Silicone elastomers for electronic applications. I. Analyses of the noncrosslinked fractions

Abstract

AbstractIn a study about silicone contamination on surfaces, crosslinked polydimethylsiloxanes have been examined focusing on the curing process and the noncrosslinked part in the bulk of the material. Curing was studied by following the development of gel as a function of curing time and temperature using Soxhlet extraction and differential scanning calorimetry (DSC) measurements. Gas chromatography–mass spectroscopy (GC‐MS), size exclusion chromatography (SEC), and thermogravimetric analysis (TGA) analyses gave information about the composition and size of the noncrosslinked fraction. The experiments demonstrate that the curing kinetics are of Arrhenius type with a strong temperature dependence. Interestingly, we find that 5–20% of the material does not undergo crosslinking reactions, although only 0–1% of the total sample mass is volatile at ambient temperature and pressure. It is likely that the volatile components mainly give rise to problems when they are confined to closed compartments or when they are in direct contact with a cold surface so that condensation on the surface occurs. Most likely, surface contamination originates from the nonvolatile fraction of the noncrosslinked portion of the material. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2073–2081, 2003