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1.
In this study, the use of diethylene glycol (DEG), triethylene glycol (TEG), n-C10H21OH, and ethylene glycol (EG) as solvents for NaOH in the dechlorination of poly(vinyl chloride) (PVC) was investigated. In the early reaction time, the degrees of dechlorination for DEG, TEG, and n-C10H21OH were notably higher than that for EG. Further, the high compatibility between PVC and the solvents was considered to result in the easy penetration of the solvent and OH into PVC particles, leading to the acceleration of dechlorination in the early reaction stage. An improvement of the dechlorination was actually observed for DEG and TEG compared with EG. The solvent with the best compatibility to PVC, n-C10H21OH, however, showed little improvement due to the formation of a protective polyene layer on the surface of the PVC particles.  相似文献   

2.
Stress relaxation modulus data, Er(t), have been determined between ?70 and +170°C on blends of three samples of poly(vinyl chloride) of different molecular weights with di-2-ethylhexyl adipate, di-2-ethylhexyl phthalate, epoxidized soybean oil, and a poly(propyl adipate), respectively. The relaxation modulus-time–temperature data could be combined into master curves. However, probably owing to the finite contributions of the crystalline phase to the elastic properties, time–temperature superposition is here just marginally valid, and the master curves are only crude, yet still useful approximations. Combination of the present data with the accumulated published information suggests that the viscoelastic properties of plasticized poly(vinyl chloride) are determined primarily by the glass transition temperàture of the plasticizer, the compatibility of polymer and plasticizer, and probably also by the crystallites (as crosslinks). The exact role of the crystallites will remain elusive until the advent of plasticized poly(vinyl chloride) with controlled crystallinity.  相似文献   

3.
A detailed review of the material published to date on the flow properties of poly(vinyl chloride) is given. The dependence of viscosity on concentration molecular weight, molecular weight distribution, shear and temperature for concentrated and molten poly (vinyl chloride) is considered. Polymer blends and plastisols are also included.  相似文献   

4.
5.
A sample of poly(vinyl chloride) (PVC) and a polar plasticizer consisting of dioctyl phthalate (DOP) and dibutyl phthalate (DBP) was prepared and found to possess inconvenient electrical properties (permittivity, dielectric loss, and conductivity). Different samples of PVC compositions were formulated from the PVC–DOP–DBP system and also variable proportions of a copolymer of 1-octadecene-maleic anhydride or its hexadecylester. Lead stearate as a heat stabilizer and kaolin as a filler were added. The effect of copolymer structure on the electrical properties of the PVC–DOP–DBP system was studied to obtain a plasticized PVC of good electrical insulation character. © 1993 John Wiley & Sons, Inc.  相似文献   

6.
The properties of poly(vinyl chlorlde)/ehlorinated poly(vinyl chloride) (61.6 percent C1) blends, prepared by melt and solution blending, were measured by various tests. Based on the chlorinated poly(vinyl chloride) (CPVC) composition, percent chlorine, and mole percent CC12 groups, these blends were expected to show intermediate properties between miscible and immiscible systems. Indicative of miscible behavior were the single glass transition temperatures over the entire composition range for both melt and solution blended mixtures. A single phase was also indicated by transmission electron microscopy. However, the yield stress showed a minimum value less than either of the pure components in the 50 to 75 percent CPVC range, which is characteristic of two-phased systems. Specific volume, glass transition temperature, and heat distortion temperature were linear with binary composition. The storage modulus showed a small maximum, suggesting a weak interaction between the two miscible polymers. Heats of melting for the residual PVC crystallinity were also less than expected from linear additivity. At 160°C and 210°C, the logarithm of the complex viscosity was essentially linear with volume fraction of CPVC, except for a very slight decrease in the 50 to 75 percent CPVC range, which may have been a result of lower crystallinity. At 140°C, the complex viscosity of the CPVC was less than that of PVC owing to the higher crystallinity of the latter. The viscosities were similar at 160°C, but at 210°C, where most of the crystallites had melted, the complex viscosity of the CPVC was higher because of its higher glass transition temperature.  相似文献   

