Nataša Stipanelov Vrandečić

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.

Kinetic analysis of the non-isothermal degradation of poly(vinyl chloride)/poly(ethylene oxide) blends

Kinetic analysis of the non-isothermal degradation of poly(vinyl chloride)/poly(ethylene oxide) (PVC/PEO) blends was performed using isoconversional Friedman method in combination with the multivariate nonlinear regression method. The dependencies of E on α have been evaluated at whole conversion range, and it was concluded that E depends on α for all investigated samples, which indicated the complex degradation mechanism. The kinetic analysis indicated four-stage degradation mechanism, except for PVC sample which showed five-stage degradation mechanism. As the PEO content increased in the investigated samples, the probable mechanism changed from the reaction of nth order with autocatalysis (Cn) to the Avrami–Erofeev reaction type (An).

Different approaches to the kinetic analysis of thermal degradation of poly(ethylene oxide)

Kinetic analysis of the non-isothermal degradation of poly(ethylene oxide) has been performed using isoconversional model-free methods, model-fitting methods, invariant kinetic parameters method and Netzsch Thermokinetics software in order to establish whether different kinetic approaches yield consistent kinetic parameters. It has been shown that these approaches yield consistent kinetic parameters and can be combined in such a way as to enhance the reliability and quality of each other and consequently the overall kinetic analysis. The most probable kinetic parameters for the non-isothermal degradation of poly(ethylene oxide) have been determined. These kinetic parameters have been used for prediction of isothermal kinetics of poly(ethylene oxide), and their potential for reliable prediction has been noticed.

The influence of poly(ethylene glycol) on thermal properties of poly(vinyl chloride)/poly(ethylene oxide) blends

The influence of poly(ethylene glycol) (PEG) on thermal characteristics and thermal degradation of poly(vinyl chloride)/poly(ethylene oxide) (PVC/PEO) blends was investigated by differential scanning calorimetry and dynamic thermogravimetry. The thermal degradation characteristics of PEO remain unchanged upon PEG addition, while for all other investigated blends their values decreased, particularly at higher PVC content. Kinetic analysis of the non-isothermal degradation of investigated PVC/PEO/PEG blends was performed using isoconversional Friedman method in combination with the multivariate nonlinear regression method. The PEG addition lowers the values of the activation energies of PVC/PEO blends. The kinetic analysis indicated four-stage degradation mechanism for all investigated blends.

Miscibility of Poly(Vinyl Chloride) with Poly(Ethylene Oxide) of Different Molecular Weights

In this work, five different techniques: dilute solution viscometry, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FT-IR), and scanning electronic microscopy (SEM) were employed in order to evaluate interactions of amorphous poly(vinyl chloride) (PVC) and semi- crystalline poly(ethylene oxide) (PEO) in solution and solid state. The results varied significantly from one experimental technique to another. The positive interactions between the investigated polymers were found over the whole composition range only in solution. However, in the solid state, by DSC and DMA analysis, the positive interactions were found only at elevated PVC content, while FT-IR and SEM analysis could not confirm interactions between the investigated polymers.