Poly(vinyl chloride)‐based miscible blends: Changes induced in the structural characteristics and in dielectric α relaxation of pure poly(vinyl chloride)

In this work we investigate by means of dielectric relaxation spectroscopy how segmental motions occurring in poly(vinyl chloride) (PVC) are modified by blending of PVC with small amounts of two different homopolymers: crystalline poly(ϵ‐caprolactone) (PCL) and glassy syndiotactic poly(methylmethacrylate) (sPMMA). The dynamics of the α relaxation of PVC is severely changed by blending it with PCL or sPMMA becoming faster or slower, respectively. Simultaneously, the shape of the relaxation function is being importantly altered. It shows a stronger non‐Debye character being broader and strongly temperature‐dependent. This fact leads us to calculate distributions of relaxation times for the blends that are wider in comparison to the one obtained for pure PVC. Complementary X‐ray diffraction measurements have been performed in order to assure the absence of crystallinity in the blends, and some small variations can be deduced at the level of interchain structural correlations of PVC. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 234–247, 2000     

Preparation and characterization of polyaniline blends with polyvinyl acetate,polystyrene and polyvinyl chloride for toxic gas sensors

The conditions of processing and gas sensing of ­polyaniline (PANi) blends with polyvinyl acetate (PVAc), polystyrene (PS) and polyvinyl chloride (PVC) were investigated. Flexible, free‐standing and stretchable films of various blends compositions were obtained by casting. The mechanisms of the conducting blends response to a selection of gases and vapours were investigated using two techniques: measurement of conductance and mass changes using a four‐point probe method and X‐ray fluorescence (XRF) device, respectively. These responses to toxic gases and vapours are better explained by polymer blends than homopolymers. Prepared films were exposed to hydrogen halides, hydrogen cyanide, halogens, monochloroacetic acid (MCAA), 1‐3‐5 trichloromethyl benzene (TCMB), methylbenzyl bromide (MBB), bromoacetone (BA) and cyanogen bromide (CB). The changes in conductivity of various polymer frequently observed are partly due to one stage in the two‐stage sorption perhaps involving the swelling of the polymer and then diffusion of gases into polymer chains. The swelling of polymers is a slow process, therefore, we have pre‐swelled polymer films which tend to decrease the response times of blends in respect to gases. The structures of the blends are examined by STA (TGA & DSC) and SEM studies. Copyright © 2001 John Wiley & Sons, Ltd.     

Thermal conductivity of poly(vinyl chloride)/polycaprolactone blends

Thermal diffusivity, heat capacity, and density of polyvinyl chloride/polycaprolactone (PVC/PCL) blends were measured by the laser flash method, DSC, and pycnometry, respectively. The thermal conductivity of the PVC/PCL blends was determined from the results. The miscibility of the blend and crystallinity of PCL were determined by DSC. The effect of blend structure on thermal conductivity is discussed. The phase compositions of the PVC/PCL blends are of three types depending on PCL content: i.e., up to 33%, from 33 to 70%, and above 70% PCL by weight. Thermal conductivity, thermal diffusivity, and heat capacity of the PVC/PCL blends are strongly affected by the phase composition of the blend, which changes in a complicated way with PCL content. © 1994 John Wiley & Sons, Inc.     

Studies on copolymers of vinyl chloride with diethyl fumarate,isobutylene and vinyl bromide as PVC models with chain irregularities—III The influence of the tacticity and of the copolymer composition on the thermal degradation: The influence of the tacticity and of the copolymer composition on the thermal degradation

The thermal degradation kinetics of pairs of vinyl chloride copolymers with diethyl fumarate, isobutylene and vinyl bromide, having the same composition but different tacticity, were followed by conductivity measurements. From the results for degradation up to 0·3% and up to 10%, it follows that syndiotactic sequences in PVC give rise to high degradation rates in agreement with results of previous work on homopolymers of vinyl chloride. On the basis of kinetic aspects as well as u.v.- visible spectra of degraded samples, the influence of tacticity on the thermal degradation of copolymers is discussed. This effect is compared to that of weak points introduced in the PVC chain by means of copolymerization.     

