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Melt spinning of graphene nanoplatelets (GnPs)‐polypropylene (PP) nanocomposite fibers are reported for the first time. PP/GnPs fibers were spun with a pilot‐plant spinning machine with varying concentration of GnPs by mixing PP/GnPs masterbatch with PP. The effect of inclusion of GnPs on the morphology and crystalline structure of PP fibers was investigated. The thermal stability of the fibers was also evaluated by thermogravimetric analysis. The light microscopy images showed that the GnPs are uniformly distributed over the PP matrix. The differential scanning calorimetry (DSC) results revealed that presence of GnPs affects both the melting and crystallization behaviors. The melting peaks of PP/GnPs nanocomposite fibers were broader than that of neat PP fibers, indicating a broader crystal size distribution in PP/GnPs nanocomposite fibers as compared to the neat PP fibers. Besides, an obvious increment in the crystallization peak temperature was observed in GnPs‐PP nanocomposite fibers. The wide‐angle X‐ray diffraction spectra (WAXD) results showed that the crystal type of nanocomposite fibers did not change and was still the α‐monoclinic crystal form. Moreover, the morphology of spherulites demonstrated that GnPs increased the nucleation sites in the nanocomposite fibers which in turn restricted the crystal growth of PP chains. This finding supported the DSC and WAXD results. Activation energies were calculated by Horowitz and Metzger's method as 77.87 and 105.41 kJ/mol for neat PP and PP/0.2 wt% GnPs fibers, respectively, suggesting an increase in the thermal stability of GnPs‐PP nanocomposite fibers. POLYM. COMPOS., 36:367–375, 2015. © 2014 Society of Plastics Engineers

Twisted nylon 6 nanofibre yarns containing microencapsulated phase change materials (MPCMs) were fabricated via electrospinning to prepare thermal regulating nanofibre yarns. Electrospun nanofibre yarns with different contents of MPCMs including 0.375, 0.75, 1.5 and 3 wt% were prepared. The surface morphology, crystallisation and thermal properties of the yarn samples were characterised by scanning electron microscopy (SEM) and differential scanning calorimetry, respectively. SEM results showed that electrospun composite fibres and yarns had good morphology with smooth surface and the MPCMs were randomly distributed on the composite yarn surface, inside the nanofibres and between the fibres in the yarn structure. Additionally, the SEM results suggested that the average diameters of nylon 6/MPCM nanofibres decreased from 0.23 § 0.03 mm for neat nylon 6 to a minimum of 0.10 § 0.02 mm for composite yarn containing 3 wt% MPCM. However, nylon 6/MPCM nanofibre yarn diameter displayed a complex behaviour; the average diameters of electrospun composite yarns increased upon addition of MPCM and reached a maximum value of 165.1 § 5.11 mm for composite yarn containing 0.75 wt% MPCM, then decreased markedly. These changes in nylon 6/MPCM nanofibres and yarn diameters have been discussed in terms of electrospinning solution properties and twist parameter. The melting enthalpy values of MPCM in the composite nanofibre yarns increased as the content of MPCMs increased up to the highest content and higher than 80% of the heat storage capacity of MPCMs was retained after electrospinning.

In the present work, effect of selective peroxide on reactor grade polypropylene (PP) (known as V30S) during melt spinning process on the physical and thermal properties of as-spun resultant multifilament yarn was studied. Attempts have also been made to compare this yarn sample with other fiber samples produced from reactor and controlled rheology grades polypropylene. The results show that the multifilament yarn spun from V30S/Peroxide sample shows higher birefringence and tensile strength and also lower modulus, elongation at break, and shrinkage compared with that of spun from pure V30S granule. Density and thermal behavior studies show low variations compared with original sample.

In this work, mechanical and structural parameters related to the optical properties of polyethylene terephthalate (PET) fibers drawn at hot multistage have been investigated. The changes in optical parameters upon changing draw ratio are used to obtain the mechanical orientation factors

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, various orientation functions f 2 (θ), f 4 (θ) and f 6 (θ), and amorphous and crystalline orientation functions (f a and f c ). Also, the numbers of random links between the network junction points (N 1 ), the average optical orientation (F av ), and the distribution function of segment ω(cos θ) were calculated. In addition, an empirical formula was suggested to correlate changes in the birefringence with the draw ratio and its constants were determined. The study demonstrated change on the molecular orientation functions and structural parameters upon hot multistage drawing. Significant variations in the characteristic properties of the drawn PET fibers were due to reorientation of the molecules caused by applied heat and external tension.