Modification of poly(vinyl chloride). XIII. Crosslinking of poly(vinyl chloride) with dithiols and properties of the crosslinked products

PVC was crosslinked by immersing PVC–dithiol blends in ethylenediamine at 30°C. Properties of the products depended on the chain length and chemical structure of the crosslinkage and on the molecular weight of the polymer chain between crosslinks M_c. Crosslinking by the agent of soft structure and long molecular chain resulted in high tensile strength at break and impact strength and low brittle temperature. The use of the crosslinking agent of short molecular chain gave high yield strength, Young's modulus, and heat distortion temperature. The relation of M_c and the chemical structure of the crosslinks to the properties of the crosslinked rigid polymer was discussed in regard to the crosslinking effect and plasticizing effect.     

Novel preparation of electrically conducting poly (vinyl chloride) by photo-dehydrochlorination from poly (vinyl chloride)/polypyrrole composite film

Polypyrrole (PPy) was deposited electrochemically on a platinum plate from a nitric acid solution of pyrrole. The PVC/PPy composite film was finally obtained by casting poly(vinyl chloride) (PVC) onto the PPy electrode from a tetrahydrofuran solution of PVC. The prepared composite film was irradiated at 90°C with a low-pressure mercury lamp in the stream of hydrogen gas saturated with steam, and the PVC film was dehydrochlorinated, leading to the formation of conjugated polyene. The electrical conductivity (σ) of the PVC film in the irradiated composite film was reveled: σ=2.51 × 10^?5S cm^?1. By iodine doping, σ was further enhanced up to 5.04 X 10^?3 S cm^?1. The tensile strength of the irradiated composite film became larger than that of the original PVC film; i.e., the stress at break was: 461 (composite film); 401 kg cm^?2 (PVC). These results were brought about by the doping of radical species to the conjugated polyene. The anion, NO^?₃, doped during the electrodeposition of PPy was photodecomposed to generate radical NO₂ and this species was doped to the polyene, resulting in the formation of electrically conductive PVC and mechanically improved composite film. © 1994 John Wiley & Sons, Inc.     

Electrical conductivity of poly(vinyl chloride) obtained by photodehydrochlorination from laminated poly(vinyl chloride)/polypyrrole films

Poly(vinyl chloride) (PVC) has been converted to an electrically conductive structure by combined electrochemical and photochemical methods. PVC was cast on a polypyrrole (PPy) film electrode which had been electrochemically prepared. The PVC layer in the laminated PVC/PPy films was first dehydrochlorinated under the illumination of UV light, and the generated polyenes were subsequently doped with I₂ and FeCl₃. The maximum electrical conductivity achieved for such PVC film was 2.51 X 10^?2 and 8.63 10^?2 S cm^?1 after I₂ and FeCl₃ doping, respectively. The temperature dependence of the electrical conductivity showed different behavior in higher and lower temperature ranges. In the former (T > 243 K), the T^?1 law held, and the activation energy and bandgap were estimated as 0.25 and 0.49 eV, respectively. In the latter (T < 243 K), the conductivity mechanism followed the variable range hopping model (T^?1/4 law) in which the radius of the localized state wave function and the density of the localized states at the Fermi level were 1.25 × 10³ Å and 1.03 X 10¹⁵ eV^?1 cm^?3, respectively. © 1995 John Wiley & Sons, Inc.     

Proton conducting membranes based on poly(vinyl chloride) graft copolymer electrolytes