The electromagnetic properties of blends of poly(p‐phenylene‐vinylene) derivatives

We report the studies on the frequency dependence of the complex permittivity, and on the electromagnetic interference (EMI) shielding of conductive blends. The blends were obtained from conjugated oligomers of (p‐phenylene‐1,3,5‐hexatrienylene) end‐capped by Schiff base units and dispersed in an insulating matrix of poly(vinyl chloride) (PVC) and doped with sulfuric acid, H₂SO₄. Permittivity measurements from 10 kHz to 10 GHz have pointed out that the electrical conductivity of composites were in a range 10⁻⁵–10⁺¹ S/cm. From these experimental data performed on 250–500 µm, the reflectivity coefficients [R(dB)] have been calculated for simulation of mm thick samples, they have values of −9 to −20 dB depending on the frequency and on the thickness of the composites. These permitivity data have also allowed us to develop modelization of the radioelectric properties of conductive blends, using McLachlan's General Effective Medium (GEM) Theory. The optimization of the GEM parameters suggests some informations about the shape of the particles as well as the micro/macrostructure of the composite materials. Copyright © 2000 John Wiley & Sons, Ltd.     

Degradation of polymer mixtures. IV. Blends of poly(vinyl acetate) with poly(vinyl chloride) and other chlorine-containing polymers

The degradation of the binary polymer blends, poly(vinyl acetate)/poly(vinyl chloride), poly(vinyl acetate)/poly(vinylidene chloride) and poly(vinyl acetate)/polychloroprene has been studied by using thermal volatilization analysis, thermogravimetry, evolved gas analysis for hydrogen chloride and acetic acid, and spectroscopic methods. For the first two systems named, strong interaction occurs in the degrading blend, but the polychloroprene blends showed no indication of interaction. In the PVA/PVC and PVA/PVDC blends, hydrogen chloride from the chlorinated polymer causes substantial acceleration in the deacetylation of PVA. Acetic acid from PVA destabilizes PVC but has little effect in the case of PVDC because of the widely differing degradation temperatures of PVA and PVDC. The presence of hydrogen chloride during the degradation of PVA results in the formation of longer conjugated sequences, and the regression in sequence length at high extents of deacetylation found for PVA degraded alone is not observed.     

Morphology, thermal stability and visco-elastic properties of polystyrene-poly(vinyl chloride) blends

The morphology, thermal and mechanical properties of polystyrene (PS) blends with 2.5-20 wt% of poly(vinyl chloride) (PVC) have been studied. The measurement of the glass transition temperature (T_g) from the maxima of tan δ data using dynamic mechanical thermal analysis showed that the blends were incompatible and homogenously distributed only within a limited range of PVC contents in PS. The value of the storage modulus was found to increase initially but then decreased with further addition of PVC in the matrix. Distribution of the phases in the virgin and degraded blends was also studied through scanning electron microscopy. The thermogravimetric studies on these blends were carried out under inert atmosphere from ambient to 800 °C at different heating rates varying from 2.5 to 20 °C/min. The thermal decomposition temperatures of blends were found higher than that of pure PS which indicated the stabilizing effects of PVC on PS. The effect varies with the heating rates and the composition of the blends and the phenomenon has been explained due to changing morphology of the blends with composition and the degradation time which affect the interfacial interaction between the degrading products from the polymer components. The kinetic parameters of the degradation process calculated from a method described by Ozawa have been reported for these blends.     

Development and characterization of reactive extruded PVC/polyacrylate blends

This paper describes a method to obtain polymer blends by the absorption of a liquid solution of monomer, initiator, and a crosslinking agent in suspension type porous poly(vinyl chloride) (PVC) particles, forming a dry blend. These PVC/monomer dry blends are reactively polymerized in a twin‐screw extruder to obtain the in situ polymerization in a melt state of various blends: PVC/poly(methyl methacrylate) (PVC/PMMA), PVC/poly(vinyl acetate) (PVC/PVAc), PVC/poly(butyl acrylate) (PVC/PBA) and PVC/poly(ethylhexyl acrylate) (PVC/PEHA). Physical PVC/PMMA blends were produced, and the properties of those blends are compared to reactive blends of similar compositions. Owing to the high polymerization temperature (180°C), the polymers formed in this reactive polymerization process have low molecular weight. These short polymer chains plasticize the PVC phase reducing the melt viscosity, glass transition and the static modulus. Reactive blends of PVC/PMMA and PVC/PVAc are more compatible than the reactive PVC/PBA and PVC/PEHA blends. Reactive PVC/PMMA and PVC/PVAc blends are transparent, form single phase morphology, have single glass transition temperature (T_g), and show mechanical properties that are not inferior than that of neat PVC. Reactive PVC/PBA and PVC/PEHA blends are incompatible and two discrete phases are observed in each blend. However, those blends exhibit single glass transition owing to low content of the dispersed phase particles, which is probably too low to be detected by dynamic mechanical thermal analysis (DMTA) as a separate T_g value. The reactive PVC/PEHA show exceptional high elongation at break (～90%) owing to energy absorption optimized at this dispersed particle size (0.2–0.8 µm). Copyright © 2005 John Wiley & Sons, Ltd.     

