Patent GB-1030155-A (GB)
Title: Elastomeric composition for use as rocket insulation
IPC: C06B23/00
Filed: 1962-11-15
Abstract: A sheet of vulcanized elastomeric composition contains evenly dispersed thereinfrom about 3 to about 80 parts per 100 elastomer of asbestos fibres which before incorporation in the composition were sufficiently large to be retained on a 325-mesh screen (Tyler series), the fibres being oriented so that they lie parallel to the surfaces of the sheet.  Specified elastomers are natural rubber, butyl rubber, butadiene-styrene, nitrile, duprene, neoprene, polyurethane, silicone, chlorosulphonated polyethylene, polybutadiene, polyisoprene, butadiene-acrylonitrile, fluorocarbon polymer, ethylene-propylene and the carbon sulphide rubbers. A preferred asbestos is composed of at least 65%, preferably 70%, of fibres which are retained on a 200-mesh screen (0.0029 inches) or larger. Even more preferably at least 14%, preferably 25%, are retained on a 14-mesh screen (0.046 inches).  The materials may be combined on a rubber mill and the usual compounding ingredients, e.g. plasticizers, vulcanization aids, tackifiers and refractants may be present; in particular auxiliary fillers may be added, e.g. carbon black, calcium carbonate, clay, "Formica" (Registered Trade Mark), kaolin, metallic oxides, slate flour and silica as well as pigments and dyes.  Silica type fillers such as the silica aerogels and zerogels are preferred.  In an example (4) the sheet has a composition of 100 parts of a poly (methylphenylsiloxane) end - blocked with methylphenylvinylsiloxane units and having a Williams plasticity of about 0.065 inch, 25 parts of a hydrophobed reinforcing silicia filler, 70 parts of chrysotite asbestos fibres of which 22% are retained on a 4-mesh screen, 23% on a 14-mesh, 20% on a 35-mesh and 7% on a 200-mesh screen together with 2 parts of dibenzoyl peroxide.ALSO:A substrate, e.g. a structural member of a propulsion unit, of metal or reinforced plastics, is protected with an insulating layer made by (1) mixing a vulcanisable elastomeric composition consisting of an elastomer and from about 3 to about 80 parts per 100 of elastomer of asbestos fibres which are sufficiently large to be retained on a 325 mesh screen (Tyler Series) to form a heterogeneous mixture without appreciable breakdown in size of the fibres applying the composition as a coating to the substrate and orientating the fibres so that they lie approximately parallel to the surface of the sheet, and curing the composition on the substrate to form a composite article.  Depending on the viscosity of the elastomer stock, a brush, putty knife or trowel may be manipulated so as to orient the fibres-multiple coatings may be applied.  Specified elastomers are natural rubber, butyl rubber, butadiene-styrene, nitrile, duprene, neoprene, polyurethane, silicone, chlorosulphonated polyethylene, polybutadiene, polyisoprene, butadiene-acrylonitrile fluorocarbon polymer, ethylene-propylene and the carbon disulphide rubbers.  A preferred asbestos is composed of at least 65%, preferably 70%, of fibres which are retained on a 200 mesh screen (0.0029 inch) or larger.  Even more preferably at least 14%, preferably 25%, are retained on a 14 mesh-screen (0.046 inch).  The usual compounding ingredients e.g. plasticizers, vulcanisation acids, tackifiers, and refractants may represent in particular auxiliary fillers such as carbon black, calcium carbonate clay, formica (RTM), kaolin, metallic oxides, slate flour and silica, pigments and dyes, the silica type fillers such as the silica aerogels and zerogels being especially preferred.