SURFACE MODIFICATION | ADDITIVES
Keeping up appearances
Plastics are versatile materials but can be susceptible to surface scratching. Peter Mapleston looks at a selection of additive technologies that help to keep that “new” look
It is a pretty frustrating experience - you’ve just got your hands on that long-awaited shiny new personal possession then, almost immediately, you scratch it. It seems that some products simply invite scratches. However, there is now a whole raft of additive technologies available for plastics that can go a long way to alleviating the disappointment. They may not completely eliminate scratching but they can make plastics surfaces much more resistant and, when that first scratch inevitably appears, make it much less visible. Christophe Paulo, Global Segment Leader at
Dow Performance Silicones, sees substantial potential for the use of additives to enhance scratch resistance and other surface properties in compounds destined for production of consumer appliances. Whether it be a new dishwasher, the latest tablet device or even an item of home medical equipment, consumers expect their purchases to retain their attractive appearance over a long period of time. “It is more important than ever to ensure that [plastics and composites used in these products] can resist scratches and marring, withstand exposure to ultraviolet (UV) radiation, avoid surface stickiness that attracts dust and dirt,
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retain texture and a consistently glossy or matte finish, and repel potentially damaging moisture,” he says. Paulo says that while many plastics offer aesthet-
ic attributes such as colorability, gloss and clarity, most can also benefit from the enhancements provided by silicone additives. For example, resins such as polycarbonate (PC) used for electronic device housings and touch screens need protec- tion against the scratching that can dull their surfaces or affect their clarity and optical quality. Other polymers – most notably polyamides but also polyesters – tend to absorb water, which can affect appearance as well as mechanical properties. The incorporation of mineral fillers and/or glass fibres can make that situation even worse. He also cites the development of unwanted surface tackiness that can attract dust and grime, dulling surface colour and shine. In moulded polypropylene (PP) containing organic slip addi- tives, for example, additives can migrate to the surface following exposure to UV light causing surfaces to collect colour and gloss-sapping dust and fingerprints.
Silicone additive technologies offer many different November 2017 | COMPOUNDING WORLD 53
Main image: Maintaining that “as new” surface finish can be a
challenge in plastics but additive
technologies can help
PHOTO: SHUTTERSTOCK
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