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.     

Thermal degradation of poly(vinyl chloride)/poly(ethylene oxide) blends: Thermogravimetric analysis

Thermal stability of poly(vinyl chloride)/poly(ethylene oxide) (PVC/PEO) blends has been investigated by thermogravimetric analysis (TGA) in dynamic and isothermal heating regime. PVC/PEO blends were prepared by hot-melt extrusion (HME). According to TG analysis, PEO decomposes in one stage, while PVC and PVC/PEO blends in two degradation stages. In order to evaluate the effect of PEO content on the thermal stability of PVC/PEO blends, different criteria were used. It was found that thermal stability of PVC/PEO blends depends on the blend composition. The interactions of blends components with their degradation products were confirmed. By using multiple heating rate kinetics the activation energies of the PVC/PEO blends thermal degradation were calculated by isoconversional integral Flynn–Wall–Ozawa and differential Friedman method. According to dependence of activation energy on degree of conversion the complexity of degradation processes was determined.     

Investigation at the chain segmental level of the miscibility of poly(vinyl chloride)/atactic poly(methyl methacrylate) blends

We employed high‐resolution ¹³C cross‐polarization/magic‐angle‐spinning/dipolar‐decoupling NMR spectroscopy to investigate the miscibility and phase behavior of poly(vinyl chloride) (PVC)/poly(methyl methacrylate) (PMMA) blends. The spin–lattice relaxation times of protons in both the laboratory and rotating frames [T₁(H) and T_1ρ(H), respectively] were indirectly measured through ¹³C resonances. The T₁(H) results indicate that the blends are homogeneous, at least on a scale of 200–300 Å, confirming the miscibility of the system from a differential scanning calorimetry study in terms of the replacement of the glass‐transition‐temperature feature. The single decay and composition‐dependent T_1ρ(H) values for each blend further demonstrate that the spin diffusion among all protons in the blends averages out the whole relaxation process; therefore, the blends are homogeneous on a scale of 18–20 Å. The microcrystallinity of PVC disappears upon blending with PMMA, indicating intimate mixing of the two polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2390–2396, 2001     

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.     

Modification and characterization of semi-crystalline poly(vinyl alcohol) with interpenetrating poly(acrylic acid) by UV radiation method for alkaline solid polymer electrolytes membrane

Semi-crystalline poly(vinyl alcohol) was modified by UV radiation with acrylic acid monomer to get interpenetrating poly(acrylic acid) modified poly(vinyl alcohol), PVAAA, membrane. The stability of various PVAAA membranes in water, 2 M CH₃OH, 2 M H₂SO₄, and 40 wt% KOH aqueous media were evaluated. It was found that the stability of PVAAA membrane is stable in 40 wt% KOH solution. The PVAAA membranes were characterized by differential scanning calorimetry, X-ray diffraction, and thermogravimetry analysis. These results show that (1) the crystallinity in PVAAA decreased with increasing the content of poly(acrylic acid) in the PVAAA membranes. (2) The melting point of the PVAAA membrane is reduced with increasing the content of poly(acrylic acid) in the membrane. (3) Three stages of thermal degradation were found for pure PVA. Compared to pure PVA, the temperature of thermal degradation increased for the PVAAA membrane. The various PVAAA membranes were immersed in KOH solution to form polymer electrolyte membranes, PVAAA-KOH, and their performances for alkaline solid polymer electrolyte were conducted. At room temperature, the ionic conductivity increased from 0.044 to 0.312 S/cm. The result was due to the formation of interpenetrating polymer chain of poly(acrylic acid) in the PVAAA membrane and resulting in the increase of charge carriers in the PVA polymer matrix. Compared to the data reported for different membranes by other studies, our PVAAA membrane are highly ionic conducting alkaline solid polymer electrolytes membranes.     

