Abstract: The base material for silance grafting is to be a mixture of at least 50% of a polyolefin (compound A) and of not more than 50% of a different polymer or elastomer serving as property modifier (compound B). The compound A is silane grafted separately or together with compound B. The grafted material is extruded around a conductor or a tube followed by crosslinking in the presence of moisture.

Abstract: A shrink-fit article is made by extruding a silane-grafted polymer which foams, at least at its surface, and cross-links. Upon completion of foaming and cross-linking, the article is expanded while (still) warm and cooled in the expanded state.

Abstract: Silane is grafted upon polymer molecules and the material is shaped (e.g., extruded or injection-molded) and caused to cross-link. Both steps must be completed before expanding (following reheating, if necessary) and cooling the object at the expanded state. Cap- and sleeve-making is disclosed, including internal as well as external exposure to water for cross-linking, possibly combined with the requisite preheating for the expansion.

Abstract: A blend of high and low density polyethylene and azodicarbonamid added as blowing agent is heated in an extruder to a temperature above the melting point of the high density component and fed to a shear head having a hollow rotating mandrel through which tubing is fed for depositing thereon a hose at the nozzle exit of the head. A peroxide is fed to the shear head for mixing with the polymer blend and immediately initiating crosslinking; blowing begins just prior to the depositing, the material being already crosslinked to a considerable extent.

Abstract: Granulated polyethylene is agitated and mixed with a solution of silane with peroxide, activators and anti-oxidants and at a temperature between 80.degree. to 100.degree. C. to obtain diffusion of these additives into the polyethylene particles which is followed by grafting through extrusion or radiation which in turn is followed by exposure to and/or development of water to obtain cross-linking. A catalyst is added preferably by mixing polyethylene powder with the catalyst and adding that powder to the powder with diffused silane, after that diffusion has been completed.