Hydrogen chloride evolution from the heating of poly(vinyl chloride) compounds

Abstract

SUMMARYThe dehydrochlorination and the thermal decomposition of five PVC materials was studied using two techniques: a batch analytical method, combining ion chromatography and atomic absorption and continuous thermogravimetry. The temperatures studied ranged from 608C to 1208C, over a period of almost one year (50 weeks). It was found that a very large proportion of the soluble chloride emitted early on by the PVC materials into the liquid phase is not hydrogen chloride. None of the five materials tested emitted significant amounts of HCl at temperatures lower than 1058C. The emissions at 908C after 50 weeks ranged from 50.01 Fg/g to 23.62 Fg/g. Furthermore, one of the materials tested emitted virtually no HCl, even at 1058C, as the amount of HCl measured was almost indistinguishable from the normal background of the analytical instruments (37.30 Fg/g after 50 weeks).Numerical calculations of kinetic reaction rates and extrapolation of the results to use temperatures (408C) indicate that properly stabilized PVC compounds will be unlikely to lose 1% of the mass of PVC as HCl until 2 billion years have passed. This number has no physical meaning as such and may be incorrect by a vast margin, but it clearly indicates that a 1% loss of HCl is unlikely to occur during the useful lifetime of a commercial product into which the PVC material has been fabricated. This is a conservative estimate, which ignores the much higher activation energy for dehydrochlorination at temperatures below the glass transition temperature (ca. 858C).

Distribution of Heat Stabilizers in Plasticized PVC‐Based Biomedical Devices: Temperature and Time Effects

“…As far as the temperature effect is concerned, the decrease of the calcium/zinc carboxylates bands on the inner surface of the tube, both for sterilized and nonsterilized samples, as a function of temperature ( Figure 2), could be ascribed to a migration phenomena of the heat stabilizers in the plastic polymer material from the surface to the bulk of the tubes or, otherwise, to reaction mechanisms of the additives themselves as a consequence of the heat treatments. Nevertheless, the latter explanation does not completely justify the experimental evidences obtained for nonsterilized samples at temperatures up to 70 • C, where the HCl formation should be negligible [34].…”

Performance Survey of PVC Insulation of LC/Gecamines Electrical Cables Subjected to Ageing and Its Life Span Evaluation

“…The Brebu's work [9], who studied waste medium voltage cables (6 -10 kV) after 18 years of operation, concludes that the PVC's deshycloration is very low under service conditions. Indeed, according Hishler [8], it would take at least 2 billion years to have a release of 1% by mass of HCl at 40˚C. clearly, this estimate has no physical significance since the material itself will not survive that many years, but it does confirm that deshychloration of PVC is a negligible phenomenon at low, near ambient temperatures.…”

“…A good insulation essentially means a relatively high resistance to current. In order to describe an insulating material, a good insulation also means "the ability to maintain a high resistance" [8].…”

“…however, at 100˚C, this loss is largely due to evaporation of the plasticizer but also to a slight deshychloration. The Hishler's work [8] shows a very low release off HCl below 105˚C (close to 100˚C) (Graphic 4).…”

Mechanisms and modes for ignition of low-voltage, PVC-insulated electrotechnical products

“…Van Luik [8] studied the production of sub-micron particles and found that PVC wire insulation produced 'large numbers' of these by the time that 1438C was attained. Hirschler [9] tested in air a flexible-PVC compound used for wire/cable making and found essentially no HCl emission at 908C, with measurable emissions occurring at 1058C, which is broadly similar to the temperature range found for pure PVC. Other investigators examining similar PVC wire/cable materials reported higher degradation temperatures, presumably due to use of experimental techniques not well suited to lower temperature regimes.…”