Partially dehydrochlorinated PVC. II. Reactions with dienophiles and hydroxylating agents

Samples of poly(vinylchloride) containing polyene sequences were made by partial dehydrochlorination by alkali in tetrahydrofuran solution, by alkali in dioxane, and thermally in dimethyl-formamide. The reactions of polyene PVC were followed by UV spectrophotometry. Dienophiles were found to have relative reactivities similar to those found in reactions with low molecular-weight dienes. The reaction with maleic anhydride yielded polymers which after hydrolysis contained carboxyl groups. Hydroxylation was made with osmium tetraoxide and performic acid. With the latter reagent the reaction proceeded to complete disappearance of the UV-absorption peaks from trienes and higher polyenes: Gel permeation chromatography analysis showed that hydroxylation could be made with only minor changes in molecular-weight distribution. The formation of gel upon thermal dehydrochlorination in DMF was shown to be due to physical cross linking probably arising by crystallization of polyene segments. The adhesion of the hydroxylated and carboxylated polymers to glass and stainless-steel surfaces was investigated. Films adhered stronger as the degree of dehydrochlorination of the polyene PVC used to make the derivative increased. Samples with long sequences adhered much stronger than those containing short sequences of corresponding degrees of total substitution.     

Partially imidized,water-soluble polymeric amides. I. Partially imidized polyacrylamide and polymethacrylamide

Five to six million molecular weight polyacrylamide and polymethacrylamides of comparable post-alkaline hydrolysis viscosities were imidized by dissolution and heating in 6N HCl. After alkaline hydrolysis, the imidized polymers demonstrated significantly better retention of viscosity to 2% NaCl than did similar partially hydrolyzed polymers. Viscosities in 0.01% NaCl and resistance to shear were not markedly affected by this modification. It is assumed that this improved performance in brine is the result of chain stiffening due to intrachain imide rings.     

Deuteration of cotton fibers. I. Partially decrystallized celluloses

Deuteration of cellulose in the fiber form has been studied by the new technique developed recently. Infrared spectra in the 3-μ region were recorded to obtain four well-resolved bands due to H-bonded hydroxyl groups in the ordered regions. The peaks at 3298 and 3400 cm^?1 were assigned to cellulose I, while those at 3445 and 3493 cm^?1 were assigned to the cellulose II lattice structure. Cotton fibers containing both cellulose I and cellulose II lattice structures (50:50%) gave six bands in the 3-μ region at 3230, 3298, 3350, 3400, 3445, and 3493 cm^?1. Deuteration of swollen and decrystallized cotton fibers revealed that ethylenediamine brings about partial conversion of cellolose I lattice structure to cellulose II lattice structure, giving the characteristic cellulose II band at 3493 cm^?1. Swelling mechanism with ethylenediamine to account for formation of cellulose II in cotton fibers has been put forward. Zinc chloride was found to retain the cellulose I structure intact. In both the decrystallized celluloses, the band at 3400 cm^?1 has been found to be completely wiped out. This band has been assigned to the group of H bonds mainly lying in rather imperfectly ordered crystalline regions in the fiber structure, which are attacked first during swelling treatment by both the swelling agents irrespective of their different mechanisms of swelling.     

Synthesis and characterization of fullerene functionalized poly(vinyl chloride) (PVC) and dehydrochlorinated PVC using atom Transfer Radical Addition and AIBN based fullerenation

The research presented details chemical modifications of poly(vinyl chloride) (PVC) and its derivative, dehydrochlorinated PVC (DH‐PVC) through the use of two grafting techniques, namely a normal fullerenation, using AIBN (2,2′‐Azoisobutyronitrile), and the atom transfer radical addition (ATRA). The products were characterized and the presence of new FTIR peaks at 528 and 577 cm^?1 along with new ¹H‐NMR signal at 3.9 ppm, suggested that fullerenes has been grafted to the polymer molecules. Percentage of C₆₀ in the fullerene grated products determined by UV/Visible spectroscopy initially increased with the amount of fullerene used to a maximum value (～5.66 % wt) before decreasing again. It was also determined that the C₆₀ content of the fullerene grafted PVC product prepared by using ATRA, was notably greater than that obtained using the normal fullerenation approach, regardless of the amount of C₆₀ used. When the dehydrochlorinated PVC was used as the starting polymer for fullerenation, the fullerene grafted DH‐PVC using ATRA, was markedly insoluble in many common solvents (THF and dichlorobenzene). This was not the cases for the fullerene grafted DHPVC prepared via an AIBN based fullerenation. Furthermore, the electrical conductivity values of the modified PVC products determined by using a four‐point probe method were found to increase linearly with the amount of C₆₀ present. Overall our data suggest that the suitable and efficient techniques for grafting C₆₀ onto PVC and DHPVC chains are ATRA and AIBN‐based fullerenation, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2410–2421, 2013     

