Tensile properties and morphology of copolymer modified blends of polystyrene and polyethylene

The mechanical behaviour of heterogeneous polymer-polymer blends depends on the mechanical properties of the polymers, on the morphology of the system and on the degree of the mechanical contact between the phases. The three aspects will be explained and illustrated on the basis of results of investigations on the system polystyrene/low density polyethylene (PS/PE) to which graft or blockcopolymers of PS and low density polyethylene (PS-g-PE or PS-b-PE) were added. Although different kinds of mechanical experiments at different speeds and temperature have been carried out, only results of tensile experiments at room temperature will be treated here

The effect of varying the polyethylene content and the co-polymer content on crazing in polystyrene-low-density polyethylene blends

The effect of varying the compn. of blends of low-d. polyethylene [9002-88-4] with polystyrene [9003-53-6] contg. 0-2% ethylene-styrene block copolymer (hydrogenated SBR) on the rates of craze initiation and craze growth was studied. The parameters in the Eyring rate coeffs. for craze initiation and craze growth are not dependent on the polyethylene content. The rates of craze initiation increased with increasing polyethylene content. This is explained tentatively by a new model for craze initiation. Effective crazes are only formed within clusters of polyethylene particles that have overlapping stress-concn. fields. The dependence of the rate of craze initiation on the vol.-fraction of dispersed phase that follows from this cluster model is qual. in agreement with exptl. results. Copolymer addn. gives rise to changes in the Eyring parameters of the rate coeffs. of craze initiation and craze growth. This may be a consequence of changes in morphol. near the interface and of the different stress state at the interfac