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The effects of organoclay and polyhedral oligomeric silsesquioxanes (POSS) nanoparticles on the crystallization behavior of high molecular weight poly(ethylene terephthalate) (HMWPET; inherent viscosity of 1.05) were investigated in terms of nanoparticle content and shear rate. Both nanoparticles played a role of nucleating agent for PET and increased the cold crystallization temperature by about 24°C. The half‐time of crystallization was also decreased with increasing the nanoparticle content. Clay proved to be more effective than POSS; a notable nucleating effect was observed at 0.3 wt% for clay and 2 wt% for POSS. Introducing 1 wt% of clay gave the highest crystallization rate among all PET nanocomposite samples examined. Isothermal crystallization of the nanocomposites under dynamic shear exhibited similar crystallization behavior. As in the DSC measurement, clay appeared to be more effective to promote the crystallization of PET under shear. The nucleating effects were more noticeable at higher shear rate. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers

This article describes the physical properties of lyocell fibers spun from an isotropic cellulose spinning dope in N-methyl morpholine N-oxide (NMMO) monohydrate (IPS lyocell fibers). Wide angle x-ray diffraction (wAxD) experiments on the crimped fibers exhibit little difference in the crystal structure of IPS and Tencel lyocell fibers: both fibers reveal a cellulose II structure. However, the IPS lyocell fibers have a lower tensile modulus than Tencel by about 12.5%, although they have a similar tensile strength. Wetting and subsequent drying shift the loss tangent values higher, which is more remarkable for the IPS lyocell fibers dried under tension. Further, the IPS lyocell fibers dried under tension have a sharper α-transition peak than the fibers dried without tension. The IPS lyocell fibers exhibit excellent wet tensile strength: 90% of tensile strength is retained after wetting twice in distilled water. In addition, the IPS lyocell fibers show good chemical stability to acids and alkalis, except for an extremely strong alkali—pH 14. Mercerization of the IPS lyocell fibers in the buffer solution of pH 14 notably decreases the tensile modulus but increases elongation.

One modi®ed poly(ethylene terephthalate) (m-PET) containing 16 mol % of isophthalic acid content and three kinds of isotactic polypropylene (i-PP) with different molecular weights were melt blended in various volume ratios by a twin screw extruder. The dynamic viscosity of the i-PP=m-PET blend showed positive deviation at lower volume content of i-PP and negative deviation at higher volume content of i-PP. The size of dispersed phase increased with an increase of the minor component. Also, the less difference between the viscosities of two polymers caused the smaller particle size in the blend and the smaller critical Weber number. After melt spinning of these binary polymer blends, m-PET and i-PP micro staple ®ber, whose diameter was about 0.13 to 2.75 mm, could be obtained by extracting the continuous phase with a proper solvent. The less the minor component in the blend, the better the spinnability of the blended polymers and the physical properties of the ®ber. Also, when i-PP was the continuous phase, the spinnability and the physical properties of the ®bers were better than the opposite case. Molecular weight of i-PP and the blend ratio had a marked in¯uence on the diameter of micro®bers. The micro ®ber obtained from i-PP which has similar viscosity with m-PET showed the smallest diameter than those obtained from other two i-PPs.

Various crimped lyocell fibers are spun from isotropic dopes of cellulose solutions in N-methyl morpholine N-oxide (NMMO) monohydrate with different compositions of hard wood and softwood pulp (IPS lyocell fibers). The physical properties of IPS lyocell fibers treated with NaOH aqueous solutions are compared with those of commercially available Tencel lyocell fibers, which are obtained by anisotropic phase spinning. WAXD reveals that pulp composition has little effect on crystalline structure, and IPS lyocell fibers yield a crystalline structure almost the same as that of Tencel fibers (cellulose II structure). Alkali treatments affect physico-mechanical properties such as compaction and tensile proper ties. Mercerization with 10 wt% NaOH solution causes the largest weight loss and the highest degree of swelling. Lyocell fibers show a notable decrease in tensile strength when treated with strong alkali solutions higher than 7.5 wt%. In addition, IPS lyocell fibers with more softwood content display less reduction in tensile properties after strong alkali treatments.