Subambient Thermal Volatilisation Analysis Research Articles

Thermal degradation studies of alternating copolymers. III. The copolymer of maleic anhydride with trans-stilbene

A comprehensive investigation of the copolymer of maleic anhydride and trans-stilbene (prepared using a free radical initiator) by IR spectroscopy, 1H-NMR spectroscopy, microanalysis and thermal analysis has justified its alternating structure. In addition, no evidence for crosslinking has been found. The thermal degradation of the copolymer has been studied by thermogravimetry under nitrogen and by thermal volatilisation analysis (TVA) under continuous evacuation, in both cases using programmed heating at 10 °C/min. The main product fractions of non-condensable gases, condensable gases and volatile liquids, tars and waxes and residue were isolated by TVA. The volatile decomposition products were further separated and characterised using subambient TVA, IR spectroscopy, mass spectrometry and GC-MS. Structural changes in the partly degraded copolymer have been examined by IR spectroscopy. A single stage of breakdown with a rate maximum in the region of 400 °C was observed by TVA. The major products consisted of a mixture of compounds which were non-volatile at ambient temperature and collected in the cold ring (tar/wax) fraction. This mixture was analysed in greater detail for isothermal degradation at 300 °C and was found to consist of stilbene, unsaturated ketones, aromatic lactones and unsaturated hydrocarbons, with or without phenyl substituents. Volatile products consisted almost entirely of carbon dioxide and carbon monoxide. On the basis of these results, a mechanism of degradation has been proposed. It is suggested that scission occurs by more than one route in the anhydride rings, accompanied by backbone scission.

Thermal analysis of blends of low density polyethylene, poly(ethyl acrylate) and ethylene ethyl acrylate copolymer with polydimethylsiloxane

The thermal stability of blends of polyethylene, poly(ethyl acrylate) and ethylene ethyl acrylate (EEA) copolymer with polydimethylsiloxane has been investigated in inert atmosphere using TG-DTC and TVA. The condensable volatile degradation products from the TVA experiments were separated by subambient TVA and investigated by FT-IR spectroscopy, GC., MS and GCMS techniques. The cold ring fraction was characterised by FT-IR spectroscopy and GC. Most of the degradation products from the blends were similar to the degradation products from polydimethylsiloxane and the corresponding polyolefin when degraded alone, but the presence of some additional products indicated interactions during degradation as a result of blending. The mechanisms of formation of degradation products from the blends are discussed in detail.

Thermal analysis and degradation mechanisms of blends of low density polyethylene, poly(ethyl acrylate) and ethylene ethyl acrylate copolymer with calcium carbonate

The thermal stability of blends of low density polyethylene (LDPE) and poly(ethyl acrylate) (PEA) with whiting type coated calcium carbonate of mean particle size 1·5 μ has been investigated in inert atmosphere using TG-DTG and TVA. Ethylene ethyl acrylate (EEA) copolymer has been investigated with different types of calcium carbonate by the same techniques and also by DSC. The condensable volatile degradation products from TVA experiments were separated by subambient TVA (SATVA) and investigated by FT-IR spectroscopy, MS and GC-MS techniques. The cold ring (tar/wax) fraction was investigated by FT-IR spectroscopy and GC. Degradation products from blends of these materials with calcium carbonate were mainly similar to those when the filler was absent but the proportion of cold ring fraction was increased. In the case of EEA copolymer, minor volatile products such as acetic and propanoic acid normally present were either formed in trace amounts or absent when the copolymer was blended with calcium carbonate. Mechanisms of formation of degradation products from the blends are discussed.

The thermo-oxidative degradation of polystyrene

The kinetics of thermal and thermo-oxidative degradation of polystyrene (PS) alone and in the presence of 4,4′-isopropylidene bis(2,6-dibromophenol) were investigated. It was shown that the retardant affects the thermo-oxidative degradation of PS. Thermal volatilisation analysis (TVA), subambient TVA, FT-IR spectroscopy and GC-MS techniques were used for the separation and characterisation of the various degradation products. The main products of thermo-oxidative degradation were styrene, carbon dioxide, water, benzaldehyde, α-methylstyrene, phenol, phenylacetaldehyde and acetophenone.

