Characterization of polyvinyl chloride part I. Molecular weight determinations by gel permeation chromatography

The universal calibration and universal correction curves for the correction of resolution dispersion and skewing are established for polyvinylchloride (PVC). The effect of solution concentration on skewing is also demonstrated. The application of these curves to the determination of number and weight average molecular weights of PVC samples is illustrated. The results obtained are consistent with those determined by membrane osmometry and light scattering.     

Characterization of polyvinyl chloride. Part III. An alternative GPC method for measuring the radii of gyration,and the degree of long-chain branching of polydispersed polymers

A method for measuring the unperturbed radius of gyration and the degree of long-chain branching in Gaussian-distribution polymers is proposed. Polyvinyl chloride (PVC) and polyvinyl acetate (PVAc) were selected to illustrate the method. It was observed that PVC samples prepared by homogeneous and heterogeneous polymerizations exhibit the same degree of long-chain branching. This conclusion is supported by viscometric data. The polydispersity ratios (M_w/M_n) indicate that both types of polymerizations would yield a very small amount of total branching (long chain and short chain.) The calculated unperturbed radius of gyration of linear PVC samples was found to be 0.185 \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {\frac{{{\rm \dot A}^{\rm 2} {\rm mole}}}{{{\rm gm}}}} \right) $\end{document}, and that of PVAc was determined to be 0.107 \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {\frac{{{\rm \dot A}^{\rm 2} {\rm mole}}}{{{\rm gm}}}} \right) $\end{document}. The value obtained for PVC is shown to be in agreement with the value determined from the viscometric method as described in our previous work.     

Study and optimization of a soaking treatment to reduce migration from plasticized polyvinyl chloride

Commercial sunflower oil was epoxidized, and epoxidized sunflower oil (ESO) was used as a thermal stabilizer for polyvinyl chloride (PVC). This work describes a process capable to reduce the additives migration between plasticized PVC stabilized with ESO and food simulants. For that purpose, samples were first soaked in n‐heptane and then dried. Soaking temperature and drying temperature with time were optimized by using the methodology of experiment plans. The optimal conditions found were applied to study the migration of additives in a fatty simulant (olive oil) at 40°C. The test conditions were 12 days. Twelve circular samples of plasticized PVC were immersed in 120 mL of olive oil. A circular sample and 10 mL of food simulant were taken off every day to be analyzed. The rate of mass variation was followed. The specific migrations of the present additives were investigated by using Fourier transform infrared spectroscopy, atomic absorption spectrometry and gas chromatography‐ mass spectrometry. The results showed that the studied process reduced considerably the additives migration. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Application of GPC to Studies of the Viscose Process. II. The Effects of Steeping and Alkali-Crumb Aging

Abstract

Changes in the distribution of degree of polymerization (DP) of cellulose during the steeping and alkali-crumb aging steps of the viscose process have been studied. A dissolving-grade pulp was used, and two mechanisms of degradation—oxidation and hydrolysis—were considered. Alkaline hydrolysis was relatively unimportant during the steeping, the major change in the DP distribution being a result of the much faster oxida-tive degradation. The extent of oxidation was determined by the solubility of oxygen in the alkali solution. Both oxidation and hydrolysis cause degradation during the aging of alkali crumb. Under the conditions used, hydrolysis was a slow, pseudo-first-order reaction, and oxidation a much faster zero-order reaction. Since there was a large difference in the rates of these reactions, the kinetics of degradation approached zero order.     

悬浮法聚氯乙烯生产废水处理技术应用与研究进展

近10年来,悬浮法聚氯乙烯(SPVC)生产量不断增加,但生产过程中需要大量的淡水资源,同时释放出相当数量的生产废水,对环境造成了严重威胁。因此很有必要采取有效措施进行水污染控制和水循环利用。作者首先简要介绍了悬浮法聚氯乙烯生产废水的来源及特点,并从工程应用及研究探索两个方面综述了国内外该类废水的治理现状和进展。对一些成功的技术工艺进行了较为详细的介绍,并在此基础上提出接触氧化一臭氧工艺有望成为该类废水处理及回用的主导工艺。     

The thermal gravimetric studies for polymer samples of polyvinyl chloride (PVC) and polyvinyl alcohol (PVA) obtained by treatment with ionic liquid [bmim]Br