7.
Correlations have been found between solubility parameters and some mechanical properties of a series of vinyl polymers containing 56.6–69.9% chlorine when tested below their glass transition temperature. It is shown that stress at yield increases similarly with chlorine content and with the volume occupied by a monomer unit in the polymer. Using the Reiner-Weissenberg theory of the dynamic strength of materials as a criterion and a rheological model based on a pair of Maxwell bodies in parallel with a Hooke spring, the amount of dissipated and conserved work to yield point was calculated. A parameter, defined as the ratio of work to cohesive energy density, describes the efficiency of the system. The overall efficiency of the system, based on work to break, and proportional efficiency, based on work to yield point, are affected by chlorine content and strain rate. In addition, a potential energy parameter is defined which describes the cohesive energy per volume occupied by monomer unit of the polymer. This parameter is proportional to the total work to break as well as to the ratio of the residual work after yield to total work at all strain rates tested. The major portion of work is conserved up to yield; only a small portion is dissipated. From the yield point to break, after the onset of viscous flow, the major part of this work is dissipated.  相似文献   

8.
The porosity of poly (vinyl chloride) (PVC) resin particles produced in bulk polymerization is sensitive to polymerization conditions. Using scanning electron microscopy, 60μ spherical beads of PVC are shown to be composed of loosely packed 1μ spherical subparticles. This complex morphology is characterized by a variability in surface area. The surface area of bulk PVC materials can be measured by a chromatographic technique. The elution time of n-octane as a probe molecule on PVC packed columns is simply related to PVC surface area. At approximately constant particle size (measured by Coulter counter and optical microscopy), surface areas measured by argon adsorption are correlated to chromatographic elution times. The bulk density, plastisol viscosity and pore volume (from mercury penetration porosimetry) are determined and related to specific surface area.  相似文献   

9.
The ultraviolet degradation of poly(vinyl chloride) films was studied in a photoreactor which supplied energy near 3000 Å. It was noted that the rate of degradation and color development was increased when the level of residual solvent in the cast films was increased. Two solvents were employed in the study: tetrahydrofuran and dichloroethane. The amount of residual solvent was correlated with the height of a characteristic peak at 2800 Å for tetrahydrofuran and 1900 Å for dichloroethane. Films which had very small traces of solvent showed excellent resistance to ultraviolet degradation, even in the absence of ultraviolet stabilizers. The analysis of solubility data showed that chain scission was controlling in the early stages of exposure, while crosslinking was controlling at later stages. As a result, it was not possible to apply Charlesby's treatment of radiation-induced degradation. Comparison with the results obtained by other workers for degradation at 2537 Å showed that degradation at this wavelength was much faster than degradation at 3000 Å. Furthermore, degradation at 2537 Å appeared to be controlled by crosslinking at all stages of exposure.  相似文献   

10.
Non-activated carbons were prepared by the thermal degradation of poly(vinyl chloride) (PVC) in air or nitrogen atmosphere in the temperature range 600-1000°C. Carbon dioxide-activated carbons from PVC were also obtained by gasification of non-activated carbon from PVC at 900°C burn-off (4-50%). Thermal degradation in air atmosphere gave high carbon yield because the oxygen of air increased crosslinking at lower temperature and chemisorbed on the carbon surface at high temperatures. Thermal degradation in air and gasification with carbon dioxide created carbon-oxygen surface groups which increased the hydrophilicity of the carbon surface and consequently increased water adsorption capacity. Gasification with carbon dioxide to high burn-off created new pores and widened already existing pores.  相似文献   

11.
This report describes the influence, of (a) degree of biaxial orientation, (b) stretching rate, and (c) stretching temperature on the tensile, dynamic mechanical and dielectric properties of non-impact modified PVC. A new parameter designated “planar strain” is used to correlate anisotropic property values with both equal and unequal biaxial stretching in a single two-dimensional plot, thereby providing a direct comparison of the effects of two or more biaxial stretching ratios. It is shown that optimum stretching conditions depend to some extent upon end use and that a 2 × 2 stretch ratio is optimum for impact resistance. The actual property/processing condition relationships exhibit very complicated interactions and are correlated empirically in this study. The dynamic measurements suggest that overall local segmental beta motion is increased after orientation but that the relative chain alignment makes it more difficult to activate this motion.  相似文献   

12.
The properties of powders depend mainly upon the characteristics of the individual particles and their interactions. In the case of PVC resins, particle characteristics vary broadly depending upon the manufacturing process used or variables within a given process. In this paper, the effects of grain size, size distribution, grain shape, degree of compaction and static on the bulk density and flow properties of PVC resins are studied. Results indicate that grain shape mainly affects bulk density while grain size and distribution mainly affect powder flow. The degree of compaction and the amount of static on the resin grains are variables which can overwhelm other powder properties.  相似文献   

13.
The thermal dependence of the surface tension of poly(vinyl chloride) (PVC) containing typical additives was determined below the glass transition temperature. From the results, the surface tension of PVC melts was evaluated and possible differences between the real value and estimate are discussed. It is suggested that the surface tension does not affect the wall-slipping properties of PVC melts.  相似文献   