Study of the thermal degradation of polychlorotrifluoroethylene, poly(vinylidene fluoride) and copolymers of chlorotrifluoroethylene and vinylidene fluoride

A systematic study of the thermal degradation of a series of homopolymers and copolymers of chlorotrifluoroethylene and vinylidene fluoride was carried out using thermogravimetry and thermal volatilisation analysis (TVA). Volatile products were separated by subambient TVA and characterised by means of infrared spectroscopy and mass spectrometry. On degradation, polychlorotrifluoroethylene gives the monomer as the major product and CO 2, C 2F 2Cl 2, C 3F 5Cl and C 2F 3Cl 3 in traces. Poly(vinylidene fluoride) forms hydrogen fluoride in appreciable quantity along with the monomer and C 4H 3F 3. The copolymers show a similar type of degradation pattern. The structural changes which take place during degradation have also been studied and mechanisms of formation of the various products are disccused.

Thermal degradation of phenyl modified fluorocarbon polymers

The effect of modification by phenyl groups on the thermal stabilities of poly(chlorotrifluoroethylene) (PCTFE) and the copolymer of chlorotrifluoroethylene and vinylidenefluoride (Kel-F) has been examined. The thermal degradation behaviour, studied by thermogravimetry (TG), thermal volatilization analysis (TVA) and subambient TVA (SATVA), shows that in the phenyl modified polymers, i.e. φ-PCTFE and φ-Kel-F, small amounts of phenylchloride along with C 2F 3Cl, C 2F 2H 2, HCl, SiF 4, CO 2, C 2F 2Cl 2, C 3F 5Cl, C 2F 3Cl 3 and C 4F 3H 3 are formed. The incorporation of phenyl groups assists depolymerization at lower temperatures and increases crosslinking at higher temperatures. The mechanism of the degradation reactions is also discussed.

Thermal degradation of chlorotrifluoroethylene-styrene copolymers

The thermal degradation of copolymers of chlorotrifluoroethylene (CTFE) and styrene has been studied by thermal volatilization analysis (TVA), thermogravimetry (TG) and pyrolysis-mass spectrometry (Py-MS). The condensable volatile products from the TVA experiments have been identified by FTIR, after separation by subambient thermal volatilization analysis (SATVA), and confirmed by Py-MS. The cold ring fraction (CRF) has been examined by FTIR spectroscopy.

Thermal degradation of glycidyl methacrylate-styrene copolymers

The thermal degradation of copolymers of glycidyl methacrylate and styrene was studied by thermal volatilisation analysis (TVA), thermogravimetry (TG) and pyrolysis mass spectrometry. The apparent activation energies for the decomposition of copolymers were calculated from the results of TG experiments. The condensable volatile products from the TVA experiments have been identified after separation by subambient thermal volatilisation analysis (SATVA). The cold ring fraction was examined by IR spectroscopy. The copolymers are intermediate in stability between polystyrene and poly(glycidyl methacrylate). The degradation products are mainly those expected by comparison with those obtained from the homopolymers. A mechanism of thermal degradation has been suggested.

Pyrolysis products of poly(vinyl chloride), dioctyl phthalate and their mixture

The pyrolysis of PVC, dioctyl phthalate (DOP) and their mixture has been conducted in air and inert atmosphere and the products studied using thermal volatilisation analysis (TVA) and subambient thermal volatilisation analysis. Gas, liquid and tar fractions were separated and analysed by GC-MS and FTIR. A large number of aromatic and alkyl aromatic compounds were found in the PVC liquid and tar fractions, confirming the results previously reported in the literature. Pyrolysis in the presence of air does not change the nature of the products, though the relative amounts may be different. Oxygen-containing volatiles are not formed. The oxygen-containing groups are formed in the polymer and pass into the tar as large fragments split from the crosslinked network. Among DOP pyrolysis products benzene, toluene, benzaldehyde, phthalic acid, phthalic anhydride, isoalkene, unsaturated ketones and alcohols are the most important. The pyrolysis of the PVC-DOP mixture produces, beside the products of the pure components, new products originating in the reactions of the free radicals formed in the individual components. PVC-DOP mixture exhibits retarded dehydrochlorination during the TVA experiment. This behaviour is similar to that previously observed in this laboratory for PVC-poly(tetramethylene sebacate) blends and supports the idea of reaction between chain carriers in PVC dehydrochlorination and the methylene groups of esters.

Thermolysis of acetylene terminated sulfone resins. I. Volatile products of degradation

Acetylene terminated sulfone (ATS) resin fractions and related model polymers have been pyrolysed to 1000°C under high vacuum conditions. Thermal volatilization analysis (TVA) experiments were performed to provide a semi-quantitative kinetic analysis of degradation processes which produce volatile by-products. Application of sub-ambient thermal volatilization analysis (SATVA) in conjunction with ancillary techniques of analysis allowed quantitative measure of the condensable volatile product distribution as a function of pyrolysis temperature. The noncondensable volatile products of degradation were determined by the technique of adsorption thermal volatilization analysis (ATVA) used in conjunction with quantitative gas phase infrared spectroscopy. Four overlapping volatile forming processes were identified and characterized through their product distributions. The yields of noncondensable products of degradation and the char yield increased with the crosslink density. In contrast, the yields of condensable volatile products remained insensitive to crosslink density.