The development related to the effective degradation or recycling of polymeric material are of high priority in research because of solid waste removal problems in the environment and to establish sustainable conditions. Ionic liquids having low vapour pressure and other useful properties are finding increasing applications in the field of polymer science. In the present report, we describe the studies related to the plasticizing effect of simple 1-butyl-3-methyl-imidazolium bromide (an ionic liquid) on polyvinyl chloride. The admixtures of PVC and IL were subjected to heating (353–453 K) as a function of time (1–7 h). The resulting product stability was studied by TGA. Similar studies were carried out with PVA via glycolysis, i.e. in presence of ethylene glycol and products obtained were studied by TGA. Our results indicate that the addition of ionic liquid stabilizes the polyvinyl chloride and prevents liberation of HCl, while the polyvinyl alcohol gets degraded rapidly. These findings support the hypothesis of solubilization and degradation depending upon structural characteristics of polymeric molecules. The implications of these findings are discussed in terms of electrostatic, ion dipole and H-bonding interactions within polymer molecules influenced by thermal energy effects.     

The recovery of chlorine from hydrogen chloride Part 1: new method using a molten salt as the electrolyte

A new method of recovering chlorine from by-product hydrogen chloride is proposed and developed. Hydrogen chloride gas is led through a carbon pipe to a gas diffusion-type porous carbon cathode, which is immersed in a molten salt of lithium chloride (58 mol%)-potassium chloride (42 mol%) at 400°C. A graphite anode is immersed in the same electrolyte. By the direct electrolysis of gaseous hydrogen chloride, hydrogen is obtained from the cathode and chlorine is obtained from the anode. Bench scale tests were also carried out.The current capacity of the cell is 20 A. The cell voltage is 4.9 V at 20 A (500°C, electrode distance 3.8 cm) and in this case, more than 65% of it is the ohmic loss. Current efficiency is more than 90%. It can be concluded that this method is very promising.     

Characterization of Lignins from Organosolv Pulping According to the Organocell Process. Part 4. Molecular Weight Determination and Investigation of Fractions Isolated by GPC

Soluble and residual spruce lignins were subjected to permanganate oxidation and thioacidolysis to elucidate changes in lignin's structure during Organocell pulping.

As expected degradation reactions known from soda pulping are dominant especially in stage 2, including extensive enol ether formation. The chemical effect of methanol appears to be restricted to a minor methylation of the α-C-atom which prevents quinone methide formation and thus suppresses subsequent condensation reactions. Other beneficial effects of methanol such as liquor diffusion into the chips and a better lignin solubility obviously contribute to the successful delignification of softwoods in Organocell pulping.     

The copolymerization of vinyl chloride with 1-olefins. I. A new method of investigation of the kinetics of homopolymerization and copolymerization of vinyl chloride

The indirect volumetric method following the amount of monomers in the heterogeneous liquid reaction mixture in a constant volume of samples periodically withdrawn by means of gas chromatography. This new method utilizes periodic sampling of the heterogeneous reaction mixture from the reactor during the reaction and gas chromatographic determination of the unreacted monomers contained in the sample. Its suitability and reliability were verified for the suspension homopolymerization of vinyl chloride. The reproducibility of sampling and the accuracy of determination of the degree of conversion and of the initial reaction rate were investigated. The conversion curves obtained by this method are compared with those obtained by the classical gravimetric method.     

The enrichment of fine particles of coal by aggregation part II. The use of the selective aggreagation method

Tests on aggregation enrichement of fine particles of coal are presented. The selective aggregation process, named ‘shear flocculation’ by Warren [7, 8], was conducted in a cylindrical beaker. The aggregation of the coal grains results from the action of shear forces while the feed is mixing with the collector (diesel oil). The aggregates formed were then separated from gangue by aeration in a flotation machine. This allows for almost complete recovery of coal. Preliminary aggregation of coal grains made it possible to eliminate the frothing agents usually needed in such a process.     

The synthesis of polyethylene glycol (PEG) with different functional groups at each end. II. Synthesis of a series of monosubstituted PEG via polyvinyl alcohol (PVA) as support

Five monosubstituted PEGs with different mol wt were synthesized and isolated using PVA as support. They were , respectively. The structure of these monosubstituted PEGs was characterized by IR, NMR, and element analysis. The effect of the reaction conditions on monosubstitution of PEGs was described. © 1993 John Wiley & Sons, Inc.     

Formation and characterization of catalytic carbons obtained from co disproportionation over an iron nickel catalyst—II: Characterization

The metal-carbon composites obtained by CO disproportionation (2CO→CO₂ + C) over an iron-nickel (containing 75 Wt%Ni) are characterized by T.E.M., X-ray diffraction and krypton adsorption at 77 K. Besides the now well known carbon filaments, two other types of morphology are described and the experimental conditions of their formation determined: the bitubes and bifilaments as low temperature products and carbon shells as high temperature products. X-Ray diffraction studies show that the structure of the alloy is not modified by fragmentation and deposition and that the d 00.2 spacing is about 3.42 Å when formed below 500°C and about 3.38 Å when formed above 500°C. Krypton isotherms confirm that the mean size of the carbon particles increases with temperature of their formation. The filamentous-shell morphology transition suggests that a change in the mechanism of metal fragmentation occurs around 500°C which is also observed in the deposition kinetics. Finally we propose two semi quantitative index numbers for characterization of the crystallographic orientation of surfaces, the two numbers being derived from the shape of krypton adsorption isotherms.     