Poly(vinyl alcohol)/poly(methyl methacrylate) blend membranes for pervaporation separation of water + isopropanol and water + 1,4-dioxane mixtures

Pervaporation (PV) separation of water + isopropanol and water + 1,4-dioxane mixtures has been attempted using the blend membranes of poly(vinyl alcohol) (PVA) with 5 wt.% of poly(methyl methacrylate) (PMMA). These results have been compared with the plain PVA membrane. Both plain PVA and PVA/PMMA blend membranes have been crosslinked with glutaraldehyde in an acidic medium. The membranes were characterized by differential scanning calorimetry and universal testing machine. Pervaporation separation experiments have been performed at 30 °C for 10, 15, 20, 30 and 40 wt.% of feed water mixtures containing isopropanol as well as 1,4-dioxane. PVA/PMMA blend membrane has shown a selectivity of 400 for 10 wt.% of water in water + isopropanol feed, while for water + 1,4-dioxane feed mixture, membrane selectivity to water was 104 at 30 °C. For both the feed mixtures, selectivity for the blend membrane was higher than that observed for plain PVA membrane, but flux of the blend membrane was lower than that observed for the plain PVA membrane. Membranes of this study are able to remove as much as 98 wt.% of water from the feed mixtures of water + isopropanol, while 92 wt.% of water was removed from water + 1,4-dioxane feed mixtures at 30 °C. Flux of water increased for both the feed mixtures, while the selectivity decreased at higher feed water concentrations. The same trends were observed at 40 and 50 °C for 10, 15 and 20 wt.% of water mixtures containing isopropanol as well as 1,4-dioxane feed mixtures, which also covered their azeotropic composition ranges. Membrane performance was studied by calculating flux (J_p), selectivity (), pervaporation separation index (PSI) and enrichment factor (β). Permeation flux followed the Arrhenius trend over the range of temperatures investigated. It was found that by introducing a hydrophobic PMMA polymer into a hydrophilic PVA, the selectivity increased dramatically, while flux decreased compared to plain PVA, due to a loss in PVA chain relaxation.     

Thermal and electrochemical characteristics of plasticized polymer electrolytes based on poly(acrylonitrile-co-methyl methacrylate)

The thermal and electrochemical characteristics of plasticized polymer electrolytes composed of poly(acrylonitrile-co-methyl methacrylate) [P(AN-co-MMA)], a plasticizer [a mixture of ethylene carbonate and propylene carbonate], and LiCF₃SO₃ were investigated. The incorporation of a MMA unit into the matrix polymer was effective for an increase in the compatibility between the matrix polymer and the plasticizer. The comparative investigation of the interfacial resistance of the Li/polymer electrolyte/Li cell for the PAN-based and the P(AN-co-MMA)-based polymer electrolytes showed that the MMA unit could improve the stability of the polymer electrolyte toward the Li electrode, which is probably due to the enhanced adhesion of the polymer electrolyte to the Li electrode. Received: 14 July 1997 / Accepted: 14 May 1998     

Poly(N,N-dimethylaminoethyl methacrylate) grafted poly(vinyl chloride)s synthesized via ATRP process and their membranes for dye separation

To functionalize poly(vinyl chloride)(PVC) for various applications, monomers containing tertiary amine group are incorporated into PVC via atom transfer radical polymerization(ATRP) initiated by the labile chlorines in their backbones. The kinetics of synthesis was carefully investigated, and it is proven that the grafting polymerization process can be effectively controlled by regulating the reaction time. The membranes are fabricated using PVC and copolymers by non-solvent induced phase separation(NIPS) process. The hydrophilicity and pore structure of copolymer membranes were enhanced as well, these membranes are endowed with positive charge. When PDMA%(i.e., the PDMA weight percentage in copolymer) is 31.1%, the flux and Victoria blue B rejection are 26.0 L?m?2?h?1(0.5 MPa) and 91.2%, respectively. Thus, the newly synthesized polymer is proven to be a promising material for dye separation with positive charges.     

Pervaporation of alcohol-toluene mixtures through polymer blend membranes of poly(acrylic acid) and poly(vinyl alcohol)

Homogeneous membranes were prepared by blending poly(acrylic acid) with poly(vinyl alcohol). These blend membranes were evaluated for the selective separation of alcohols from toluene by pervaporation. The flux and selectivity of the membranes were determined both as a function of the blend composition and of the feed mixture composition. The results showed that a polymer blending method could be very useful to develop new membranes with improved permselectivity. The pervaporation properties could be optimized by adjusting the blend composition. All the blend membranes tested showed a decrease in flux with increasing poly(vinyl alcohol) content for both methanol—toluene and ethanol—toluene liquid mixtures. The alcohols permeated preferentially through all tested blend membranes, and the selectivity values increased with increasing poly(vinyl alcohol) content. The pervaporation characteristics of the blend membranes were also strongly influenced by the feed mixture composition. The fluxes increased exponentially with increasing alcohol concentration in the feed mixtures, whereas the selectivities decreased for both liquid mixtures.     

