Time-temperature creep behaviour of poly(propylene) and polar ethylene copolymer blends

Polymers commonly undergo deformation under an applied stress over their lifetime; some deformations are irrecoverable once the source of stress is removed. Therefore an understanding of the response of a polymer can be achieved by investigating the viscoelastic properties using creep experiments, where the behaviour can be monitored under small deformational. loads. Poly(propylene) (PP) was blended with a polar elastic, thermoplastic, poly[ethyleneco-(methyl acrylate)] (EMA), to toughen the matrix. EMA formed a dispersed phase in PP that maintained its strength through its crystallinity rather than crosslinking. EMA can form a compatible interface with PP through inclusion of maleated-PP as a compatibiliser. The viscoelasticity of the PP-EMA blends, particularly the creep behaviour is an important factor if the properties of PP are to be maintained. The creep and recovery of PP-EMA blends with varying compositions were investigated under different loads and number of cycles. High EMA content provided an alternative deformation pathway due to its elastomeric properties. The experimental creep behaviour has been evaluated using the 4-element model with some limitations evident in the viscoelastic transitional region.