Satılmış Basan

A comparison of various isothermal thermogravimetric methods applied to the degradation of PVC

Abstract Various isothermal methods of thermogravimetric analysis were applied to the degradation of poly(vinyl chloride) (PVC). The kinetic parameters, such as the reaction order, activation energy and pre-exponential factor, were evaluated according to existing differential and integral methods of analysis. The major drawbacks and advantages pertaining to five different methods were pointed out and discussed.

Thermal degradation of blends of PVC with poly(tetramethylene sebacate)

Abstract The thermal degradation of PVC-PTMS blends has been studied over the whole composition range, using thermal volatilisation analysis and thermogravimetry. In the TVA studies, degradation products have been separated and investigated and in the TG experiments both temperature programmed and isothermal conditions have been used. It has been found that these blends are homogeneous over most of the composition range when cast as films from solution. Powder mixtures of the two polymers show no evidence of interaction during degradation, but in the case of film blends, the PVC is stabilised at low to moderate PTMS contents and destabilised at very high PTMS concentrations. There is an increase in the residue of degradation to 500°C in most of the blends. The interactions are explained in terms of reaction of chlorine chain carriers in the PVC dehydrochlorination with methylene groups in the PTMS, followed by crosslinking of macroradicals.

Thermal degradation of blends of PVC with bisphenol A polycarbonate

The thermal degradation of blends of PVC with bisphenol A polycarbonate has been studied by thermogravimetry and thermal volatilisation analysis. In the TG experiments, both programmed heating and isothermal heating (at 280°C) were used and the full composition range from PVC to polycarbonate was examined. In the TVA experiments, blends of equal weights of the polymers were employed and the volatile and tarwax fractions of products were both studied. As initial separation of the volatile product fraction by subambient TVA was used to assist product identification, which was based on IR and MS methods. In the degradation of the blends, the PVC is slightly stabilised, but there is a considerable destabilisation of the polycarbonate. The latter phenomenon has been explained in terms of a reduction in molecular weight in the temperature region in which dehydrochlorination is occurring due to migration of chlorine radicals from the PVC phase to the polycarbonate phase, where hydrogen abstraction from methyl groups in the polycarbonate is believed to occur.

Thermal degradation of blends of PVC with poly(ethylene adipate)

Abstract The thermal degradation of PVC-PEAD blends has been studied over the whole composition range, using thermal volatilisation analysis and thermogravimetry. In the TVA studies, degradation products have been separated and characterised and in the TG experiments both temperature programmed and isothermal conditions have been used. The blend system has been found to show very similar behaviour to the PVC-poly(tetramethylene sebacate) system previously investigated, involving some stabilisation of PVC at low to moderate PEAD compositions, but destabilisation at high PEAD contents. A similar degradation mechanism in the blends is proposed, involving interaction of chlorine radicals from the PVC with PEAD, following by cross-linking.

Thermal degradation of blends of PVC with polydimethylsiloxane

Abstract The thermal degradation of blends of PVC with polydimethylsiloxane (PDMS) has been studied by thermogravimetry (TG) over the whole composition range and by thermal volatilisation analysis (TVA) for 1:1 by weight blends. From the TG data, curves have been constructed to enable the experimental weight loss behaviour to be compared with that expected for the composition in the absence of any effects due to mixing. The results show destabilisation at low loadings of PDMS for degradations at atmospheric pressure, but for compositions with 50% or more PDMS, both polymers are stabilised, particularly the PDMS, which shows much slower weight loss than expected when 10% PVC is present. Degradation products in the TVA experiments have been separated and investigated: there are no new volatile products in the case of the blends. An interpretation of the reasons for the observed effects is presented.

Thermal degradation of γ-irradiated poly(vinyl chloride)

Abstract The thermal degradation of unstabilized poly(vinyl chloride) irradiated with γ-rays has been investigated by dynamic thermogravimetry in a nitrogen atmosphere. The overall effect of irradiation is to render PVC more susceptible to thermal degradation. The change in activation energy of degradation with dose showed a behavior parallel with the change of intrinsic viscosity with dose. The minimum and maximum Ea values were found to correspond with the minimum and maximum observed on [η] versus dose curves. This behavior indicates an inverse relationship between the rate of thermal degradation and molecular size.

Investigation of miscibility of poly(vinyl chloride) with poly(ethylene-co-vinyl acetate) by viscosimetric method

Abstract In this study, miscibility of blends of poly(vinyl chloride) with poly(ethylene-co-vinyl acetate) (PVC/EVA) have been investigated in tetrahydrofuran (THF) by a viscosimetric method. In order to study the miscibility of the polymer pair in solution, the interaction parameter, Δb, obtained from the modified Krigbaum and Wall theory was used. Polymer blends with EVA content of 10%, 20%, 40%, 60% and 80% at a concentration of 6.0 g dm−3 were prepared. Turbidity measurements and the values of the relative viscosities of each of the polymer solutions and their blends were determined. In consequence of the study, it was observed that PVC and EVA miscible each other as limited.

Modification and characterization of maleic anhydride-styrene-methyl metacrylate terpolymer using various alcohols

In this study, the anhydride units in maleic anhydride-styrene-methyl metacrylate terpolymer (MA-St-MMA) were reacted with n-propyl, n-butyl, n-pentyl and n-benzyl alcohols, and the ester derivatives of MA-St-MMA terpolymer were obtained. These were named n-alkyl maleate ester derivatives, abbreviated as nPrMA-St-MMA, nBuMA-St-MMA, nPnMA-St-MMA and nBzMA-St-MMA. The aim of this study was to obtain more elastic polymers by replacement with the maleic anhydride units in MA-St-MMA terpolymer of alkyl groups having a linear chain structure. All the polymers synthesized were characterized by FT-IR, TMA, the solvent definition, the number of esters and solution viscosity. The TMA experiments of all the polymers were studied under increasing and temperature. All these studies have showed that the n-alkyl maleate ester derivatives are more elastic than original MA-St-MMA terpolymer.

Thermal degradation of γ-irradiated poly(vinyl acetate)

Abstract The thermal degradation (TG) of poly(vinyl acetate) irradiated with γ-rays has been investigated by dynamic thermogravimetry in a nitrogen atmosphere. The overall effect of irradiation is to render poly(vinyl acetate) more susceptible to thermal degradation. The change in activation energy of thermal degradation with dose showed a behaviour parallel to the change of intrinsic viscosity with dose. The maximum E a values were found to correspond with the maximum observed on [η] versus dose curves. This behaviour indicates a relationship between the thermal stability and molecular size.

Determination of thermal gelation points of a vinylidene chloride/acrylonitrile copolymer by a spectrophotometric technique

Abstract In this study, the thermal gelation points of a vinylidene chloride/acrylonitrile random copolymer have been determined using a spectrophotometric technique. In the first part, the thermal gelation temperature and the thermal gelation weight loss have been determined as 219°C and 4·6%, respectively. In the second part, isothermal gelation times at 150, 160, 170 and 180°C have been determined as 256, 105, 44 and 27 min, respectively. At these temperatures the isothermal gelation weight losses have been found to be 0·37, 0·68, 0·92 and 1·26%, respectively. In conclusion, it has been shown that the crosslinking reaction in vinylidene chloride/acrylonitrile copolymer begins at lower temperatures and weight losses in isothermal heating than in dynamic heating.