Raychem Limited

David D Nyberg

Travers K Cammack, Ii

John A Midgley

Rong Jong Chang

Bernard J Lyons

Lester T Toy

Nicodemus E Boyer

A shrinkable tubular article comprises a tubular inner elastomeric member held in a radially expanded configuration by a tubular outer restraining means. The restraining means is prepared from a blend of a relatively rigid thermoplastic material and a segmented copolymer having at least one segment compatible with the thermoplastic and at least one segment compatible with the elastomer of the inner member. Optionally, the restraining means contains a tackifier. The inner surface of the outer member and the outer surface of the inner member are directly bonded together (i.e. without an interfacial adhesive). The bond between the members is sufficiently strong to restrain the inner elastomer member from shrinking to, or toward, its unexpanded configuration. In addition, the bond weakens sufficiently on application of solvent to permit the elastomeric member to peel away from the restraining outer member. Use of a blend of a thermoplastic and a segmented copolymer and optional tackifier, described above, for the restraining member permits the article to be produced in a continuous manner, e.g. by coextrusion.

Coextruded recoverable articles

Flexible hollow articles comprise an expanded elastomeric inner member and an outer restraining means. The restraining means is made of a notch-sensitive material so that when score lines are made in the restraining means, they can be propagated through the material by distorting the article. The stiffness and elongation of the restraining means, and the peel strength of the bond between the inner member and the restraining means, are so chosen that when suitable score line are made in the restraining means, at least part of the restraining means can be pulled away from the inner member, thus permitting the inner member to recover. The articles are useful for covering substrates, especially splices and terminations in electrical cables.

Recoverable articles

New high voltage insulating compositions are disclosed. The compositions comprise a polymer (e.g. a polysiloxane, epoxide resin or a polymer of one or more olefins or substituted olefins), an antitracking additive (e.g. an alumina hydrate), and certain phosphorus-containing compounds which have been found to provide the compositions with greatly improved resistance to erosion by high voltage stress. The phosphorus-containing compounds include phosphonates, phosphates, phosphites, phosphinates, phosphonites, phosphinites, phosphine oxides and sulfides, and phosphines, and salts and complexes thereof. The phosphorus-containing compound can react in situ with the polymer or other ingredients of the composition.

High voltage insulating compositions containing phosphorus compounds

An article such as a tube formed of heat-shrinkable material is bonded exteriorly or interiorly to an elastomeric member to form a laminated article. The bonding preferably takes place before heating and expanding of the heat-shrinkable tube. After expansion and cooling, the parts remain in the heat recoverable position. Subsequent heating of the parts causes them to recover radially about a substrate.

Heat-shrinkable laminate

New high voltage insulating compositions are disclosed. The compositions comprise a polymer (e.g. a polysiloxane, epoxide resin or a polymer of one or more olefins or substituted olefins), an antitracking additive (e.g. an alumina hydrate), and certain organic polymerizable phosphorus-containing compounds which have been found to provide the compositions with greatly improved resistance to erosion by high voltage stress. The phosphorus-containing compounds include phosphonates, phosphates, phosphites, phosphinates, phosphonites, phosphinites, phosphine oxides and sulfides, and phosphines, and salts and complexes thereof. The phosphorus-containing compound can react in situ with the polymer or other ingredients of the composition.

High voltage insulating compositions containing organic polymerizable

Flexible hollow articles comprise an expanded elastomeric inner member and an outer restraining means. The restraining means has score lines thereon, and is made of a notch-sensitive material so that the score lines can be propagated through the material by distorting the article. The stiffness and elongation of the restraining means, and the peel strength of the bond between the inner member and the restraining means, are so chosen that at least part of the restraining means can be pulled away from the inner member by manual force. The articles are useful for covering substrates, especially splices and terminations in electrical cables.

Process for making recoverable tubular article

Crosslinking, e.g., by irradiation, of a polymer comprising poly(tetramethyleneterephthalate) is made possible by the addition of a member selected from the group consisting of triallyl cyanurate and N,N'-m-phenylenedimaleimide. The resulting crosslinked modified polymer may be rendered heat recoverable.

Poly(tetramethyleneterephthalate) crosslinked by irradiation

An improved high voltage insulating material comprising one or more polymers and an anti-tracking and erosion inhibiting composition comprising a hydrate of alumina and one or more compounds selected from the groups consisting of nickel phosphate, phosphinic acid or a derivative thereof, phosphonous acid or a derivative thereof, and phosphonic acid or a derivative thereof. The composition functions to prevent failure by tracking and to substantially retard failure by erosion.

High-voltage insulating material comprising anti-tracking and erosion

Crosslinking, e.g., by irradiation, of a polymer comprising poly(tetramethyleneterephthalate) is made possible by the addition of N,N'-m-phenylenedimaleimide. The resulting crosslinked modified polymer may be rendered heat recoverable.

Growing community of inventors

Sunnyvale, CA, United States of America

David D Nyberg