SEMICOSIL® 811 is processed together with a catalyst as a two-component silicone rubber, and cures via an addition-reaction to form a low-modulus elastomer with very little resistance to deformation. The vulcanized rubber thus compensates for thermomechanical stresses in bonded assemblies. For processing, SEMICOSIL® 811 is mixed with the catalyst component in a ratio of 10:1. The processor can choose between thermal or UV-activated curing by choosing the appropriate catalyst.
The new adhesive sealant can easily be conveyed in conventional dispensing processes. It contains a UV marker that permits automated quality control of the adhesive coat. With no need for a primer, the new adhesive sealant bonds to polybutylene terephthalate, polyamide, aluminum, coated display glass and many other substrates that are widely used in electronics.
SEMICOSIL® 811 can be processed much more rapidly than conven-tional addition-curing silicone adhesive sealants. After the two components have been mixed and – if a UV-activated catalysts is used – irradiated with UV light, the adhesion strength builds up within an hour at room temperature to a level at which the bond can be tested for leak tightness.
The new adhesive sealant permits curing without an oven. Processors therefore do not need to invest in expensive oven systems, thus greatly simplifying production. SEMICOSIL® 811 can also be used on sensitive substrates, which should not be exposed to heat.
A small amount of energy after bonding – for example by briefly exposing the bond to a moderate temperature or infrared light – speeds up curing and adhesion development considerably.
For many substrates, a bonding strength of over one newton per square millimeter can be achieved in less than ten minutes by subjecting the bond to a temperature of 80 °C for only two minutes. If a high-temperature test step takes place during the process, the manufacturer can also use this step to speed up curing and adhesion development. Such a test is required for many electronic items and is therefore often provided as part of the production cycle.
SEMICOSIL® 811 clears the way for electronics manufacturers to integrate bonding, together with leak testing, in their overall production in a cost-effective mass-production process with fast cycles. As a silicone elastomer, the vulcanized rubber of the new adhesive sealant is characterized by high aging and heat resistance, and also remains flexible at low temperatures down to -40 °C. SEMICOSIL® 811 is thus especially suitable for use in automotive electronics.
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