Supermolecular organization of as‐spun fibers form melts of crystalline polyolefines

Abstract

SYNOPSISWhen polymers are converted into films or fibers, the crystallizing melt is subject to considerable jet stretching and the cooling of the melt proceeds under complex temperature conditions. The occurrence of the temperature and the rate gradients can profoundly affect the supermolecular organization of the final polymer systefn. The investigation of the supermolecular organization of polyethylene and polypropylene fibers and films shows that practically in all cases the polymer contains spherulites elongated transversally to the direction of the stretching of the crystallizing melt. The value of the spherulite radius and the degree of its flattening are definitely associated with quite different components of the formation process. Thus, the value of the spherulite radius is inversely porportional to jet stretching, while the change in temperature conditions (e.g. the melt temperature or the cooling conditions) shift the hyperbolae R = f(@) downwards or upwards. The .factors causing the formation of flattened spherulites are analyzed. Probably in the case of thin fibers the major factor is the occurrence of the two temperature gradients while in the case of films it is the mechanical field of the longitudinal rate gradient.