Crosslinking is a powerful tool for stabilizing structure in many applications such as wire and cable insulation, weatherstripping, fibers, seals, gaskets, foams, footwear, flexible tubing, pipes, bellows, and tapes. Silane-peroxide blends crosslink the majority of thermoplastics, but they are so reactive that control is difficult during processing, such as extrusion. Problems arise because of early activation of the peroxide during melting and mixing. Less-reactive silanes are used, but they reduce grafting efficiency. Furrer et al. use an unsaturated silane with at least two free-radical initiators as well as an organic tin condensation catalyst. The first initiator is a peroxide such as dibenzoyl peroxide with a 0.1-hour half-life temperature of 90[degrees]C to 155[degrees]C. The second initiator, such as dicumyl peroxide, has a 0.1-hour half-life temperature of 125[degrees]C to 190[degrees]C. The result is an early-stage grafting of the silanes to the polymer chains and a later crosslinking by moisture for the final crosslinked material.
Roger D. Corneliussen is Professor Emeritus of Materials Engineering, Drexel University, in Philadelphia, Pennslvania, USA. He is editor of Maro Polymer Alerts and the Maro Polymer website (www.maropolymeronline.com). He has been active in SPe since 1962 and has served on the board of the Philadelphia Section and as SPE Councilor. For Maro Patent Alerts he reviews all U.S. Patents weekly, makes links to the polymer-related patents, and sends the links daily to subscribers. These patent abstracts are based on the weekly selection process. To sample MAro Patent Alerts, email a request to email@example.com.
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|Title Annotation:||industry PATENTS|
|Article Type:||Brief article|
|Date:||Jul 1, 2007|
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