ETU. Vulcanization of silicones Room-temperature vulcanizing (RTV) silicone is constructed of reactive oil-based polymers combined with strengthening mineral fillers. There are two types of room-temperature vulcanizing silicone: RTV-1 (One-component systems); hardens due to the action of atmospheric humidity, a catalyst, and acetoxysilane. Acetoxysilane, when exposed to humid conditions, will form acetic acid. The curing process begins on the outer surface and progresses through to its core. The product is packed in airtight cartridges and is either in a fluid or paste form. RTV-1 silicone has good adhesion, elasticity, and durability characteristics. The Shore hardness can be varied between 18 and 60. Elongation at break can range from 150% up to 700%. They have excellent aging resistance due to superior resistance to UV radiation and weathering. RTV-2 (Two-component systems); two-component products that, when mixed, cure at room-temperature to a solid elastomer, a gel, or a flexible foam. RTV-2 remains flexible from . Break-down occurs at temperatures above , leaving an inert silica deposit that is non-flammable and non-combustible. They can be used for electrical insulation due to their dielectric properties. Mechanical properties are satisfactory. RTV-2 is used to make flexible moulds, as well as many technical parts for industry and paramedical applications. See also ISO 2921 Polymer stabilizers Sulfur concrete Vulcanized fibre References Chemical processes