scratch and mar | Additives
Right: Car makers in
Europe and Korea are
already using Genioplast
silicone-based SMR additives, says manufac- turer Wacker
additive also acts synergistically with flame-retardant fillers. In addition, the plastic surface does not become tacky when exposed to UV light, and the additive performs well in fogging tests because it does not migrate even at high temperatures. The additive also improves filler dispersion and flow during compound- ing, which can reduce processing costs. Genioplast is used commercially in car interiors particularly in German and South Korean cars, and the US automotive industry has reportedly been showing interest. Dow Corning’s ultra-high molecular weight (UHMW)
silicone masterbatches have been available for many years in various resin carriers for improved scratch resistance in filled and unfilled resins. The company says the degree of benefit will depend on the level of siloxane added (typically 0.5-3% by weight) and the resin system. “Silicone (siloxane) additives act by reducing surface friction and reducing/eliminating the microscopic surface tearing that can occur during scratching. As a result, even though the surface could still be scratched, the scratch does not show. In addition to providing scratch resistance, the masterbatch products will not contribute to fogging, nor will they degrade during aging (UV and heat) to create a tacky surface. Plus, silicone additives will provide processing benefits such as reduced extruder torque, enhanced surface quality, and improved flow into molds, without affecting MFI,” says Dow Corning’s Shawn Mealey. The company has recently improved its masterbatch technology by incorporating reactivity between the silicone polymer chains and the carrier resin. This inter-material reaction serves to improve dispersion of the silicone and to reduce the domain sizes during production of the masterbatch. One of the benefits of this is increased levels of scratch resistance with Dow Corning HMB-0221Masterbatch for PP and HMB-1103 Masterbatch for acetal (POM). Excista’s Silaplast silicone masterbatches find use in functional components in all industries, says Khanolkar. Any component with high surface contact (for example
Right: Cross- cut tests show Dow Corning’s UHMW silicone masterbatches (right hand
sample) reduce visible
scratching on thermoplastic surfaces
38 COMPOUNDING WORLD | February 2016
door handles, doors, seat backs, center consoles, and instrument panel trim components) and moving components such as latches and air vents may need improved SMR, and additives provide a cost-effective solution. “By adding Silaplast masterbatches in conventional materials like PP, ABS, or PC-ABS, manufacturers can keep their costs down by not having to purchase highly engineered resins for SMR compo- nents,” says Khanolkar. Silaplast does not negatively affect mechanical properties, and allows lower cycle time, lower energy usage, lower pigment usage in colored parts, lower maintenance costs of machines and tooling, and lower scrap cost, he adds. Evonik’s organic modified siloxane Tegomer An-
tiScratch 100 (TAS 100) finds use in automotive and other applications where OEMs are looking for long-term anti-scratch protection during consumer use as well as the shorter-term protection needed during manufactur- ing and shipping, says Kathrin Lehmann, Head Innovation Management Polymers, Interface & Performance at Evonik. Another new application area is domestic appliances, such as washing machines, where some manufacturers are switching to PP and thus need improved scratch resistance. In small appliances with glossy surfaces, such as coffee machines, OEMs also want scratch resistance to differentiate their product, adds Lehmann. In automotive interiors, thermoplastics elastomers such as TPE-S and TPE play a growing role, and Evonik’s M-Si 2650, which gives good mar resistance in addition to scratch resistance, is designed for this area. BASF’s Irgasurf SR 100 B, available since 2005, is a
non-migrating but non-silicone based additive designed for automotive PP-TPOs that can also be used in TPEs, PE, polyamides, styrenics and blends as well as other polymers. It can impart scratch and mar performance up to 15 Newtons in the 5-finger and the cross-cut Erichsen tests, says the company. It also performs in combination with various light stabilizers and does not show detrimental surface effects such as stickiness or exudation during use.
www.compoundingworld.com
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