Degradation of polymer mixtures. VI. Blends of poly(vinyl chloride) with polystyrene

The degradation of films containing both PS and PVC has been examined by TVA and TG. Stabilization of both polymers, more notably PS, is observed, but the degradation products are the same as when the polymers are degraded alone. Molecular weight measurements indicate a more rapid decrease in the molecular weight of PS when PVC is present. The possibility of grafting or other processes leading to chlorine incorporation in PS has been excluded by the results of experiments using ³⁶Cl-labeled PVC. The mechanisms of possible interactions between the degrading polymers are discussed. Processes involving reaction of chlorine radicals with PS at lower temperatures and reaction of PS radicals with the residue of PVC dehydrochlorination or its decomposition products at higher temperatures appear probable.     

Degradation of polymer mixtures. IV. Blends of poly(vinyl acetate) with poly(vinyl chloride) and other chlorine-containing polymers

The degradation of the binary polymer blends, poly(vinyl acetate)/poly(vinyl chloride), poly(vinyl acetate)/poly(vinylidene chloride) and poly(vinyl acetate)/polychloroprene has been studied by using thermal volatilization analysis, thermogravimetry, evolved gas analysis for hydrogen chloride and acetic acid, and spectroscopic methods. For the first two systems named, strong interaction occurs in the degrading blend, but the polychloroprene blends showed no indication of interaction. In the PVA/PVC and PVA/PVDC blends, hydrogen chloride from the chlorinated polymer causes substantial acceleration in the deacetylation of PVA. Acetic acid from PVA destabilizes PVC but has little effect in the case of PVDC because of the widely differing degradation temperatures of PVA and PVDC. The presence of hydrogen chloride during the degradation of PVA results in the formation of longer conjugated sequences, and the regression in sequence length at high extents of deacetylation found for PVA degraded alone is not observed.     

Degradation of polymer mixtures. VII. Blends of poly(vinyl acetate) with polystyrene

The degradation of films containing both PVA and PS has been investigated for comparison with the behavior already reported for PVC/PS blends. The presence of PS had little, if any, effect on the behavior of PVA, but PVA had an effect similar to that of PVC on the degradation of PS. Styrene production was retarded in the blend, compared to PS alone, and an increase in the rate of chain scission was observed for a high molecular weight sample. The molecular weight effect, however, was much smaller than in corresponding experiments with PVC/PS blends. Interference with intermolecular transfer in PS is again advanced as the probable explanation of the stabilization of PS.     

Structure of chlorinated poly(vinyl chloride). V. Molecular parameters of chlorinated poly(vinyl chloride)

The molecular parameters of samples of chlorinated poly(vinyl chloride) (CPVC) and chlorinated β,β-dideuterated poly(vinyl chloride) (β,β-d₂-CPVC) were determined by gel permeation chromatography (GPC), light scattering, osmometry, and viscometry. Comparison of GPC, light scattering, osmometric, and viscometric data resulted in a discussion of the possibility of degradation and the causes of changes in the solution properties in chlorination of PVC and ββ-dideuterated poly(vinyl chloride) (ββ-d₂-PVC). The results obtained are discussed in relation to the mechanism of chlorination of PVC.     

Degradation of polymer mixtures. VIII. Blends of poly(vinyl acetate) with poly(methyl methacrylate)

The degradation of blends of PVA and PMMA in the form of films cast from a common solution of the polymers has been studied by TVA, TG, and EGA (evolved gas analysis) for acetic acid. Volatile degradation products have been characterized by spectroscopic and GLC techniques. Molecular weight, spectral and thermal stability changes in PMMA extracted from partially degraded blends have been examined. These blends behave in a closely analogous manner to PVC-PMMA blends already investigated. The results suggest that the PMMA component of the heterogeneous blends is modified in two ways: (1) in a destabilization reaction series initiated by attack of acetate radicals generated in the PVA phase which migrate into the PMMA phase, and (2) in a stabilization reaction involving conversion of ester side groups to acid and subsequently to anhydride ring structures which act as blocking points for depolymerization. The rate of acetic acid production in the blend is less than in PVA degraded alone. The mechanism of degradation of PVA is reconsidered in the light of these results.     

