Materials
standard- or scrap-grade ABS and transform it into value-added high-heat ABS using SMA resin, which is less costly and far more accessible than competitive heat-boosting technologies like N-phenyl maleimide (NPI) and alpha-methyl styrene acrylonitrile (AMSAN). SMA additives allow customisable improvements in the thermal performance of ABS, with Vicat B ranges of 85–120˚C (185–248˚F) or higher typically seen. Since SMA is fully miscible in PMMA and is also clear,
it offers the ability to improve acrylic’s thermal performance as well as resistance to stress cracking and exposure to chemicals like detergents – all while maintaining its water-clear transparency and optical properties, with minimal impact on the refractive index of moulded acrylic parts. These are attractive features for PMMA used in a variety of industries. Depending on the grade of acrylic XIRAN SMA used, generally for every 1 per cent of SMA added to the compound, the thermal performance of the base resin is shifted upward by 0.4 to 0.6˚C (0.8 to 1.0°F). Or, said another way, for every 1˚C increase in thermal performance desired in the base compound, between 1.8 and 2.3 per cent SMA should be added to the compound (1.0 to 1.3 per cent to increase 1˚F). Another useful property that can be improved in ABS
and PMMA resins through the addition of SMA additive is a change in the base resin’s polarity. By increasing polarity or surface reactivity/adhesion, moulded parts are easier to paint, plate, print on, or bond with adhesives, skins, foams, and other decorative or functional treatments. In fact, use of SMA additive can often allow processers to skip the primer step in painting operations, saving both time and cost to produce finished parts. This feature is especially attractive to processors supplying parts for painted, metalised, in-mould decorated, or slush-
Fig. 3. Typical automotive
applications include instrument- panel carriers.
Fig. 2. SMA is a cost-effective way to boost thermal performance in PMMA and ABS resins.
moulded automotive-interior applications, or for other industries with similar needs for high aesthetic and greater thermal performance on parts requiring secondary-finishing operations. Yet another area of functional improvement in PMMA
and ABS base resins when SMA additives are used is compatibilisation with various reinforcements and other polymers in multi-material systems. The broad miscibility and adjustable polarity of SMA helps reduce phase separation and improves bonding between the base resin and glass or natural fibres, rubber particles, thermoplastic polyurethanes (TPUs),
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