Thermal volatilisation analysis of γ-irradiated tetraphenylboron sodium

The effect of γ-irradiation on tetraphenylboron sodium (TPBS) has been studied by thermal volatilisation analysis (TVA) and sub-ambient TVA. When TPBS is subjected to programmed heating to 500°C under TVA conditions, benzene and hydrogen are observed as volatile products and the residue, after exposure to the atmosphere, consists of sodium carbonate and sodium tetraborate, together with some black char material. Irradiation of TPBS at ambient temperatures also leads to the formation of benzene and hydrogen and the irradiated salt gives larger amounts of benzene in the TVA experiment. It is suggested that the salt decomposes first by loss of benzene and conversion of the TPB anion to an anion with three aromatic rings, which subsequently undergoes further decomposition.

Thermal degradation of poly(methyl methacrylate)-poly-4-bromostyrene blends and methyl methacrylate-4-bromostyrene copolymers

The thermal degradation behaviour of poly-4-bromostyrene (PBrS), a blend of PBrS with poly(methyl methacrylate) (PMMA) and a copolymer of BrS and MMA has been studied using thermogravimetry, differential thermal analysis and thermal volatilisation analysis (TVA). The condensable volatile products from the TVA experiments have been subjected to initial separation by subambient TVA and the less volatile liquids have been further examined by GCMS. The cold ring fraction of products volatile at degradation temperature but not at ambient temperatures has also been characterised. The degradation behaviour of PBrS has been found to be closely analogous to that of polystyrene. A blend of PBrS and PMMA, however, unlike the corresponding polystyrene-PMMA blend, showed some interaction during degradation, resulting in some stabilisation of the PBrS. The copolymer of BrS and MMA behaved upon degradation rather like PBrS. In all these experiments, the major products were the monomers, accompanied (in contrast to the behaviour of PMMA) by a significant cold ring fraction: for blend and copolymer, this contained both types of repeat unit. A mechanism of interaction has been suggested.

Thermal degradation of blends of polystyrene and poly-4-methoxystyrene with bisphenol A polycarbonate

Blends of polystyrene (PS) and poly-4-methoxystyrene (PMeS) with bisphenol A polycarbonate (PC) (1:1 by weight) have been studied using thermogravimetry (TG) and thermal volatilisation analysis (TVA). The condensable volatile products obtained in the TVA experiments were separated by subambient TVA and the less-volatile liquids were examined by GC-MS. The cold ring fraction of products was characterised by IR spectroscopy. On degradation, both PS-PC and PMeS-PC blends show an interaction which is observed as a destabilisation. It is suggested that in the degrading blends, the PC component is destabilised as a result of transport of small radical species from the other polymer phase. These radicals may abstract hydrogen atoms, leading to an increase in backbone scission reactions and consequently a lower degradation temperature than when the polymer is degraded alone.

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 tar wax 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 styrene-methacrylic acid copolymers

Copolymers of styrene and methacrylic acid (MAA) with widely differing compositions have been studied by thermal volatilisation analysis (TVA) and thermogravimetry. The condensable volatile degradation products have been identified after separation by subambient TVA. The cold ring fraction (tar/wax products) and the structural changes in the residue in the course of degradation have also been examined. The copolymers are intermediate in stability between polystyrene (PS) and poly(methacrylic acid) (PMAA). The degradation products are mainly those expected by comparison with those obtained from the homopolymers, but methacrylic acid is formed in greater amount in the copolymer degradation and the distribution of MAA units leads to less intramolecular dehydration. Anhydride rings formed, however, reduce the zip length of depolymerisation to monomers, and both rings and isolated MAA units reduce the possibilities for transfer by polystyryl radicals.

