共查询到20条相似文献,搜索用时 15 毫秒
1.
H. Kaczmarek J. Kowalonek Z. Klusek S. Pierzgalski S. Datta 《Journal of Polymer Science.Polymer Physics》2004,42(4):585-602
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 相似文献
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Wenwei Zhao Yukio Yamamoto Seiichi Tagawa 《Journal of polymer science. Part A, Polymer chemistry》1998,36(17):3089-3095
Radiation effects on the formation of conjugated double bonds in the thermal degradation of poly(vinyl chloride) (PVC) and poly(vinyl alcohol) (PVA) were investigated. Thin films of PVC and PVA were either irradiated with γ-rays at ambient temperature (pre-irradiation) and then subjected to thermal treatment, or irradiated at elevated temperatures (in situ irradiation). An extensive enhancement of the thermal degradation was observed for the pre-irradiation of the PVC films, which was more effective than the effect of the in situ irradiation at the same absorption dose. For the PVA degradation, however, the effect of the in situ irradiation was larger than that of the pre-irradiation. The results were explained and related mechanisms were discussed based on radiation-induced chemical reactions and their individual contributions to the thermal degradation behaviors of the two polymers. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 3089–3095, 1998 相似文献
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K. Ogura K. Kisaka H. Furukawa 《Journal of polymer science. Part A, Polymer chemistry》1995,33(8):1375-1380
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. 相似文献
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Kotaro Ogura Jun Yano Kotaro Kisaka Hideo Goto 《Journal of polymer science. Part A, Polymer chemistry》1994,32(1):33-38
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. 相似文献
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Yuchuan Zhang Jiasheng Qian Zhuo KeXiangcheng Zhu Hong BiKangming Nie 《European Polymer Journal》2002,38(2):333-337
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. 相似文献
6.
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 T1ρ(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 T1ρ(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 相似文献
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Blends of poly(vinyl chloride) and a polyurethane elastomer were investigated by DSC and tensile testing. Up to 30 wt% single glass transition was found. It was concluded that the polyurethane forms partly a true blend and is partly disperged in the continuous blend phase. 相似文献
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Measurements of the complex relative permittivity of poly(vinyl acetate) from 35 °C to 190 °C and poly(vinyl chloride) from 90 °C to 150 °C in the frequency range 10–2 –107 Hz and the pressure range 1–5000 bar are reported. Details of the pressure generating system and of the dielectric equipment are described. 相似文献
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Thermal stability, smoke emission and mechanical properties of poly(vinyl chloride)/hydrotalcite nanocomposites 总被引:2,自引:0,他引:2
Yong-zhong Bao Huang Zhi-ming Li Shen-xing Weng Zhi-xue 《Polymer Degradation and Stability》2008,93(2):448-455
Poly(vinyl chloride)/hydrotalcite (PVC/HT) nanocomposites were prepared through vinyl chloride suspension polymerization in the presence of HT nanoparticles surface modified with alkyl phosphate (AP). The thermal stability, smoke emission and mechanical properties of PVC/HT nanocomposites were investigated. It was found that AP molecules were effectively absorbed by HT particles with no intercalation into the interlayer of HT. The dispersion morphologies of PVC/HT nanocomposites were observed by transmission electron microscopy showing that the majority of HT particles were dispersed in the PVC matrix in the nanoscale. The Congo Red measurement and thermogravimetric analysis showed that the thermal stability time, and the temperatures at 10% weight loss and at the maximum weight loss rate of PVC resins increased as the weight fraction of HT in the composite resins increased. The well-dispersed nano-sized HT showed an obvious smoke suppression effect on PVC. The maximum smoke density decreased about 1/3 and 1/2 when 2.5 wt% and 5.3 wt% nano-sized HT were incorporated into PVC, respectively. Furthermore, PVC/HT nanocomposites exhibited greater tensile strength and impact strength than the pristine PVC. 相似文献
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PVB存在下PVC化学法脱氯化氢的研究刘恒*李大成陈朝珍(四川联合大学化工学院成都610065)关键词聚氯乙烯,脱氯化氢,聚乙烯醇缩丁醛1996-09-08收稿,1997-05-26修回国家教育委员会留学归国人员资助费资助课题近年来在PVC脱氯化氢制... 相似文献
14.
B. B. Troitskii L. S. Troitskaya 《Journal of polymer science. Part A, Polymer chemistry》1993,31(1):75-81
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, lav. The most probable interval of the values of lav 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. 相似文献
15.
