Dependence of solid particle erosion on the cross-link density in an epoxyresin modified by hygrothermally decomposed polyurethane

Solid particle erosion of epoxy resin (EP) modified by various amounts of h ygrothermally decomposed polyester-urethane (HD-PUR) was studied at oblique (30, 45, and 600) and normal impact (90 degrees). The cross-linked structu re of the modified EP was characterised by the mean molecular weight betwee n cross-links (M-c). It was established that the initial brittle erosion of the densely cross-linked EPs (M-c less than or equal to 200 g/mol) changed to a rubbery one by increasing HD-PUR modification due to which a less cro ss-linked network was formed (Mc > 1000 g/mol). This change was reflected b y the impact angle dependence: compositions of low M-c showed the minimum r esistance at normal (90 degrees), whereas those of high M-c at 30 degrees i mpact angle. The resistance to solid particle erosion changed linearly with increasing fracture energy (G(c)) of the resins. G(c), on the other hand, followed the prediction of the rubber elasticity theory and increased linea rly with M-c(1/2). (C) 2001 Elsevier Science B.V. All rights reserved.