Electronic transport properties of polyaniline/PVC blends

The electrical conductivity and thermoelectric power of polyaniline/PVC blends was measured. Surprisingly, the conductivity of the blends is greater at low temperatures than that of the pure polyaniline sample. The conductivity follows approximately an exp (?T^?1/2) law over a considerable range of temperature, with deviations from this law observed at high temperature increases (with positive sign) except at very low temperatures, where negative peaks are observed. Possible models to interpret these observations are mentioned. © 1993 John Wiley & Sons, Inc.     

FT‐IR Investigation into the miscible interactions in new materials for optical devices

In this article we determine the miscibility of azobenzene derivative (poly(4‐(N‐(2‐methacryloyloxyethyl)‐N‐ethylamino)‐4′‐nitroazobenzene)₉₀‐co‐(methyl methacrylate)₁₀)/poly(vinyl acetate) (PVAc) and azobenzene derivative/poly(vinyl chloride) (PVC) blends using Fourier Transform infrared (FT‐IR) spectroscopy. With this method we can clearly identify the exact interactions responsible for miscibility. In the azobenzene derivative 50:50PVAc blend new peaks were evident at 2960, 2890, 1237 and 959 cm^?1, these peaks depict miscible interactions. These wavenumbers indicate that the miscible interactions occurring are from the C? H stretching band, the vinyl acetate C?O, conjugated to the ester carbonyl, the cis‐transformation N?N stretch frequency and the acetate ester weak doublet. The azobenzene derivative 80:20PVC blend display peaks identical in profile to the blend homopolymers, indicating no miscible interactions. However, this could be due to overlapping of peaks within the same wavenumber region, making resolution difficult. This research demonstrates FT‐IR can deduce favorable interactions for miscibility and therefore numerous miscible blends can successfully be calculated if possessing the same groups responsible for miscibility. This paves the way for a new generation of designer optical materials with the desired properties. Copyright © 2003 John Wiley & Sons, Ltd.     

Miscibility of Some Polycarbonates with Polyvinyl Chloride and Chlorinated Polyvinyl Chloride

The phase behavior of several polycarbonate homopolymers and copolymers blended with PVC and chlorinated PVCs (CPVCs) has been investigated. Tetrachlorobisphenol-A polycarbonate (TCPC) is miscible in all proportions with PVC and CPVCs containing up to70.2 wt% chlorine. CPVCs having chlorine contents greater than 70.2% (by weight) are immiscible with TCPC. Tetrabromobisphenol-A polycarbonate (TBPC) exhibits phase mixing with PVC and CPVCs; however, the high T_g of this polycarbonate (260°C) prevents adequate investigation of equilibrium phase behavior. Bisphenol-A polycarbonate (BPC), tetramethylbisphenol-A polycarbonate (TMPC), and hexafluorobisphenol-A polycarbonate (HFPC) form two-phase mixtures with the vinyl polymers. Microstructural differences in the CPVCs due to chlorination method (solution chlorination vs. slurry chlorination) have no effect on the miscibility results. Miscibility was observed in several copolycarbonate/CPVC blends and was found to be dependent on copolymer composition. Using a binary interaction, mean-field theory, segmental interaction parameters were estimated for repeat unit interactions. Based on the estimated interaction parameters, miscibility in these blends is primarily the result of intramolecular repulsive effects, rather than strong intermolecular attractive forces.This revised version was published online in November 2005 with corrections to the Cover Date.     

