Organopolysiloxane and a composition comprising the same

Abstract

One of purposes of the present invention is to provide an organopolysiloxane that has a low viscosity and allows a cured coating to achieve both high hardness and crack resistance, and provide a composition comprising the organopolysiloxane. An organopolysiloxane represented by the following average unit formula (1) and having a kinetic viscosity of 10 to 350 mm/s at 25° C., wherein a proportion (%) of the number of silicon atoms in a unit represented by the following formula (1') to a total number of silicon atoms in all siloxane units of the organopolysiloxane is 10% or less, wherein R, R, and Rare, independently of each other, an unsubstituted or substituted, cyclic or non-cyclic alkyl group having 1 to 12 carbon atoms that may include an ether bond, or an unsubstituted or substituted aryl group having 6 to 12 carbon atoms, Ris a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and a, b, c, d and e are numbers satisfying the equations 0.2≥a≥0, 1≥b>0, 0.75≥c≥0, 0.2≥d≥0 and 1≥e>0, provided that a+b+c+d=1.