EFFECT OF TEMPERATURE ON GAMMA-IRRADIATED POLY(VINYL ALCOHOL) STUDIEDBY POSITRON-ANNIHILATION

Positron lifetime measurements were performed on pure poly(vinyl alcoh ol) (PVA) and on PVA treated with 10% Na(acac) after gamma irradiation . Three components could be resolved in each spectrum; the long-lived component (tau(3)) and the probability of its formation (I-3) have bee n studied as a function of temperature from 20 to 150 degrees C. The o bserved shift in the glass transition temperature (T-g) to lower value s is attributed to the increase in the electrical conductivity sigma T he average free volume as a function of temperature can be extracted f rom the value for the long-lived component. Also, values of the therma l expansion coefficients (alpha) for pure and treated PVA are deduced. These values confirm the increase in the electrical conductivity in P VA due to gamma-irradiation.