Selectively cross-linked, heat shrinkable irradiated polyolefin tubing

In the past, molded encapsulation of components and wire junctions could be accomplished only through the use of expensive equipment specifically designed for each size and configuration. The process of selective cross-linking makes it possible to produce a dual-wall, polyolefin tubing in which the outer wall, when heated, becomes elastic and shrinks toward its original diameter, while the inner wall becomes viscous, melting and flowing to fill voids and interstices. By this technique it is possible to effect shrinkage ratios up to ten to one. Upon cooling, the entire mass becomes a hard, tough homogeneous molding. The purpose of this paper is twofold: (1) to describe the nature of this material, and (2) to discuss its application for encapsulating capacitors, resistors, miniature circuit boards and wire junctions such as splices, shield terminations and breakouts.