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Wacker Introducing Self-adhesive High Consistency Silicone Rubber Grades (HCR) for the Cost-effective Coextrusion

Published on 2010-10-29. Author : SpecialChem

Munich -- Wacker, the Munich-based chemical group, is introducing new self-adhesive high consistency silicone rubber grades (HCR) for the cost-effective coextrusion or molding of hard-soft material combinations at the 18th International Trade Fair for Plastics and Rubber (K 2010) Düsseldorf, Germany. The silicone products bond to different metal and plastic substrates without the need to pretreat the substrate surface. ELASTOSIL® R plus 4370 self-adhesive extrusion grades allow the one-step production of hard-soft profiles. ELASTOSIL® R plus 4070/60 molding grade can significantly increase productivity of multicomponent parts in small to medium production runs.

To achieve good silicone substrate adhesion and therefore a firm bond, it used to be necessary first to prepare the surfaces of metall substrates mechanically and with an adhesion promoter. This represented an additional work operation.

The new self-adhesive silicone grades avoid this with an innovative, patented bonding technology that produces a firm bond without any pretreatment. In the multicomponent part, the silicone is directly chemically bonded to the hard component. The bond develops rapidly during vulcanization. With no time-consuming, error-prone pretreatment, two-component parts and profiles can be produced faster, more simply and therefore more cost effectively. There are no associated solvent emissions nor are there any costs for adhesion promoters.

The new self-adhesive HCR silicone rubber grades cure by platinum-catalyzed addition to achieve good to very good mechanical properties. Silicones can be bonded to a variety of substrates, such as many metals, particularly aluminum and steel, and various plastics and elastomers.

ELASTOSIL® R plus 4370 extrusion grades are two-component products (regarding the platinum catalyst). The bonding system in these HCR silicone grades ensures bonding to the hard component during vulcanization. Since no pressure is required, they can be coextruded with the hard component. A permanent bond forms between the two components in the heating tunnel. The process allows two-component profiles to be produced rapidly in a one-step, largely automated process - with no pretreatment or adhesive.

Tailored for Molding: ELASTOSIL® R plus 4070/60

Regarding the platinum catalyst, ELASTOSIL® R plus 4070/60 is a one-component silicone elastomer. It is tailored for conventional molding processes, with the aim of offering a flexible process for manufacturing small runs of two-component parts.

The HCR rubber is formulated to adhere firmly to the hard component during vulcanization, but not to the tool. By eliminating primer, processors can achieve higher productivity. The composite part can thus be produced more cost effectively than with a conventional HCR silicone, even in small to medium production runs.

About Wacker

Wacker has produced Silicones in China since 2004 for use in many challenging applications, including in the automotive, construction and electronics sectors. At Wacker's Nanjing site, production of dispersions and dispersible polymer powders began last November. Primarily supplied to the construction sector, these products are found, for example, in insulation systems, tile adhesives and ready-mix mortars. In total, Wacker's Chinese operations comprise four production sites, two technical competence centers and seven sales offices spanning the country's key economic centers. In 2009, Wacker posted sales of over €730 million in China, including Taiwan. The Munich-based chemical company has been present in China with own sales offices since 1995.

Source: Wacker


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