Blends of a chlorinated poly(vinyl chloride) with a polyurethane

Blends of a 67% chlorinated poly(vinyl chloride) with a low-molecular-weight polyurethane are partially miscible over the 0–80% urethane compositional range. A single, composition-dependent glass transition temperature is observed from both DSC and dynamic mechanical measurements. The blends exhibit a cocontinuous morphology with domain sizes varying from 0.15 to 1.5 μm. These results point out that the relation between miscibility characteristics and domain size is a complex one, not only dependent upon the degree of miscibility, but also on the nature of the blend components and the test method used. Thus the domain size for a certain degree of miscibility is not a universal constant as was previously believed. The melt rheology of the blends as a function of composition is strongly “positive deviating” from the log additivity rule and fits a simplified version of the McAllister model. The strongly “positive deviating” rheological behavior of the blends is most likely a result of the cocontinuous morphology which makes the system behave as a highly entangled network.     

Graft polymers from poly(vinyl chloride) and chlorinated rubber

Graft polymers from poly(vinyl chloride) (PVC) and chlorinated rubber (CIR) with side chains of poly(methyl methacrylate) (PMMA), poly(methyl acrylate) (PMA), or poly(ethyl methacrylate) (PEMA) were synthesized. For this purpose, a vinyl monomer was polymerized in the presence of small quantities of PVC or CIR with benzoyl peroxide as catalyst. The graft polymers were separated from both homopolymers by precipitation with methanol from methyl ethyl ketone solutions of the reaction products and the grafting efficiency was calculated. The graft polymers were characterized by infrared spectra, elemental analysis, NMR, and osmometric or light-scattering determinations. From the results it is concluded that the PVC or CIR molecules contain side chains of PMMA, PMA, or PEMA. The graft polymers showed higher molecular weights, and the values of second virial coefficient for these polymers were much different from those of the starting polymers.     

Processability characteristics of chlorinated poly(vinyl chloride)

Chlorinated poly(vinyl chloride) (CPVC) is known to have a higher softening temperature than conventional poly(vinyl chloride) (PVC). Its processability characteristics are, however, different; it has been reported that CPVC is more difficult to process. However, only limited information on the processability characteristics is available. This paper describes some studies of the flow behavior of CPVC melts in a capillary rheometer. The true melt viscosity and activation energy were determined between 190° and 210°C for a number of samples, and they appear to be related to the cohesive energy density of the samples. It was observed that melt fracture, i.e., gross distortion of the extrudate, occurs even at low shear rates in samples having a high chlorine content. This has been attributed to the relatively high pressures that have to be used, the pronounced non-Newtonian nature of the melt, and melt elasticity. It is postulated that melt elasticity could result from crosslinking at the site of the double bond which is known to be formed by dehydrochlorination.     

Thermal decomposition of poly(vinyl chloride) and chlorinated poly(vinyl chloride). II. Organic analysis

A concerted study of poly(vinyl chloride), chlorinated poly(vinyl chloride), and poly(vinylidene chloride) polymers by spectroscopy, thermal analysis, and pyrolysis-gas chromatography resulted in a proposed mechanism for their thermal degradation. Polymer structure with respect to total chlorine content and position was determined, and the influence of these polymer units on certain of the decomposition parameters is presented. Distinguishing differences were obtained for the kinetics of decomposition, reactive macroradical intermediates, and pyrolysis product distributions for these systems. It was determined that chlorinated poly(vinyl chloride) systems with long-chain ? CHCI? units were more thermally stable than the unchlorinated precursor, exhibited increasing activation energy for the dehydrochlorination, and produced chlorine-containing macroradical intermediates and chlorinated aromatic pyrolysis products. The poly(vinyl chloride) polymer was relatively less thermally stable, exhibited decreasing activation energy during dehydrochlorination, and produced polyenyl macro-radical intermediates and aromatic pyrolysis products.     

