Thermal and structural properties of poly(vinyl alcohol) doped with hydroxypropyl cellulose

The growth and importance of medical and related health care and hygiene textile sectors are attributed to the improvement and innovations in both textile technology and medical procedures. The aim of this study was to examine some of the structural properties of pure poly(vinyl alcohol) (PVA) and hydroxypropyl cellulose (HPC) doped PVA of different weight percentages. This will lead to the choice of the optimum conditions suited for specific medical and surgical applications for which textile materials are currently used. Thermogravimetry was used to develop an instrumental system for the study of thermal stability and for identification of the individual components of several polymer blends. Derivative thermogravimetry provided clear information and distinguished between different generic types. Also, differential scanning calorimetry and its derivatives gave accurate values of glass‐transition temperature and melting temperature and gave detailed features of the steps of weight loss and changes in the heat of fusion. The X‐ray diffraction technique was used to determine the crystallinity/amorphosity ratio and the change in crystallite size at different dopant concentrations. The effect of doping with HPC on PVA structure was studied with spectrophotometric analyses. Variations in the group coordination in the IR region were followed. The data obtained indicated that measurable and remarkable changes in the thermal stability of PVA occurred at different doping concentrations. This may have been because the diffusion of dopant caused structural changes in the polymer matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1914–1923, 2005     

Thermal and spectroscopic studies of poly(N‐vinyl pyrrolidone)/poly(vinyl alcohol) blend films

Poly(N‐vinyl pyrrolidone) (PVP) and poly (vinyl alcohol) (PVA) homopolymers and their blended samples with different compositions were prepared using cast technique and subjected to X‐ray diffraction (XRD) measurements, infrared (IR) spectroscopy, ultraviolet/visible spectroscopy, and thermogravimetric analysis (TGA). XRD patterns of homopolymers and their blended samples indicated that blending amorphous materials, such as PVP, with semicrystalline polymer, such as PVA, gives rise to an amorphous structure with two halo peaks at positions identical to those found in pure PVP. Identification of structure and assignments of the most evident IR ‐ absorption bands of PVP and PVA as well as their blends in the range 400–2000 cm^?1 were studied. UV–vis spectra were used to study absorption spectra and estimate the values of absorption edge, E_g, and band tail, E_e, for all samples. Making use of Coats‐Redfern relation, thermogravimetric (TG) data allowed the calculation of the values of some thermodynamic parameters, such as activation energy E, entropy ΔS^#, enthalpy ΔH, and free energy of activation ΔG^# for different decomposition steps in the samples under investigation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Structural properties of CrF3‐ and MnCl2‐filled poly(vinylalcohol) films

Poly(vinylalcohol) (PVA) films filled with different filling levels of CrF₃ and MnCl₂ have been prepared by the casting method. Differential scanning calorimetry (DSC) and X‐ray diffraction (XRD) analysis were used to study the changes in structure properties that occur due to filling. The changes occurring in the measured parameters with increasing the filler content was been interpreted in terms of the structural modification of the PVA matrix. It was found that all studied samples had the main melting temperature due to the main crystalline phase of PVA. The intensity and position of this peak depended on the filling level. On the other hand, the samples of CrF₃‐filled PVA films with filling level W ≥ 10 wt % revealed another melting temperature, indicating the presence of a new crystalline phase besides the main crystalline phase. Changes occurring in the degree of crystallinity of the studied samples were discussed. The calculated degree of crystallinity was formulated numerically to be an exponential function of filling level. The X‐ray diffraction patterns of the studied samples confirmed the DSC results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 516–521, 2003     

Influence of apple flavor absorption on physical and mechanical properties of poly(ethylene terephthalate) films

Poly(ethylene terephthalate) (PET) films (280‐μm film thickness), which are used in food packaging, were immersed into 160‐ and 320‐ppm apple flavor solution for 14, 28, and 56 days at 5, 25, and 40°C, respectively. At the end of this period, the changes in the PET films were investigated by measuring the mechanical and physical properties. The mechanical properties were determined by examining changes in the Young's modulus. The changes in the physical properties were investigated by Fourier transform IR spectroscopy and scanning electron microscopy (SEM). The formation of microcracks in the structure of PET films was observed by SEM. According to the results of those investigations, the apple flavor affects PET films, even at very low concentrations and temperatures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1802–1807, 2006     

Properties of branched and network poly(vinyl alcohols) prepared with poly(vinyl alcohol) having aldehyde groups at the chain ends

Branched and network poly(vinyl alcohols) (PVAs) were prepared with inter-acetalization of the PVA with aldehyde groups at the chain ends which was prepared by the cleavage of 1,2 glycol bonds in commercial PVA. The numbers of branches estimated from molecular weights were compared with those estimated by theory. Huggins' constant and crystallinity decreased with increasing branch number. Dissolution of branched PVAs into dimethylsulphoxide was not so easy compared with commercial PVA. The colour of branched PVA–iodine complex decreased rapidly with standing while that of commercial PVA decreased gradually. Network PVAs with Young's modulus of 1–8 MPa were prepared.     

