Introduction to RTV Silicone Rubber

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It is just like what we introduced before, besides the high-temperature vulcanized (HTV) silicone rubber, there is another type of silicone rubber which is room-temperature (RTV) vulcanized silicone rubber. Today’s article will shift focus from HTV silicone rubber to RTV silicone rubber field.

RTV silicone rubber is a new type of organic silicone elastomer which is developed from 20^th 60s by the U.S. The most unique feature of RTV is it could be used to make adhesive materials which have different viscosity which could be coated on clothes in room temperature and no need to be heated and compressed. The vulcanization of RTV is so simple to make itself becomes one important part of the whole organic silicone products fast.

Now RTV is widely used as adhesive, sealing agent, protective coating and moulding materials. It is due to the low molecular quantity of RTV silicone rubber, therefore it is also called liquid silicone rubber. Its physical form is usually flowing liquid or thick grease. Its viscosity is between 100 and 1000000 cP. It is according to the requirement of usage; the RTV could be mixed to other products. The fillers of RTV is similar with HTV which is silica and could lead to the tensile strength of 10 to 60 kgf/cm². To fill in different additives could grant the rubbers to have different densities, hardness, strengths and flowing abilities. It could grant the vulcanized rubbers properties like heating resistance, conductivity and fire resistance.

Categories & Properties

RTV silicone rubber’s molecular structure has the features that the two edges of the main chain contain active functional groups like OH group or acetyloxy groups. Under certain circumstance, these functional groups could be condensate and form crosslinking structure to become elastomers. It could be added some filling agents, vulcanizing agent and catalysts, and to be in some certain conditions to make these functional groups to have condensation, which is to be crosslinked to make elastomers. When the vulcanization is fully completed, the product will have excellent heating resistance, cold resistance and some other unique features, the only weakness is the low mechanical strength.

RTV silicone rubber could be divided further to single-group RTV (RTV-1) silicone rubber and double-group RTV (RTV-2) silicone rubber according to its packaging methods. Therefore, RTV silicone rubbers could be divided into 3 subcategories according to the differences in components, mechanism of vulcanization and using methods – single-group RTV silicone rubber, double-group condensation RTV silicone rubber and double group additional RTV silicone rubber. Each of them has their own pros: single-group is easy to be used but it is hard for it to enhance the speed of deep solidification; double-group condensation silicone rubber will not release any heats when been under solidification processes with small shrinkage rate, it solidification could occur on both inside and surface; additional RTV silicone rubber’s vulcanization time is mainly determined by temperature and could use temperate to control its vulcanization speed.

Single group condensation RTV silicone rubber (or RTV-1 silicone rubber) is one of the main products in condensation liquid silicone rubbers. It is usually made of base polymer, crosslinking agent, catalyst, filler and additive. The product will be packed in sealed hoses and will be pressed when being used. When it is contacted with air it will be self-vulcanized to be elastomer which is very convenient. Vulcanized rubbers could be used for a long-term under a temperature range between -60 and 200℃. It has excellent electrical isolation, chemical stability, heating resistance, water resistance, odor resistance, weather aging resistance, fire resistance, humidity resistance and breathability. It will not release or collect heats in solidification processes and has a very small shrinkage rate which is very good to the adhesion of materials. Therefore, it has very good adhesion to many metal and non-metals. For example, for naked aluminums, the cutting strength could be 200lbf/in², tear strength could be maximum 20lbf·ft/in². When the adhesion is difficult, it is good to paint at the bottom of the base materials to enhance the adhesive strength, the painted material could be resin or siloxane which has reactive activity, when they are solidficated on base materials there will be a new modified surface which is suitable to adhesion of organic silicone.  They are mainly for coating of electronic parts and electrical devices, the sealing material will be used for isolation, humidity resistance and shocking resistance.

Double-group condensation RTV silicone rubber (or RTV-2 rubber) is not as convenient as RTV-1 silicone rubber. However, it is since RTV-2 silicone rubber has more types of component ratios, one category of RTV-2 silicone rubber could get many different types of vulcanized products which could even be deeper vulcanized. Therefore, RTV-2 silicone rubber is widely used in electronics, vehicles, mechanics, construction, chemical industry, soft industries and painting for isolation, sealing, humidity resistance and shocking resistance. Besides these, it is due to RTV-2 silicone rubber has excellent demoulding ability, therefore it is widely used as the soft moulding materials which are used in copying and manufacturing of cultural relics, artifacts, toys, electronics, mechanic gadgets.

Summary

RTV silicone rubber is always mentioned together with HTV silicone rubber and both of them have been applied widely in different industries. To be more specific, the different subcategories of HTV and RTV silicone rubbers are more specifically targeted in one or some specific fields, goals or industries which are developed on purposes by researchers and scientists.

Anyway, not only for HTV and TRV silicone rubbers, there are many other types of silicone rubbers are being used in real industrial world to increase the effectiveness and efficiency of manufacturing processes of other products.

In next blog, we will write more about RTV silicone rubber and tell you why they are so popular in today’s organic silicone product markets.