Three different polyolefins, a linear polyethylene, an isotactic polypropylene, and an isotactic polybutene‐1, were melt‐spun into filaments. The degree of orientation of the filaments was measured by polarized‐light microscopy, x‐ray diffraction, and a retraction technique, and the results were then related to the melt‐draw ratio. The increase in the elastic deformation ratio of polymer chains by spin‐stretching, estimated by thermal retraction at a temperature above Tm, was monotonic with respect to the melt‐draw ratio. On the other hand, as‐spun filaments of polyethylene and polypropylene were characterized by a plateau in birefringence over the range of melt‐draw ratios from 8 to 80. The change in orientation functions for crystals in these filaments was similar to the change of birefringence. On the other hand, the birefringence and the crystalline orientation functions for polybutene‐1 increased smoothly with increasing melt‐draw ratio. The most highly melt‐drawn filaments of these polymers had a strongly oriented structure, corresponding to that in highly cold‐drawn specimens.

synopsisFive series of two-component blend filaments, comprising nylon 6 (N6) and nylon 66 (N66), nylon 610 (N610), nylon I1 (Nll), nylon 12 (N12), or poly(ethy1ene terephthalate) (PET), were prepared by using a research spinning machine and a conventional drawing machine. The microstructure and the physical properties of the resultant filaments were evaluated with a tensile tester, a optical microscope, a density-gradient column, and a DTA instrument. When both components were mixed homogeneously so that they would form a three-dimensional network, the tensile properties of the blend filament were at least equivalent t o the values predicted from those of both components. On the other hand, as in the cases of 30/70 and 70/30 N6-PET, when the minor component was discretely distributed as short fibrils in the matrix of the major component, the blend filament had an extremely weak tenacity. A supertenacity filament was obtained from 50/50 NbN610. The marked increase of the tensil strength and the initial modulus of 50/50 N6-N610, about 12 g/den and 520 kg/mmz, respectively, may be due t o a significant increase in the crystallinity and the orientation of the blend. 2633

synopeieThe elastic deformation ratio by spin-stretching was estimated by means of thermal retraction technique, data for a melbspun filament from a crystalline polymer were compared with those from an amorphous one. The neceseary conditions for equilibrium retraction were determined as 7 min at 170°C for amorphous polystyrene and 30 min at 18OOC for high-density polyethylene. The effects of molecular weight and melt draw ratio on the retraction behavior were d i s c d and concluded to be negligible. The apparent activation energies of viscous flow were calculated from the temperature dependence of the retraction curvea. The activation energy for polystyrene decreases with increasing temperature of retraction, as predicted by the WLF equation, and that of polyethylene obeys Arrhenius law (about 12 tcsl/mole). This may be attributed to the difference in glass transition temperatures of the two polymers. By measuring the effective melt draw ratio of the reeultsnt filaments of different melt draw ratio, it was made cleat thet the elastic deformation incrsasea with increasing apparent melt draw ratio. Finally, the optical anisotropy of the filaments was related to the deformation ratio. It was cuncluded that Kuhn and Griin's equation may be applicable for polystyrene but not for polyethylene. 299

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