Thermal characteristics of poly(ethylene terephthalate) fiber grafted with poly(vinyl acetate) and poly(vinyl alcohol)

Poly(ethylene terephthalate) (PET) fibers were grafted with poly(vinyl acetate) (PVAc) and poly(vinyl alcohol) (PVA). The effects of graft copolymers PVAc and PVA on morphological properties of PET were evaluated by differential thermal analysis, differential scanning calorimetry, and thermogravimetric analysis. Melting temperature, heat of fusion, and mass fractional crystallinity of PET was not affected by graft PVAc and PVA. No individual glass transition and melting points corresponding to the graft PVAc and PVA were observed, indicating thereby that graft copolymer mainly exists in the form of free chains inside the PET matrix. Poly(vinyl alcohol) graft copolymer degraded at much lower temperatures than poly(vinyl alcohol) in powder form. Thermal stability of PET fiber was not affected by graft PVAc, where as PET–g–PVA showed an additional degradation point at 360°C.     

Surface and adhesion properties of poly(ethylene glycol) on polyester(polyethylene terephthalate) fabric surface: Effect of air‐atmospheric plasma treatment

The surface and adhesion properties of different molecular weight poly(ethylene glycol) (PEG) (400, 1500, and 3000 g/mol) on untreated and air‐atmospheric plasma‐treated PET woven fabrics were studied, with the aim of developing durable hydrophilic PET fibrous structures. PEG application was carried out by padding of the PET fabric in aqueous solution of PEG followed by curing and drying. The surface properties of the PEG‐coated PET fabrics were then characterized using wicking test to measure the water contact angle (θ°) and capillary weight (W_c), and using atomic force microscopy (AFM) images in the tapping mode. Results showed that without a prior air‐atmospheric plasma treatment of the PET fabric, the water contact angle decreased and capillary weight increased with the three PEGs, implying an increase in the hydrophilicity of both inner and outer PET fabric fiber surface. Air‐plasma treatment of the PET fabrics before PEG coating increases further the hydrophilicity of the inner fabric fiber surface: the capillary weight was almost doubled in the case of the three PEGs. Best results were obtained with PEG 1500: water contact angle decreasing from 82° to 51°, and the capillary weight increasing from 11 mg to 134 mg. Moreover, wash fastness test at room temperature and at 80°C confirms improved adhesion of PEG‐1500 to the plasma‐treated PET woven fabric surface, while under the same conditions the plasma‐treated PET without PEG loses completely its hydrophilic character. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Sorption of dye wastes by poly(vinyl alcohol)/poly(carboxymethyl cellulose) blend grafted through a radiation method

The instability in water of poly(vinyl alcohol) (PVA)/poly(carboxymethyl cellulose) (CMC) was improved through radiation-induced grafting with a styrene monomer. The PVA/CMC blend graft copolymer was used as a sorbent for dye wastes normally released from textile factories. The factors that may affect the sorption process such as time, temperature, weight of the blend graft copolymer, and volume of the dye waste were investigated. The sorption of dyestuffs by the blend graft copolymer was determined by a method based on spectroscopic analysis. The results showed that the blend graft copolymer has a high affinity for basic, acid, and reactive dyes. Meanwhile, it was observed that the sorption of dyes is more effective at the high temperature of 70^oC. Moreover, it was found that the sorption of dyes depends on the weight of the blend graft copolymer and does not depend on the volume of the waste solution. The sorption of the dyestuffs by a PVA/CMC graft copolymer may be considered to be a practical method to remove organic pollutants. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 136–142, 2001     

Oleophilic modification of poly(vinyl alcohol) films by functionalized soybean oil triglycerides

