Infrared studies of crystallinity in poly(vinyl chloride)

The infrared spectrum of a solvent-cast film of commercial poly(vinyl chloride) (PVC) can be very sensitively compared to a rapidly quenched film of the same material by using a compensation technique. When this is done, crystalline bands, as seen in urea canal complex PVC, can be detected and measured in the solvent-cast film. The melting and recrystallization behavior as well as the broad melting range from 120° to 210°C indicate the presence of crystallites of widely different degrees of perfection. Crystallization kinetics from the quenched glassy state indicate that time-temperature superposition applies with an activation energy of 90 kcal/mole. Molecular mobility is indicated as the rate-controlling mechanism.     

Structure and Properties of Poly(vinyl chloride)/Halloysite Nanotubes Nanocomposites

Poly(vinyl chloride)(PVC)/halloysite nanotubes (HNTs) nanocomposites were prepared by melt blending. The effects of HNT content on the mechanical properties, morphology, and rheological properties of the nanocomposites were investigated. The results showed that HNTs were effective in toughening and reinforcing PVC nanocomposites. The notched impact, tensile and flexural strength, and flexural modulus of the nanocomposites were remarkably increased compared with those for the pure PVC. Scanning electron microscopy (SEM) results illustrated the ductile behavior of the nanocomposites, with a possible cavitation mechanism. Transmission electron microscopy (TEM) results showed that HNTs were uniformly dispersed in the PVC matrix. Interfacial interaction of hydrogen bonding between the HNTs and PVC matrix was substantiated. The plasticization times of PVC/HNTs nanocomposites were found to be shorter and the equilibrium torque was higher than that for the pure PVC.     

Effect of flexibility of grafted polymer on the morphology and property of nanosilica/PVC composites

In this study, poly(methyl methacrylate)-grafted-nanosilica (PMMA-g-silica) and a copolymer of styrene (St), n-butyl acrylate (BA) and acrylic acid (AA)-grafted-nanosilica (PSBA-g-silica) hybrid nanoparticles were prepared by using a heterophase polymerization technique in an aqueous system. The grafted polymers made up approximately 50 wt.% of the resulted hybrid nanoparticles which showed a spherical and well-dispersed morphology. The silica hybrid nanoparticles were subsequently used as fillers in a poly(vinyl chloride) (PVC) matrix to fabricate PVC nanocomposite. Morphology study of PVC nanocomposites revealed that both PMMA- and PSBA-grafted-silica had an adhesive interface between the silica and PVC. The tensile strength and elongation to break were found to be improved significantly in comparison with that of untreated nanosilica/PVC composites. Finally our results clearly demonstrated that the properties (e.g. chain flexibility, composition) of the grafted polymer in the hybrid nanoparticles could significantly affect the dispersion behavior of hybrid nanoparticles in PVC matrix, dynamic mechanical thermal properties and mechanical properties of the resulted PVC composites.     

In Situ Dynamic Vulcanization of Poly(Vinyl Chloride)/Acrylonitrile-butadiene Rubber Blends

Poly(vinyl chloride) (PVC)/acrylonitrile-butadiene rubber (NBR) blends can be obtained through a dynamic vulcanization process as a melt-processible thermoplastic elastomer which produces parts that look, feel and perform like vulcanized rubber with the advantage of being processible as a thermoplastic material. In this study, a vulcanized thermoplastic was obtained by in situ dynamic vulcanization of PVC/NBR blends using a sulphur/ tetramethylthiuram disulphide (TMTD) and mercaptobenzothiazyl disulphide (MBTS) curative system during processing at the melt state. The blends were melt-mixed using a Haake Rheomix 600. The curing behavior of NBR was then investigated by a Monsanto rheometer. The thermal analyses were performed and the cross-linking at different mixing times was calculated using DSC. FT-IR was also performed for characterization of the blends. The cross-link densities of the samples were measured by a swelling method. The degree of cure increases with the mixing time. The cross-linking formation was verified through the formation of C─ S bonds in the blends.     

