Quantitative measurement of physisorbed silane on a silica particle surface treated with silane coupling agents by thermogravimetric analysis

Abstract

ABSTRACTWe investigated a new method for estimating the amount of silanes physisorbed on a silica particle surface treated with silane coupling agents from a weight loss curve measured by thermogravimetric (TG) analysis. The silica particles were treated with 3‐glycidoxypropyl trimethoxysilane (GPTMS) or 3‐mercaptopropyl trimethoxysilane (MrPTMS) with both dry and wet treatment methods. In the TG curve for silica particles treated with GPTMS, the weight decreased in three steps: 100–170°C (first step), 170–250°C (second step), and 250–400°C (third step). The weight loss in the first step decreased with heating or acetone washing to remove the physisorbed molecules as the posttreatment. The three weight losses were found to be based on physisorbed monomeric silanes (first step), physisorbed polycondensed silanes (second step), and chemisorbed silanes (third step), respectively. The amount of physisorbed silanes on the silane‐treated layer could be estimated from the TG curve without solvent washing to remove the physisorbed molecules. The amounts obtained were almost equal to those measured from a comparison of the weight losses for the treated particles before and after acetone washing. A similar tendency was observed for MrPTMS‐treated silica. Thus, the amount of physisorbed silanes in silane‐coupling‐agent‐treated silica particles was successfully estimated from the TG measurements. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43256.