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The inner and surface morphology of the polyphenylene sulfide membrane could be well optimized by controlling the phase separation during the thermally induced phase separation process.

A type of quick water-responsive shape memory hybrids is fabricated by introducing cellulose nanofibrous mats as the filler in a polymeric matrix. Cellulose nanofibrous mats are obtained through hydrolyzing electrospun cellulose acetate (CA) nanofibers, then casted in thermoplastic polyurethane (TPU) solution to form the hybrids. The quick shape memory behavior of the formed hybrids is demonstrated using dynamic mechanical analysis (DMA) and stress–strain cyclic test. According to a predetermined protocol, the hybrids present desirable shape fixation and recovery, and the elastic modulus (E′) is shown to be responsive promptly and reversibly against drying and wetting cycle. Shape memory mechanism of the hybrids involves the reversible and competitive hydrogen bonds within cellulose before and after water immersion as well as the entropy elasticity of the TPU matrix. This study can pave a way to design novel smart materials by facile methods through incorporating natural nanomaterials as water sensitive fillers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016

Polyoxymethylene (POM) fiber was produced by melt spinning with a high take-up speed, which imposed a strong flow field. An unexpected formation of a shish-kebab morphology with multiple shish of POM fibers was reported for the first time. This morphology is a large-scale shish kebab with a diameter of 10.5 µm. Further orientation of the POM fiber was obtained by hot stretching twice at 160°C. Two crystalline morphology evolution processes were also observed: (i) the process from the large-scale shish-kebab to the deformed small shish-kebab and (ii) the process from the deformed small shish-kebab to the perfect whiskers. Compared with the melt spinning fiber, fiber tensile strength with first and second hot stretching increased by 976% and 1705%, respectively. The crystalline melting behavior of fibers significantly changes after the first and second hot stretching. The flow field induces a large number of extended chain crystals. Copyright © 2014 John Wiley & Sons, Ltd.

A series of polyarylates containing phosphorus (pho-PARs) were synthesized from bisphenol A with different molar ratios of bis-(4-carboxyphenyl) phenyl phosphine oxide (BCPPO) to terephthalic acid (TPA). When the contents of BCPPO are in the range of 0.4–1.0, the pho-PARs are readily soluble in a wide range of organic solvents and have the glass transition temperatures of 243.0–260.4°C. The initial degradation temperatures of these pho-PARs are all above 450°C and their char yields at 800°C under nitrogen atmosphere are in the range of 28.7–33.0%, suggesting they have excellent thermal stability. The results of TG-FTIR and FT-IR show the introduction of BCPPO change the decomposition model of the pho-PARs. The limiting oxygen indexes are at a range of 30.7–34.5%, which suggests that the pho-PARs are a kind of excellent inherent flame retardant materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3521–3529, 2013

In order to reduce the melt temperature (Tm) of the thermotropic crystalline polyarylate and improve its compatibility with poly(ether ether ketone) (PEEK), a series of poly(ether ketone)arylates (PEKARs) containing aryl ether ketone units (AEK) are synthesized through melt transesterification reaction from p-acetoxybenzoic acid, 1,3-bis(4′-carboxylphenoxy)benzene and 4,4′-bis(p-acetoxyphenoxy)benzophenone. The inherent viscosities of these polymers are in the range 0.35–0.81 dL/g. The morphologies and properties of PEKARs are characterized by polarized optical microscopy, wide-angle X-ray diffraction, differential scanning calorimetry, thermal gravimetric analysis, etc. The results show that all PEKARs are semi-crystalline polymers, and the introduction of AEK units can reduce the symmetry of the main chains, leading to decreasing the crystallizability and changing the crystalline form. The PEKARs with AEK less than 30% can exhibit thermotropic liquid crystalline state. The initial and the maximum decomposition temperatures increase with the increase in AEK content. These PEKARs are expected to act as processing agents for PEEK to reduce its processing viscosity. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

