| abstract |
Solid compositions of organosiloxane block copolymers are disclosed having a tensile strength greater than 1.0 MPa and a % elongation at break greater than 40%. The organosiloxane block copolymers comprise: 40 to 90 mole percent disiloxy units of the formula [R 1 n 2 SiO 2/2 ] 10 to 60 mole percent trisiloxy units of the formula [R 2 SiO 3/2 ] 0.5 to 35 mole percent silanol groups [≡SiOH] where R 1 is independently a C 1 to C 30 hydrocarbyl, R 2 is independently a C 1 to C 20 hydrocarbyl, wherein; the disiloxy units [R 1 n 2 SiO 2/2 ] are arranged in linear blocks having an average of from 10 to 400 disiloxy units [R 1 n 2 SiO 2/2 ] per linear block, the trisiloxy units [R 2 SiO 3/2 ] are arranged in non-linear blocks having a molecular weight of at least 500 g/mol, 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, and the organosiloxane block copolymer has a molecular weight (M w ) of at least 20,000 g/mole. |