Application of composite models to isotactic polypropylene for the determination of phase specific stress–strain curves

Semicrystalline isotactic polypropylene has been uniaxially compressed up to different strains, and the relaxation after unloading has been studied. Two simple rheological models were used to find out the phase specific stress–strain behaviour. Both of them satisfactorily fit the experimental stress–strain characteristics although the stress controlled approach yields a better agreement.