Thermal degradation studies of alternating copolymers: I—maleic anhydride-vinyl acetate

The thermal degradation of the alternating copolymer of maleic anhydride and vinyl acetate has been studied by thermal volatilisation analysis (TVA). An investigation of the decomposition products and a comprehensive analysis of the residues have been made using subambient TVA, IR spectroscopy, 1H and 13CNMR spectroscopy, the GC-MS technique and UV spectroscopy. On the basis of this evidence, a mechanism of degradation has been suggested. Under programmed heating at 10°C min −1, two stages of breakdown, with rate maxima at 260 and 420°C, were observed. The products consisted of acetic acid, carbon dioxide, carbon monoxide, maleic anhydride and water. Acetic acid, carbon dioxide and traces of carbon monoxide were also observed in a detailed isothermal investigation at 205°C. It is suggested that, following the initial loss of acetic acid, structural rearrangements in the polymer chain can occur, with the formation of conjugated double bonds, so accounting for the colour of the partially degraded residues. Some hydroxyl groups are also formed. During degradation, insolubility develops, which has been attributed to reduction in the flexibility of the backbone and some intermolecular dehydration of OH groups. The interaction between the copolymer (or its residue) and water is discussed in relation to potential applications of this material.

Characterization of acetylene terminated sulfone (ATS) resin. II. Thermal analysis of the resin

AbstractThe kinetics and thermodynamics of the cure and post‐cure reactions of an acetylene terminated sulfone (ATS) resin mixture and pure fractions from that mixture were studied using differential scanning calorimetry. Thermal stabilities were measured by programmed thermogravimetry under helium, and oxidative stabilities using isothermal thermogravimetry in air. Microstructural changes accompanying the cure reaction were identified using infrared spectroscopy. Early products of thermal degradation were trapped for identification and quantitative analysis using the technique of sub‐ambient thermal volatilization analysis. We found that glass transition temperatures increase with crosslink density in the resin, that oxygen is able to copolymerize or couple with the polyenes to produce peroxides or hydroperoxides (respectively) which subsequently decompose to form terminal alcohols on the polyene, that weight loss in air at 600°F is an oxidative process that is insensitive to resin crosslink density, and that sulfone functionality constitutes the thermal weak link in the ATS resin system.

Degradation studies of some polyesters and polycarbonates—8. Bisphenol A polycarbonate

The thermal degradation of bisphenol A polycarbonate has been studied using thermal volatilisation analysis (TVA), thermogravimetry and differential scanning calorimetry. A detailed investigation of the various decomposition products has been made, using subambient TVA, IR spectroscopy, mass spectrometry and GC-MS techniques. The degradation behaviour, when the polymer is heated under continuous evacuation, is explained on the basis of the results obtained. Under programmed heating, the polymer is stable up to over 300°C and the main decomposition process is observed with a rate maximum around 460°C. There is a considerable solid residue of decomposition at 500°C and the main products of decomposition consist of cyclic dimer plus bisphenol A, together with smaller amounts of volatile products including carbon dioxide, p-cresol, p-ethyl phenol, phenol, p-vinyl phenol, p-isopropyl phenol, carbon monoxide and methane. No evidence has been found to support the argument presented previously that the initial stage in the degradation involves hydrolysis. The nature and wide range of products suggests that the decomposition in the absence of air and moisture probably proceeds mainly by homolysis of the polymer chain and reactions of the radicals so formed, rather than by ester interchange.

Degradation of an acetylene terminated sulfone (ATS) resin

A study of the rates and mechanisms of degradation of an acetylene terminated sulfone resin, more precisely, bis[4-(3-ethynyl phenoxy) phenyl] sulfone and its higher oligomers, under high vacuum conditions, and under a flowing atmosphere of nitrogen, was made using techniques such as programmed thermogravimetry (TG), Thermal Volatilization Analysis (TVA), and Sub Ambient Thermal Volatilization Analysis (SATVA). Gravimetric product analyses made in conjunction with quantitative Infrared and Nuclear Magnetic Resonance Spectroscopy were used to develop a quantitative product distribution for the process. By so doing, we established the sulfone residue as the thermal weak link in the system, and identified two overlapping processes of backbone polyphenylether thermal decomposition; a low temperature process involving scissions promoted by the sulfone moiety, and a higher temperature process involving more random scissions of residual sulfone free polyphenylethers.

Thermal degradation of poly(glycidyl methacrylate)

The degradation behaviour of poly(glycidyl methacrylate) (PGMA) has been studied using thermogravimetry in dynamic nitrogen and thermal volatilisation analysis (TVA) under vacuum, with programmed heating at 10°C/min. Volatile products have been separated by subambient TVA and identified. The cold ring fraction and partially degraded polymer have been examined by IR spectroscopy. When the polymer decomposes thermally at temperatures up to 500°C, the major product is monomer due to a depolymerisation reaction. Minor products arising from ester decomposition are acrolein, allyl alcohol, glycidol, carbon dioxide, isobutene, propene and carbon monoxide. A mechanism which accounts for all these products has been formulated.