| 主权项 |
1. A curable composition comprising:
a resin-linear organosiloxane block comprising: 50 to 85 mole percent disiloxy units of the formula [R12SiO2/2], 15 to 50 mole percent trisiloxy units of the formula [R2SiO3/2], 2 to 30 mole percent silanol groups [≡SiOH]; wherein:
each R1, at each occurrence, is independently a C1 to C30 hydrocarbyl,each R2, at each occurrence, is independently a C1 to C20 hydrocarbyl, wherein:
the disiloxy units [R12SiO2/2] are arranged in linear blocks having an average of from 40 to 250 disiloxy units [R12SiO2/2] per linear block,the trisiloxy units [R2SiO3/2] are arranged in non-linear blocks having a molecular weight of at least 500 g/mole, and at least 30% of the non-linear blocks are crosslinked with each other, each linear block is linked to at least one non-linear block, andthe organosiloxane block copolymer has an average molecular weight (MW) of at least 20,000 g/mole; and wherein the curable composition exhibits stress-relaxation behavior when the curable composition maintains a tan δ value greater than about 0.05 and a G′ value greater than 1kPa over a temperature ranging from about −25° C. to about 250° C. |
