Mechanical properties and superstructure of isotactic polypropylene fibers prepared by continuous vibrating zone‐drawing

Abstract

ABSTRACT:A continuous vibrating zone-drawing (CVZD) was applied to study the effect of vibration on the mechanical properties and superstructure of isotactic polypropylene fibers. The CVZD treatment was a new drawing method by which the fiber was continuously drawn at a rate of 0.5 m/min under vibration using the specially designed apparatus. The CVZD treatment was carried out in five steps at a drawing temperature of 150°C and a frequency of 100 Hz, and applied tensions increased step by step with processing in the range of 14.8 to 207 MPa. The obtained fiber had a birefringence of 0.0373, crystallinity of 62.4%, tensile modulus of 17.6 GPa, and tensile strength of 1.11 GPa. These values are higher than those of the continuous zone-drawn isotactic polypropylene fiber previous reported. The vibration added to the fibers during the zone-drawing was effective in developing amorphous orientation and improving the mechanical properties.

Study on thermal expansion in injection‐molded isotactic polypropylene and thermoplastic elastomer blends

“…The orientation function $ f_{{\rm{am}}}^{{\rm{FD}}} $ of the iPP amorphous region in FD was determined from the birefringence (Δ n ) (measured), degree of crystallinity ( X c ), and c ‐axis orientation function ($ \,f_c^{{\rm{FD}}} $ ) in the FD obtained by the X‐ray pole figure9 using where $ \Delta n_c^0 $ and $ \Delta n_{{\rm{am}}}^0 $ were the intrinsic crystal birefringence and the intrinsic amorphous birefringence, 0.0331 and 0.0468, respectively 13, 14…”

Relationship between the structure and mechanical properties of polypropylene: Effects of the molecular weight and shear‐induced structure

“…Typically for PP, there are three different relaxation processes due to molecular motions activated by thermal energy. [49][50][51][52] First, very short range motions, such as methyl group rotation in side-chain ends, occur at approximately À508C; this motion is termed the g-relaxation process. The b-relaxation process at higher temperatures of about 08C is the dominant relaxation and can be attributed to the transition from the glassy state to the rubbery state in amorphous polymers, but it should be taken into account that the amorphous region in a crystalline polymer is different from that in a completely amorphous polymer, in that the molecular motions of the amorphous phase are constrained by the crystallites.…”

“…Distinctive a-relaxation behavior, as can be observed for the lower molecular weight samples in Figure 15, is well known for oriented samples, for example, because of special drawing processes. 50,51,54 This is due to the fact that molecules arranged parallel to the direction of deformation can slip more easily.…”

Drawing behavior and characteristics of laser‐drawn polypropylene fibers

“…The lower temperature peaks appeared at around 10 °C corresponds to the α a , that is amorphous relaxation or glass transition, whereas the higher temperature peak shoulder appeared at 55 °C for as‐spun fiber and peak at around 100 °C for DR 4 fiber represent the α c or crystalline transition 5. From the molecular viewpoint, the α c relaxation can be identified as the c‐shear relaxation process, that is a c‐slip process 7. The peaks' height of DR 4 sample in comparison with the same of as‐spun and other higher DR fiber are inexplicable.…”

“…As is commonly known, high modulus and high strength can be achieved by the aligning and straightening of polymer molecules in an axial direction. Based on this, various methods, such as zone‐drawing/zone‐annealing,5 coextrusion method,6 continuous vibrating zone‐drawing,7, and so forth, have been adopted till now to enhance the performance of PP fiber. In all the methods, at least two or multiple stages of drawing or annealing were required.…”