Vinyl Chloride-vinyl Acetate Copolymer Research Articles

On the formation of contacts between particles of dispersed polymeric phase in processes of film formation from dispersions in normal paraffins

A study has been made of films prepared from the partially hydrolyzed vinyl chloride-vinyl acetate copolymer by baking the copolymer in air, and also films prepared from dispersions of the latter in some n-paraffins (tridecane, pentadecane). It was found that there are marked differences in relations between strength properties of the films and the degree of contact between copolymer particles, which varies according to the time of heat treatment in film formation processes. Model experiments were carried out to determine the behaviour of isolated particles during heating in air and in the presence of n-paraffins. An explanation of the existence of such a relationship is given, and a hypothesis about the nature of the effect is proposed.

Depolarization current studies of vinyl chloride-vinyl acetate copolymer thin films

Depolarization current characteristics of vinyl chloride-vinyl acetate (VC- VAc) copolymer thin films grown from solution by an isothermal immersion technique were studied as functions of the polarizing field (6.25 × 10 5−2.25×10 6 V m −, time (7.20 × 10 3−5.04×10 4 s), the temperature of polarization (305−425 K), the nature of the vacuum-evaporated electrode metals (gold, copper, silver and aluminium) used during polarization, the thickness of the copolymer fims (4000−10 000 Å) and the heating rates of depolarization (0.033−0.20 K s −1). Three relaxation processes at 340, 412 and 460 K were observed with activation energies of 0.59, 1.01 and 1.37 eV and relaxation times at 300 K of 3.66×10 3, 8.78×10 6 and 1.46×10 10 s respectively. The peak at 340 K is associated with orientation of the dipoles of the main polymer chain; that at 412 K is attributed to ionic movements in the amorphous region of the VC-VAc copolymer film; and that at 460 K is attributed to release of charge which is the resultant of the charge already present and that due to the injected charge carriers. The peaks at 340 and 412 K shift towards higher temperatures and their activation energies increase with increases in the polarizing time and temperature. This is attributed to a distribution of the relaxation times and activation energies and suggests that these two peaks are complex in nature and cannot be represented by a discrete level of activation energy having a single relaxation time.

Relaxation of the surface energy of solid polymers

The surface energy of a polymer can be increased by compression moulding against a metal substrate. After removal of the substrate relaxation to the equilibrium value sets in. We determined the rate of polymer surface energy relaxation as a function of temperature. For a vinyl chloride-vinyl acetate copolymer we determined an activation energy of the relaxation process that could be correlated to segmental motions in this polymer. For a plasticized polyvinylchloride we found a lower activation energy and a larger rate of relaxation, which is the result of the action of plasticizers on segmental motions. In the case of polyethylene the results indicate segmental motions in amorphous regions in the polymer. With polyethylene the activation energy drops when nearing the melt temperature. The movements of molecular segments correspond to a desorption process at the polymer surface, after removal of the substrate. This agrees with the adsorption during compression moulding, as repotted in earlier work.

Separation of vinyl chloride-vinyl acetate copolymers according to their chemical composition by thin-layer chromatography

The separation of model samples of vinyl chloride-vinyl acetate copolymers by thin-layer chromatoraphy was investigated. Model samples with vinyl acetate contents ranging from 6 to 28% (w/w) were prepared by copolymerization carried out to low degrees of conversion to ensure high homogeneity of chemical composition. No separation was achieved in simple solvents; the samples either migrated with the solvent front or remained at the start. Reasonable separations of samples either migrated with the solvent front or remained at the start. Reasonable separatios of samples containing 10–28% of vinyl acetate were attained with the mixed solvent 1,2-dichloroethancetetrahydrofuran (100:1-5.5), while samples containing 6–15% of vinyl acetate were separated by isocratic elution with 1,2-dichloroethane-tetrahydrofuran- n-heptane (100:3:30). Gradient elution gave reasonable separations with vinyl acetate in the range 0–28% contents using as the solvent methyl ethyl ketone-1,2-dichloroethane-carbon tetrachloride. It was shown with fractions of copolymers with various molecular weights that the molecular weight does not affect the separation under the experimental conditions adopted.