Preparation and characterization of thermoplastic elastomer of poly(vinyl chloride) and chlorinated waste rubber

In order to develop applications for the abundant waste rubber powder, chlorinated waste rubber (Cl-WR) was prepared by a water based chlorination method using chlorine as chlorinating agent. In this paper, Cl-WR was used as an elastic filler and blended with poly(vinyl chloride) (PVC) matrix to develop a new thermoplastic elastomer PVC/Cl-WR. The mechanical properties, hydrophilicity, swelling resistance, morphology and thermal properties of PVC/Cl-WR were characterized and compared with those of PVC/waste rubber powder (PVC/WR) blends. The results indicated that the mechanical properties, hydrophilicity, swelling resistance and thermal properties of the PVC/Cl-WR blends showed noticeable improvements over PVC/WR blends due to the improved polarity of Cl-WR. Also, the excellent miscibility and compatibility of Cl-WR with PVC was demonstrated by scanning electron microscope (SEM) images of the resulting blends.     

用DSC研究线形多嵌段聚氨酯与聚氯乙烯、氯化聚氯乙烯共混相容性

用示差扫描量热法（DSC）研究了线形多嵌段聚氨酯（PU）与聚氯乙烯（PVC）、氯化聚氯乙烯（CPVC）共混相容性，说明了PU／VC、PU／CPVC的相容是由于共混物中形成了新的氢键的缘故．聚酯型聚氨酯与PVC、CPVC的相容性要好子聚酸型聚氨酯，CPVC与PU的相容性又要好于PVC．聚氨酯中硬段的引入不利于PU／PVC、PU／CPVC的相容性．     

Thermal decomposition of poly(vinyl chloride) and chlorinated poly(vinyl chloride). I. ESR and TGA studies

Significant effort has been made in the past by many workers to investigate the mechanism of thermal decomposition of poly(vinyl chloride) (PVC). The presence and role of free radicals has been controversial in this regard. Our data on PVC and chlorinated PVC systems demonstrate the existence of macroradicals in the early stage of thermal decomposition under inert and oxidative atmospheres. Data from conventional thermogravimetric experiments are used in conjunction with the electron spin resonance findings.     

Investigations on poly(vinyl chloride). II. Pyrolysis of chlorinated polybutadienes as model compounds for poly(vinyl chloride)

The pyrolysis of chlorinated polybutadienes (CPB) was investigated by using a pyrolysis gas chromatograph. CPB corresponds to poly(vinyl chloride) (PVC) constructed with head–head and tail–tail linkages of the vinyl chloride unit. Benzene, toluene, ethyl-benzene, o-xylene, styrene, vinyltoluene, chlorobenzenes, naphthalene, and methylnaphthalenes were detected in the pyrolysis products from CPB above 300°C, and no hydrocarbons could be detected at 200°C. The pyrolysis products from CPB were similar to those from PVC and new products could not be detected. Lower aliphatics, toluene, ethylbenzene, o-xylene, chlorobenzenes, and methylnaphthalenes were released more easily from pyrolysis of CPB than from PVC; amounts of benzene, styrene, and naphthalene formed were small. These results support the conclusion that recombination of chlorine atoms with the double bonds in the polyene chain takes place and that scission of the main chain may depend on the location of methylene groups isolated along the polyene chain during the thermal decomposition of PVC.     