Polymers as fuel for laser-based microthrusters: An investigation of thrust, material, plasma and shockwave properties

The micro-laser plasma thruster (μ-LPT) is a micropropulsion device, designed for steering and propelling of small satellites (1-10 kg). A laser is focused onto a polymer layer on a substrate to form a plasma, which produces the thrust that is used to control the satellite motion. Three different polymers were tested to understand the influence of their specific properties on the thrust performance: poly(vinyl chloride) (PVC) as a low-energetic material, a glycidyl azide polymer (GAP), and poly(vinyl nitrate) (PVN) as high-energetic polymers. Different absorbers (carbon nanoparticles or an IR dye) were added to the polymer to achieve absorption at the irradiation wavelength (1064 nm). The influence of the material and dopant properties on the decomposition characteristics and the energy release were investigated by thrust measurements and ns-shadowgraphy. Mass spectrometry and time- and space-resolved plasma emission spectroscopy in air and vacuum were used to analyze the degree of fragmentation as function of the material properties. The kinetic energies of selected fragments were calculated from the spectra. GAP + C showed the best performance in all measurements at high fluences, while at low fluences PVN + C revealed the best performance.     

Dielectric response of PVC polymer loaded with Ba0.3Na0.7Ti0.3Nb0.7O3 ceramic powder

Dielectric response of poly(vinyl chloride), (PVC), loaded with different amount of Ba_0.3Na_0.7Ti_0.3Nb_0.7O₃ (BNTN) ceramic powders was investigated in frequency range 100 Hz–1 MHz and temperature range 100–450 K. Ceramic solid solution of barium titanate and sodium niobate with composition Ba_0.3Na_0.7Ti_0.3Nb_0.7O₃ was obtained from BaCO₃, TiO₂, Na₂CO₃ and Nb₂O₅ by conventional method. Powders were prepared by grinding of ceramics. The obtained ceramics, used to produce BNTN–PVC composites, are characterized by the relaxor behaviour with a broad peak of dielectric permittivity ε′ at T _m ≈ 230 K. The microstructure of the powders was observed and the grain size was estimated using scanning electron microscope Hitachi S-4700. The EDS analysis confirms the qualitative and quantitative chemical composition of powders and ceramics. The BNTN–PVC composite samples of 0-3 connectivity were prepared from ceramic and polymer powders by hot-pressing method. The dielectric response of the composites displays features originated from the PVC polymer modified by those of BNTN ceramics. The relaxation time of the α-process of PVC obeys the Vogel–Fulcher law and decreases with increasing volume fraction of the ceramics.     

Thermally stimulated currents in poly(vinyl chloride): Tacticity and molecular weight influence

Thermally stimulated currents (TSC) have been measured in several samples of poly(vinyl chloride) differing in tacticity and molecular weight as a result of polymerizing them at different temperatures. This has allowed us to characterize the relaxation behavior of PVC. No dielectric relaxation can be observed by this experimental technique at temperatures between liquid helium and liquid nitrogen. The β relaxation is observed around 173°K, with similar parameters in all samples studied. Around the glass transition the relaxation times isolated in the α peak follow a compensation law. Molecular weight and tacticity have a strong influence on the temperature of the maximum and the intensity of this relaxation, respectively.     

The gelation of PVC: Characterization and control

Poly(vinyl chloride), PVC, can be gelled from 10% (w/w) solutions in a number of solvents so as to give model networks where the junctions are directly accessible by crystallographic techniques, and where the extent and properties of the network can be correlated with the nature of these junctions. The resulting network structure has been studied as a function of polymer crystallinity and polymer-solvent interaction, and a correlation between gel-forming ability and solubility parameters was found. As in previous and accompanying work [1, 2], the gel system was found to consist of two crystal populations, the gel-forming micellar (B) and the better-developed, presumably lamellar (A) crystals incorporated in the gel. The thermal behavior of wet and dried gels was followed by DSC and by high-temperature x-ray diffraction, in the course of which the distinctness of the two crystal classes became apparent also as regards thermal stability.

The gelation behavior of PVC is discussed in the wider perspective of polymer crystallization and in relation to plasticization and the stereochemistry of PVC. The explicit connections between industrial plasticization and the present gelation behavior are being pointed out, hopefully with benefit for the understanding and control of the former. The crystallization effects themselves raise further questions as regards the necessity of long syndiotactic runs in the chain (as opposed to the usually envisaged random distribution of stereoisomers) or alternatively the incorporation of substantial amounts of isomeric defects into the syndiotactic lattice. Arguments for and against these obviously fundamental alternatives are invoked.     