Pyrolysis mass spectrometry analysis of polycarbonate/poly(methyl methacrylate)/poly(vinyl acetate) ternary blends

Direct insertion probe pyrolysis mass spectrometry (DIP-MS) analyses of polycarbonate/poly(methyl methacrylate)/poly(vinyl acetate), (PC/PMMA/PVAc), ternary blends have been performed. The PC/PMMA/PVAc ternary blends were obtained by coalescing from their common γ-cyclodextrin-inclusion compounds (CD-ICs), through the removal of the γ-CD host (coalesced blend), and by a co-precipitation method (physical blend). The coalesced ternary blend showed different thermal behaviors compared to the co-precipitated physical blend. The stability of PC chains decreased due to the reactions of CH₃COOH formed by deacetylation of PVAc above 300 °C, for both coalesced and physical blends. This process was more effective for the physical blend most likely due to the enhanced diffusion of CH₃COOH into the amorphous PC domains, where it can further react producing low molecular weight PC fragments bearing methyl carbonate chain ends. The decrease in thermal stability of PC chains was less significant for the coalesced ternary blend indicating that the diffusion of CH₃COOH was either somewhat limited or competed with intermolecular reactions between PMMA and PC and between PMMA and PVAc, which were detected and were associated with their close proximity in the intimately mixed coalesced PC/PMMA/PVAc ternary blend.     

Viscometric study of poly(vinyl chloride)/poly(vinyl acetate) blends in various solvents

The intermolecular interactions between poly(vinyl chloride) (PVC) and poly(vinyl acetate) (PVAc) in tetrahydrofuran (THF), methyl ethyl ketone (MEK) and N,N^′-dimethylformamide (DMF) were thoroughly investigated by the viscosity measurement. It has been found that the solvent selected has a great influence upon the polymer-polymer interactions in solution. If using PVAc and THF, or PVAc and DMF to form polymer solvent, the intrinsic viscosity of PVC in polymer solvent of (PVAc+THF) or (PVAc+DMF) is less than in corresponding pure solvent of THF or DMF. On the contrary, if using PVAc and MEK to form polymer solvent, the intrinsic viscosity of PVC in polymer solvent of (PVAc+MEK) is larger than in pure solvent of MEK. The influence of solvent upon the polymer-polymer interactions also comes from the interaction parameter term Δb, developed from modified Krigbaum and Wall theory. If PVC/PVAc blends with the weight ratio of 1/1 was dissolved in THF or DMF, Δb<0. On the contrary, if PVC/PVAc blends with the same weight ratio was dissolved in MEK, Δb>0. These experimental results show that the compatibility of PVC/PVAc blends is greatly associated with the solvent from which polymer mixtures were cast. The agreement of these results with differential scanning calorimetry measurements of PVC/PVAc blends casting from different solvents is good.     

离子交联聚氯乙烯的结构与性能

由氯乙烯/丙烯酸悬浮共聚合成了不同羧基含量的PVC树脂,采用溶液反应和熔融加工法制备离子交联PVC,对其结构和性能进行了研究.结果表明,共聚物中羧基主要以二聚体形式存在,用金属离子中和能形成部分络合结构;用Ca²⁺、Mg²⁺离子络合的羧基含量较高的VC/AA共聚物存在离子对聚集态结构;离子对含量、金属离子种类和增塑剂浓度影响离子聚集相的比例和稳定性,离子聚集具有热可逆性;离子交联使PVC的T_g、熔体粘度和回弹性提高.     

