Thermorheological analysis of PVC blends

The effect of temperature on dynamic viscoelastic measurements of miscible poly (vinyl chloride) (PVC)/ethylene‐vinyl acetate–carbon monoxide terpolymer (EVA‐CO) and immiscible PVC/high‐density polyethylene (HDPE) and PVC/chlorinated polyethylene (CPE) molten blends is discussed. PVC plasticized with di(2 ethyl hexyl) phthalate (PVC/DOP) and CaCO₃ filled HDPE (HDPE/CaCO₃) are also considered for comparison purposes. Thermorheological complexity is analyzed using two time–temperature superposition methods: double logarithmic plots of storage modulus, G′, vs. loss modulus, G″, and loss tangent, tan δ, vs. complex modulus, G*, plots. Both methods reveal that miscible PVC/EVA‐CO and PVC/DOP systems are thermorheologically complex, which is explained by the capacity of PVC to form microdomains or crystallites during mixing and following cooling of the blends. For immiscible PVC/HDPE and PVC/CPE blends the results of log G′ vs. log G″ show temperature independence. However, when tan δ vs. log G* plots are used, the immiscible blends are shown to be thermorheologically complex, indicating that the morphology observed by microscopy and constitued by a PVC phase dispersed in a HDPE or CPE matrix, is reflected by this rheological technique. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 469–477, 2000     

An analysis of the reaction–diffusion mechanism governing the chlorination process of poly(vinyl chloride)

Chlorinated poly(vinyl chloride) (CPVC) obtained through a dry chlorination of PVC films or grains can show a heterogeneous repartition of its chlorine atoms because the reaction process is limited by the mass transfer of the chlorine gas in the material. In order to describe the evolution of such a system, a set of coupled equations is derived where only two dimensionless constants have to be determined: K_S, which depends on the solubility of the chlorine gas in the PVC, and K_T, the ratio between the diffusion and the reaction characteristic times. The kinetics of chlorination obtained for the different regimes matches the available experimental data, and the corresponding concentration profiles for the chlorinated PVC chains are displayed to demonstrate how a heterogeneous chlorination can arise from this dual process. In particular, a sharp interface appears in the diffusion‐limited regime that separates the chlorinated region from an unchlorinated core and is shown to progress deeper into the film with the square root of time. To a larger extent, this analysis shows how heterogeneity of reaction and nonlinear effects can arise from a coupling between a diffusive phenomenon and a reactive phenomenon. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 3201–3209, 2000     

Cooperative motions in PVC studied by thermally stimulated currents: Comparison with A.C. dielectric derivative analysis

The thermally stimulated current–thermal sampling (TSC–TS) technique was used to study the broadened glass transition in conventional “atactic” poly(vinyl chloride), PVC. The activated parameters obtained from the TSC–TS data, mainly the apparent activation energy (E_a), characterize the breadth of glass transitions in a very sensitive way. These results are compared with those values of E_a obtained from the literature, using a recently proposed method of analyzing a.c. dielectric constants and their derivatives, over the temperature range of −100–130°C. Both techniques detect weak cooperative glass transition-like relaxations well below the main glass transition of ca. 80°C. As is the case with “atactic” PMMA, the data suggest that compositional heterogeneity related to a small fraction of predominantly isotactic sequences contribute to the broad glass transition extending ca. 60°C below the main glass transition in atactic PVC. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 913–918, 1998     

硬质PVC/ACR共混体系的增韧机理研究

通过TEM、SEM等方法研究了不同结构丙烯酸酯类抗冲改性剂（ACR）对聚氯乙烯（PVC／ACR共混体系形态结构的影响,对ACR增韧硬质PVC的机理作了探讨,当PVC中含有8phr以上完善核壳结构的ACR时,在共混体系能形成网络结构,这一结构在受冲击时产生多重银纹,并实现银纹的纯化,在PVC／ACR共混体系的增韧机理中占主导地位,同时,ACR诱发PVC产生剪切形变也是提高其增韧效果的因素。     

Study of the properties of rigid and plasticized PVC/PMMA blends

The aim of this work is to study the structure-properties relationship of rigid and plasticized PVC/PMMA blends. For that purpose, blends of variable compositions were prepared in the absence and in the presence of a plasticizer di (ethyl-2 hexyl) phtalate or DEHP. The miscibility of the two polymers was investigated by differential scanning calorimetric analysis (DSC) and Fourier transform infrared spectroscopy. The weight loss from 30 to 600°C was investigated by thermogravimetric analysis (TGA). The thermal degradation under nitrogen at 185°C was studied and the amount of HCl released from PVC was measured by the pH method. Furthermore, the variation of mechanical properties such as tensile behavior, hardness and impact resistance was investigated for all blend compositions.     

