Silicone tube viscosity softening

- Mar 14, 2018-

      1) The surface blasting of silicone tube should be related to the extrusion type;

      (2) Before the secondary vulcanization after extrusion of the silicone tube, add isolation agent;

The main reason is that the proportions of the silane coupling agent, hydroxy silicone oil, zinc stearate, and the vulcanizing agent in the mixed silica gel need to be specifically designed to solve both the mixing proportion of the silica gel material and the mixing process.

The first step: preparation of prefabrication

Once the high-consistency elastomer is fully mated, this is prepared for the next step in the manufacturing process. This does not require special equipment, but it is very labor-intensive, especially in large-volume applications that are essentially continuous. For extrusion and injection molding applications, the preform is cut into strips by cutting the elastomer sheet, which is simply prepared for a feed extruder. In transfer molding operations, the preform is typically cut with a die cutter and will fit into the plug of the transfer reservoir of the transfer press. For compression-molded applications, the process is somewhat more complicated because the preform must be cut at the basic geometry of the final part.

The second step: extrusion

For high consistency elastomers, extrusion is accomplished using a single screw extruder. The preformed tape is fed to the extruder from the roller feed wheel to the extruder barrel, and the elastomer is extruded through a die and mandrel assembly to form the desired profile. In addition, support extrusion with high-consistency silicone elastomers can also be performed. This is accomplished by assembling a crosshead assembly in the extruder, passing through the crosshead at the support geometry, and extrude a layer of silicone rubber in it.

The third step: forming

High-viscosity silicon applications follow the type of molding equipment used. The transfer and injection molding process requires the operator to load the elastomer into the equipment and demold the finished part. For compression molding, the operator must place all single cavity preforms in each mold. Because of the relatively slow cure cycle used with high viscosity elastomers, it is possible to have a large number of cavities for the mold.

Fourth step: vulcanization

The vulcanization of extruded products is usually achieved with a hot air vulcanization furnace, or HAVS. These HAVS are in horizontal and vertical configuration. In the horizontal mode, the extruded profile passes through the oven, and hot air is forced through the extrudate to induce the vulcanization mechanism to pass through in a continuous belt. In a vertical furnace configuration, the HAV is equipped with a variable speed drum at the top through the oven, where it is solidified and pulls the extruded profile upwards.

The fifth step: finishing

The degree of finishing required depends on the specific application. For the extrusion method, finishing involves visual inspection and cutting of the tubing into specific lengths. If the tube is already cured with peroxide, the finishing process also requires an oven post-cure by-product to remove the peroxide. For molding applications, finishing includes trimming or trimming of the molded parts, often using a die cutting machine to cut individual parts from a larger molded sheet, and any post oven curing is necessary.