Structural properties of CrF3‐ and MnCl2‐filled poly(vinyl alcohol) films

Poly(vinyl alcohol) (PVA) films filled with different amounts of CrF₃ and MnCl₂ were prepared by the casting method. Differential scanning calorimetry (DSC) and X‐ray diffraction (XRD) analysis were used to study the changes in the structure properties that occurred because of filling. The changes occurring in the measured parameters with increasing filler contents were interpreted in terms of the structural modification of the PVA matrix. All the studied samples had a main melting temperature due to the main crystalline phase of PVA. The intensity and position of this peak depended on the filling level. However, the samples of CrF₃‐filled PVA films with a filling level greater than or equal to 10 wt % revealed another melting temperature, which indicated the presence of a new crystalline phase in addition to the main crystalline phase. The changes that occurred in the degree of crystallinity of the studied samples were examined. The calculated degree of crystallinity was formulated numerically to be an exponential function of the filling level. The XRD patterns of the studied samples confirmed the DSC results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1115–1120, 2003     

Interpolymer associations between poly(vinyl alcohol) and poly(diallyldimethylammonium chloride) in aqueous dilute solution

This article studied the compatibility of poly(vinyl alcohol) (PVA) with poly(diallyldimethylammonium chloride) (PDADMACl) in a dilute aqueous solution. At a total mixture concentration and a constant molecular weight of PDADMACl, it was found that interpolymer associations increase with the molecular weight and decrease with the degree of hydrolysis of the PVA sample (87–89 and 98–99%). From these results, it can be deduced that the compatibility of PVA and PDADMACl is due to specific intermolecular interactions that could be assigned mainly to electrostatic interactions between hydroxyl groups within PVA chains and ion atoms within PDADMACl. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 433–435, 2002     

Thermal characteristics of poly(vinyl alcohol) and poly(vinylpyrrolidone) IPNs

Interpenetrating polymer network (IPN) hydrogels based on poly(vinyl alcohol) (PVA) and 1‐vinyl‐2‐pyrrolidone (VP) were prepared by radical polymerization using 2,2‐dimethyl‐2‐phenylacetophenone (DMPAP) and methylene bisacrylicamide (MBAAm) as initiator and crosslinker, respectively. The thermal characterization of the IPNs was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dielectric analysis (DEA). Depressions of the melting temperatures of PVA segments in IPNs were observed with increasing VP content via the DSC. The DEA was employed to ascertain the glass transition temperature (T_g) of IPNs. From the result of DEA, IPNs exhibited two T_gs indicating the presence of phase separation in the IPN. The thermal decomposition of IPNs was investigated using TGA and appeared at near 270°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1844–1847, 2002     

The influence of poly(vinyl alcohol) suspending agents on suspension poly(vinyl chloride) morphology

The requirements for PVC suspension resin have changed considerably in the last few years, so much so that few companies have products on their ranges that are more than 4 or 5 years old. The suspending agent has a crucial influence on the morphology of the resin, so the changes in resin characteristics have largely been achieved by changes in the suspending agent systems. After a brief review of the mechanism of PVC suspension polymerisation, the properties of polymers made using PVOH suspending agents are related to changes in the latter. The effect of variations in PVAc degree of hydrolysis and viscosity are related to changes in surface tension. Methods of achieving higher porosity by using low hydrolysis co-suspending agents are described. It is shown that higher bulk densities can be achieved by delayed addition of the PVOH. Levels of conjugated unsaturation and copolymer distributions are also shown to have important influences.     

