EFFECTS OF PLASTICIZATION ON THE DIELECTRIC-PROPERTIES OF POLY(VINYL CHLORIDE) MEMBRANES

Electrode bodies and biosensors are engineered from membranes that oft en contain poly(vinyl chloride) (PVC) as the structural component. Cit roflex B-6 (CF), dibutyl sebacate (DBS), dioctyl sebacate (DOS), epoxi dized linseed oil (ELO), epoxidized soybean oil (ESO), ortho-nitrophen yl octyl ether (o-NPOE), and propylene glycol dioleate (PGDO) were use d to plasticize the PVC membranes. After adding tridodecylamine (TDDA) and potassium tetrakis-4-chlorophenyl berate (KTpCIPB) as neutral cha rge carriers and negative sites, respectively, the dielectric properti es of the plasticized PVC membranes were measured with a TA Instrument s' DEA 2970. Using parallel plate sensors, the plasticizers were scann ed at 3 degrees C min(-1) from -100 to + 100 degrees C at seven log fr equencies: - 1, 0, 1, 2, 3, 4, and 5. Generally, increasing the amount of plasticizer in the membrane improved the ionic conductivity (sigma ) and lowered the temperature of the tan delta peak. A positive linear correlation existed between the log sigma and the log(phr ratio) for a given temperature and frequency. The slopes and intercepts of the lo g sigma versus log(phr ratio) lines were linear functions of the log f requency but non-linear functions of temperature. The positive slope o f the log sigma versus log(phr ratio) lines was greatest at about 0 de grees C and 10(-1) Hz, and the peak values of the slopes diminished as they shifted to higher temperatures and frequencies. The intercepts o f the log sigma versus log(phr ratio) lines increased monotonously and tended to converge at the highest temperatures and frequencies. In th e final analysis, the traditional phr ratios, which are associated wit h 200 parts of plasticizer per 100 parts of polymer, were not necessar y since sufficient performance was achieved for all plasticizers at lo wer phr ratios.