The direct preparation of proton conducting poly(vinyl chloride) (PVC) graft copolymer electrolyte membranes using atom transfer radical polymerization (ATRP) is demonstrated. Here, direct initiation of the secondary chlorines of PVC facilitates grafting of a sulfonated monomer. A series of proton conducting graft copolymer electrolyte membranes, i.e. poly(vinyl chloride)‐g‐poly(styrene sulfonic acid) (PVC‐g‐PSSA) were prepared by ATRP using direct initiation of the secondary chlorines of PVC. The successful syntheses of graft copolymers were confirmed by ¹H‐NMR and FT‐IR spectroscopy. The images of transmission electron microscopy (TEM) presented the well‐defined microphase‐separated structure of the graft copolymer electrolyte membranes. All the properties of ion exchange capacity (IEC), water uptake, and proton conductivity for the membranes continuously increased with increasing PSSA contents. The characterization of the membranes by thermal gravimetric analysis (TGA) also demonstrated their high thermal stability up to 200°C. The membranes were further crosslinked using UV irradiation after converting chlorine atoms to azide groups, as revealed by FT‐IR spectroscopy. After crosslinking, water uptake significantly decreased from 207% to 84% and the tensile strength increased from 45.2 to 71.5 MPa with a marginal change of proton conductivity from 0.093 to 0.083 S cm^?1, which indicates that the crosslinked PVC‐g‐PSSA membranes are promising candidates for proton conducting materials for fuel cell applications. Copyright © 2008 John Wiley & Sons, Ltd.     

Mathematical models of the initial stage of the thermal degradation of poly(vinyl chloride). II. The thermal degradation of poly(vinyl chloride) with effective removal of HCl

The dehydrochlorination of different samples of PVC under vacuum with continuous removal of HCl by freezing, has been studied at 180–210°C. The comparison of the kinetic curves of the dehydrochlorination of various samples of PVC which were obtained by us and other investigators, with the theoretical curves for the thermal degradation of idealized PVC in the absence of HCl has been carried out. This had made it possible to evaluate the influence of unstable fragments present in the original polymer on the initial rate of PVC degradation quantitatively. It has been shown that the distinction between the stationary rates of the dehydrochlorination of various samples of PVC is determined by the difference of the values of the average length of dehydrochlorination chain, l_av. The most probable interval of the values of l_av has been ascertained to be 4–12. It is established that the most probable value of the constant of the rate of dehydrochlorination of normal links of PVC, k₀, is 2.1 × 10^?7?2.5 × 10^?7 s^?1 at 200°C. © 1993 John Wiley & Sons, Inc.     

Small‐angle x‐ray scattering study of thermoreversible poly(vinyl chloride) gels

Poly(vinyl chloride) (PVC)/bis(2‐ethylhexyl)phthalate (DOP) gels were prepared at room temperature from tetrahydrofuran solutions of PVC and DOP. PVC/DOP gels of different molecular weights at various PVC concentrations (c) were investigated with small‐angle X‐ray scattering (SAXS). The mean distance between two neighboring inhomogeneities (D) and two characteristic lengths, the intrainhomogeneity distance (d₁) and interinhomogeneity distance (d₂), were evaluated from Bragg's law and the distance distribution function, respectively. Both D and d₂ can be expressed by a power‐law relation (e.g., D and d₂ ∝ c^?0.5). After a period of rapid cooling to 25 °C from the sol state, the structural evolution was examined with time‐resolved SAXS measurements. An Avrami analysis with the SAXS invariant data revealed that the growth kinetics of PVC/DOP gels was one‐dimensional growth from predetermined nuclei, regardless of c. These results suggest that the PVC/DOP gels are constructed from a fibrillar structure that forms gel structures at high concentrations or low temperatures. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2340–2350, 2001     

Preparation and characterization of rigid poly (vinyl chloride)/MMT nanocomposites

In this article, a Haake torque rheometer equipped with an internal mixer is used to study the influence of the amount of sodium montmorillonite (Na⁺‐MMT) and organically modified MMT (O‐MMT) on the characteristics of rigid poly (vinyl chloride) (PVC)/Na⁺‐MMT and PVC/O‐MMT nanocomposites, respectively. It is observed that the fusion time and temperature of the rigid PVC/Na⁺‐MMT nanocomposites are decreased with increasing the amount of Na⁺‐MMT. On the contrast, the fusion time and temperature of the rigid PVC/O‐MMT nanocomposites are increased with increasing the amount of O‐MMT. Results of X‐ray diffraction (XRD) and transmission electron microscope (TEM) indicate that MMT is partially encapsulated and intercalated in the rigid PVC/Na⁺‐MMT nanocomposites. However, results of XRD and TEM show MMT is partially intercalated and exfoliated in the rigid PVC/O‐MMT nanocomposites. Tensile strength, yield strength, and elongation at break of the rigid PVC/MMT (including PVC/Na⁺‐MMT and PVC/O‐MMT) nanocomposites were improved simultaneously with adding 1–3 wt % Na⁺‐MMT or O‐MMT with respect to those of pristine PVC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1465–1474, 2005     

