Right: 30% glass rein-
forced PA6/66 injection
moulded parts produced without and with (right) Clariant’s
Addworks LXR 701 additive showing a
reduction in
fi bre visibility and stronger coloration
polyamides | Additives Last year Dow Corning introduced it 31-441
Additive, which is designed to improve the surface coeffi cient of friction (CoF) of polyamides (Figure 4), as well as enhancing processing characteris- tics such as fl ow and demoulding. The new grade (a silicone polyamide copolymer) is also said to reduce the torque required during processing and to improve scratch, although the company’s MB50-011 Masterbatch (which contains 50% high molecular weight silicone gum) is still recommended when this is the principal objective.
PTFE alternative Dow Corning considers 31-441 as an alternative to PTFE, often added to compounds to reduce CoF in moving parts such as gears. Paulo says the 31-441 product provides similar benefi ts at an addition rate around fi ve times less. It also improves surface aspects. Compounds used for applications such as gears often contain glass fi bres, he says, and the silicone additives’
tendency to move to the surface of the part pushes these fi bres down into the core . The effectiveness of the additive can be assessed by measuring the noise created when two parts are rubbed together. “When we made CoF measurements with the new additive, we got almost no noise, much less than with PTFE,” says Paulo. He adds that one customer switched from using 12% PTFE to 2% 31-441, saving around 30% on additive costs as a result. Mar resist- ance of the new additive is “not great” but, he says, it can be combined with PTFE in applications where this is a prime requirement. PolyAd Services’ main line of business is providing
Above: Test bars moulded in recycled PA from carpet fi bres. The top bar is stabilized with 2% Recycloblend 731 from PolyAd Services and shows a much improved surface
formulation and incorporation expertise for polyamide additives. It offers inorganic and organic thermal stabilizers as well as other performance blends. Systems are tailored to meet each customer’s individual specifi ca- tions and are available in multiple forms from pre-blend- ed powders to easy-to-incorporate 100% active pellets. Jamie Ginn, Marketing and New Business Development Manager, says the company’s thermal stabilizers are capable of meeting current automotive standards for
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