Properties of poly(vinyl chloride)/wood flour/montmorillonite composites: Effects of coupling agents and layered silicate

Organomodified montmorillonite (OMMT) was prepared using cetylalkyl trimethyl amine bromide. OMMT and wood flour (WF) were surface-modified by silane coupling agent. They were melt-blended with polyvinyl chloride (PVC) and extruded into wood-plastic composite samples using one conical twin screw extruder. The effects of their contents on the composite mechanical properties were investigated. X-ray diffraction, transmission electron microscopy and scanning electron microscopy observed intercalation and dispersion of the OMMT. FTIR and X-ray photoelectron spectroscopy were used to analyze the silane-modification effects. The possible reaction mechanisms were proposed. After wood flour was modified by 1.5 phr silane, the impact strength and the tensile strength of wood flour-PVC composite were increased by 14.8% and 18.5%, respectively. Mechanical tests showed that the addition of OMMT did not enhance the untreated wood flour-PVC composites. However, adding 0.5% OMMT did improve the mechanical properties of the treated ones. The grafting improved the interfacial compatibility between components producing higher properties of the composites. Further addition of OMMT reinforced the composites. Too higher contents of silane and OMMT impaired some properties because of weak interfacial layer and higher concentrated stress. Cone calorimetry showed that the fire flame retardancy and smoke suppression of composites were strongly improved with the addition of OMMT.     

The miscibility of poly(vinyl alcohol)/poly(N-vinylpyrrolidone) blends investigated in dilute solutions and solids

Poly(vinyl alcohol) (PVA) (polymer A) and poly(N-vinylpyrrolidone) (PVP) (polymer B) are known to form a thermodynamically miscible pair. In the present study the conclusion on miscibility of PVA/PVP solid blends, confirmed qualitatively (DMTA, FTIR) and quantitatively (DSC, χ_AB = − 0.69 at 503 K) is compared with the miscibility investigations of PVA/PVP solution blends by the technique of dilute solution viscometry. The miscibility of the ternary (polymer A/ polymer B/ solvent) system is estimated on the basis of experimental and ideal values of the viscosity parameters k, b and [η]. It is found that the conclusions on miscibility or nonmiscibility drawn from viscosity measurements in dilute solution blends depend: (i) on the applied extrapolation method used for the determination of the viscosity interaction parameters, (ii) on the assumed definition of the ideal values and (iii) on the thermodynamic quality of the solvent, which in the case of PVA depends on its degree of hydrolysis. Hence, viscometric investigations of dilute PVA/PVP solution blends have revealed that viscometry, widely used in the literature for estimation of polymer-polymer miscibility can not be recommended as a sole method to presume the miscibility of a polymer pair.     

Thermal degradation of poly(ethyl methacrylate) and its copolymer with poly(ethyl acrylate)

The thermal degradation behaviour of poly(ethyl methacrylate) homopolymers and poly(ethyl methacrylate) and poly(ethyl acrylate) copolymers synthesized by using the benzoyl peroxide-di-methyl aniline redox pair at different temperatures (18–35C) was investigated. Contrary to some reports in the literature, the thermal degradation of PEMA was observed to take place in multi steps. These are assigned to be loss of labile end groups, side chain scission, anhydride formation and main chain degradation steps. Dominating chemical formations at the end of these steps were characterized by FTIR spectroscopy.The homopolymer samples synthesized at 18C showed a greater thermal stability against degradation. Copolymerization with small amounts of ethyl acrylate was observed to impart thermal stability to PEMA by stabilizing mainly the end groups against degradations.     

Determination of the glass transition temperature of polystyrene,poly(vinyl chloride) and poly(methyl methacrylate) using gas chromatography

The glass transition temperatures, Tg, of polystyrene, poly (vinyl chloride) and poly(methyI methacrylate) have been determined from gas chromatographic measurements using n-hexane, n-heptane, meta-xylene and para-xylene solvents. The glass transition temperatures were detected on the z-shaped retention diagrams which were produced from the plot of the logarithm of the specific retention volumes of the above-mentioned solvents against the reciprocal of temperature, i.e. log V${}_{\text{g}}^{\text{º}}$ vs. 1/T. The glass transition temperature is specified by the temperature where the slope of log V${}_{\text{g}}^{\text{º}}$ vs. 1/T changes abruptly. The observed glass transition temperature of polystyrene produced by this technique was found to be in good agreement with those produced by other techniques such as the differential scanning colorimeter. The industrial importance of the glass transition temperature, T_g, might be due to the dramatic changes in the physical properties of the polymer, such as hardness and elasticity, which take place in the vicinity of this temperature. However, perfectly crystalline polymers do not exhibit glass transitions, because their chains are incorporated in regions of three-dimensional order, called crystallites. Completely amorphous polymers and semi-crystalline polymers usually exhibit both glass transition and melting.     