In this study, maleinized (SOMAP) and isocyanated soybean oil (SONCO) triglycerides have been successfully grafted onto one surface of poly(vinyl alcohol)(PVA) films to give films that are hydrophilic on one side and hydrophobic on the other. The surface grafting was accomplished by the reaction of succinic anhydride or isocyanate functionalities of soybean oil derivatives and the hydroxyl groups of PVA films. The reaction was run in toluene, using PVA films on glass slides so that only one side of the film was accessible. After grafting, the films were rinsed with hot toluene to remove ungrafted triglycerides from the surface. The reaction on the surface was confirmed by ATR‐FTIR and ¹H‐NMR spectroscopic techniques. A series of films were prepared at different concentrations of SOMAP or SONCO in toluene. The increase in hydrophobicity with an increase in SOMAP or SONCO concentrations was observed by water contact angle measurements. The contact angles on the grafted side of the film reach their maximum value of 88° and 94° for 26 and 2.5% SOMAP and SONCO concentrations in toluene, respectively, while the ungrafted side gives contact angle of 48°. Surface morphologies of PVA‐g‐SOMAP and PVA‐g‐SONCO films were investigated by atomic force microscopy, whereas optical microscopy and staining was used to determine the homogeneity of the films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Solid‐state grafting of succinic anhydride onto poly(vinyl alcohol)

The graft reaction of succinic anhydride onto poly(vinyl alcohol) (PVA) was catalyzed by p‐toluenesulfonic acid monohydrate in solid state. The infrared spectra and ¹H‐NMR spectra confirmed that succinic anhydride was successfully grafted onto PVA backbone. The influences of reaction temperature, reaction time, the amount of succinic anhydride, and the amount of catalyst on the graft reaction were studied. Uncrosslinked PVA graft copolymer with grafting degree up to about 6.5% could be obtained under low reaction temperature, short reaction time, and low amount of catalyst, whereas crosslinked PVA with high gel content could be obtained under high reaction temperature, long reaction time, and high amount of catalyst. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 848–852, 2007     

Revisiting the thermal relaxations of poly(vinyl alcohol)

The molecular dynamics of poly(vinyl alcohol) (PVA) were studied by dielectric spectroscopy and dynamic mechanical analysis in the 20–300°C range. The well-established plasticizing effect of water on the glass-transition temperature (T_g) of PVA was revisited. Improper water elimination analysis has led to a misinterpretation of thermal relaxations in PVA such that a depressed T_g for wet PVA films (ca. 40°C) has been assigned as a secondary β relaxation in a number of previous studies in the literature. In wet PVA samples, two different Vogel–Fulcher–Tammann behaviors separated by the moisture evaporation region (from 80 to 120°C) are observed in the low- (from 20 to 80°C) and high- (>120°C) temperature ranges. Previously, these two regions were erroneously assigned to two Arrhenius-type relaxations. However, once the moisture was properly eliminated, a single non-Arrhenius α relaxation was clearly observed. X-ray diffraction analysis revealed that the crystalline volume fraction was almost constant up to 80°C. However, the crystallinity increased approximately 11% when temperature increased to 180°C. A secondary β_c relaxation was observed at 140°C and was related to a change in the crystalline volume fraction, as previously reported. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Swelling kinetics of modified poly(vinyl alcohol) hydrogels

Interpenetrating polymer network (IPN) hydrogels composed of poly(vinyl alcohol) (PVA) and monomer, N‐isopropylacrylamide (NIPAAm), diallyldimethylammonium chloride (DADMAC), or methacrylic acid (MAA) were prepared by using the sequential‐IPN method. The equilibrium swelling ratios of PVA/NIPAAm (VANP), PVA/DADMAC (VADC), and PVA/MAA (VAMA) are 412, 370, and 297 at 25°C, respectively. VANP had the highest swelling ratio in time‐dependent swelling behavior, whereas the swelling ratio of VAMA had the lowest. The n values of VANP, VADC, and VAMA are 0.72, 0.81, and 0.96, respectively. Transport of all IPN hydrogels is anomalous and their transport mechanisms are dominated by a combination of diffusion‐controlled and relaxation‐controlled systems. VAMA has the highest activation energy and VANP has the lowest activation energy. The values of all IPN hydrogels are from 4.66 to 16.49 kJ/mol, which proves that all IPN hydrogels are hydrophilic. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3310–3313, 2003     