Transition metal-doped titanium(IV) dioxide: Characterisation and influence on photodegradation of poly(vinyl chloride) 总被引:1,自引:0,他引:1
The effects of transition metal dopants (V(IV), V(V), Mn(II), Cr(III), Mo(V), and W(V)), introduced into TiO2, upon the rate of photodegradation of poly(vinyl chloride) (PVC) films containing TiO2 have been measured. The rates were determined mainly by monitoring carbonyl group formation. In another set of experiments, the rates of chloride ion release from irradiated PVC particles suspended in water undergoing agitation with air or O2 in the presence of particles of doped TiO2 were measured electrochemically. The doping of TiO2 (rutile) with Cr(III), V(V) or Mn(II) reduces the photoactivity of the pigment, while doping by Mo(V) or W(V) enhances its photoactivity; the results obtained from carbonyl index measurements are paralleled closely by those from chloride ion release. Even the most aggressive doped pigments were less reactive than Degussa P25 pigment, while the greatest protection to PVC film was offered by TiO2 particles coated with Al2O3 or SiO2. Overall, the photoactivity of doped TiO2 is a complex function of dopant concentration, the energy levels of the dopants in the TiO2 lattice, their d electronic configuration and their local distribution. Photoactivity is also linked to other factors such as crystal type, particle size distribution and surface area. There is a clear relationship between the tendency of the dopant to induce the rutile-to-anatase transition and its effect in enhancing the photoactivity of the pigment. The characterisation of the doped pigments was achieved using X-ray powder diffraction, EPR spectroscopy, diffuse reflectance UV-vis spectrophotometry, scanning optical and electron microscopy and particle size analysis using LALLS. 相似文献
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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. 相似文献
18.
Oleg N. Tretinnikov Natalya I. Sushko Anastasia V. Protosovskaya Artsiom V. Radkevich Eryk I. Pavalanski 《先进技术聚合物》2022,33(1):254-259
Radiochromic films composed of polymer matrices and organic dyes are widely used for routine dosimetry purposes in operation of various radiation facilities—gamma and X-ray-irradiation, electron accelerators, and so on. However, the sensitivity of these films rapidly decreases at doses exceeding 30–50 kGy due to a saturation of their optical response, making them unsuitable for accurate dosimetry in radiation processing of polymers and composites where doses up to 200 kGy are typically employed. To overcome this limitation, the use of inorganic substances as the coloring agents of polymer-based radiochromic films was proposed in this paper, specifically, heteropolyacidacid H3PW12O40 (tungstophosphoric acid) in the matrix of poly(vinyl alcohol) (PVA). Nanocomposite PVA/H3PW12O40 films were prepared by solution casting and their optical responses toward 60Co gamma radiation and beams of 6 MeV electrons for a dose range of 10–200 kGy were investigated. It was established that upon exposure to gamma rays and electron beams, the films turn blue and a broad absorption band at 750 nm appears in their spectra. Importantly, the radiation-induced optical absorption increases in a linear fashion up to the dose of 150 kGy and only slightly deviates from linearity at 200 kGy. Moreover, it was found that the PVA/H3PW12O40 films have a long shelf life, are dose-rate independent within a wide range, and color-stable after irradiation. All these features make the nanocomposite PVA/H3PW12O40 films promising for use as routine dosimeters and dose labels in a much wider range of high doses as compared to radiochromic films based on organic dyes. 相似文献
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Co-pyrolysis of olive residue with poly(vinyl chloride) using thermogravimetric analysis 总被引:1,自引:1,他引:0
Pyrolytic process has a promising potential for the environmentally friendly upgrading of lignocellulosic materials and plastic
waste. The co-pyrolysis of olive residue and poly(vinyl chloride) was investigated under nitrogen atmosphere by dynamic thermogravimetric
analysis in the temperature range of 300–975 K. Two main stages of mass loss have been evidenced by TG analysis. The first
occurs in the temperature range of 420–684 K, and the second occurs at 631–840 K. This research was focused on the interaction
between olive residue and poly(vinyl chloride) during the pyrolysis process. Discrepancies between the experimental and calculated
TG/DTG profiles were considered as a measurement of the extent of interactions occurring on co-pyrolysis. It was found that
reactivity of olive residue was increased in olive residue/PVC mixture. In addition, a kinetic analysis was performed to fit
thermogravimetric data, the mixture is considered as multistage process. A reasonable fit to the experimental data was obtained
for all materials and their mixture by isoconversional Friedman method. 相似文献
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