Polyester dimethacrylate oligomers and networks

Dimethacrylate matrix resins and composites are becoming increasingly important in structural and coating components in the development of civil infrastructure. Service lives in excess of 50 years in outdoor environments are desirable for these materials. Aliphatic matrix resins derived from cycloaliphatic epoxies and dicarboxylic acids are under investigation as a means of obtaining coatings and fiber reinforced composites with such extreme durability to sunlight. The cycloaliphatic backbone shows reduced ultraviolet adsorption relative to bisphenol-A/epichlorohydrin resins. A series of new dimethacrylate resins and networks were prepared with 800 and 1200 g/mol oligomers 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 weight between crosslinks was controlled by both the oligomer molecular weight as well as the amount of the reactive diluent to tailor network properties. The aliphatic networks exhibit glass transition temperatures ranging from ≈93–115°C with the higher Tgs associated with lower molecular 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 oligomers. The fracture toughness, K1C, increases with the percentage of methacrylate diluent due to the increase in the molecular weight between crosslinks. However, networks cured with styrene as the reactive diluent show the reverse trend in fracture toughness.