| 摘要 |
Apparatus and method for the production of hopper feedable thermoplastic pellets having zones or compartments which contain physically separated reactants which react only after being melt-mixed, as in a screw type extruder, reciproscrew injection machine, or similar device which heat forms pellets into a larger mass. This new class of thermoplastic molding materials relies mainly on the relatively slow reaction kinetics of contained large molecule molding materials to provide a time interval after melt-mixing of zoned pelletized reactants in an extruder barrel or inflection molding machine. During this time period, the thermoplastic molding material is easily filled into injection molds. As the reaction progresses, the material becomes more viscous and such flow is difficult or impossible. The involved reactions may continue after demolding at room temperature during a post molding cure, or appliance service generated heat may cause post molding cure. Where a delayed reaction involves crosslinking and/or additional polymer molecular growth after molding, such crosslinking can bond adjacent molecules and reduce or prevent stress memory warpage of molded parts. Fibrous reinforcements may be included to aid in reducing post molding warpage. Foaming agents contained can, when molded by the Bradt Process, virtually eliminate weld lines in molded parts.
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