A dynamic mechanical thermal analysis was performed on allylester composites filled with alumina. Alumina was treated with various concentrations of four silane coupling agents. We determined the glass transition temperatures and the values of the storage moduli in both the glassy and rubbery states in each system and compared the mechanical-thermal behavior of pristine allylester polymers with that of composites filled with unmodified or modified alumina. At optimum concentrations of silane coupling agents in each system, the maximum crosslinking reaction occurred and the maximum glass transition temperature appeared at the same concentrations by their effective surface coverage. Differential scanning calorimetry experiments proved this fact. The order of the glass transition temperatures was 3-aminopropyltriethoxysilane (APS) vinyltrimethoxysilane (VTS) > 3-methacryloxypropyltrimethoxysilane (MPS) E (3-glycidoxypropyl)trimethoxysilane (GPS) modified systems because MPS and GPS have flexible ether linkages in their structures but APS and VTS do not. The structures of each silane coupling agent influenced significantly on the glass transition temperature, the storage modulus, and tan 6 . 0 1996 John Wiley & Sons, Inc.
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Allylester resin has many advantages, including a range of mechanical properties, long shelf-life, and thermal stability. It is cured after preparation of a prepolymer by transesterification, differently from other ally1 system polymers.'-* It also has weathering stability, chemical resistance, heat resistance, corrosional resistance, distinguished optical properties, and excellent electric resistance at elevated temperature and high humidity. Therefore, allylester resin can be widely used in applications such as optical materials, building materials, artificial marble, and wire b ~a r d . ~. ~ Especially, as the prepolymerization is accomplished not by radical reaction but by transesterification, it is easy to change the content and types of polyol and diallyl ester. It is also easy to modify the molecular structure and performance of polymer at will.