14.
Measurements of the extent of vinyl chloride migration from specimens of processed poly(vinyl chloride) (PVC) are used to calculate the diffusivity of vinyl chloride in PVC pipe compound. The migration is strongly affected by temperature and is slightly larger into water than into air. The equation for calculating vinyl chloride migration from PVC must be generalized to recognize a variable diffusivity to be useful for non-isothermal situations, as in the case of the measurements. The diffusivities calculated from the data with the generalized equation were confirmed by migration measurements from one in. pipe. Predictions with the calculated diffusivities and the generalized equation show that PVC pipe with a 3 mg/kg concentration of residual vinyl chloride will not release quantitatively detectable amounts of vinyl chloride (< .002 mg/kg) in a realistic time frame in potable water distribution.  相似文献   

15.
The behavior of unplasticized poly(vinyl chloride) (UPVC) during single screw extrusion was studied. The melting and gelation mechanisms under a variety of operating conditions were identified using microscopy, density measurements, and thermal analysis. The compound followed the behavior of wall-slipping materials, the melt forming a pool near the passive flight of the screw. Gelation involved the progressive destruction of the original powder morphology and the development, upon cooling, of an entanglement network with primary and secondary crystallinity. Both the breakdown and internal fusion of the grains were observed, depending on the location of the material around the screw. Tensile yield parameters were found to be independent of the gelation level. The values of the post-yield parameters reached a maximum for gelation levels in the range of 70% to 85%.  相似文献   

16.
The solubility of vinyl chloride monomer (VCM) in PVC powders has been studied by equilibrium vapor pressure and microbalance gravimetric techniques at temperatures from 30 to 110°C. At temperatures and VCM concentrations above the glass transition, the solubility closely follows the Flory-Huggins equation with χ = 0.98 and is independent of temperature and of the PVC type, molecular weight, or history. In the glassy state, the VCM solubility is higher than the Flory-Huggins value and shows pronounced dependence upon time and the PVC history. These results have been interpreted through the dual-mode sorption concept of Michaels, Vieth, and Barrie: Normal dissolution follows the Flory-Huggins relation, and the additional glassy-state solubility represents the contribution of a hole-filling process. Changes in solubility with time and sample history parallel well-known volume relaxation processes, indicating that vapor solubility measurements offer a direct and sensitive measure of the free-volume state of glassy polymers.  相似文献   

17.
18.
As a preliminary treatment in the PVC-electroplating procedure, treatment with dimethylformamide followed by sensitization leads to a finely roughened and a highly hydrophilic surface with reducing power. This is caused by the formation of an ionic complex compound between dimethylformamide and tin(II) chloride absorbed in the PVC surface. A much more finely and deeply etched surface which exhibits higher adhesion through the mechanical interlocking effect is obtained with the PVC blends containing the plasticizer with a low value of interaction parameter and with a solubility parameter approximate to that of PVC. Adhesion of the metal layer to the PVC surface thus obtained is improved about 1.5 times by thermal aging at 120°C for 20 min.  相似文献   

19.
Empirical correlations of flow properties of poly(vinyl chloride) were made using data reported by a number of investigators. Correlation was made by plotting the reduced variable viscosity η/η0 versus \documentclass{article}\pagestyle{empty}\begin{document}$ (\eta _0 \dot \gamma \bar M_w )/(_\rho RT) $\end{document} or \documentclass{article}\pagestyle{empty}\begin{document}$ (\eta _0 \dot \gamma \bar M_w ^{0.5} )/(_\rho RT) $\end{document} for unplasticized PVC and versus \documentclass{article}\pagestyle{empty}\begin{document}$ (\eta _0 \dot \gamma \bar M_w ^{0.5} )/(_\rho RTW_2 ^a ) $\end{document} with polymer concentration, W2, for PVC containing plasticizer.  相似文献   

20.
The dependence of rheological properties of a plasticized, filled poly(vinyl chloride) compound on three different methods of thermomechanical treatments has been studied. These three different states of the compound are the dry blend mixed at a maximum temperature of 93°C, the two-roll milled sample prepared at 150°C from the dry blend and the molded sample pressed at 170°C from the previously milled material. At 150°C the viscosity and elasticity of the molded sample are considerably higher than those of the dry blend and the milled sample. At higher temperatures, although their flow curves more or less merge, extrudate swell, extrudate appearance and extrudate tensile properties of the three samples vary. The mechanical and Theological properties of the quenched and annealed molded samples and those of the same compound without filler have also been investigated.  相似文献   

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