MATERIALS: New LSR For Automotive Cooling System

Wacker adds another liquid silicone to its new portfolio of LSRs for injection-molded radiator gaskets.

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Liquid silicone rubber recently became a contender for injection molding gaskets used in automotive cooling systems with the introduction of Elastosil LR 3033/60 by Germany’s WackerChemie (U.S. office in Adrian, Mich.) Now Wacker has added Elastosil RT 728. Like its predecessor, it has a similar hardness (Shore A 60 vs. Shore A 63, respectively) and excellent coolant resistance. Cured parts reportedly retain low compression set under long-term load in direct contact with cooling systems. However, the new LSR is also room-temperature curable by open dispensing.

Gaskets made with RT 728 exhibit no more than 30% compression set after 1000 hrs in coolant at temperatures of 221 F. Even after 1000 hrs at 257 F, the permanent deformation is less than 65% as soon as the stress is removed. While the material supports cost-efficient series production of parts by injection molding, it can also be applied by dispensing equipment straight onto the part to be sealed—automotive subcontractors use this method to produce two-component parts. Because of its shear-thinning properties, it can be applied by dispensing equipment and is self-adhesive. According to Wacker, automotive suppliers, such as Germany’s Mahle, have opted to use this LSR to make radiator components. (888) 922-5374 •

Want to find or compare materials data for different resins, grades, or suppliers? Check out Plastic Technology’s Plaspec Global materials database.



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