NMR studies of chlorinated poly(vinyl chloride) and polybutadiene

Molecular structures of chlorinated poly(vinyl chloride) and polybutadiene have been studied by high resolution NMR. The spectra of the chlorinated polymers give broad signals. New peaks appear in the lower fields of the ? CH₂? and ? CHCl? groups with increasing chlorine content. The chlorination of poly(vinyl chloride) takes place predominantly on ? CH₂? rather than on ? CHCl? , e.g., a 70% chlorinated polymer has about 10 mole-% of ? CCl₂? groups. Polybutadiene reacts first with chlorine by addition to give a head-to-head poly(vinyl chloride), and then the substitution of the hydrogen atom takes place. Chlorinated polybutadiene with 70% Cl has about 18 mole-% of ? CCl₂? . The multiplets characteristic of spin-spin couplings in the spectrum of the original poly(vinyl chloride) are still observed in that of the highly chlorinated product. This fact shows that a considerable number of poly(vinyl chloride) sequences of certain lengths persist in the highly chlorinated polymer.     

Properties of poly(vinyl chloride) blends with polycarbonates and chlorinated polyethylene

The miscibility of polycarbonates derived from Bisphenol A or 2,5,2′,5′-tetramethyl-Bisphenol A with poly(vinyl chloride), chlorinated poly(vinyl chloride), and vinyl chloride-vinylidene chloride copolymers has been investigated. In miscible blends a shift of the position of the carbonyl absorption in the IR spectra indicates dipolar interactions between the polymers. The miscibility of chlorinated polyethylenes and reduced poly(vinyl chloride)s among each others demonstrates besides the importance of polar groups the influence of their distribution within the polymer chains for the compatibility of the polymers. The investigations on the miscibility have been carried out by differential scanning calorimetry, and by casting films with microscopical observation of the resulting structures.     

用FTIR研究线形多嵌段聚氨酯与聚氯乙烯、氯化聚氯乙烯共混相容性

用溶液法得到线形多嵌段聚氨酯（PU）与聚氯乙烯（PV）、氯化聚氯乙烯（CPVC）的共混物。用FTIR研究PU/PVC、PU／CPVC共混物的相容性，发现PVC、CPVC的加入破坏了PU中原来的氢键，并且PU中的炭基（C=0）与PVC、CPVC中的α－H形成了新的氢键，因而说明了PU／PVC、PU／CPVC共混物具有良好的相容性。     

Degradation of polymer mixtures. IX. Blends of polystyrene with polybutadiene

The degradation of cis-1,4-polybutadiene, polystyrene, and blends of PB and PS has been studied by thermogravimetry, thermal volatilization analysis, and differential scanning calorimetry. Volatile products have been investigated and separated by subambient TVA and characterized spectroscopically. In the degradation of the blends, there is no change in the nature of the volatile products of degradation, but the rate of degradation of the PS component is markedly reduced. The PB component is the first to break down, and during the initial period of degradation of the PB, the PS degradation is apparently inhibited. It is suggested that some of the volatile products of decomposition of PB, most notably 4-vinylcyclohexene, may diffuse into the PS phase in the blend and act as radical inhibitors.     

Degradation of poly(vinyl chloride) by U.V. radiation—I. Kinetics and quantum yields

The kinetics of the photodegradation of films of poly(vinyl chloride) (PVC) has been studied both in the presence and in the absence of oxygen. The value of the quantum yield of hydrogen chloride evolved, φ_HCl = 0.011, indicates that only one in every 100 photons absorbed induces the dehydrochlorination of PVC, with formation of polyenes. The independence of φ_HCl on the irradiation time and on the initial amount of unsaturation in the polymer argues in favour of an alkene-photosensitized degradation process. The low rate of degradation observed when Pyrex-filtered light is used results primarily from both low absorbance of the PVC film in the 300–400 nm region and photobleaching of the polyenes by the hydrogen chloride evolved. The decrease of φ_HCl for extended irradiation times is attributed to the formation of a highly absorbing surface layer consisting of totally degraded PVC. Competitive chain scission and crosslinking processes develop in the PVC film photolyzed either in nitrogen or in oxygen, with a limiting value of 0.5 for the gel fraction.