Inestigation of Readily Processable Thermoplastic-Toughened Thermosets. V. Epoxy Resin Toughened with Hyperbranched Polyester

摘要

This article describes the use of hyperbranched polyester oligomes (HBPs) as modifiers for epoxy thermosets. The effect of HBP molar mass, end group, and loading on prepolymer viscosity ,thermoset fracture toughness, T_g, and high-temperature dynamic storage modulus 9E') were measured. The HBP molar mass was system-actically increased from nominal of approx 1750 g mol (Generation 2, or G2) up to approx 14, 000 g mol (Generation 5, or G5), which corresponds from a low of two layers of monomer up to a maximum of five layers of monomer around the central core .Thoughness increased only modestly with the molar mass of the HBP. at 7% loading in the epoxy thermoset, the G5 HBP increased toughness by approx 60% over the untoughened control. Toughness increased to 82% above the untoughened control as a loading of 19% G5 HBP, but the toughness decreased at 28% HBP loading. The T_g and E' were influenced by the HBP modifier, but the effect was not systematic and may have been due to competing effects of HBP molar mass and end group. The effect of the architecture of the thermoplastic modifier was investigated by introducing a linear aliphatic polyester (approx 5400 g mlo) with a repeat unit structure, which was similar to that of the HBP. At the molecular weight range investigated, neither the prepolymer viscosity nor the thermoset toughness of the HBP-epoxy was significantly different from that of the linear polyester in epoxy. Preliminary results are presented showing the effect of thermoplastic molecular weight and architecture on morphology.