Structure and properties of hydrophobic cationic poly(vinyl alcohol)

A new class of derivatives of poly(vinyl alcohol) (PVA) was prepared through hydrophobic cationic modification. The structure and composition of PVA grafted with glycidyl‐N‐alkyl‐N,N‐dimethyl‐ammonium chloride (DA) (PVA‐ graft ‐DA) was confirmed with Fourier transform infrared spectral analysis and ¹H NMR spectral analysis. The stress‐strain curves of PVA‐ graft ‐DA samples all exhibited an elastic deformation stress plateau, and strain hardening behavior can be observed, indicating the transition of PVA from brittle fracture to ductile fracture. Compared with virgin PVA, the relaxation peak (T_g) of PVA‐ graft ‐DA shifted to a lower temperature. With increasing alkyl chain length and grafting ratio of DA, T_g decreased, and PVA‐ graft ‐DA exhibited a gradually decreasing storage modulus over the whole temperature range of testing due to the relatively weak intermolecular hydrogen bonding and increasing flexibility of molecular chains by introduction of long alkyl chains. PVA crystallites were not affected by grafting with DA, while the crystallization temperature and crystallinity of PVA were improved and the grain size decreased. On grafting with DA, the fracture surface of PVA changed from a smooth surface to regularly distanced striations, displaying much obvious character of tough fracture, indicating that appropriate intermolecular association of the hydrophobic groups facilitated the formation of physical entanglement of molecular chains to strengthen and toughen the PVA matrix. PVA‐ graft ‐DA showed a significant decreasing surface tension with polymer concentration, while the surface tension of PVA‐ graft ‐DA12 dropped most dramatically and declined with increasing grafting ratio of DA12, indicating improvement of the surface activity of PVA by introduction of hydrophobic alkyl chains and hydrophilic cationic groups. Copyright © 2011 Society of Chemical Industry     

Synthesis,characterization, and swelling behavior of poly(N-hydroxymethylacrylamide) grafted poly(vinyl alcohol)

In this study, the graft copolymerization of N-hydroxymethylacrylamide (NHMAAm) with poly(vinyl alcohol) (PVA) was carried out by using potassium persulfate/N,N,N,N-tetramethylethylenediamine (K₂S₂O₈) to improve physicochemical properties and functionality of PVA. The structures of PVA-g-poly-NHMAAm (PNHMAAm) copolymers were characterized by Fourier transform infrared, elemental analysis, nuclear magnetic resonance (¹H-NMR), ¹³C-NMR, and size exclusion chromatography. Their thermal behaviors were investigated by differential scanning calorimetry and thermogravimetric analysis (TGA). The TGA results indicated that the graft copolymers show better thermal stability then PVA. The effects of reaction time, temperature, NHMAAm, and K₂S₂O₈ concentrations on grafting parameters were examined. The maximum grafting yield (34.01%) was provided when reaction was carried out under optimum conditions (time = 2 hr, T = 40°C, [NHMAAm] = 0.25 M, [K₂S₂O₈] = 4.56 × 10⁻³ M). Moreover, PVA-g-PNHMAAm membranes were prepared and their swelling behaviors were studied. The results demonstrated that swelling degree of graft membranes increased almost 3.5-fold compared to PVA membrane.     