Kinetics of thermal degradation of poly(vinyl chloride)

Extensively studied thermal degradation of polyvinyl chloride (PVC) occurs with formation of free hydrogen chloride and conjugated double bonds absorbing light in visible region. Thermogravimetric monitoring of PVC blends degradation kinetics by the loss of HCl is often complicated by evaporation and degradation of plasticizers and additives. Spectroscopic PVC degradation kinetics monitoring by absorbance of forming conjugated polyenes is specific and should not be affected by plasticizers loss. The kinetics of isothermal degradation monitored by thermal gravimetric analysis in real time was compared with batch data obtained by UV/Visible absorption spectroscopy. Effects of plasticizer on kinetics of polyene formation were examined. Thermal degradation of PVC films plasticized with di-(2-ethylhexyl) phthalate (DEHP) and 1,2,4-benzenedicarboxylic acid, tri-(3-ethylhexyl) ester (TOTM) was monitored by conjugated double bonds light absorption at 350 nm at 160, 180, and 200 °C. Plasticizer-free PVC powder degradation kinetics and that of plasticized films were also obtained thermogravimetrically at temperatures ranging from 160 to 220 °C. Plasticizer-free PVC powder degradation and spectroscopically monitored degradation of plasticized PVC films occurred with the same apparent activation energy of ≈150 kJ mol⁻¹. No difference in degradation kinetics of films plasticized with DEHP and TOTM was detected.     

Diffusion and partition coefficients of small organic solvents in molten miscible polymer blends: Correlations with thermodynamic interactions

The transport properties of small organic molecules in molten poly(vinyl chloride) (PVC)/atactic poly(methyl methacrylate) (PMMA) blends and their homopolymers were studied with inverse gas chromatography. The elution profiles resulting from various organic solvents and different experimental conditions were used for measuring diffusion and partition coefficients. With the van Deemter equation and retention volumes at infinite dilution, diffusion coefficients of 10^?7 to 10^?8 cm²/s and partition coefficients of 10–50 were calculated. The dependence of the diffusion and partition coefficients on experimental variables such as the blend concentration, temperature, and solute nature was examined. The presence of PMMA in PVC blends affected the sorption behavior of the PVC matrix up to a certain concentration. Beyond that, it was hard to derive any composition–diffusivity dependence. On the contrary, the diffusion and partition coefficients were greatly influenced by changes in the temperature and by the nature of the solute. For those solutes (e.g., chlorinated hydrocarbons) showing stronger interactions with polymer blends (higher negative values for the Flory–Huggins interaction parameter χ₁₍₂₃₎), higher diffusion and partition coefficients were obtained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 267–279, 2004     

Structure of reactively extruded rigid PVC/PMMA blends

A novel route for producing polymer blends by reactive extrusion is described, starting from poly (vinyl chloride)/methyl methacrylate (PVC/MMA) dry blend and successive polymerization of MMA in an extruder. Small angle X‐ray scattering (SAXS) measurements were applied to study the monomer's mode of penetration into the PVC particles and to characterize the supermolecular structure of the reactive poly(vinyl chloride)/poly(methyl methacrylate) (PVC/PMMA) blends obtained, as compared to the corresponding physical blends of similar composition. These measurements indicate that the monomer molecules can easily penetrate into the PVC sub‐primary particles, separating the PVC chains. Moreover, the increased mobility of the PVC chains enables formation of an ordered lamellar structure, with an average d‐spacing of 4.1 nm. The same characteristic lamellar structure is further detected upon compression molding or extrusion of PVC and PVC/PMMA blends. In this case the mobility of the PVC chains is enabled through thermal energy. Dynamic mechanical thermal analysis (DMTA) and SAXS measurements of reactive and physical PVC/PMMA blends indicate that miscibility occurs between the PVC and PMMA chains. The studied reactive PVC/PMMA blends are found to be miscible, while the physical PVC/PMMA blends are only partially miscible. It can be suggested that the miscible PMMA chains weaken dipole–dipole interactions between the PVC chains, leading to high mobility and resulting in an increased PVC crystallinity degree and decreased PVC glass transition temperature (T_g). These phenomena are shown in the physical PVC/PMMA blends and further emphasized in the reactive PVC/PMMA blends. Copyright © 2005 John Wiley & Sons, Ltd.     

