RTV-2 silicone rubbers are pourable, spreadable or kneadable compounds, which will crosslink in the presence of a second component to form athletic rubbers. They are outstanding as mould-making materials because of their excellent properties:
Easy to use
For more info Natural rubber sheet.
Excellent within make a get grip of of properties
Accurate reproduction of surface details
Good heat resistance
Little or no shrinkage
RTV-2 silicone rubbers can along with be use for encapsulation and sealing, or for making nimble parts.
RTV-2 silicone rubbers always consist of two components, namely the rubber base itself and a catalyst, or the components A and B. They are cured or vulcanised at room temperature (RTV= room temperature vulcanising).
Different grades are lighthearted, gone vary properties okay for a broad range of applications. They can be classified according to the gone criteria.
1. Vulcanising system (synopsis-curing or extra-curing)
2. Consistency (pourable, spreadable or kneadable)
3. Mechanical properties of the cured rubbers (e.g. tear resistance and elasticity)
Condensation-curing RTV-2 silicone rubbers
These cure at room temperature after connect in crime of catalyst, volatile alcohols being liberated during the reply. Shrinkage occurs, which is completed after more or less a week. Although not enormously full of life, the vulcanising process can be speeded going on by heating. The temperature should under no circumstances exceed 70oC. It is plus most important that freshly made moulds, i.e. which yet contain the alcohol produced during the curing response, are not subjected to temperatures greater than 80oC, by now this would cause a loss of elasticity and softening or stickiness of the silicone rubber (see with Mould pre-treatment).
Addition-curing RTV-2 silicone rubbers
These vulcanise without the formation of right of entry products, hence that there is not quite no shrinkage. The cured rubbers can so be used hastily after they are adequately cured. Vulcanisation can also receive place at far away ahead temperatures (going on to 200oC) which greatly reduces the required curing time. In this conflict however, one must endure the tall coefficient of thermal impinge on into the future of silicone rubber into account.
Cleanliness is especially important previously doling out assistant-curing RTV-2 rubbers, back the platinum catalyst can lose its show through contamination. Catalysts used for digest-curing silicone rubbers, for example, can interfere once vulcanisation already in little amounts. Furthermore, vulcanisation of buildup-curing rubbers can be delayed or highly prevented if they are in entre behind appreciative materials such as natural and synthetic rubbers, PVC, amine-cured epoxy resins, plasticine, adhesives, soldering tin etc. Preliminary tests are thus vitally important.
Storage stability
RTV2 silicone rubbers will remain in usable condition for at least 12 months, provided they have been stored chilly and abstemious, in tightly closed containers. The T series of catalysts have a shelf cartoon of at least 6 months in closed containers, and should be protected from heat and moisture. All containers should be tightly on the order of-strong the entire epoch some of their components have been removed.
RTV-2 silicone rubbers and food regulations
Finished products made from pedigree-curing silicone rubbers are grow out of date-lucky for food entre applications in flexibility bearing in mind food regulations.
Condensation-curing RTV-2 silicone rubbers
These are vulcanised by tallying a liquid or pin-gone catalyst. The pot simulation of the resultant incorporation, as quickly as its vulcanising time, will reorganize in the middle of a few minutes and several hours, depending concerning the type of catalyst and the amount used, the ambient temperature and relative humidity, as accurately as the amount of leisure ruckus in the song. Optimum characteristics of the cured rubber can unaided be achieved if a going on to period-lucky catalyst is used in the prescribed amounts.
Addition-curing RTV-2 silicone rubbers
Here the mixing ratio for components A and B is beatific and must be adhered to precisely in order to comply the desired interruption product properties.
Preparation of components
All pourable components should be stirred sufficiently since use to ensure even distribution of the filler. Stirring in addition to improves flow in similar to viscosity systems.