Synthesis,characterization, flocculation,and rheological characteristics of hydrolyzed and unhydrolyzed polyacrylamide‐grafted poly(vinyl alcohol)

Graft copolymers of poly(vinyl alcohol) and polyacrylamide (PVA‐g‐PAM) were synthesized using a ceric ion–induced solution polymerization technique at 28°C. Three grades of graft copolymers were synthesized with varying acrylamide concentrations. Three grades of hydrolyzed products of PVA‐g‐PAM were synthesized with varying concentrations of sodium hydroxide solution. Hydrolyzed and unhydrolyzed PVA‐g‐PAM were characterized by viscometry, X‐ray diffractometry, infrared spectroscopy, and thermal analysis. Rheological investigation was also carried out on the aqueous solutions of various samples. The flocculation characteristics of various materials were investigated by the use of jar and settling tests in 0.25 and 5 wt %, respectively, using kaolin and iron ore suspensions. Among the series of graft copolymers, the one with fewest but longest PAM chains showed superior performance. The flocculation characteristics of the best‐performing graft copolymer were compared with those of various commercially available flocculants in the two suspensions under investigation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2109–2122, 2006     

Modification of polypropylene through intercrosslinking graft copolymerization of poly(vinyl alcohol): Synthesis and characterization

Modification of polypropylene (PP) has been successfully carried out through intercrosslinking of poly(vinyl alcohol) (PVA), by chemical graft copolymerization method using benzoyl peroxide (BPO) as radical initiator. Prior to grafting, PP was irradiated by gamma rays at a constant dose rate of 3.40 kGy/h to introduce hydroperoxide groups. Optimum conditions pertaining to maximum percentage of grafting were evaluated as a function of different reaction parameters. Maximum percentage ofgrafting of PVA (75%) was obtained at [BPO] = 5.51 × 10^?2 mol/L in 120 min at 70°C using 15 mL of water. Characterization of pristine PP and PP‐g‐PVA was carried out by FTIR, thermogravimetric analysis, and scanning electron micrography. Swelling studies were carried out in pure, binary, ternary, and quaternary solvent systems comprising of water, ethanol (EtOH), dimethylsulfoxide (DMSO) and N, N‐dimethylformamide (DMF) in different ratios. Maximum swelling values of PP‐g‐PVA (both composite and true graft) was observed in pure DMSO followed by DMF, EtOH, and water and it was also higher than that observed in mixed solvent system. Water retention studies of pristine PP and PP‐g‐PVA (both composite and true graft) were investigated at different time periods, temperature, and pH. Maximum % water retention of PP‐g‐PVA (composite) (108%) was observed in 8 h at 50°C in neutral medium (pH = 7). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Heterogeneous formalization of poly(vinyl alcohol)

The distributions of formaldehyde content from the surface to the inner part of poly(vinyl alcohol) (PVA) films formalized in a aqueous solution of sodium chloride and in a methanol/water mixture both containing formaldehyde and hydrochloric acid were investigated using rolled films. The formaldehyde content at the surface was higher than that in the inner part. When the PVA film was formalized in such a reaction condition that the rate of formalization was fast, a PVA film of high formaldehyde content at the surface and of large difference in the formaldehyde content between the surface and the inner part was prepared. Assuming that the formalization occurs in proportion to the amount of diffusing solution for formalization and that the diffusion obeys the FICK'S Law, the diffusion coefficients of the solution for formalization were estimated from the distribution of the formaldehyde content to be about 1.8 × 10^?6 cm²/min at 50°C for the methanol solution containing 5% formaldehyde, 18.1% water and 5% hydrochloric acid and 1.7% × 10^?6cm²/min at 50°C for an aqueous solution containing 1% formaldehyde, 10% sodium chloride and 5% hydrochloric acid.     

Tribological properties of PBO fabric composites modified by poly (vinyl alcohol)

Friction and wear behaviors of poly (vinyl alcohol) (PVA) modified PBO fabric composites were evaluated in a pin‐on‐disc friction and wear tester, and the relationship between the properties and the structure change resulting from PVA modification were intensively investigated using thermogravimetric analysis (TG) and scanning electronic microscope (SEM) equipped with an energy dispersive spectrometer (EDS). The results indicated that the PVA thin film formed on the fabric surface by chemical crosslinking reaction could improve the antiwear property of the PBO fabric composites efficiently. In argon‐300°C condition, the antiwear property of the PBO fabric composites was improved by 35%, which was due to the improvement of the bonding strength between the fabric and resin and the dispersion of the shear stress induced by the shear creep and plastic deformation of the PVA film in friction. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1313‐1320, 2013     

