Tonka Kovačić

Kinetic analysis of the thermooxidative degradation of poly(vinyl-chloride) in poly(vinyl chloride)/methyl methacrylate–butadiene–styrene blends 2. Nonisothermal degradation

Abstract The thermal degradation of poly(vinyl chloride)/poly(methyl methacrylate-butadiene-styrene) (PVC/MBS) blends was investigated by means of isothermal thermogravimetry in air. During 120 min the main process in the blends is the dehydrochlorination of PVC. The reaction rate constants were determined by applying the Prout–Tompkins model, which assumes autocatalytic degradation. Their values are about three times higher in air than in nitrogen. MBS in such conditions retards the thermo-oxidative dehydrochlorination of PVC in the blends. Applying the Arrhenius equation, apparent activation energies and pre-exponential factors were calculated. Their relationship through compensation effect was discussed and a false compensation effect was found.

Kinetics of Isothermal Thermogravimetrical Degradation of PVC/ABS Blends

The PVC/ABS blends were degradated by means of isothermal thermogravimetry at temperatures at 210...240°C in nitrogen. Applying the stationary point method to the data obtained from thermogravimetric curves, apparent activation energy, preexponential factor and compensation parameter for each blend were calculated. The constancy of compensation parameters points to an unchanged mechanism of poly (vinyl-chloride) (PVC) thermal degradation in the presence of acrylonitrile butadiene-styrene (ABS). Upon increasing the fraction of ABS in the blend up to 50% only the kinetics of the process is changed.ZusammenfassungMittels isothermischer Thermogravimetrie in Stickstoff bei Temperaturven von 210 bis 240°C wurden PVC/ABS-Gemische zersetzt. Unter Anwendung der Methode kritischer Punkte an den anhand der thermogravimetrischen Kurven gewonnenen Angaben wurden die scheinbare Aktivierungsenergie, der präexponentielle Faktor und der Kompensationsparameter für jedes Gemisch berechnet. Die Konstantheit der Kompensationsparameter deutet auf einen unveränderten Mechanismus des thermischen Abbaues von Polyvinylchlorid (PVC) in Gegenwart von Acrylonitrilbutadien-Styrol (ABS) hin. Durch Anheben der ABS-Fraktion im Gemisch bis zu 50% wird lediglich die Kinetik des Prozesses verändert.

Thermal degradation of poly(vinyl chloride)/poly(α-methylstyrene-acrylonitrile) blends

Abstract The thermal degradation of immiscible blends of poly(vinylchloride)/poly(α-methylstyrene-acrylonitrile) (PVC/PMSAN) has been studied by means of dynamic thermogravimetry, in a nitrogen atmosphere. PMSAN accelerates the degradation of PVC while PVC retards the degradation process of PMSAN. The stability of the blend depends upon its composition. Blends containing 5 and 10% of PMSAN are least stable. With increasing amounts of PMSAN in the blend the thermal stability gradually increases, so that the blends with more than 50% of PMSAN are more stable than PVC.

Thermooxidative degradation of poly(vinyl chloride) and chlorinated polyethylene with different Ca/Zn carboxylates

The thermooxidative degradation of poly(vinyl chloride) (PVC), chlorinated polyethylene (CPE) and PVC/CPE blend 50/50 was investigated by means of dynamic and isothermal thermogravimetric analysis in the flowing atmosphere of air. To estimate the thermooxidative stability of the samples the characteristics of thermogravimetric (TG) curves were used. Kinetic parameters (the apparent activation energy E and preexponential factor Z) were calculated after isoconversional method for the first stage of dynamic degradation where dehydrochlorination (DHCl) of PVC and/or CPE is the main degradation reaction. Despite the chemical resemblance, the degradation mechanisms of CPE and PVC are different, as a consequence of differences in microregularity of the corresponding polymer chains. The addition of Ca/Zn carboxylates as well as the ratio of Ca and Zn carboxylates have considerably different influence on the investigated polymers.

Study of the Compatibilizer Effect on Blends Prepared from Waste Poly(ethylene-terephthalate) and High Density Polyethylene

Abstract In this work mechanical recycling of waste poly(ethylene-terephthalate) (PET) in the presence of high density polyethylene (HDPE) was studied. The fraction of HDPE in PET/HDPE blends was 3, 5, 6 and 10 wt.%. Isocyanate HI compatibilizer was first synthesized and then added to the blends at a fraction of 5 wt.%. Ethylene-propylene-diene masterbatch (EPDM-M) was prepared by mixing and added in fraction of 15, 30 and 50 wt.%. All PET/HDPE blends studied were characterized by scanning electron microscopy SEM, differential scanning calorimetry DSC and melt flow rate (MFR). Blends prepared with isocyanate HI compatibilizer were also studied by FTIR spectroscopy. Appearance of new vibrations in the FTIR spectra confirms that during the blending reactions between isocyanate HI compatibilizer and blend components appear. Results show that used compatibilizers significantly improved compatibility of polymers in studied blends. From the results it is obvious that immiscibility of PET and HDPE can be overcome.

Effect of homogeneity on the thermal degradation of poly(vinyl chloride)/poly (α-methylstyrene-acrylonitrile-methylmethacrylate) blends

Abstract The thermal degradation of homogeneous and heterogeneous poly(vinyl chloride)/poly(α-methylstyrene-acrylonitrile-methylmethacrylate) (PVC/ MS-AN) blends were investigated by means of dynamic thermogravimetry. The blends were prepared by precipitation from solution in a common solvent (homogeneous PVC/MS-AN-MMA blend) and by pressing the mixture of solid polymers in a cold hydraulic press (heterogeneous PVC/MS-AN-MMA blend). From the thermogravimetric curves and by determining the kinetic parameters of thermal degradation, the effect of the degradation products of one polymer on the degradation process in the other polymer in the blend was established. The homogeneous compositions show no particular differences in characteristics of degradation at high temperatures when compared with the heterogeneous compositions of either precipitated or pressed samples. This effect is due to the fact that the phase diagram of PVC/MS-AN-MMA blend shows an upper critical solution temperature. This means that all of the blend systems, precipitated and pressed, are miscible at temperatures above the critical solution temperature.

Miscibility of poly(vinyl chloride) with terpoly(α-methylstyrene-acrylonitrile-methyl methacrylate)

Abstract The miscibility of poly(vinyl chloride)/terpoly(α-methylstyrene-acrylonitrile-methyl methacrylate) (PVC/MS-AN-MMA) blend was investigated by differential scanning calorimetry. The parameters of thermal transitions and phase behaviour of the blend were determined. Using the criterion that miscible blend exhibits one glass transition temperature T g , the miscibility of the blends with 0–40 and with more than 80 mass% of MS-AN-MMA was found. The dependence of glass transition temperature on the composition was well described by the Couchman, Gordon-Taylor and Fox equations. The blends with 50–80 mass% of MS-AN-MMA were partially miscible. The apparent mass fraction of PVC and MS-AN-MMA in the PVC-rich and MS-AN-MMA-rich phases was estimated. The phase diagram of PVC/MS-AN-MMA blend indicated miscibility upon heating.