Henry's law and diffusion constants of vinyl chloride in poly(vinyl chloride) at high temperature

The Henry's law and diffusion constants of vinyl chloride in poly(vinyl chloride) were determined at temperatures of 24, 90, 120, 150, and 170°C for weight fractions of vinyl chloride between 0.2 × 10^?3 and 0.8 × 10^?3. Above 90°C, Henry's law applies; values of the constant increase with temperature from 1.8 × 10² to 5.5 × 10² atm per unit weight fraction of dissolved vinyl chloride. The heat of desorption is about 15 kJ/mole. At 24°C, the nominal Henry's law constant was smaller than would have been obtained by extrapolating the values found at higher temperature. The diffusion constants increase with temperature from about 2 × 10^?13 to 3 × 10^?7 cm²/sec. The activation energy for diffusion is about 110 kJ/mole between 90 and 170°C. Although all values were determined in the absence of air, it is likely that they apply to polymer in air. They may, therefore, be used to calculate the vinyl chloride content in the gas above poly(vinyl chloride) under specific processing conditions.     

Synthesis and gas permeation properties of poly(vinyl chloride)‐graft‐poly(vinyl pyrrolidone) membranes

A series of amphiphilic graft copolymers consisting of poly(vinyl chloride) (PVC) main chains and poly(vinyl pyrrolidone) (PVP) side chains, i.e. PVC‐g‐PVP, was synthesized via atom transfer radical polymerization (ATRP), as confirmed by ¹H NMR, FT‐IR spectroscopy, and gel permeation chromatography (GPC). Transmission electron microscope (TEM) and small angle X‐ray scattering (SAXS) analysis revealed the microphase‐separated structure of PVC‐g‐PVP and the domain spacing increased from 21.4 to 23.9 nm with increasing grafting degree. All the membranes exhibited completely amorphous structure and high Young's modulus and tensile strength, as revealed by wide angle X‐ray scattering (WAXS) and universal testing machine (UTM). Permeation experimental results using a CO₂/N₂ (50/50) mixture indicated that as an amount of PVP in a copolymer increased, CO₂ permeability increased without the sacrifice of selectivity. For example, the CO₂ permeability of PVC‐g‐PVP with 36 wt% of PVP at 35°C was about four times higher than that of the pristine PVC membrane. This improvement resulted from the increase of diffusivity due to the disruption of chain packing in PVC by the grafting of PVP, as confirmed by WAXS analysis. Copyright © 2011 John Wiley & Sons, Ltd.     

Pulsed photoconductivity and current oscillations in poly(vinyl chloride)

Transient photocurrents in poly(vinyl chloride) films are shown to be due to photo-injection of electrons from metallic cathodes. Most of the injected electrons are promptly trapped, but some drift across the sample to the anode under the influence of an external electric field. The mobility of these electrons, determined by transient photoconductivity techniques, is 4.7 ± 0.5 × 10^?4 cm²/V-sec at 27°C, and rises to 3.4 ± 0.5 × 10^?3 cm²/V-sec at 43°C, the measuring cell having been evacuated to a pressure of 10^?6 torr at both temperatures. Diffusion of helium into the samples appears to decrease the electron, mobility. It is suggested that electron transport is correctly described by using an energy-band model for intramolecular motion and an activated hopping model for intermolecular transfer. Oscillations observed in the transient photocurrents in the frequency range 10³–10⁵ Hz are attributed to electron avalanche formation at the anode, with photosuccessors.     