Simple and fast preparation of graphene oxide@ melamine terephthaldehyde and its PVC nanocomposite via ultrasonic irradiation: Chemical and thermal resistance study

Melamine terephthaldehyde modified graphene oxide (MTR-GO) with optimum content was easily prepared via ultrasonication method and used as anti-corrosion additive for Poly (vinyl chloride) (PVC). The effects of ultrasonicated MTR-GO on the mechanical, chemical and thermal resistance of the PVC were thoroughly studied. Change percentage of tensile strength and weight change percentage of PVC (P) and PVC/MTR-GO nanocomposite (PN) in acetone and sodium hypochlorite (NaClO) media at two different exposure temperature (20 °C and 50 °C) were examined. The PN sample showed lower change loss percentage of tensile strength in acetone uptake as compared with P sample at 20 °C. In higher temperature (50 °C), P sample was decomposed while PN still showed tensile data. The change loss percentage in tensile strength of PN sample showed 13% change at 50 °C in sodium hypochlorite while P sample showed 63% change for the parameter. Protective behavior of MTR-GO nanofiller on PVC matrix against thermal HCl releasing was investigated by Congo red tests. The results showed that the nanocomposite release less amount of HCl as compare to the neat PVC.     

CORRELATION AMONG MORPHOLOGY,INTERFACE, AND MECHANICAL PROPERTIES: EXPERIMENTAL STUDY

The effect of the disperse phase and the diffuse interface between phases on the tensile and impact strengths of polypropylene (PP)/poly(ethylene terephthalate) (PET) (75/20 by weight) blends compatibilized with maleic anhydride–grafted PP derivatives and on the tensile modulus of poly(vinyl chloride)/polystyrene (PVC/PS) nanoparticle blends compatibilized with polystyrene/poly(vinyl acetate) (PS/PVAc) block copolymers were investigated experimentally. The weight fraction of the diffuse interface between the PP and PET phases in the PP/PET blends was determined by modulated differential scanning calorimetry (MDSC). A correlation between the diffuse interface content and mechanical properties was found. With increasing diffuse interface weight fraction, the impact and tensile strengths of the PP/PET blends increased. There is a brittle-tough type transition in these PP/PET blends. With increasing diffuse interface content in the PVC/PS nanoparticle blends in which the particle size was fixed at about 100 nm, the tensile modulus also clearly increased.     

The Peculiar Temperature Response of Dynamic Rheological Behaviors of Poly (Vinyl Chloride)/trioctyl Trimellitate (100/70) System

The dynamic rheological behavior, application of time-temperature superposition (TTS) and the failure mechanism of TTS are studied for the poly(vinyl chloride) (PVC)/trioctyl trimellitate (TOTM) (100/70) system. The Arrhenius equation, Williams–Landel—Ferry (WLF) equation, mathematical non-linear fitting and manual shift are applied to TTS fitting. For the PVC/TOTM (100/70) system, none of those methods can give well-superimposed master curves with either single horizontal shift or two-dimensional (horizontal and vertical) shift. The failure reason is attributed to the thermorheological complexity of the PVC/TOTM (100/70) system. Curves of the storage modulus versus the frequency can be well fitted with an empirical equation (G′=G′₀+Kω ⁿ ) usually used to describe filled polymer systems, indicating the multilevel flowing unit characteristic in this system. With the increase of test temperature, the structure of the PVC/TOTM (100/70) system changes and an apparent transition appears in the rheological behavior. Differential scanning calorimetry (DSC) results reveal that for the PVC/TOTM (100/70) system there are microcrystallites present below 220°C, but above the rheological transition temperature (190°C) the bulk of the microcrystallites melted, which corresponds to the appearance of viscous flow participating in the rheological behavior. It verifies the fact that the gel networks crosslinked by microcrystallites dominate the rheological behavior below the transition temperature in the PVC/TOTM (100/70) system. The quantity of microcrystallites remaining in the melt determines the perfection of the physical gel networks. With the increase of test temperature, the microcrystallites melted gradually and the gel networks are broken up.     

