Comparative study of structure development in melt processing (polyethylene and isotactic polyolefins: Polypropylene, polybutylene, and poly-4-methylpentene-1)

A comparative study of crystallization and orientation development under uniaxial stresses in thin filaments is presented for four polyolefins: high density polyethylene (HDPE), isotactic polypropylene (iPP), isotactic polybutylene (iPB-1), and isotactic poly-4-methylpentenel-1 (iP4MP). In addition, the characteristic of crystallization in thick filaments or rods was investigated. The purpose is to compare the behavior of two relatively unknown polyolefins PB-1 and P4MP with the much better known and characterized PE and PP.; Melt spinning is carried out at different temperatures. Melt spun filaments were characterized by wide angle x-ray diffraction (WAXS), birefringence and differential scanning calorimetry (DSC) measurements.; Polymorphism (multiple crystalline states) is noted in the filaments of polybutylene that exhibits aging from one form to another as well as in polypropylene.; Careful attention is given to heat transfer during cooling. The orientation of flexible chains in the melt state is well known to be determined by the stress field. The crystalline orientation of the solidified crystalline filaments as a function of spinline stress is found by WAXS to be highest for the P4MP and lowest for the PE.; Birefringences of the melt spun PE fiber are however higher than PP or PB-1 and P4MP which had the lowest values when comparisons are made at the same spinline stress. However if intrinsic birefringence was used, the data order the same as the WAXS results.; A study of structure development in thin melt spun isotactic polypropylene filaments is described which is them applied to the prediction of the behavior of thick parts. Conditions under which different crystalline forms of polypropylene are obtained as a function of cooling rate and spinline stress were investigated. Continuous cooling transformation (CCT) curves are developed. This also allows us to develop a map of crystalline form as a function of these variables. We have applied the CCT curves and this map to predict the development of cross-sectional variation structure in thick filaments and rods. This is applied in particular to the quenching of a cylindrical rod and the structural characterizations observed through the cross-section are compared with predictions from the CCT curves and solutions of Fourier's transient heat conduction equation.; We also made the thick parts of polybutylene. We studied about the polymorphic phenomena through the cylindrical shape rod. We calculated the transformation percentage as a function of the aging time.