Characterization of poly(vinyl alcohol)

Molecular weight distributions, long chain branching frequency, and solution viscosities of samples of commercial poly(vinyl alcohol) (PVA) are reported. The PVA was fully reacetylated to poly(vinyl acetate) (PVAc) for characterizations by size exclusion chromatography using a low angle light scattering detector. The Mark–Houwink constants for PVAc in toluene were determined to be K = 0.106 cm³ g^?1 and α = 0.59, at 25°C. Long chain branching frequency in the commercial PVAs studied was small and was little affected by polymer molecular weight. Some 95% or more of the branches in these species were short. Aqueous solutions at 10% (w/v) of PVA were Newtonian. The polymers examined differed in chemical composition, molecular weight distributions, and mean block lengths of vinyl acetate residues. Variations in a single characteristic, like a solution or intrinsic viscosity, cannot be used to deduce structural differences between PVAs.     

Grafting of poly(vinyl alcohol) on natural rubber latex particles

Poly(vinyl alcohol) (PVA) was grafted on natural rubber (NR) latex particles (NR‐g‐PVA) using potassium persulfate to generate active radicals on both NR particle surface as well as PVA molecules. ¹H‐ and ¹³C‐nuclear magnetic resonance spectroscopy suggested a possibly chemical attachment of PVA on the NR. The amount of graft‐PVA expressed in term of grafting percentage (%G) increased almost linearly with the amount of PVA adding to the NR latex. Measuring by dynamic light scattering, the particle size of NR‐g‐PVA particles was larger than the size of unmodified NR, also it increased with the molecular weight and %G of PVA. Transmission electron microscopy images of the NR‐g‐PVA latex particles revealed that the size of PVA‐grafted NR particle was enlarged by a layer of graft‐PVA surrounding the NR particle. Given by the graft‐PVA layer surrounding NR particles, the NR‐g‐PVA latex particles possessed better colloidal stability as lowering pH compared with the unmodified NR latex. Comparing with unmodified NR particles, the electrophoretic mobility of NR‐g‐PVA particles was lower due to the presence of graft‐PVA that shifted the shear plane further away from the surface of the particles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Viscometric and conductometric studies of poly(vinyl alcohol)-g-polyacrylamide composites

Poly(vinyl alcohol)-g-polyacrylamide composites have been prepared by γ-radiation-initiated polymerization of acrylamide (AAm) in the presence of poly(vinyl alcohol) (PVA) in aqueous medium by the mutual method in air. Percentage conversion of AAm has been studied as a function of total dose, monomer concentration, and amount of water. Optimum conditions leading to maximum percent conversion of the monomer to give the composite have been evaluated. The products of polymerization of AAm in the presence of PVA consisted of unreacted PVA, the graft copolymer, PVA-g-PAAm, and the homopolymer polyacrylamide, PAAm, and this mixture is referred to as PVA-g-PAAm composite. AAm was also polymerized in the absence of PVA under similar conditions, and optimum conditions leading to maximum conversion of AAm to PAAm have been evaluated. A comparative study of the polyelectrolytic behavior of PVA, PAAm, and the composite has been made by viscometric and conductometric methods. © 1995 John Wiley & Sons, Inc.     

Crystallization kinetics of poly(vinyl alcohol)

The kinetics of crystallization of solvent-free poly(vinyl alcohol) were investigated by isothermal crystallization at temperatures of 142–192°C, for up to 18 min. The crystallization isotherms were analyzed by Avrami's theory. The magnitude of the exponent n was almost constant (0.67–0.71) in the range of 142–182°C, increasing to 1.53 for crystallization at 192°C. Based on thermodynamic analysis of the isotherms and the crystallite growth rate, there are strong indications that crystallization of PVA is one-dimensional. In the absence of water or other swelling agents, kinetic hindrances predominate due to the interactions of the hydroxyl groups. Therefore, the maximum attainable weight fraction of crystallized PVA is considerably lower than that of hydrated PVA samples. Additional parameters affecting the growth rate are discussed, including the degree of undercooling and the average chain length, as controlled by crosslinking.     

