Stress analysis of the low-temperature deformation of polypropylene

Abstract

The low-temperature deformation of crystalline polypropylene (PP) first discovered by Kardash and coworkers [1] was investigated in greated detail in reference [2]. The factor underlying the low-temperature deformation of crystalline PP is a particular level of supermolecular ordering which gives rise to the possibility of large reversible deformations in the stretching of films in a temperature region extending at any rate down to the boiling point of nitrogen (−196°). Since low-temperature deformations of PP take place at temperatures much below the glass transition temperature of PP ( T g is taken as −10−15°) the suggestion was advanced in [2] that the possibility of large of deformations could be due to the sliding of structural blocks in the absence of changes in the chain conformations. The absence of conformational changes in determined by the imposibility of the chains retaining their flexibility at temperatures 100–150° below T g.