The effect of filler content on the lower yield stress of polymer composites

The effect of the concentration of the dispersed elastic filler on the lower yield stress of matrix composites based on plastic polymers is studied. As the matrix polymers, LDPE-HDPE and LDPE-(medium-density PE) are used. The elastic filler is rubber crumb prepared by roll grinding of worn tires or by deformation worn ethylene-propylene-diene rubber. Irrespective of the type of filler particles and their adhesion to grinding of ethylene the polymer matrix, the lower yield stress sigma(d) of the composite is described by the linear law sigma(d) = sigma(dm) (1 - V-f), where sigma(dm) is the lower yield stress of the polymer matrix and V-f. is the volume content of the filler. Analysis of the published data shows that this relationship is quite general and describes the effect of rigid inorganic particles on the lower yield stress when adhesion between the filler particles and the matrix is poor.