Detemination of the composition and molecular-weight distribution of a poly(vinyl chloride-vinyl acetate) copolymer by gel-permeation chromatography and infrared spectroscopy

A combination of infrared (IR) analysis with gel-permeation chromatography (GPC) has permitted the determination of both the molecular-weight distribution and the composition of a vinyl—vinyl acetate copolymer as a function of molecular weight. A sample of the copolymer was fractionated by repeated injection into an analytical scale GPC. Copolymer films made from the fractions were then subjected to IR analysis for the determination of the vinyl acetate content. The latter was high at low molecular weight and decreased with increasing molecular weight. Q factors for the copolymer at each increment of elution volume have been calculated from the Mark—Houwink equations for polyvinyl chloride, polyvinyl acetate and polystyrene and from the vinyl acetate of the copolymer. Molecular-weight averages of the copolymer have been calculated using a polystyrene calibration curve and the Q factors for the copolymer which are a function of elution volume and vinyl acetate content. The values calculated by this method are in good agreement with those measured by other workers.

The properties of vinyl chloride-vinyl acetate copolymer films produced from organo-dispersions in a series of normal paraffin homologues

The kinetics of strengthening the films produced from organo-dispersions of vinyl chloride-vinyl acetate copolymers in a series of n-paraffin homologues as solvents, as well as those of the solvent evaporation during film formation, have been studied. The conclusion reached on the basis of the results is a kinetic dependence of the critical strength (porosity) of the films on the number of carbon atoms present in the paraffin molecule.

Delayed Foreign-Body Tumorigenesis in Mice Infected With Lactate Dehydrogenase-Elevating Virus: Brief Communication2

Female and male CBA/H mice were infected with lactate dehydrogenase virus (LDV). Two weeks later, these mice and noninfected controls received double sc implants of unplasticized vinyl chloride-vinyl acetate copolymer films (0.2 X 15 X 22 mm). Foreign-body (FB) tumorigenesis was delayed in LDV-infected females and males by 2 months. This result could not be explained by an effect of LDV on cellular immunity, inasmuch as cellular immunity does not influence the course of FB tumorigenesis.

Acid-Catalyzed Methanolysis of Vinyl Acetate Polymers and Copolymers. II. Vinyl Chloride-Vinyl Acetate Copolymers

Abstract Acid (HCL) catalyzed methanolysis of vinyl acetate-vinyl chloride copolymers was carried out in solvent mixtures with various amounts of methanol and tetrahydrofuran. The effect of the sovent composition on the initial rate suggests the existence of preferential solvation. The initial rate may be explained in terms of sequence distribution. The acceleration noted in polyvinyl acetate homopolymers disappears as soon as the vinyl chloride content is higher than 30±.

Pyrolysis-Gas Chromatographic Analysis of Vinylchloride-Vinylacetate Copolymer

Abstract Pyrolysis-gas chromatography was applied to rapid and precise determination of vinylchloride-vinylacetate copolymer by use of the yields of acetic acid and of benzene. The separation column was filled with packing of polymer beads (porapak Q) which are free from deterioration by hydrogen chloride evolved during the thermal degradation of copolymers. Relative yields of acetic acid, which originated from the side chains of the polymer and corresponded to vinylacetate content, and of benzene, formed mainly from successive vinylchloride units, were calculated from the relative peak area appearing on the pyrogram by making relative sensitivity correction for the flame ionization detector. By this method the composition of copolymer can be determined using 0.5–2.0 mg of sample with mean absolute deviation 0.5–0.4 wt%, with the yields of acetic acid and of benzene.

Thermal degradation of vinyl chloride-vinyl acetate copolymers—II: Degradation in solution

The degradation of a series of copolymers and the two homopolymers has been studied in tritoluyl phosphate solution. Yields of acetic and hydrochloric acids have been measured and the ratio of the two products compared with that expected from the proportions of the monomers present. It is concluded that neither acid is evolved preferentially. A minimum of stability occurs at about 30–40 per cent vinyl acetate in the copolymer. ultra-violet spectroscopic studies of degraded solutions have been used to examine the development of conjugation along the polymer chain, and it is found that longer sequences are formed, for a given extent of degradation, for copolymers containing 20–30 per cent of vinyl acetate. Acid catalysis of the degradation has also been studied. Mechanisms are proposed to account for the observed stability minimum and the u.v. results.

