DSC investigation on the thermal degradation of PVC in blends

Abstract

The thermal degradation of poly(viny1 chloride) (PVC) has been studied by differential scanning calorimetry (DSC). Due to crosslinking, the glass transition temperature (Tg) of PVC raises during the degradation. The thermal degradation of PVC has also been studied for heterogeneous 1: 1 (w/w) blends of PVC with polystyrene (PS), poly(styrene-co-acrylonitrile) (SAN), high-impact PS (poly(styrene-g-butadiene)) (HIPS) and poly(SAN-g-butadiene) (ABS). Tg of the PVC phase raises slower during degradation in the PVC/PS-blend, whereas in the other blends the crosslinking is accelerated, due to a negative influence of the double bonds and/or the nitrile groups on the thermal stability of PVC. Since most methods use the determination of eliminated HCI to study the degradation of PVC, the DSC method is very useful in investigations on PVC-containing polymer blends, if there might be a reaction of HCI with one of the blend components. ZUSAMMENFASSUNG:Der thermische Abbau von PVC wurde mittels DSC untersucht. Durch die Vernetzung des PVC steigt die Glastemperatur mit zunehmender Abbaudauer an. Abbauversuche wurden auch an mehrphasigen 1 : 1-Mischungen (w/w) von PVC mit PS, HIPS, SAN und ABS durchgefiihrt. Wahrend der Abbau von PVC/PS-Mischungen einen langsameren Abstieg der Glastemperatur des PVC zur Folge hat, steigt sie bei den anderen Mischungen starker an als beim reinen PVC. Dies bestatigt den negativen EinfluB von Doppelbindungen und/oder Nitrilgruppen auf die thermische Stabilitat des PVC. Wahrend die Mehrzahl der Methoden zur Untersuchung der Dehydrochlorierung auf der Detektion des abgespaltenen HCI beruht, eignet sich die DSC-Methode insbesondere zur Untersuchung des thermischen Abbaus von PVC in Mischungen, bei denen mit einer Reaktion des Mischungspartners mit dem entstehenden HC1 gerechnet werden mu& 0

Principles of Thermal Degradation

“…Improved stability of the blend is more noticeable when concentration of polysiloxane is at least 50%. 316 In earlier studies, 260 PS was also found to decrease PVC degradation but HIPS increased PVC degradation rate (see Figure 4.49 and Section 4.5.1.6). 319 Figure 4.58 shows the effect of addition of PS on thermal stability of PVC blend.…”

Kinetic investigation of thermooxidative degradation of poly(vinyl chloride)/acrylonitrile–butadiene–styrene blends by isothermal thermogravimetric analysis

“…The type of interaction will depend on the degree of miscibility of the components, as well as on their ratio in the blend. 1,2,17 Therefore, the effect of certain polymer modifiers on the thermal stability of PVC can be different.…”

Kinetic investigation of thermooxidative degradation of poly(vinyl chloride)/acrylonitrile-butadiene-styrene blends by isothermal thermogravimetric analysis

“…It is well established that, under degradation conditions, considerable interactions may occur between the components in the polymer blend and their degradation products. The type of interaction will depend on the degree of miscibility of the components, as well as on their ratio in the blend 1, 2, 17. Therefore, the effect of certain polymer modifiers on the thermal stability of PVC can be different.…”