Preparation and properties of poly(vinyl alcohol)-clay nanocomposite materials

A series of polymer-clay nanocomposite (PCN) materials that consist of poly(vinyl alcohol) (PVA) and layered montmorillonite (MMT) clay are prepared by effectively dispersing the inorganic nanolayers of MMT clay in organic PVA matrix via an in situ free radical polymerization with AIBN as initiator. Organic vinyl acetate monomers are first intercalated into the interlayer regions of organophilic clay hosts and followed by a one-step free radical polymerization. The prepared poly(vinyl acetate)-clay (PVAc-clay) solution are then saponified via direct-hydrolysis with NaOH solution to form PVA-clay nanocomposite materials. The as-synthesized PCN materials are typically characterized by Fourier-Transformation infrared (FTIR) spectroscopy, wide-angle X-ray diffraction and transmission electron microscopy.The molecular weights of poly(vinyl alcohol) (PVA) extracted from polymer-clay nanocomposite (PCN) materials and bulk PVA are determined by gel permeation chromatography (GPC) analysis with THF as eluant. The viscosity property of PCN materials with different feeding amount of MMT clay is studied by an ubbelohode capillary viscometer. The morphological image of as-synthesized materials is studied by scanning electron microscopy (SEM) and optical polarizing microscope (OPM). Effects of the material composition on the thermal stability, mechanical strength, optical clarity of PVA along with a series of PCN materials, in the form of fine powder and free-standing film, are also studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analyzer (DMA) and UV-visible transmission spectra, respectively.     

Role of CoBr2 on the structural,optical and magnetic properties of polyvinyl alcohol films

Polyvinyl alcohol (PVA) films filled with different concentrations of CoBr₂ were prepared using the casting method. These films were characterized by FTIR, UV–visible, XRD, and ESR techniques. FTIR spectra were used to clarify the structural variations due to the filling level from CoBr₂. The observed bands at 3484, 1733, and 1640 cm^?1 were assigned to O? H, C?O, and C?C stretching vibrations, respectively. UV–visible spectra shows the absorption band at 280 nm which is assigned to π → π* transition. This indicates the presence of unsaturated bonds in tail to head of PVA. Optical energy gap decreased with increasing the concentration of CoBr₂. X‐ray diffraction scans show some decrease in the degree of crystallinity in the filled films which reveals an increase in amorphous phase of PVA due to the interaction between Co⁺² and polymeric matrix causing a molecular rearrangement within the amorphous phase of PVA. The observed complex ESR spectrum due to hyperfine interactions confirms the role of free radicals. Spectroscopic and magnetic properties of PVA/CoBr₂ composite films were investigated and compared with those of PVA alone. The results show that the change of the structure due to the interaction of filler with the polymer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of CsBr–MnCl2 mixed fillers on the crystal structure and optical and electrical properties of poly(vinyl alcohol)

Poly(vinyl alcohol) (PVA) films filled with (x)CsBr(15 ? x)MnCl₂, where 0.0 ≤ x ≤ 15%, were prepared by a casting technique. The crystal structure properties of the prepared films were examined by XRD, DTA, and FTIR. A correlation between XRD, DTA, and FTIR of the filled polymer was discussed. Optical absorption measurements revealed two optical band gaps (E_g1 and E_g2). The electrical properties were studied using dc electrical conductivity. The filling level (FL) dependency of E_g1 and E_g2, thermal activation energy (ΔE), and hopping distance (R₀) are given to illustrate the behavior of the filled polymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2178–2186, 2004     

Development and characterization of poly(vinyl alcohol) and casein blend films

Blends of plasticized casein (CA) and poly(vinyl alcohol) (PVA) at various ratios were prepared using the solution‐casting method. The prepared blend solutions were cast onto polystyrene petri plates and bend films were obtained. The characterization of films was performed using Fourier transform infrared spectroscopy, tensile testing, thermogravimetric analysis, contact angle measurements and water vapour permeability. According to spectroscopic analysis, there were interactions between the CA and PVA molecules. The tensile test results showed that the tensile strength of CA increased with increasing PVA content. The flexibility of plasticized CA film increased with the incorporation of PVA. The thermal stability and water vapour barrier properties of plasticized CA improved on blending with PVA. As a result, it was seen that blend films were successfully produced using plasticized CA and PVA with potential for use in biodegradable packaging applications. © 2019 Society of Chemical Industry     

Uniaxial tensile and structural properties of poly(vinyl alcohol) films: The influence of heating and film thickness

Poly(vinyl alcohol) as pure or composite materials is widely used in the food and textile industries, andbiomedical applications due to some important properties such as uniaxial tensile, biocompatibility, and noncarcinogenicity. Investigation of the influence of the film thickness and heating on the uniaxial tensile, spectroscopic, and surface properties of PVA films investigated in this study is quite important for improving the properties of such materials and their applicability in different conditions. In this study, with the influence of heating, a necking behavior was observed at around 2% for thin films and 4–9% strain for thicker PVA films for which a kind of transition point at around 1–2% strain was observed. The mechanical strength of PVA films, strain at break, and Young's modulus were enhanced greatly as the temperature increased from 80 to around 110 °C, and then most of them decreased. The degree of crystallinity increased linearly with the heat temperature from around 36–40%. Although PVA thin films obtained a very smooth surface structure after being heated at 80 °C, with increasing heat temperature, the surface roughness of both thin and thick PVA films increased and the PVA thin films obtained more degraded film surface. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44915.     