Thermal degradation of vinyl chloride-vinyl acetate copolymers — I. Bulk degradation studies by thermal volatilization analysis

The rates of production of volatile material from PVA, PVC and vinyl acetate-vinyl chloride copolymers, covering the entire composition range, bave been compared using thermal volatilization analysis. It is found that, at each extreme of the composition range, incorporation of the co-monomer unit results in a copolymer less stable than the homopolymer. Minimum stability occurs for compositions of approximately 40–50 per cent VA. The proportions of acetic acid and hydrogen chloride produced from the copolymers appear to remain constant during degradation, indicating that neither is evolved preferentially, once reaction has begun.

Investigations on the chemical and physical non-uniformity of copolymers of vinyl chloride-vinyl acetate

Two kinds of commercially available vinyl chloride-vinyl acetate copolymers with about 46 per cent chloride content have been divided by fractional precipitation in the following solvent-precipitant systems: acetone-petroleum ether, acetone-methanol and methylene chloride-methanol. The intrinsic viscosity and chloride content of all fractions have been determined. From a general point of view and according to investigations of Fuchs, methanol as a precipitant should mainly divide the copolymers according to chemical composition but petroleum ether mainly according to molecular weight. The opinion was confirmed in general by the experimental results. There was however only a small deviation in our fractionations because the copolymers investigated have only a slight chemical heterogeneity. This can be explained in terms of the copolymerization parameters and the comparatively high content of vinyl chloride of the samples.

Toxicity of pyrolysis products of vinyl plastics.

Polyvinyl chloride polymers and formulations were pyrolyzed in a stream of air by gradually raising the temperature from ambient to approximately 600 C. The pyrolysis air stream was diluted with twice its volume of room air, and rats were exposed to it. Exposure to an air stream containing the pyrolyzed products of 1 to 2 gm of polyvinyl chloride polymer resulted in the death of 50% of the animals. Most deaths were due to carbon monoxide (CO), and carboxyhemoglobin (COHb) levels correlated well with the amount of plastic pyrolyzed. Little histological evidence of lung damage was evident. When oxygen (O2) was added to the air stream to prevent deaths from CO, pulmonary edema and interstitial hemorrhage developed. The lungs of some animals exposed to high levels of pyrolysis products of vinyl chloride-vinyl acetate copolymer also showed focal edema and intra-alveolar hemorrhage. Polyvinyl chloride formulations, containing additives and inert materials, were in general less toxic per gram of sample pyrolyzed.

Chronic oral toxicity to rats of a vinyl chloride-vinyl acetate copolymer

Starting in 1944, albino rats of both sexes caged together were maintained for two years upon diets containing 1.5% and 12% of a vinyl chloride-vinyl acetate copolymer. No effect attributable to the resin was found.

The preparation and plasticizing characteristics of pipendides of long chain fatty acids and n‐fatty acyl derivatives of other cyclic imines

AbstractForty‐six N‐acyl derivatives of cyclic imines have been prepared, characterized, and screened as primary plasticizers for poly (vinyl chloridevinyl acetate) copolymer. Among these were the piperidides of decanoic, palmitic, stearic, oleic, erucic, ricinoleic, epoxystearic, epoxyoleic, diepoxystearic, sebacic, pinic, cottonseed, hydrogenated cottonseed, rapeseed,Limnanthes douglasii, animal, 2‐ethylhexanoic, naphthenic, and dimer acids, as well as the N‐oleoyl derivatives of a number of substituted piperidines and other cyclic imines including pyrrolidine, piperazine, hexamethylenimme, tetrahydroquinolme, 3‐azabicyclo [3.2.2] nonane, dipyridylamine, and carbazole.In general these amides of the 5‐,6‐, and 7‐membered cyclic imines exhibited exceptionally high plasticizing efficiencies. The compatibilities observed were the best to date for fatty acid derivatives on the basis of both individual and ternary fatty acid composition‐compatibility data. Several of these amides exhibited low‐temp characteristics in the adipate plasticizer range without the adverse volatility characteristics of the adipates. There are indications that some of them have appreciable antifungal activity. It has been concluded that cyclic imines will, in general, produce fatty acid derivatives of better than average compatibility as vinyl plasticizers.

熱天秤による高分子物質の研究(第8報)塩化ビニル・酢酸ビニル共重合体およびモノクロル酢酸化ポリビニルアルコール

熱天秤による高分子物質の研究(第8報)塩化ビニル・酢酸ビニル共重合体およびモノクロル酢酸化ポリビニルアルコール