To improve the processability and properties of the poly(phenylene sulfide) (PPS) fibers at room temperature and high temperatures, a series of composite fibers based on PPS and multiwalled carbon nanotubes were prepared by melt spinning. We researched the processability with a high-pressure capillary rheometer, and the properties of the composite fibers were investigated in detail by scanning electron microscopy, differential scanning calorimetry, fiber sonic velocity measurement, and single-fiber strength testing. The results show that the carbon nanotubes (CNTs) had good interfacial adhesion with PPS and dispersed homogeneously in the PPS matrix. When the shear rate was higher than 500 s−1, the oriented CNTs induced the orientation of PPS molecular chains; this resulted in a decline in the apparent viscosity and an increase in the orientation degree of the molecular chains. Meanwhile, the CNTs acted as nucleating agents to effectively improve the crystallization of PPS. The strength of the fibers at room temperature were improved by 28.8% after the addition of 0.2% CNTs, and the initial modulus was also significantly enhanced. The strength retention at 160 °C was promoted from 60.58 to 88.32% with the addition of 1.0% CNTs. The shrinking percentage decreased to almost zero from higher than 15%; this suggested that the CNTs could efficiently improve the dimensional stability at high temperatures. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 134, 44609.

To improve the processability of the poly(p-hydroxybenzoic acid), copolyarylates containing m-aryl ether units were synthesized using p-acetoxybenzoic acid, 1,4-diacetoxybenzene and 1,3-bis(4'-carboxyphenoxy)benzene by melt transesterification reaction. The structure and properties of these polyarylates were characterized using infrared spectra, differential scanning calorimetry, thermogravimetric analyses, wide-angle X-ray diffraction and polarized optical microscopy etc. The results showed that all polyarylates were semicrystalline materials and could form a thermotropic liquid crystalline intermediate state. As the content of aryl ether units increased, the crystallization and melting temperatures of the polyarylate decreased; meanwhile, the crystalline ability became lower. The introduction of the aryl ether could restrain the formation of a liquid crystalline structure and reduce the thermal stability to some extent. After solid state polymerization (SSP), the intrinsic viscosity, melting temperature, crystallinity and thermal stability of the polyarylate increased while the melting range narrowed. However, the SSP reaction might be accompanied by degradation and crosslinking.

In order to obtain poly(ether ether ketone)s having enhanced solubility and processability without extreme loss of other properties, a series of copoly(ether ether ketone)s (Co-PEEKs) with pendant phenyl groups were synthesized from 1,1-bi(4-hydroxyphenyl)-1-phenylethane (ph-BPA), hydroquinone and 4,4′-difluorobenzophenone via aromatic nucleophilic substitution reaction. The structures and properties of the Co-PEEKs were characterized using Fourier transform infrared and 1H NMR spectroscopies, differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffraction and solubility testing. These Co-PEEKs have inherent viscosities in the range 0.14–1.09 dL g−1, and their number-average and weight-average molecular weights reach 72 659 and 163 400 g mol−1, respectively. The Co-PEEK with the lowest content of ph-BPA has a semi-crystalline nature and is only soluble in 98% sulfuric acid. However, with an increase of ph-BPA in the Co-PEEKs, they become amorphous and readily soluble in a wide range of organic solvents and can afford tough films. These Co-PEEKs have glass transition temperatures of 137–180 °C depending on the content of ph-BPA. All the Co-PEEKs have initial degradation temperatures above 480 °C in nitrogen atmosphere. Thus, these Co-PEEKs with excellent thermal stability, good solubility and processability have potential for use in high-performance films, coatings, hollow fiber membranes, etc. Copyright © 2011 Society of Chemical Industry

The nonisothermal crystallization kinetics of linear Poly(phenylene sulfide) (PPS) was studied with differential scanning calorimetry. Ozawa theory, Jeziorny model, and Mo equation were applied to describe the crystallization kinetics and to determine the crystallization parameters and mechanism of the linear PPS resin. The crystallization activation energies were also calculated using Kissinger formula and Flynn-Wall-Ozawa equation, respectively. According to the Ozawa model, it is found that instantaneous nucleation takes place during crystallization of PPS; the Ozawa exponent m is 3 in initial stage of crystallization; as the crystallization temperature decreases, the value of m reduces, and the growth rate of crystal almost keeps a constant. The Avrami exponent n obtained from Jeziorny model fluctuate around 1.84. Based on the Jeziorny model, the crystallization rate increases with increasing the cooling rate, but it does not change any longer when the cooling rate rise to a certain value. Mo equation also exhibits great advantages in treating the nonisothermal crystallization kinetics of PPS. The activation energy E of nonisothermal crystallization process of PPS is calculated to be −162.73 kJ/mol by the Kissinger formula, and the mean value of E determined by Flynn-Wall-Ozawa equation is −152.40 kJ/mol. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