Preparation and characterization of rigid poly(vinyl chloride)/MMT nanocomposites. II. XRD,morphological and mechanical characteristics

A Haake torque rheometer equipped with an internal mixer is used to study the influence of the amount of sodium montmorillonite (Na⁺‐MMT) and organically modified MMT (O‐MMT) on X‐ray diffraction (XRD), morphology, and mechanical characteristics of rigid poly (vinyl chloride) (PVC)/Na⁺‐MMT and PVC/O‐MMT nanocomposites, respectively. Results of XRD and transmission electron microscopy (TEM) indicate that MMT is partially encapsulated and intercalated in the rigid PVC/Na⁺‐MMT nanocomposites. However, results of XRD and TEM show MMT is partially intercalated and exfoliated in the rigid PVC/O‐MMT nanocomposites. Tensile strength, yield strength, and elongation at break of the rigid PVC/MMT nanocomposites were improved simultaneously with adding 1–3 wt % Na⁺‐MMT or O‐MMT with respect to that of pristine PVC. However, the addition of Na⁺‐MMT or O‐MMT should be kept as not more than 3 wt % to optimize the mechanical properties and the processing stability of the rigid PVC/MMT nanocomposites. SEM micrographs of the fractured surfaces of the rigid PVC/Na⁺‐MMT and PVC/O‐MMT nanocomposites both before and after tensile tests were also illustrated and compared. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2145–2154, 2006     

Effects of humidity on Young's modulus in poly(methyl methacrylate)

Tensile tests on poly (methyl methacrylate) (PMMA) were conducted to clarify the effects of humidity and strain rate on tensile properties, particularly Young's modulus. Prior to the tensile tests, specimens were kept under various humidity conditions at 293 K, which were the same as the test conditions, for a few months to adjust the sorbed water content in the specimens. The tensile tests were performed under each humidity condition at three different strain rates (approximately 1.4 × 10^?3, 1.4 × 10^?4, and 1.4 × 10^?5 s^?1). Stress‐strain curves changed with humidity and strain rate. Young's moduli were also measured at small applied stresses (below 6.7 MPa) under various humidity conditions at 293 K. Young's modulus decreases linearly with increasing humidity and a decreasing logarithm of strain rate. These results suggest that Young's modulus of PMMA can be expressed as a function of two independent parameters that are humidity and strain rate. A constitutive equation for Young's modulus of PMMA was proposed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 460–465, 2002; DOI 10.1002/polb.10107     

Novel sulphonated poly (vinyl chloride)/poly (2-acrylamido-2-methylpropane sulphonic acid) blends-based polyelectrolyte membranes for direct methanol fuel cells

Proton-conducting and methanol barrier properties of the proton exchange membrane (PEM), as well as the high cost of direct methanol fuel cell (DMFC) components, are the key determinants of the performance and commercialization of DMFCs. Therefore, this study aimed to develop cost- and performance-effective membranes based on sulphonated poly (vinyl chloride) (SPVC)/poly (2-acrylamido-2-methyl-1-propane sulphonic acid) (PAMPS) blends. Such membranes have been simply prepared by blending SPVC and PAMPS solutions, followed by solvent evaporation via casting. Interaction of SPVC with PAMPS was confirmed by different characterization techniques such as Fourier Transform Infra-red (FTIR) and Raman scattering spectroscopy in which the two characteristic absorption bands of sulfonic groups appeared at 1093 and 1219 cm⁻¹ additionally, strong peaks at around 1656 cm⁻¹ attributed to vibration of amide groups of PAMPS portion in the polymer blend. Furthermore, the interaction of SPVC with PAMPS improves the thermal properties along with ion exchange capacity in turn decreasing the methanol permeability through the membrane in comparison with the SPVC membrane. The IEC of PVC and Nafion 117 membranes were 1.25, 0.91 meq/g; respectively. And the maximum water uptake of PVC and Nafion 117 membranes were 75 and 65.44%; respectively. Methanol permeability value of 7.7 × 10⁻⁷ cm²/s which was noticeably lower than the corresponding value recorded for Nafion® (3.39 × 10⁻⁶ cm²/s). Therefore, these fabricated membranes can be considered a low-cost efficient candidate for use in DMFC, especially for its capability to resolve the methanol cross-over issue.     