Interactions between PVC and binary or ternary blends of plasticizers. Part I. PVC/plasticizer compatibility

Solid–gel transition temperatures, t_m, were measured for PVC in binary and ternary mixtures of plasticizers. Data were used to investigate interactions between plasticizers, and their effect on t_m and polymer–plasticizer interaction (χ) values. The UNIFAC-FV method was used to predict Gibbs free energy of mixing, and χ for a range of plasticizers, and interactions for one quaternary mixture. Synergy was observed when one or more branched phthalates were mixed with ODPP, but none when three phthalates were mixed. Mixtures of DOP with aliphatic ester plasticizers again produced synergy. Equations were produced to enable interaction coefficients of different plasticizer blends to be predicted. It was found that interaction coefficients increase as the difference in molar mass between the two plasticizers increases. Calculated χ values were generally similar to experimental values. The lower limit of Gibbs free energy of mixing required for plasticization of PVC using monomeric plasticizers was calculated to be about −0.9 J/g, and that for polymeric plasticizers −0.15 J/g. Equations were produced enabling Gibbs free energy of mixing to be predicted from the amount of C atoms in the plasticizer.     

Damage zone in PVC and PVC/MBS blends. I. The effect of rubber content and temperature

The damage zone development in poly (vinyl chloride) (PVC) and its transparent blends with methyl methacrylate-butadiene-styrene (MBS) core/shell rubber was studied as a function of temperature and rubber content in a triaxial stress state under slow tensile loading. Failure at the semicircular notch occurred by shear yielding followed by stress whitening. In unmodified PVC, the shear yielded plastic zone size was not affected by temperature in the range between —40 and 40°. In the blends, the plastic zone preceding stress whitening increased in size with temperature and rubber content, shifting the stress-whitened zone further away from the notch root. Below 0°, stress whitening initiated at the notch root and the stress-whitened zones had a crescent shape similar to those of PVC/CPE blends studied previously. In unmodified PVC, stress whitening initiated from the growth of preexisting microvoids at the tip of the shear yielded zone containing two families of curving slip lines emanating from the notch root. In contrast, stress whitening in the blends was more intense and was initiated by the cavitation of the rubber particles.     

Silane cross-linking of PVC. I. Grafting of mercaptoalkylalkoxysilanes onto PVC: Properties of the grafted and cross-linked product

The reaction of poly(vinyl chloride) (PVC) with mercaptoalkyltrialkoxysilanes yielded silane-grafted PVC that can be cross-linked by the hydrolytic mechanism. The grafting of the silanes on the plasticized and unplasticized PVC was carried out at 180° C during processing in the presence of basic lead-containing stabilizers. The reaction is favorably affected by the presence of plasticizers and lubricants containing polar, preferably ester, groups. The silane-grafted and cross-linked polymers have satisfactory thermal stability. The results of strength measurements at elevated temperatures after cross-linking by water indicate that the material obtained has greatly improved parameters that are suitable for a number of applications. © 1993 John Wiley & Sons, Inc.     

Degradation studies of plasticized PVC. I. Multiple internal reflection infrared spectroscopy

Multiple internal reflection infrared spectroscopy (MIR) was used to study surface degradation in commercial and laboratory prepared plasticized PVC samples. Samples were subjected to accelerated (UV exposure) and natural weathering. Ultraviolet-exposed samples show peak formation at 3200 cm^?1 (OH), and 1400cm^?1(CH bend), as well as increased absorption at 1720 cm^?1 (CO). Outdoor-exposed samples show essentially similar changes, but the variation in peak ratio shows large variations of a random nature; it has been proposed that rainfall has a major influence on surface plasticizer concentration.     

Crystal Structure of Orthorhombic Zirconia in Partially Stabilized Zirconia

A neutron powder diffraction investigation confirms that, in tough magnesiapartially-stabilized zirconia cooled to 30 K, most of the tetragonal zirconia transforms to an orthorhombic phase. This phase is retained on heating to room temperature; the lattice parameters at 295 K are a = 0.5068, b = 0.5260, and c = 0.5077 nm. The room-temperature crystal structure (space group Pbc2₁) is determined by multiphase Rietveld refinement from the neutron diffraction pattern. This orthorhombic structure is compared with the parent tetragonal structure and with the structure of monoclinic zirconia, which it closely resembles.     

Studies of the solid-state thermal degradation of PVC. I. Autocatalysis by hydrogen chloride

The thermal degradation of virgin and HCI-treated PVC in powder form, as well as of PVC films of different thicknesses, has been studied as a function of time and temperature. The rate of dehydrochlorination was determined conductimetrically and from the polyene sequence distributions as obtained by UV spectroscopy. Increases in the rate of dehydrochlorination, ranging between 30 and 45%, were observed at all temperatures for the samples pretreated with HCI, while the corresponding activation energies were found to be lower by about 20%. For the PVC films, the rate increased with thickness, i.e., with longer residence time of evolved HCI within the sample. The results offer insight regarding the autocatalytic role of evolved HCI.     