Thermoresponsive and biocompatible poly(vinyl alcohol)‐graft‐poly(N,N‐diethylacrylamide) copolymer: Microwave‐assisted synthesis,characterization, and swelling behavior

Novel thermoresponsive poly(vinyl alcohol)‐graft‐poly(N,N‐diethylacrylamide) (PVA‐g‐PDEAAm) copolymers were prepared by microwave‐assisted graft copolymerization using a potassium persulfate/N,N,N′,N′‐tetramethylethylenediamine (KPS/TEMED) initiator system. The structures of PVA‐g‐PDEAAm copolymers were characterized by ¹H‐NMR, Fourier transform infrared spectroscopy, differential scanning calorimetry/thermogravimetric analysis, gel permeation chromatography, X‐ray diffraction, and scanning electron microscopy. The effects of various process parameters on grafting were systematically studied: microwave power, KPS, monomer and PVA concentrations, and ultraviolet irradiation. Under optimal conditions, the maximum grafting percent and graft efficiency were 101% and 93%, respectively. Furthermore, a lower critical temperature of copolymers was measured in the range 29–31 °C by ultraviolet spectroscopy. The swelling behavior of graft membranes was carried out at various temperatures, and the results showed that the swelling behavior of membranes was dependent on the temperature. In vitro cell culture studies using L929 fibroblast cells confirmed cell compatibility with the PVA‐g‐PDEAAm copolymer and its membrane, making them an attractive candidate for drug delivery systems. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45969.     

Preparation of poly(vinyl alcohol)-graft-N-isopropylacrylamide copolymer membranes and permeation of solutes through the membranes

Thermosensitive copolymers were prepared by graft copolymerization of N-isopropylacrylamide onto poly(vinyl alcohol) in dimethyl sulfoxide (DMSO) using potassium peroxodisulfate as an initiator. The phase transition temperature was measured by differential scanning calorimetry. The copolymers exhibited almost the same transition temperature (about 33°C) as that of poly(N-isopropylacrylamide) regardless of the composition of the copolymers. The copolymer membranes were obtained by evaporating solvent from the DMSO solution of the graft copolymers and were insolubilized by annealing the membranes at 120°C for 10 h. Permeation of the lithium ion and Methylene Blue through the membranes was investigated at various temperatures. The permeation of solutes was greatly affected by temperature, i.e., the permeation of the solutes could be controlled at temperatures below and above 33°C. © 1994 John Wiley & Sons, Inc.     

Solid state grafting copolymerization of acrylamide onto poly(vinyl alcohol) initiated by redox system

A solid state grafting copolymerization of acrylamide (AM) onto poly(vinyl alcohol) (PVA) was conducted with ammonium persulfate and sodium bisulfite redox system as initiators. Before the reaction the PVA powder and required amount of AM were mixed evenly, and sprayed with water to swell the PVA powder and to dissolve AM. Then the swollen PVA powder was sprayed with the redox solution, and the reaction temperature was controlled at a temperature between 30°C and 80°C for 120 min. The grafting percentage and efficiency were determined as functions of monomer/PVA ratio, initiator concentration and reaction temperature. The structure and performance of the graft copolymers were confirmed by FTIR‐ATR, XRD, ¹³C NMR, and thermogravimetric analysis, together with mechanical property and apparent viscosity measurements. It has been confirmed that grafting copolymerization of AM onto PVA initiated by this redox system occurred with higher grafting percentage and efficiency in the solid state. The thermal stability and water‐solubility of grafted PVA were found to be better than those of unmodified PVA. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39938.