The extraction of platinum from Pt(II) chloride solution by a quaternary ammonium compound

The fundamental aspects of the extraction and stripping of platinum (II) from its chloride solution by Aliquat 336 diluted with toluene have been studied. The extraction and stripping was at 99.5 and 97.6% equilibrium within 30 s and 20 min respectively. The percentage extraction increased slightly with decreasing hydrochloric acid concentration. In 0.1 mol dm^?3 hydrochloric acid, 1.0 volume percent Aliquat 336 in toluene could load 9.8 mmol dm^?3 of platinum (II). The percentage stripping of platinum (II) from Pt(II)-load organic solvent increased with increasing sodium bisulphite concentration. The enthalpy changes of extraction and of stripping were 12.8 and 114.9 kJ mol^?1 respectively. Both of the reactions were endothermic.     

Following of the relaxations in a polymer's behavior part II: Characterization by quasistatic and dynamic forced bending

The aim of this work is to quantify the internal loss in polymers, for frequencies near 1 Hz, and including the domain (100 and 3000 Hz). The quasistatic experiment used the double-pendulum method; the other experiments were forced vibrations in bending. Two materials were tested between 20 and 60°C, PMMA and wood. Owing to the anisotropy of the wood, the different mechanisms that induce internal loss are located in the matrix or in the reinforcement (fiber) of this composite. The results were plotted on the correlation diagrams, presented in the first part of this study.     

The copolymerization of vinyl chloride with 1-olefins. II. An investigation of the copolymerization reaction of vinyl chloride and propene

The conversion curve of the copolymerization of vinyl chloride with propene and the conversion curves of both monomers were determined, their initial reaction rates compared, and the copolymerization parameters determined by a method which utilizes periodical sampling of a heterogeneous reaction mixture from the reactor during the reaction and gas-chromatographic determination of unreacted monomers contained in the sample. The agreement between the final conversion values determined chromatographically and gravimetrically was evaluated by using results of a series of copolymerizations of vinyl chloride containing various amounts of propene in the initial monomeric mixture (5–30 wt %) carried out under the same conditions.     

A new way to obtain acid or bifunctional catalysts. II. Straightforward calcination of as-synthesized [Ga,A1]-ZSM-5 zeolites obtained from alkali-free media

The acid or bifunctional behavior of catalysts obtained by the straightforward calcination (530–800°C) of as-synthesized [GaA1]-ZSM-5 zeolite, obtained from alkali-free media, was determined using propane, cyclohexane and cyclohexene transformations (T = 530°C, P = 1 atm) as reaction models. Solids were characterized by XRD, FTIR, N₂ adsorption,²⁷A1 and ₇₁Ga MAS NMR and chemical analysis. The catalyst acidities were evaluated using n-heptane cracking and m-xylene isomerization as reaction models. Results show that calcination temperatures (T_c)between 530 and 550°C, causes only the removal of organic molecules used for the synthesis of the zeolite, leading then to pure acidic catalysts. At 700 T_c 800°C, simultaneously with the removal of those organic molecules, a significant chemical change of the zeolite framework composition take place (degalliation and dealumination). The presence of extraframework gallium species (EFGS), led to acid gallium promoted bifunctional catalysts with catalytic properties for propane and naphthenes aromatization almost identical to those for gallium promoted zeolites obtained by conventional methods (ion exchange and/or impregnation).     

Studies of polymer electrets. II. Factors governing the stabilities of homoelectrets obtained from polystyrene and its derivatives

Polystyrene and its various alkyl and halo derivatives have been studied as homoelectrets and their stabilities under different environmental conditions determined. The stabilities of the homoelectrets prepared from these polymers depended on their volume resistivities, glass transition temperatures, and interactions with electron-acceptor impurities. Excellent stabilities were exhibited by the homoelectrets prepared from polystyrene, poly(vinyltoluene), poly(chlorostyrene), and poly(t-butylstyrene). It is postulated that the charged particles are trapped by the π-orbitals of the phenyl rings present in these polymers and that they are adversely affected by the presence of electron-acceptor compounds that generally from charge-transfer complexes with the phenyl groups.