When it comes to outdoor exposure, ABS (acrylonitrile-butadiene-styrene) struggles a bit because the butadiene in the rubbery phase is prone to oxidation and yellowing on exposure to uv light, particularly after heat ageing. This makes it difficult to maintain brilliant whites and bright colours with ABS.
Blending an acrylate rubber with the styrene-acrylonitrile rigid phase, gives acrylic-styrene-acrylonitrile (ASA). The weathering resistance is greatly improved. Also retained are the other attractive properties of ABS – toughness, high gloss finish, friendly processing and low mould shrinkage.
In the same way that blending ABS with Polycarbonate (PC) increases the high temperature working limits by up to 20 degrees celsius and improves fire performance ratings, PC-ASA blends not only improve heat resistance and fire performance, compared to ASA itself, but has the added benefit of good weathering resistance and full colour choice, compared to PC-ABS.
Automotive manufacturers have spotted that PC-ASA blends for grilles and also internal components in cars and trucks do not require the additional cost of painting. Healthcare, consumer electronics, electrical equipment and also street furniture are other markets that have seen the benefits of PC-ASA.
Registered Trade names: PC-ASA: Bayblend, Geloy, Luran S
PC-ABS: Bayblend, Cycoloy, Pulse
This Looking for colour stability in plastics for outdoor exposure? article was written by Dr. Charlie Geddes for Hardie Polymers.
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