Influence of Molecular Structure and Packing on Sorption and Transport Properties of Dichloromethane in Polyetherimides

The effects of thermal history on dichloromethane vapor sorption and transport properties of polyetherimides were studied. Films were prepared by solution casting at room temperature and heat treated for 24 h at different temperatures below the corresponding glass transition temperature of each material. Changes of the transport properties due to heat treatment were observed and are correlated to changes in density, free volume, and thermal transitions. Deviation from Fick's and Henry's laws was observed for all the samples studied. Without heat treatment and at low activities of the penetrant, the materials studied show sorption kinetics similar to the Fickian behavior. On the other hand, sorption measurements tests for the heat‐treated films at high activities of dichloromethane show kinetics similar to Case II diffusion. Equilibrium sorption data obtained at different penetrant concentrations show deviation from Henry's law behavior depending on the thermal history of the sample.     

Thermo-mechanical performance of PVC/ZnO nanocomposites

The present paper deals with the study of thermo-mechanical performance of PVC/ZnO nanocomposites. The samples have been prepared by solution casting technique with different (0, 2, 4, 6 and 8) wt. % of ZnO nanoparticles in poly (vinyl chloride) (PVC) matrix and structurally characterized through scanning electron microscopy. In thermo-mechanical analysis, dynamic mechanical analyzer gives the information about storage modulus and phase transition temperature (T_g). From these viscosities, profile at elevated temperature and activation energy of phase transition can be evaluated. This study reveals that dispersion of nano-ZnO significantly altered the thermo-mechanical properties of neat PVC but the effect is composition-dependent.     

Studies on wettability of medical poly(vinyl chloride) by remote argon plasma

The paper studies surface modification of medical poly(vinyl chloride) (PVC) by remote argon plasma and characterized surface structure, performance of treated PVC by the water contact angle measurement, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Results show that the remote argon plasma makes the surface of the PVC film higher hydrophilic than the direct argon plasma and does not give remarkable degradation on the PVC film surface. The hydrophilicity depends on sample position as well as the RF power and the plasma exposure time. The remote argon plasma contributes more effectively to the dechlorination (Cl/C = 0.01) from the PVC film than the direct argon plasmas (Cl/C = 0.03) and more effectively to the formation oxygen functionalities on the PVC film surface. These experimental results show the possibility that remote argon plasma treatment can enhance interaction reactions with argon radicals relative to those with electron and argon ions.     

Properties of blends of poly(vinyl chloride) and chlorinated polyethylene. I. Optical methods of characterization of PVC multiphase systems

Hitherto it has not been possible to produce a microscopic image with adequate resolution of the high-impact two-phase system poly(vinyl chloride) (PVC)/chlorinated polyethylene (CPE) due to inadequate phase contrast. With the aid of various chemical staining methods and through ion etching, a way has been found for studying the microstructure of the PVC/CPE system by light microscopy and electron microscopy. These independent visualization techniques and scanning electron micrographs of fracture surfaces show, as the morphology with optimal mechanical and rheological properties, networklike distribution of the rubber phase and, imbedded in this, a PVC phase consisting of primary particles.     

Modification of a Theoretical Model for the Prediction of the Thermal Expansion Behavior of Particulate Composites: Application to Poly(vinyl chloride)/Talc Composites

The coefficients of thermal expansion (CTE) of poly(vinyl chloride) (PVC)/talc composites were tested and the experimental data showed that the CTE of PVC/talc composites were closely related to the talc particle size and its distribution; for a given talc volume fraction, the smaller the talc particle size, and the lower the CTE of the PVC/talc composites. The theoretical equations proposed by Sideridis and Papanicolaou and by Lombardo, which were based on a single, spherical particle size, were found to predict well the CTE of PVC/talc composites, but with the obtained interphase thicknesses were too large to be believed. In order to overcome the shortcomings of these equations, being without variation of filler particle size and its distribution, a modified model was proposed. It was found that the modified model can predict well the CTE of PVC/talc composites, with almost the same and more reliable interphase thicknesses for different talc particle sizes, confirming the correctness of the modified model to some extent.     