Influence of the wood fibre filler on the internal recycling of poly(vinyl chloride)-based composites

The recycling of internal waste of poly(vinyl chloride) (PVC) and wood fibre-reinforced PVC composite was investigated and compared. Twenty extrusion-milling cycles were performed and the mechanical and thermal properties evaluated. This comparison provided evidence of the influence of the vegetable fibres on the thermo-mechanical degradation of the composite material. Up to five cycles, the composite properties remained stable. But after 10 cycles and especially at 20 cycles, the flexural strength increased, whereas the other mechanical properties remained almost constant. At the same time, a decrease of the degradation temperature revealed a deterioration of the molecular structure. The PVC properties remained constant, whereas a great increase in the impact strength was observed after 20 cycles without deterioration of the molecular structure. The different behaviours between the composite and the PVC were explained by the influence of the fibres, which accelerated the PVC degradation, characterized by dehydrochlorination followed by crosslinking reactions.     

Environmental stress cracking of poly(vinyl chloride) in alkaline solutions

The environmental stress cracking (ESC) effects on PVC of various high pH sodium hydroxide environments have been studied. The behaviour of PVC specimens in air and pH 12, 13, 13.5 and 14.39 sodium hydroxide solutions has been examined under three-point bend, tensile and creep conditions. Two parameters were used in three-point bend testing to determine the effect of an applied strain and high pH environment on the stability of PVC, namely time to craze initiation and width of crazing. It was found that, in general, crazing occurred sooner and to a greater degree with increasing strain and pH, although there was some evidence that craze growth was most rapid at pH 13.5. The results also indicated a critical strain value of 1.5–1.6%, below which crazing was not observed in any of these alkaline environments. Creep and tensile testing revealed that the time for which a PVC specimen was immersed in the environment was very important in determining the severity of the environmental effect. Creep tests at elevated temperatures showed that the time for the effects to be manifest decreased with increasing temperature. Creep rates were highest in pH 13.5 sodium hydroxide solution indicating that this was the most hostile of the environments considered.     

Ionic liquids: New generation stable plasticizers for poly(vinyl chloride)

Room temperature ionic liquids (ILs), based on ammonium, imidazolium and phosphonium cations, were studied as novel plasticizers for poly(vinyl chloride), PVC. All the ILs tested were able to produce flexible PVC. Upon 20 wt% plasticization, some of the ILs lowered the glass transition temperature (T_g) of PVC more than that done by several traditional plasticizers. They showed good thermodynamic compatibility as well. Several ILs showed better leaching and migration resistance than the traditional plasticizers. This was, in particular, a significant observation considering the ongoing controversy regarding the leaching and migration issues of the commonly-used phthalate plasticizers. High temperature and ultraviolet (UV) ray stability of IL-plasticized PVC samples were also studied.     

Thermal stability and thermal aging of poly(vinyl chloride)/MgAl layered double hydroxides composites

MgAl-LDH(layered double hydroxides) were prepared with CO(NH_2)_2, NH_4 Cl and NH_3·H_2O by the coprecipitation method, respectively. Corresponding composite membranes were prepared by the coating method. LDHs were characterized by WAXS, CO_2-TPD and SEM. The morphology of the PVC/LDHs composite membranes were characterized by means of SEM. The thermal stability of the membranes was analyzed by air aging box and TGA-FTIR. The SEM results show that nano-particles can be compatible with poly(vinyl chloride)(PVC) matrix homogeneously by the stirring-ultrasound blend method with two steps. Furthermore, the air aging box results proved that MgAl-CO(NH_2)_2-LDH has the best effect on thermal stability of PVC. TGA-FTIR results show that MgAl-CO(NH_2)_2-LDH could adsorb more HCl that resulted from the degradation of PVC and improve the pyrolysis temperature of the first degradation stage by 15 K compared with PVC.