Properties of interpenetrating polymer network hydrogels composed of poly(vinyl alcohol) and poly(N‐isopropylacrylamide)

Interpenetrating polymer network (IPN) hydrogels based on poly(vinyl alcohol) and poly(N‐isopropylacrylamide) were prepared by the sequential‐IPN method. The IPN hydrogels were analyzed for sorption behavior of water at 35°C and at a relative humidity of 95% using a dynamic vapor sorption system, and water diffusion coefficients were calculated. Differential scanning calorimetry was used for the quantitative determination of the amounts of freezing and nonfreezing water. Free water contents in the IPN hydrogel of IPN1, IPN2, and IPN3 were 45.8, 37.9 and 33.1% in pure water, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2041–2045, 2003     

Effects of the tacticities of poly(vinyl alcohol) on the structure and morphology of poly(vinyl alcohol) nanowebs prepared by electrospinning

The effects of tacticities on the characteristics of poly(vinyl alcohol) (PVA) nanowebs prepared by an electrospinning technique were investigated. PVA webs composed of uniform nanofibers with syndiotactic dyad (s‐dyad) contents of 53.5 and 57.3% were successfully obtained with electrospinning. By changing processing parameters such as the initial polymer concentration, applied voltage, and tip‐to‐collector distance, we found suitable conditions for forming PVA webs with uniform nanofibers. PVAs of higher s‐dyad contents were prepared at a lower solution concentration and at a higher applied voltage because of the easy formation of syndiotactic PVA chain entanglements at a very low polymer concentration. The average diameter of the nanofibers in a PVA web with the higher s‐dyad content of 57.3% (ca. 240 nm) was thinner than that of the nanofibers in a PVA web with the lowers‐dyad content of 53.5% (ca. 270 nm). In addition, the crystallinity and thermal stability were greatly increased with an increase in the s‐dyad content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Diffusion of solvents in poly(vinyl acetate) and partially and fully hydrolyzed poly(vinyl alcohol)

Diffusivities of methyl acetate, methanol and water in poly(vinyl acetate) and fully and partially hydrolyzed poly(vinyl alcohol) have been measured by capillary column inverse gas chromatography and/or gravimetric sorption. Data from the literature have been used when available for comparison. Overall the diffusivities show good consistency in terms of their temperature and concentration dependences. The free‐volume model has been applied to all the data with excellent results. In most cases the dramatic changes in diffusivities with temperature and concentration can be captured using only a few experimental data points and two regression parameters. This demonstrates that the free‐volume theory is a valuable tool for the design of equipment for processing and devolatilization of polymer ? solvent systems. © 2013 Society of Chemical Industry     

Effect of plasticizers in poly(vinyl alcohol)‐based hybrid solid polymer electrolytes

Hybrid solid polymer electrolyte films consisting of poly(vinyl alcohol) (PVA), poly(methyl methacrylate) (PMMA), LiBF₄, and ethylene carbonate/propylene carbonate (EC/PC) were prepared with a solvent‐casting technique. The complexation was investigated with Fourier transform infrared and X‐ray diffraction. The ionic conductivities of the electrolyte films were determined with an alternating‐current impedance technique for various temperatures in the range of 302–373 K. The maximum conductivity value, 1.2886 × 10^?3 S/cm, was observed for a PVA–PMMA–LiBF₄–EC complex. Thermogravimetry/differential thermal analysis was performed to ascertain the thermal stability of the electrolyte with the maximum conductivity value. For an examination of the cyclic and reversible performance of the film, a cyclic voltammetry study was carried out. The surface morphology of the EC‐and PC‐based electrolytes was examined with scanning electron microscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2794–2800, 2003     

Thermal and optical properties of gelatin/poly(vinyl alcohol) blends

Differential scanning calorimetry, thermogravimetric analysis, X‐ray diffraction, and ultraviolet–visible spectroscopy of gelatin and poly(vinyl alcohol) (PVA) homopolymers and their blended samples were studied. The data revealed that the gelatin and PVA polymers were compatible over the investigated range of compositions; this contributed to the formation of hydrogen‐bonding interaction between their polar groups. The associated enthalpy‐of‐melting transition and thermal stability of the blended samples increased with increasing PVA content. This indicated that the crystalline structure of PVA was not destroyed completely in the blends, which was consistent with the X‐ray diffraction pattern of the 50/50 (wt %/wt %) blended gelatin/PVA sample. The absorption edge and optical band gap for allowed direct transition were determined from ultraviolet–visible spectra. The induced changes in the band structure are elucidated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010