老化PVC分子结构的表征

叙述了PVC材料的应用以及回收再利用的方式,强调了再生利用之前进行分子结构表征及品质鉴定的必要性。结合PVC老化降解的微观机理,重点论述了分子结构表征的三个方面:共轭双键及羰基的含量、氯含量、分子量及其分布的变化。所涉及到的表征方法主要有:FTIR、UV、XPS、GPC、DSC。     

核壳型粒子改性聚氯乙烯的发展

分别介绍了国内外有关核壳结构粒子增强增韧PVC的研究工作，核壳结构的粒子包括弹性体、有机刚性粒子和无机刚性粒子。     

水滑石填充PVC形态结构的研究

采用超分散剂(CH-1)处理水滑石(LDH)填充聚氯乙烯(PVC),研究了LDH填充PVC在加工过程中的结构变化。结果表明：CH-1促进了LDH在PVC中的分散,使PVC的热稳定性能和冲击强度提高,PVC降解产生的HCl与LDH层间CO3^2-进行层间交换反应,其层状结构未发生破坏。     

Photodegradation of rigid PVC formulations. I. Wavelength sensitivity to light-induced yellowing by monochromatic light

Light-induced yellowing of extruded rigid poly(vinyl chloride) formulations containing 0, 2.5, and 5 phr of titanium dioxide under exposure to monochromatic light was studied. Both photoyellowing and photobleaching were observed as wavelength-dependent phenomena in the range of 280–500 nm. Action spectra for yellowing of the different compounds were similar. In the case of the formulation with no titanium dioxide, significant color changes were observed on the back surface of the sample, indicating transmission of the longer wavelength light through the 1-mm thickness of the sample.     

Plate‐out in PVC extrusion. I. Analysis of plate‐out

Samples of extruder plate‐out from industrial rigid PVC production lines were investigated by using a number of analytical techniques. The combined use of SEM‐EDX (scanning electron microscopy – energy dispersive X‐ray analysis), thermal analysis, FTIR (Fourier transform infrared spectrophotometry), and LIMA (laser‐induced mass analysis) enabled most plate‐out components to be identified and linked to likely formulation ingredients. The FTIR and thermal analyses were used to identify organic components. The FTIR analysis was also useful for identifying some inorganic compounds present in sufficient quantities, while EDX detected the elements present. The LIMA was the most sensitive technique, detecting trace quantities of both cations and anions. Calcium carbonate, titanium dioxide, and lead stabilizers were found in all die plate‐out samples studied, together with small amounts of lubricants. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers.     

Rheology of flexible PVC compounds. Part I: The influence of resin crystallinity

The changes occurring in torque during PVC processing in a torque rheometer have been interpreted in terms of the destruction of the supramolecular structure followed by a fusion of the grain fragments. In contrast to changes in torque, changes in elasticity occur in the absence of grain breakdown. It is proposed that the change in elasticity during processing is the result of changing crystallinity of the resin. In the early stages of processing, crystallites melt and elasticity decreases. As grains fuse together, new crystallites are formed in the previously unoccupied grain boundaries and the elasticity increases.     

Properties of PVC. II. Properties of PVC compounds with solvents

It was the aim of this paper to study the influence of the solvent residues in PVC compounds on physical and mechanical properties of samples prepared from them as well as the rheologic properties of their melts. Besides tetrahydrofuran other solvents are also partly retained in PVC even after processing at higher temperatures. The properties of samples prepared from PVC compounds containing solvents depend on the solubility parameter of the solvent used. Solvents with a solubility close to that of PVC have the same effect as plasticizers. Solvents with very high solubility parameters, e.g., water, influence the flow and dynamic properties in just the opposite way than plasticizers and behave rather like fillers. A mechanism for influencing the properties of PVC by the presence of solvent residues is suggested.     

PVC／蒙脱土复合材料的制备与结构研究

采用钠基蒙脱土及经有机化处理后的蒙脱土分别通过纳米粒子直接填充分散法和熔融插层法与PVC混合制备PVC/蒙脱土纳米复合材料。对有机蒙脱土的结构进行了表征；对上述两类纳米复合材料的结构及力学性能进行了研究。此外，考察了采用硅烷偶联剂KH570处理钠基蒙脱土后与PVC熔融混合制备的纳米复合材料的力学性能。结果表明，经硅烷偶联剂处理后，纳米复合材料的拉伸强度和冲击强度均有明显的提高。     

核壳结构ACR改性PVC研究

研究并制备出具有较好冲击性能的PVC/ACR共混合金。着重研究了改性剂和填料的粒径、用量等对共混合金力学性能的影响。结果表明:ACR能较大幅度提高PVC的冲击强度,而其拉伸强度下降并不大。