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Z. Dobkowski, M. Zielecka

Characterization of the polysiloxane—polytetrafluoroethylene system (SIL—PTFE) by using the DSC method.


Polimery 1999, No 3, 222

DOI: dx.doi.org/10.14314/polimery.1999.222


A calorimetric study of the SIL—PTFE system (SIL = polymethylhydrosiloxanol) was carried out over -130—380°C (Perkin-Elmer DSC-7, He or N2 atmosphere, 20°C/min). The transition temperatures for SIL (Tg = -121.66°C, Tm = -40.1°C) and PTFE (Tg = -58.58°C, Tm = 327.40°C and 341.7°C) were consistent with those reported for silicone rubbers and teflon, respectively. At PTFE < 30 wt. %, a distinct Tg occurs within the range of Tg characteristic for SIL and the values obey the reciprocal law for a single phase blend. At higher PTFE proportions, neither the glass transition nor the melting peak were observed for SIL. Condis crystal melting transitions, characteristic of PTFE, were found to occur at room temperature and a broad melting peak was found to occur over 325—364°C. New transitions (nonexistent in the components) were found, viz., an exothermic peak at ca. 150°C (attributed to ordering phenomena due to crystallization of semi-IPN structures) and an endothermic peak at ca. 250°C (attributed to melting of semi-IPN structures). These suggestions were confirmed in terms of the balance of the thermal effects due to melting, DH(Tms-F)x + DH(Tm)x, which made it possible to calculate the PTFE contents in the SIL—PTFE system.
Keywords: polysiloxane—polytetrafluoroethylene system, DSC study of physical transitions, formation of semi-IPN structures, melting heat balance

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