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The analysis for the hydroxyl (OH) group is one of the most important functional group analyses fir silicones. Hydroxyl functionality may be present as silanol (sioh) water (HOH) and possibly as carbinol (coh) or carboxyl (cooh) amine groups on silicon substituents may also be a source of active hydrogen The silanol group is particularly important in silicone chemistry because it is through this function that condensation polymeriz-ation occurs to produce silicones it is also an active catalyst for siloxane bond rearrangement water is a condensation by-product so the concentra-tion of water in silicones is directly related to the amount of silanol and silane condensation the chemical or instrumental analysis for silanol and water in silicones is complicated by several factors First the fact that silanol and water generally occur together requires silanol and water-specific analyses Unfortunately there are few if any silanol-specific chemical analyses Most chemical analyses are nonspecific methods for total active hydrogen thus silanol and water and other active hydrogens including carbinols and carboxyl are determined in total Second the reactivity of the silanol group can vary widely depending on the molecular structure or environment Third concentrations of interest range from low parts per million to percent levels. The most common methods for the chemical analysis of silanol and water in silicones are disussed below Additional information on less common methods is available in the first edition of this book the analysis of functional groups such as carbinol or carboxyl less commonly found in silicones can be accomplished with some of the procedures described below Much more information is available in texts on general organic functional group analysis |
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baoqiang133 
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