The line- and the cross-crack healing of Poly(methyl methacrylate) (PMMA) under the ethanol treatment at 40 C~60 C have been studied. The cross-crack means that the crack plane is vertical to the crack plane of the line-crack. The effective glass transition temperature of PMMAis reduced after the ethanol treatment. Both crack healings only occur at the effective glass transition temperature lower than the transport temperature. Both crack closure rates are constant. The closure rate of the cross-crack is higher than that of the line-crack. The analyses of the surface morphology and mechanical strength show that there are also two stages for crack healing which is wetting and diffusion. The tensile fracture stress of the healed specimen increases with a rise in volume fraction of the absorbing ethanol. The tensile fracture stress of healed PMMA with cross-crack only can be recovered to the virgin material. The tensile fracture stress of healed PMMAwith cross-crack is larger than that with the line-crack.
淡江理工學刊 = Tamkang journal of science and engineering 11(1), p.7-16