Polyester dimethacrylate oligomers and networks

Dimethacrylate matrix resins and composites are becoming increasingly impor tant in structural and coating components in the development of civil infra structure. Service lives in excess of 50 years in outdoor environments are desirable for these materials. Aliphatic matrix resins derived from cycloal iphatic epoxies and dicarboxylic acids are under investigation as a means o f obtaining coatings and fiber reinforced composites with such extreme dura bility to sunlight. The cycloaliphatic backbone shows reduced ultraviolet a dsorption relative to bisphenol-A/epichlorohydrin resins. A series of new d imethacrylate resins and networks were prepared with 800 and 1200 g/mol oli gomers and different concentrations of methyl methacrylate as the reactive diluent. Their thermal and mechanical properties have been compared to the bisphenol-A/epichlorohydrin-based dimethacrylate resins, which have either styrene or methyl methacrylate as the reactive diluent. The molecular weigh t between crosslinks was controlled by both the oligomer molecular weight a s well as the amount of the reactive diluent to tailor network properties. The aliphatic networks exhibit glass transition temperatures ranging from a pproximate to 93-115 degreesC with the higher Ts associated with lower mole cular weight oligomers and higher network densities. The aliphatic networks , in general, also have lower fracture toughness and higher hardness values as compared to networks prepared from bisphenol-A/epichlorohydrin oligomer s. The fracture toughness, K-1C, increases with the percentage of methacryl ate diluent due to the increase in the molecular weight between crosslinks. However, networks cured with styrene as the reactive diluent show the reve rse trend in fracture toughness. (C) 2001 Published by Elsevier Science Ltd .