Comparative study of structure development in melt spinning polyolefin fibers

A comparative study of crystallization and orientation development in melt spinning is presented for four polyolefins: high density polyethylene (PE), polypropylene (PP), polybutylene (PB-1), and poly-4-methylpentene-1 (P4MP). The purpose was 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 was 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 which 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 wizen comparisons are made at the same spinline stress. However if intrinsic birefringence was used, the data order the same as the WAXS results.