煤矿井下瓦斯抽采PVC管静电场试验

 针对矿井瓦斯抽采在PVC 管壁电荷积聚产生强静电场而导致静电放电的危害,通过搭建塑性管瓦斯流动静电场测试装置,模拟测试瓦斯流动过程中塑性管道的静电场,同时数值计算静电放电有效点火能量。研究结果表明,改变瓦斯流速、管径和瓦斯浓度,PVC 管静电场总体趋势是开始时电场随时间逐渐增大,而后趋于稳定,流动瓦斯与PVC 管壁面摩擦产生电荷积聚而导致的静电场可达20 kV/m 以上。以甲烷的最小点燃能量0.28 mJ 为标准,大多时刻PVC 管静电放电有效点火能量小于0.28mJ,处于安全状态,但某些时刻有效点火能量大于0.28 mJ,使得瓦斯处于爆炸的最小点火能量范围。从试验分析瓦斯抽采PVC 管静电场及有效点火能量,可为矿井瓦斯抽采防静电措施提供科学依据。     

Inactivation of Escherichia coli and properties of medical poly(vinyl chloride) in remote-oxygen plasma

This paper reports the germicidal effect (GE) of Escherichia coli on the surface of medical poly(vinyl chloride) (PVC) in remote-oxygen plasma. The concentration of active species in plasma is determined by means of double Langmuir electron probe and electron-spin resonance (ESR) diagnosis. Moreover, surface properties of sterilized PVC are characterized by the water contact angle measurement, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The distribution of electrons, ions, and radicals in plasma reactor is different. High-purity radicals are obtained at 40 cm from the induction coil which is called remote-plasma zone. By remote-oxygen-plasma sterilization, GE value reach 4.12 under the conditions of treatment time of 60 s, plasma RF power of 100 W and oxygen flux of 60 cm³/min. Compared with direct-oxygen-plasma sterilization, remote plasma can enhance the hydrophilic property and limit the degradation of the PVC surface. After remote-plasma sterilization, PVC surface energy is increased more than twice, which mainly resulted from the increase of surface polar force , and hydrogen bonding force . Moreover, remote-plasma sterilization can increase oxygenated functional groups on PVC surface. Experimental results show that remote plasma can inactivate E. coli on the medical PVC substrate effectively. Furthermore, it can optimize the surface properties.     

Effect of irradiation of LASER beam on polymer blends

Irradiation of He-Ne LASER beam on polystyrene (PS) and poly vinyl chloride (PVC) polyblend sample for different time intervals viz. 3, 5,7, 10 and 15 min. Structural and electrical properties have been studied before and after irradiation. It has been found that irradiation increases the dc electrical conductivity due to creation of new charge carriers in the polyblend sample.      

MMA接枝改性PVC/CaCO3纳米复合材料的力学性能

采用熔融共混法制备PMMA接枝改性纳米CaCO3增韧PVC（PVC/CaCO3）复合材料,并研究了复合材料的力学性能.结果表明,通过表面PMMA的接枝改性,可以显著提高纳米CaCO3增韧聚氯乙烯复合材料的拉伸强度和拉伸模量,在纳米CaCO3颗粒表面PMMA包覆层厚度为2nm时,复合材料的拉伸强度和拉伸模量达到极大值.对比于未处理纳米CaCO3和钛酸酯偶联剂处理纳米CaCO3,PMMA接枝改性纳米CaCO3增韧PVC复合材料的拉伸强度得到较大幅度提高.SEM显示,经过PMMA接枝改性后的碳酸钙在PVC基体中分散均匀,与基体界面结合良好.