoint to many of the applica- tions it enables (for example by reducing compo- nent weight, wear, or corrosion), the spinning of
primary aramid fibre comes with an elevated CO2 footprint and requires the use of sulphuric acid. And, finally, the outstanding thermal and chemical stability of aramid fibre imply that it cannot easily be eliminated – or disposed of.” On the other hand, he says aramid fibre lends
Below: Plastic gears could benefit from the perfor- mance attributes provided by recycled aramid fibre, according to Apply Carbon
itself to recycling, since it can be reused without any performance loss. Procotex, through its subsidiary Apply Carbon, sources high-quality post-industrial waste from major aramid fibre producers and processers, and converts it into various products. Binders are applied to ensure full compatibility with the matrix polymer in the targeted final compound. Apply Carbon typically produces pulled aramid
fibre, supplied in 300kg bales. For applications demanding fibres with a well-defined length, it can supply precision-cut yarns in a range from 250µm to 120mm.
”Significant demand nowadays comes from the compounding industry, where short aramid fibre is chosen as a low-density additive to impart strength, toughness, durability and friction and wear performance,” says Miltner. Aramid fibre is substantially less abrasive than
glass or carbon fibre and is, for this reason, often used in friction and wear applications such as bearings, clutch linings, or brake pads, he says. Synergistic effects can also result from the com- bined use of aramid fibre and PTFE in friction and wear formulations based on PEEK or POM, or acetal, where dramatically reduced coefficient of friction and wear rate has been seen in compo- nents in contact with moving metal surfaces. Miltner says e-mobility could significantly drive demand for recycled aramid fibre over the coming years. “Aramid fibre offers a set of highly desirable performance attributes that enable metal-to-plastic conversion in electric drivetrains and especially in gears,” he says. These include lightweight and absence of corrosion, long term dimensional stability and resistance to creep and fatigue, and good damping properties. The latter can reduce gearbox vibration and improve the noise, vibration and harshness (NVH) characteristics of a vehicle. The performance spectrum of Apply Carbon
recycled fibres, which is claimed to be close to the level of primary fibre, enables development of innovative friction and wear compounds while exploiting an estimated 30-50 % lower cost versus primary aramid fibre and generating a fraction of its CO2 footprint, according to Miltner. ”There is more than sufficient recyclable aramid fibre feedstock available in the market to ensure security of supply,” he says.
CLICK ON THE LINKS FOR MORE INFORMATION: �
www.mocom.eu �
www.lati.com �
www.colloids.com �
www.wittenburggroup.com �
www.shamrocktechnologies.com �
www.procotex.com
50 COMPOUNDING WORLD | February 2021
www.compoundingworld.com
IMAGE: SHUTTERSTOCK
IMAGE: APPLY CARBON/PROCOTEX
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