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additives feature | Coupling agents

mould release and consistent processing. Compounders and end-users want as much

versatility as possible from additives. One recent trend cited by Kerstin Weissenbach, senior technical manager at silane producer Evonik Degussa, is added functional- ity in coupling agents. The company developed two product lines to meet this need: Dynasylan Oligomers for wire and cable, moisture-cured cross-linked PE and mineral-filled polyolefins; and Dynasylan Silfin for wire and cable, pipe and other thermoplastic applications. Dynasylan Oligomers improve coupling functionality

Dynasylan Silfin coupling agents from Evonik Degussa are used in silane moisture cross-linking of these PE-X pipes

game-changer for major tyre companies that use it to differentiate their products from those of competitors, and for small manufacturers that already produce outstanding tyres and will use the label program for greater market visibility. Either way, the rolling resistance program could

shake up the tyre industry, thereby giving coupling agents from Cray Valley, Dow Corning, Struktol (also a silane producer) and others a major role in the ratings competition, albeit behind the scenes. One area Cray Valley works in is non-halogenated

flame retardants, where grades permit high loadings of mineral fillers and hydrated flame retardants, reducing resin use and boosting flame resistance, with little trade-off in mechanical properties. Austin says the company took a flame-retardant grade of PP with a 30% loading of CaCO3

and increased that to 55% “without

giving up a lot in mechanical properties.” The decline was “only by a single-digit percentage.” Recent developments from Struktol include RP 28, a

compatibilizer and blending aid that improves the incorporation of regrind or recycled material in a wide range of polymers. The additive is said to deliver improvements physical properties and processability. It can also be used as an alloying agent for engineered plastics, providing improved dispersion of the discreet phase polymer as well as mechanical bonding charac- teristics that can result in better physical performance. Struktol has also introduced TR 451, which it describes as a special combination product for improving the incorporation of fillers into polyolefin compounds. Studies show that it allows higher loadings of CaCO3

in PP without sacrificing processability or

performance. Alternatively, compounders using treated fillers may be able to switch to untreated fillers in combination with TR 451 to reduce overall costs. In addition, the additive can provide viscosity reduction,

20 COMPOUNDING WORLD | January 2013

as well as reduce alcohol release, and thus VOCs, during compounding, which is a plus for compliance with environmental regulations. The materials also have a high degree of hydrophobicity, which is espe- cially suited for applications like wire and cable, where external layers must resist water and other forms of moisture.

Dynasylan Silfin grades are described as easy-to- dose liquids with all ingredients for grafting and cross-linking polyethylene. The materials contain vinyl silanes and initiators, cross-linking catalysts and additives such as antioxidants, metal deactivators and processing aids. Weissenbach says that these materials meet the needs of compounders who want additives that widen process windows, thereby helping to reduce scrap and keeping production costs down; help comply with environmental workplace rules; and of course meet their needs for coupling agent functionality. To achieve these and other benefits, Evonik Degussa is “pushing the boundaries of applications,” she remarks. In the future, coupling agents will play a greater role with other additives in building properties and expanding performance in new and traditional applications. Weissenbach says that her company’s coupling

agents are already used in such areas as alternative energy (wind turbines), corrosion protection and in replacement of environmentally suspect materials, and that developments will continue as users seek to optimize their processes. An observation that all makers of coupling agents will doubtless agree with.

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