A series easily soluble polyarylates were synthesized from either 1,1-bis(4-hydroxyphenyl)-1-phenylethane or tetramethylbisphenol A with various aromatic diacid chlorides by the two-phase interfacial polycondensation. These polyarylates have the inherent viscositiesin the range of 0.36–0.97 dL/g, and their number-average and weight-average molecular weights determined by gel permeation chromatography are 14,200–43,200 and 31,900–102,500, respectively. All these polyarylates are readily soluble in a wide range of organic solvents, thus these polymers can be convenient to process into heat resistance films by cast, spin- or dip-coating. The polyarylates have the glass transition temperatures in the range of 165.0–201.6°C. The pendent phenyl-containing polyarylates reveal excellent thermal stability, and their initial degradation temperatures are all above 480°C and char yields at 700°C are 37.97–40.53% in nitrogen atmosphere. However, the polymers prepared from tetramethylbisphenol A have a large decrease in thermal stability, and their initial degradation temperatures in nitrogen are only about 440°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Acrylic fibers [polyacrylonitrile (PAN) fibers] have excellent flame-retardant properties after they are modified by hydrazine hydrate and metal ions; however, their widespread applications are restricted because of poor mechanical properties. To improve the mechanical properties of these modified PAN fibers, poly(vinyl alcohol) (PVA) was added to the spinning solution of PAN as an effective reinforcing agent. The structure of the fibers before and after modification was studied by Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy, and wide-angle X-ray diffraction. The mechanical properties and flame resistance of the fibers after treatment were also tested by a single-fiber tensile tester and a limiting oxygen index (LOI) analyzer, respectively. We found that the LOI of the modified fibers was reduced from 54.7 to 29.1 after the introduction of 50 wt % PVA; however, the tensile strength was dramatically improved from about 1.50 cN/dtex to more than 4.00 cN/dtex. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43006.

The sodium ions were introduced into the acrylic fibers by post-treating the fibers with hydrazine hydrate and aqueous sodium hydroxide to improve the flame resistance of the fibers. The molecular structure of the modified acrylic fibers was characterized by FTIR spectra. The flame resistance of the acrylic fibers was significantly increased after post-treatment and was relied mostly on the content of sodium ions. The flame-retardant mechanism of the modified fiber was studied in details. The micro calorimeter tests showed that the total heat release and the peak heat release rate were largely reduced after post-treatment. Photographs of the char residues and the results of TGA and TG-IR technique revealed that the flame retardance of the modified acrylic fiber was provided through the combination effect of the gas phase and condensed phase. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41996.

A series of composite fibers based on poly(ether ether ketone)s (PEEK) and a thermotropic liquid crystalline poly(ether ketone)arylates (PEKAR) have been prepared by melt spinning. The structure, compatibility, and properties of these composite fibers were investigated in detail by rheological measurements, differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffraction, scanning electron microscopy, orientation degree test, and mechanical properties test. The results showed that the addition of PEKAR could reduce the apparent melt viscosity of the blends obviously, which is beneficial in improving the processibility of PEEK at a relatively low temperature. After adding 1 wt % PEKAR to PEEK, the tensile strength of the post-treatment fiber improved by 8.8%, whereas the crystallinity of the as-spun fiber increased from 21.76% to 31.51%, and the orientation degree also increased with the addition of PEKAR. The result of morphology research suggested that PEKAR had a good compatibility with PEEK resin. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40595.

To improve the paper properties of the poly(1,3,4-oxadiazoles) (POD), the POD pulps were prepared by prechemical and mechanical methods to increase their polarity, contact area, and interaction. The fibrillated degree of the staple fibers was evaluated by the Canadian Standard Freeness and the specific surface area, while the surface free energy was calculated by the Micro–wilhelmy method. Meanwhile, the functional groups and compositions on the surface of the POD fibers were confirmed by the FTIR–ATR and the X-ray photoelectron spectroscopy, and the surface morphological structure and the crystalline structure of the POD fibers were observed by the fiber analyzer, scanning electron microscope, and Wide-angle X-ray diffraction, respectively. It was found that the pronounced abrasive and distinctive grooves were formed on the surface of the POD fibers after prechemical and mechanical treatment. The surface free energy of POD fibers increased 8.41%, and the polar part increased by 32.10% after treatment. It was confirmed that the polar functional groups and fibril were formed after chemical and mechanical treatment, so the interaction of the POD fibers was highly enhanced, and as a result the apparent density, tensile strength, fold endurance, and tear strength of the paper formed by those treated fibers were all improved apparently. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39818.