M. Zulfiqar

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

Abstract 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 2 F 2 Cl 2 , C 3 F 5 Cl and C 2 F 3 Cl 3 in traces. Poly(vinylidene fluoride) forms hydrogen fluoride in appreciable quantity along with the monomer and C 4 H 3 F 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 poly(glycidyl methacrylate)

Abstract 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.

Thermal degradation of poly(2-methoxyethyl methacrylate)

Abstract When poly(2-methoxyethyl methacrylate) decomposes thermally at temperatures up to 500°C, two separate reactions occur. The major reaction is depolymerization giving monomer as the only product. The minor reaction is ester decomposition which results in a very small yield of volatile products including carbon monoxide, carbon dioxide, methane, ethylene, isobutene, methyl vinyl ether, methanol and formaldehyde. A mechanism which accounts for all these products has been formulated.

Thermal degradation of some transition metal (cobalt, nickel and copper) salts of poly(methacrylic acid)

Abstract The thermal stabilities of cobalt, nickel and copper polymethacrylates, synthesized by free radical polymerization of methacrylic acid followed by the replacement of the carboxylic proton with the respective metal ion, have been examined. Various thermoanalytical techniques have been utilized. The results reveal that cobalt and nickel polymethacrylate are much more stable than copper polymethacrylate, although the products are similar. A general mechanism for their thermal degradation has been proposed.

Comparison of the thermal degradations of barium and lead polymethacrylates

Abstract A comparison of the thermal degradations of barium and lead polymethacrylates has been made using thermal volatilization analysis, thermogravimetry and mass spectrometry. Mechanisms of thermal degradation have been suggested.

Electrical conductivity of poly(nickel methacrylate)-I

A Ni-polymethacrylate pellet of diameter 1·4 cm, thickness 0·114 cm, cross-sectional area 1·539 cm2, weighing 470 mg and prepared under a pressure of 8 tons PSI was used for electrical conduction measurements in the temperature range 292–369 K. The electrical behaviour of the sample results from two distinct conduction mechanisms. Ohmic conduction is observed up to 325 K and 300 V. Ionic conduction is operative because of (i) the high value of activation energy in the low (T < 325 K) and high (325 < T < 369 K) temperature regions in contrast to our investigation of Pd-polymethacrylate, (ii) the appearance of reverse current by reversing the polarity of the applied voltage, (iii) current-voltage hysteresis and (iv) a time-relaxation phenomenon. At T < 325 K, the ionic conduction is due to weakly trapped impurity ions, whereas at 325 < T < 369 K, H+ ions are the main source of ionic conduction. The material exhibits semiconducting behaviour in the temperature range under investigation.

Thermal degradation of gamma irradiated cobalt, nickel and copper polymethacrylates

Cobalt, nickel and copper polymethacrylates, which have possible applications as radiation shields, were studied for their radiation resistance. The samples were irradiated with 200 kGy to 600 kGy in an oxygen free atmosphere. The changes in degradation pattern, studied by employing various thermoanalytical techniques, are reported and discussed.

Pyrolysis gas-chromatographic studies of homopolymers and copolymers of chlorotrifluoroethylene with vinylidene fluoride and methyl methacrylate

Homopolymers of chlorotrifluoroethylene (CTFE), vinylidene fluoride (VDF) and methyl methacrylate (MMA) and their copolymers were studied by PGC/IR with regard to the separation and identification of the degraded products and clarification of the degradation mechanism. Besides monomers, HCl CO2, C2H2, HF, C5H10O2, C3F5Cl and dimers are the observed pyrolysis products. Mechanisms for different degradation reactions have also been studied.ZusammenfassungMittels PGC/IR wurden Homopolymere von Chlorotrifluorethylen (CTFE), Vinylidenfluorid (VDF) und Methylmethacrylat (MMA) und deren Kopolymere in Bezug auf die Trennung und Identifizierung der Abbauprodukte und auf die Klärung des Abbaumechanismus untersucht. Aufße den Monomeren wurden HCl, CO2, C2H2, HF, C5H10O2, C3F3Cl und Dimere als Pyrolyseprodukte beobachtet. Mechanismen für verschiedene Abbaureaktionen wurden ebenfalls untersucht.

Comparison of the thermal degradations of gamma-irradiated lead and barium polymethacrylates

Abstract Barium and lead polymethacrylates, which can be used as radiation shields, were subjected to gamma irradiation at doses ranging from 200 to 600 kGy in an argon atmosphere. The effects of radiation have been assessed by utilizing various thermoanalytical techniques. The changes noted in the thermal degradation patterns have been discussed.

Radiolysis of poly(phenyl methacrylate)

Powdered poly (phenyl methacrylate), synthesized by free-radical bulk polymerization, has been irradiated to doses, between 200 kGy and 600 kGy, of cobalt-60 γ-rays under an argon atmosphere. A G (scission) value of 1·8 has been calculated from the changes in number-average molecular weight as determined by gel permeation chromatography. Energies of activation for the decomposition of irradiated polymers have been calculated from the results of thermogravimetric experiments.