Sioplas process

The third process for cross-linking is the Sioplas process developed by Dow. The first stage of this involves the grafting of an easily hydrolysable trialkoxyvinylsilane onto the polyethylene chain, the site activation having been achieved with the aid of a small amount of peroxide. The compound is then extruded onto the wire, which is collected on a drum. The drum is then exposed to hot water, or, more commonly, low-pressure steam. The water hydrolyses the alkoxy groups, which then condense to form a siloxane cross-link. ... 

Two-step (Sioplas) process, which involves a step to prepare cross-linkable PE and another step to create the final product. 

The Sioplas process was developed in 1968 by Midland Silicones (Dow Corning), using peroxide-activated grafting of vinyl silane onto the polymer chain, usually in compounding units or twin-screw extruders. The liquid silane/peroxide mixture is added to the polymer melt by membrane or piston pumps, producing a grafted granular product which, after a catalyst has been added, can be processed to cable, pipe or other finished parts. 

Mixtures of VTMO - with 7.5% dicumylperoxide Sioplas process... 

The benefits of the Sioplas moisture crosslinking process for the manufacture of crosslinked PE foam and the end-uses of such foams are discussed. The process involves grafting of alkoxysilanes onto ethylene homo- or copolymers to provide moisture crosslinkable polymers suitable for the manufacture of flexible, rigid, open-ceUed, closed-cell or very low density foams. 11 refs. 

The REX process is normally carried out in two steps, with the first step occurring at 180-200 "C. The mixture is passed through another REX reactor for mixing, and then through a final shaping REX reactor to complete the water curing reaction. The final cross-linked product (Sioplas ) is used as a wire or cable coating. 

This process requires lower capital investment than for peroxide crosslinking, but offers an output rate about 2.5 times higher. The capital investment is higher than for Sioplas, but elimination of one stage can reduce manufacturing costs. 

TABLE 9 Silane products for sioplas and monosil crosslinking processes... 

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