Method for the preparation of polydimethylsiloxanes having low reactivity endgroups and high reactivity endgroups wherein the polydimethylsiloxanes contain ethylene chain linkages

摘要

A method of making a polydimethylsiloxane which has both low reactivity endgroups of the formula (R''O)R2SiO- where R'' is an alkyl group of 1 to 4 carbon atoms, and high reactivity endgroups of the formula (R''O)3-fMefSiCH2CH2 or <IMAGE> in which a polydimethylsiloxane having the high reactivity endgroups is mixed with a hydroxyl terminated polydimethylsiloxane and then a difunctional silane, R2SiX2 where R is methyl or vinyl and X is N-methylacetamido. These polydimethylsiloxanes are useful for making sealants with reduced modulus.