TOUGHENING OF POLYMERIC MATERIALS

Some methods for toughening of polymeric materials have been proposed here on the basis of the fracture mechanism of polymeric materials. This mechanism described interns of the characteristic volumes, that is, yield stress, critical stress for craze nucleation and critical stress of crack nucleation from the craze. (1) The nucleation of craze or crack from the craze can be suppressed by the relaxation of stress concentration due to the release of the constraints of strain. (2) The critical stress of craze nucleation or the critical stress of crack nucleation from the craze can be improved. The improvement of toughness is possible through the formation of numerous voids which are developed at interfaces between dispersed particles and matrixes, when the incompatibility polymer alloy is used as an example of method (1). This results shows the mechanism of the toughness of polymer alloy can understood by simple elastic-plastic analysis. In addition, the critical content of dispersed particles for the development of shear plastic deformation between particles without the nucleation of craze can be calculated from the critical stress for craze nucleation and the shear yield stress in the ductile matrix. A concrete example of method (2) is obtained by the contrail of the critical stress of craze nucleation and/or the stress of crack nucleation due to the molecular weight and the rigidity of molecular chain. © 1990, The Society of Polymer Science, Japan. All rights reserved.