Naslov
Effect of an Impact Modifier on Thermooxidative Degradation of PVC

Autori
Andričić, Branka ; Kovačić, Tonka ; Erceg, Matko

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
European Polymer Federation Congress 2001 / - Eindhoven, 2001, CD-ROM

Skup
European Polymer Federation Congress 2001

Mjesto i datum
Eindhoven, Nizozemska, 15.07.2001. - 20.07.2001

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Sažetak
Due to its inherent characteristics poly(vinyl chloride ) (PVC) need to be modified for certain applications. Methylmethacrylate-butadiene-styrene (MBS) acts as the effective impact modifier of PVC, as well as the processing aid. It is well known that oxygen accelerates thermal degradation of PVC generating hydroperoxy radicals which initiate dehydrochlorination. MBS is very susceptible to the oxidation due to the presence of oxidizable alylic groups and easier diffusion of oxygen throughout elastomeric phase. This is the reason why PVC/MBS blends are not suitable for outdoor conditions. But this disadvantage becomes an advantage in the treatment of the polymeric waste. In fact, in some formulations of polymer blends an unsaturated compound is added to facilitate the oxidation of less reactive polymer. In this work the thermooxidative degradation of PVC blends with different amounts of MBS was investigated thermogravimetricaly in order to determine the influence of MBS on thermooxidative behaviour of PVC. The materials were commercially available bulk polymerized PVC M 570 with K-value of 57 supplied by Polikem, Croatia, and MBS with trade name Kane Ace B28-A supplied by Kaneka Belgium NV. PVC/MBS blends with 5, 10, 15, 20, 30 and 40 phr of MBS were prepared by homogenization of premixed polymer powders using a laboratory roll mill at 1400C for 2 minutes and than hot pressed at 1300C. The foils were transparent and about 0.20 mm thick. The thermooxidative stability was carried out using Perkin-Elmer TGS-2. Oxidative degradation was monitored in the nonisothermal conditions in temperature range from 50 to 6500C at four different heating rates and air flow of 30 ml/min. In these conditions PVC decomposes through three degradation steps and the first is dehydroclorination. The mass loss in this step is the same as in nitrogen suggesting no or negligible effect of oxygen on the mass loss of the first degradation step of PVC. But, thermal degradation in air is faster and begins at lower temperatures than in nitrogen. It was established that degradation of pure PVC starts approximately 600C before thermooxidative degradation of pure MBS. It seems that degradation of PVC did not influenced by degradation products of MBS. Decomposition of PVC/MBS blends has three or even four steps, depending on heating rate. As the amount of MBS increases up to 20 phr, oxidative induction temperature remains the same, but temperature of the maximum dehydroclorination rate depends on composition. The apparent activation energy and preexponential factor of the first degradation step were determined according Flynn-Wall and Ozawa method. Also, compensation behaviour was observed and related compensation factors were calculated.

Izvorni jezik
Engleski

Znanstvena područja
Kemijsko inženjerstvo

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