Journal of Polymer Science · 1959 · 190 citations · 4 references
Natural SciencesChemistryMaterials SciencePolymer ChemistryPolymer MaterialsSpectroscopyPolymer CharacterizationPolymer DegradationPolymer Physical ChemistryPolymer PhysicsPolymer StabilityPolymer StabilizationAdditivesAging Of Thin FilmsHeat Treatment EffectsInfrared Absorption SpectraInfrared SpectraPolymer AgingStability Of Polymer SystemsStabilization Against Degradation
Deterioration of poly(vinyl chloride) occurs mainly through hydrogen chloride elimination that forms colored, oxidizable polyenes, a process initiated by rupture of labile C–Cl bonds, and the addition of barium, cadmium, or zinc 2‑ethylhexanoate salts is known to enhance stability. The study aims to elucidate how these metal carboxylate additives retard PVC deterioration by analyzing infrared spectra of heat‑treated films with and without the additives. Infrared spectroscopy of the treated films revealed a 5.75 µm band attributed to ester carbonyl stretching, indicating that the additives esterify labile chlorine atoms and thereby inhibit HCl elimination. The 5.75 µm ester band appears only in PVC films containing the 2‑ethylhexanoate salts, its intensity increasing with salt type, temperature, and heating duration, confirming the proposed esterification mechanism.
Abstract Deterioration in poly(vinyl chloride) is due primarily to zipperlike elimination of hydrogen chloride from the polymer chain, with formation of colored and easily oxidizable polyenes. Baum and Wartman have shown that elimination is initiated by rupture of certain particularly labile carbon‐chlorine bonds. The stability of poly(vinyl chloride) is enhanced by incorporation of various additives, among which are the barium, cadmium and zinc salts of certain carboxylic acids. To gain insight into the way these compounds retard deterioration, the infrared spectra of a series of poly(vinyl chloride) films, with and without admixed barium, cadmium, and zinc 2‐ethylhexanoate, were studied after various heat treatments. These studies have shown the presence of a band at 5.75 μ in the spectra of the films containing the 2‐ethylhexanoates which is absent from the spectra of the unmixed components. The intensity of the band varies with the particular salt, temperature, and duration of heat treatment. Absorption at 5.75 μ is attributed to the carbonyl stretching frequency of an aliphatic ester. The spectra of vinyl acetate–vinyl chloride copolymers show such bands. We propose that the stabilizing action of barium, cadmium, and zinc salts of carboxylic acids arises in part from esterifying displacements of labile chlorine atoms.
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