The Effect of OMMT on the Morphology and Mechanical Properties of PVC/ABS Blends

Poly(vinyl chloride) (PVC)/acrylonitrile-butadiene-styrene (ABS) blends containing organically modified montmorillonite (OMMT) were prepared using a twin-screw extruder followed by injection molding. The OMMT dispersion was evaluated by X-ray diffraction and transmission electron microscopy. The clay was preferentially situated in the PVC phase and across the interfaces of PVC/ABS. The effect of the addition of OMMT on the morphology and mechanical properties was also evaluated. Scanning electron microscopy revealed a large reduction in domain size when OMMT was used. The mechanical properties were studied through tensile and impact tests. The yield stress increased when an appropriate amount of OMMT was used without impairing the impact strength.     

Effect of Unplasticized Poly Vinyl Chloride (UPVC) Molecular Weight and Graft-Acrylonitrile-Butadiene-Styrene (g-ABS) Content on Compatibility and Izod Impact Strength of UPVC/g-ABS Blends

In this study three grades of rigid poly vinyl chloride (PVC) having different molar masses were melt blended with graft-acrylonitrile-butadiene-styrene (g-ABS) in different compositions. The effect of PVC molecular weight and g-ABS composition on the compatibility and Izod impact strength of the blends were investigated. Differential scanning calorimetry (DSC) results showed a single glass transition temperature (T_g) for all the blends, representative of miscibility between the PVC phase and the styrene-acrylonitrile copolymer (SAN) phase of g-ABS which, in turn, led to compatibility of the PVC/g-ABS blends. It was observed that in all the PVC grades the blends Izod impact strength increased with increasing g-ABS content. Also, at a given composition of g-ABS, by increasing the molecular weight of the PVC phase the impact strength of the blends increased. The morphology of the fracture surfaces from the impact tests were analyzed using scanning electron microscopy (SEM) micrographs and the results showed that with increasing g-ABS content in the blend, cloudy regions increased and eventually begin to overlap each other, and the deformed material on the fracture surfaces increased. This was attributed to the blend compatibility causing greater energy dissipation in the fracture process.     

Nanocomposite materials based on poly(vinyl chloride) and bovine serum albumin modified ZnO through ultrasonic irradiation as a green technique: Optical,thermal, mechanical and morphological properties

In this project, physicochemical properties of poly(vinyl chloride) (PVC) reinforced by ZnO nanoparticles (NPs) were studied. Firstly, ZnO NPs were modified with bovine serum albumin (BSA) as an organo-modifier and biocompatible substance through ultrasound irradiation as environmental friendly, low cost and rapid means. Nanocomposite (NC) films were prepared by loadings of various ratios of ZnO/BSA NPs (3, 6 and 9 wt%) inside the PVC. Structural morphology and physical properties of the ZnO-BSA NPs and NC films were investigated via Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis (TGA), transmission electron microscopy and field emission scanning electron microscopy. According to the obtained information from the TGA, an increase in the thermal stability can be clearly observed. Also the results of contact angle analysis indicated with increasing percent of ZnO/BSA NPs into PVC the hydrophilic behaviors of NCs were increased.     

Preparation and Evaluation of the Morphology,Flammability, and Mechanical Properties of the Acrylonitrile‐Butadiene‐Styrene/Poly (vinyl chloride) Blends

Blends of two grades of acrylonitrile‐butadiene‐styrene (ABS) with three different compounds of poly (vinyl chloride) (PVC) were prepared via melt processing and their morphology, flammability, and physical and mechanical properties were investigated. SEM results showed that the ABS/PVC blend is a compatible system. Also, it can be inferred from fracture surface images that ABS/PVC blends are tough, even at low temperatures. It was found that properties of these blends significantly depend on blend composition and PVC compound type; however, the ABS types have only a small effect on blend properties. On blending of ABS with a soft PVC compound, impact strength, and melt flow index (MFI) increased, but tensile and flexural strength decreased. In contrast, blending of ABS with a rigid PVC compound improved fire retardancy and some mechanical properties and decreased MFI and impact strength.