INFLUENCE OF PLASTICIZER CONFIGURATIONAL CHANGES ON THE DIELECTRIC CHARACTERISTICS OF HIGHLY PLASTICIZED POLY(VINYL CHLORIDE)

Three citrate-related compounds [Citroflex A-4 (CFA4), Citroflex A-6 ( CFA6), and Citroflex B-6 (CFB6)] and six sebacate-related compounds [d imethyl sebacate (DMS), diethyl sebacate (DES), dibutyl sebacate (DBS) , dioctyl sebacate (DOS), dioctylazelate (DOZ), and dioctyl adipate (D OA)] were used to evaluate the effects of configurational changes in p lasticizer on the dielectric properties of ion-selective poly(vinyl ch loride) membranes. Tridodecylamine (TDDA) and potassium tetrakis-4-chl orophenyl borate (KTpClPB) were used as neutral charge carriers and ne gative sites, respectively. Using parallel plate sensors, the dielectr ic properties [ionic conductivity (sigma) and tan delta] of the plasti cized PVC membranes were determined at temperatures from -100 to + 100 degrees C and seven log frequencies ( -1, 0, 1, 2, 3, 4, and 5 Hz). G enerally, increasing the amount of plasticizer in the membrane improve d the sigma and lowered the temperature of the tan delta peak. A posit ive linear correlation existed between the log sigma and the log phr r atio for a given temperature and frequency, when no data was included for membranes below the melting temperature of the plasticizer. When p lotted versus temperature, the slopes of all these lines passed throug h a maximum between 0 and 60 degrees C. The intercepts of all these li nes increased monotonically with increasing temperature. These interce pts were highly dependent on the frequency at low temperatures, becomi ng less frequency dependent as the temperature increased. Having estab lished that configurational changes of the plasticizers had no effect above the melting point of each plasticizer, global nomograms were onl y required for the citrate-and sebacate-related plasticizers, respecti vely. Using the appropriate nomogram for a selected plasticizer, the s igma could be predicted at a given phr ratio, temperature, and frequen cy. (C) 1998 Elsevier Science Ltd. All rights reserved.