Effects of plasticizers on novel electromechanical actuations with different poly(vinyl chloride) gels

Four different plasticizers were applied to make different poly(vinyl chloride) (PVC) gels, poly(vinyl chloride)‐bis(2‐ethylhexyl)phthalate (PVC‐DOP), poly(vinyl chloride)‐di‐n‐butylphthalate, poly(vinyl chloride)‐bis(2‐ethylhexyl)adipate, and poly(vinyl chloride)‐tris(2‐ethylhexyl)trimellitate. In our previous work, we reported that PVC‐DOP gel exhibits novel and reversible deformations of creeping and jointlike bending induced by direct current electric fields. In this article, we scrutinize the effects of plasticizers on electromechanical actuations, that is, reversible creeping and bending actuation with four of the different aforementioned gels. We measured the relative creeping distance, creeping area, creeping velocity, current observed, and bending angle as a function of applied electric fields for different PVC gels and found significant differences among them. To explain these variations, we compared the utility of plasticizers on the basis of the properties of different PVC gels, such as plasticizer‐retention ability, bending modulus, elongation at break, and the dielectric constant. The mentioned properties of the PVC gels played vital roles on their electromechanical actuations. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2119–2127, 2003     

Preparation of conducting poly(vinyl chloride)/polyindole composites and freestanding films via chemical polymerization

This study covers the synthesis of conducting polyindole (PIN) homopolymer, poly(vinyl chloride)/polyindole (PVC/PIN) composites, and preparation of their freestanding films. PIN and composites were synthesized chemically by radicalic mechanism using FeCl₃ as an initiator. Films of PVC and PVC/PIN composites were prepared by casting on glass Petri dishes. Mechanical properties of films were examined by stress–strain experiments. From FTIR spectra of polymers, it was revealed that polymerization reaction occurred by 2–3 mechanism. The conductivities of polymers at different temperatures were also measured by four‐probe technique and found in the range 10^?4 to 10^?5 S cm^?1. Magnetic properties of the polymers were analyzed by Gouy scale measurements and were found that their conducting mechanisms are of polaron and bipolaron natures. Thermal properties of polymers were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) and found that they had shown adequate thermal stability. X‐ray diffraction (XRD) spectra showed the amorphous nature of the polymers. Scanning electron microscopy (SEM) was used for microstructural analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1290–1298, 2010     

Photo-oxidation of poly(vinyl chloride)

The photo-oxidation of PVC has been studied over the temperature range 30–150°C. Initiation with ultraviolet (2537A) radiation has been correlated with the presence of minute amounts of ozone. The contribution of atomic oxygen and singlet oxygen (¹Δ_g) molecules to the initiation mechanism is discussed. The β-chloroketones probably formed in the photo-oxidation of PVC, decomposed according to a Norrish type I reaction without loss of chlorine atoms. The gaseous products of the photo-oxidation of PVC at 30°C were carbon dioxide, carbon monoxide, hydrogen, and methane. Hydrogen chloride was obtained only when PVC was heated at high temperatures. When PVC was photo-oxidized and then heated at high temperature, benzene was obtained in addition to hydrogen chloride. The gaseous products from the photo-oxidations of model compounds, such as 4-chloro-2-butanone and 2,4-dichloropentane, were also compared with those from PVC. Hydrogen chloride was detected only after photo-oxidation at temperatures of 25°C or higher. Therefore, it was concluded that hydrogen chloride is mainly a product of thermal decomposition. Since unsaturation was not observed in photo-oxidized PVC films, the cause of discoloration is unclear. When PVC was modified by stabilizers or additives, the oxidative degradation was further complicated by side reactions with the additives.     

Modification of poly(vinyl chloride). XXIX. Cross linking of poly(vinyl chloride) with 2-dibutylamino-4,6-dithiol-s-triazine and MGO

Thermal crosslinking of poly(vinyl chloride) (PVC) with 2-dibutylamino-4,6-dithiol-s-triazine (DB) and MgO has been studied to determine the kinetic parameters such as induction period (t₀), rate constant (k), and activation energy (E), and to elucidate the structure of crosslink and the crosslinking mechanism. The thermal crosslinking was treated as a pseudo-first-order reaction. In the crosslinking, k and t₀ were about 0.075 min^?1 and 6.8 min at 180°C, respectively, and E was 16.6 and 14.2 kcal/mole for k and 1/t₀, respectively. The structure of crosslink was confirmed to be indicated as the following scheme (I) from the results of model reactions and IR spectra of crosslinked products The crosslinking reaction was found to proceed through the following three processes: (1) formation of DB-Mg from DB and MgO; (2) formation of DB-Mg pendants by the reaction of PVC with DB-Mg; and (3) formation of crosslink by the reaction of PVC with DB-Mg pendants.     