Studies of photooxidative degradation of poly(vinyl chloride)/poly(ethylene oxide) blends

The photooxidative degradation of blends (in a full range of compositions) of amorphous poly(vinyl chloride) (PVC) with semicrystalline poly(ethylene oxide) (PEO) in the form of thin films is investigated using absorption spectroscopy (UV–visible and Fourier transform infrared) and atomic force microscopy (AFM). The amount of insoluble gel formed as a result of photocrosslinking is estimated gravimetrically. It is found that the PVC/PEO blendsí susceptibility to photooxidative degradation differs from that pure of the components and depends on the blend composition and morphology. Photoreactions such as degradation and oxidation are accelerated whereas dehydrochlorination is retarded in blends. The photocrosslinking efficiency in PVC/PEO blends is higher than in PVC; moreover, PEO is also involved in this process. AFM images showing the lamellar structure of semicrystalline PEO in the blend lead to the conclusion that the presence of PVC does not disturb the crystallization process of PEO. The changes induced by UV irradiation allow the observation of more of the distinct PEO crystallites. This is probably caused by recrystallization of short, more mobile chains in degraded PEO or by partial removal of the less stable amorphous phase from the film surface. These results confirm previous information on the miscibility of PVC with PEO. The mechanism of the interactions between the components and the blend photodegradation are discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 585–602, 2004     

Phosphonated fully aromatic polyethers for PEMFCs applications

New homopolymers and copolymers based on aromatic polyethers bearing side diphosphonate and diphosphonic groups have been synthesized. These synthetic efforts resulted in homo and copolymers of high thermal stability but moderate molecular weights. To evaluate the influence of the immobilized phosphonate ester and phosphonic acid moieties on polymer electrolyte membranes for fuel cells applications, blends of the newly synthesized homo and copolymers with a pyridine‐based aromatic polyether were prepared. These blends were miscible with high glass transition temperatures and high thermal stabilities. Furthermore, the introduction of these groups to a polymeric backbone significantly increases the doping ability in phosphoric acid compared to the net matrix as well as the ionic conductivity for high doping levels. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2817–2827, 2010     

Mechanism of decoloration by solvent of thermally degraded poly(vinyl chloride)

The mechanism of decoloration of thermally degraded poly(vinyl chloride (PVC)) by solvents has been investigated systematically. The main results obtained are as follows. Good solvents for PVC, especially tetrahydrofuran, methyl ethyl ketone, and dioxane are effective for decoloration. The solvent peroxide which is formed by autoxidation of solvent contributes to decoloration. The number of double bonds in degraded PVC decreases as the decoloration proceeds and at the same time the solvent peroxide existing in solvent is consumed. Moreover, the existence of solvent fragments in decolored PVC is recognized. From these results, it is most reasonable to conclude that the decoloration mechanism is as follows: the solvent partially is changed to a solvent peroxide by autoxidation, and the solvent peroxide reacts with polyene double bonds of degraded PVC and breaks down conjugated double bonds, and consequently degraded PVC is decolored.     

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.     

Transition from crazing to shear deformation in ABS/PVC blends

ABS/PVC blends were prepared over a range of compositions by mixing PVC, SAN, and PB‐g‐SAN. All samples were designed to have a constant rubber level of 12 wt % and the ratio of total‐SAN to PVC in the matrix of the blends varied from 70.5/17.5 to 18/80. Transmission electron microscope and scanning electron microscope have been used to study deformation mechanisms in the ABS/PVC blends. Several different types of microscopic deformation mechanisms, depending on the composition of blends, were observed for the ABS/PVC blends. When the blend is a SAN‐rich system, the main deformation mechanisms were crazing of the matrix. When the blend is a PVC‐rich system, crazing could no longer be detected, while shear yielding of the matrix and cavitation of the rubber particles were the main mechanisms of deformation. When the composition of blend is in the intermediate state, both crazing and shear yielding of matrix were observed. This suggests that there is a transition of deformation mechanism in ABS/PVC blends with the change in composition, which is from crazing to shear deformation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 687–695, 2006     

Synthesis and characterization of polymethylphenylsilane–polystyrene block copolymers

Block copolymers of polymethylphenylsilane (PMPS) and polystyrene (PS) have been successfully prepared by the condensation of α,ω-dichloro-polymethylphenylsilane with polystyryl-lithium. These new materials have been characterized by UV spectroscopy, ²⁹Si-NMR, and size exclusion chromatography. These block copolymers show a good emulsifying activity to compatibilize blends of the two homopolymers (PMPS and PS). © 1993 John Wiley & Sons, Inc.