| 摘要 |
<p>A silicone elastomeric compsn. comprises (A) 100 pts.wt. of a triorganosiloxy endblocked polydimethylsiloxane fluid in which the triorganosiloxy units are selected from dimethylvinylsiloxy and methylphenylvinylsiloxy, the fluid being a mixt. of polymeric species of varying mol.wt where each species in present in an amt. sufficient to collectively provide a mol.wt. distribution such that there is present at least one polymeric species (1) at a concn. greater than the concns. of adjacent polymeric species of high and lower mol.wt. and is identified as a peak mol.wt. as determined by GPC of 68,000-135,000, the mol.wt. of the lowest mol.wt. polymeric species is 854-3146 and the mol.wt. of the highest mol.wt. species is 174,000-370,000, the mixt. of polymeric species has a mol.wt. distribution such that a dispersity index has a value greater than 3.8; (B) 20-60 pts.wt. of a reinforcing amorphous silica having a surface area greater than 100 m2/g, the surface of the silica having Si atoms to which are bonded organosiloxane gps. selected from: (a) Me3S iO-; (b) ViMe2SiO(Me2SiO)x-; (c) ViMePhSiO(Me2SiO)x-; and (d) -O(MeVi)Si-(OSiMe2)y-O- (Me = methyl, Vi =- vinyl, Ph = phenyl, x = 0-20, and y = 1-5), the organosiloxane gps. being present in an amt. such that there is 0.05-0.32 wt.% vinyl based on the wt. of silica and the organosiloxane gps. are present in a mole ratio such that there are 7-50 moles of (a) for each mole of (b), (c) and/or (d); (C) 0.3-1.8 wt.% hydroxy end-terminated polydimethylsiloxane having a viscosity at 25[deg]C of 20-60 mPa.s; (D) an amt. of fluid organohydrogensiloxane sufficient to provide 1-3 Si-bonded hydrogens per vinyl radical in (A) and (B) combined, the organohydrogensiloxane has an average of at least 3 Si-bonded hydrogen atoms per molecule and consists of units selected from methylhydrogensiloxane, dimethylsiloxane, dimethylhydrogensiloxy, trimethylsiloxy and SiO2 units; and (E) an amt. of Pt catalyst sufficient to provide at least 1 pt.wt. Pt per 1,000,000 pts.wt. of (A).</p> |