Characterization of poly(vinyl chloride) powder produced by emulsion polymerization

The effect of emulsion process formulation ingredients on the morphology, structure, and properties of polyvinyl chloride (PVC) powder has been considered in this study. PVC powder was extracted with ethanol and films were obtained by solvent casting from tetrahydrofurane. Characterization of powders, films, and ethanol extract was performed through FTIR spectroscopy, DSC, AFM, SEM, EDX analysis, methylene blue, and nitrogen adsorption. PVC powder was composed of spheres of a large particle size range from 10 nm to 20 μm as shown by SEM. The specific surface area of the PVC powder was determined as 16 and 12 m² g⁻¹ from methylene blue adsorption at 25 °C and from N₂ adsorption at −196 °C, respectively. AFM indicated the surface roughness of the films obtained by pressing the particles was 25.9 nm. Density of PVC powder was determined by helium pycnometry as 1.39 g cm⁻³. FTIR spectroscopy indicated that it contained carbonyl and carboxylate groups belonging to additives such as surface active agents, plasticizers, and antioxidants used in production of PVC. These additives were 1.6% in mass of PVC as determined by ethanol extraction. EDX analysis showed PVC particles surfaces were coated with carbon-rich materials. The coatings had plasticizer effect since, glass transition temperature was lower than 25 °C for PVC powder and it was 80 °C for ethanol extracted powders as found by using differential scanning calorimetry. These additives from polymerization process made PVC powder more thermally stable as understood from Metrom PVC thermomat tests as well.     

Preparation,characterization, and mechanical properties of microcellular poly(aryl ether ketone) foams

High‐performance microcellular closed‐cell foams were prepared by a two‐stage batch foaming process from fluorinated poly(ether ether ketone) and characterized by scanning electronic microscopy, tensile, and dynamic mechanical analysis (DMA). The effects of saturation pressure and temperature on the cell size, cell density, and bulk density of porous materials had been discussed. The resulting materials had average cell diameters in the range 3–17 μm, and cell densities (N_f) in the order of 0.6 × 10⁹–1.39 × 10¹⁰ cells/cm³. The porosity (V_f) was in the range of 0.2–0.85. In contrast, experimental values of Young's moduli were in good agreement with theoretically predicted values, but the relative strengths were somewhat lower than that predicted. The relaxation mechanism of microcellular was systematically investigated by DMA. The dynamic mechanical spectrometry showed that the storage modulus curve at high temperature region appeared a peak and the loss modulus was lower as compared to their solid counterparts. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 173–183, 2007     

Investigations on poly(vinyl chloride). I. Evolution of aromatics on pyrolysis of poly(vinyl chloride) and its mechanism

Poly(vinyl chloride) (PVC) alone or mixed with 10 wt-% and 50 wt-% TiO₂, SnO₂, ZnO, and Al₂O₃ were pyrolyzed by using a pyrolysis gas chromatograph. Benzene, toluene, ethylbenzene, o-xylene, styrene, naphthalene, and various chlorobenzenes were identified. No hydrocarbons could be detected in pyrolysis products of any samples at 200°C. More aromatic hydrocarbons than aliphatic hydrocarbons are released from the PVC–TiO₂ system and in preheated PVC. The contrary result is observed in the PVC–ZnO and PVC–SnO₂ systems. Aromatics having methyl endgroups are easily released from the PVC–ZnO and PVC–SnO₂ systems and at elevated pyrolysis temperature, because methylene groups are easily isolated along the chain by ZnO, SnO₂ and the heating. The release of ethylbenzene o-xylene, and chlorobenzenes suggests a repeated dehydrochlorination and recombination of HCl and Cl₂ to double bonds along the chain. Possible decomposition mechanisms of PVC are discussed.