Increasing tear resistance in heat shrinkable plastic film - extruding strip, partially cross-linking, stretching at temp. below crystalline m.pt. and finally cross-linking during shrinkage.

摘要

The method involves extruding a plastic strip at a temp. below a peroxide reaction temp. and initiating partial crosslinking. The strip is stretched at a temp. below the crystalline m.pt of the plastic. The strip is fully crosslinked during the heat shrinking stage. Pref. initial cross-linking involves using a mixture of peroxides, with different reaction temps. and times and can be initiated by irradiation, peroxide and/or silane. The degree of crosslinking can be varied by passing the plastic strip through a salt bath or steam and altering the passage time or temp.. The partially crosslinked strip is heated to a temp. below the crystalline m.pt. by passing through oil or heating with microwaves before stretching. Final crosslinking is achieved by heating the peroxide with microwaves and simultaneously cooling the surface. USE/ADVANTAGE - Producing heat shrinkable product, esp. for cable connectors or branches. Increased tear resistance and eased opening of shrink-wrapped component.