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Transverse vibrations of thinly metallized reeds of y-irradiated polyethylene were excited electrically and detected capacitively over a relaxation range of temperature. The real part of Young's modulus at low strains was determined from the resonance frequency and the resonance width.The polymer was dissolved in Tetraline at constant temperature of 105°C.The concentration ranged from 0.2 to 1 % gm/cc.The viscosity of the solution was measured and the molecular weight of the polymer was calculated after each exposure. The electrical conductivity of the polymer, was measured before and after irradiation using methods previouslyThe results obtained show that the material undergoes crosslinking.reported by Owen.'

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By the addition of nucleating agent (NA), the molecular weight of gamma-irradiated polypropylene (PP) decreases more than that of PP without NA. In the first run of differential scanning calorimetric (DSC) measurement, the melting point (T,) of PP with NA was lower than the one without NA because of larger molecular scission which occurred during irradiation. On the contrary, in the second run, T, of PP with NA was found to be higher than that of PP without NA. Due to the presence of NA, the molecular chains become shorter during irradiation and therefore rearrangement of the chains is easier during crystallization after the first run, this contributes to an increase in T,. ZUSAMMENFASSUNG:Die Gamma-Bestrahlung von Polypropylen (PP) verringert dessen Molekulargewicht; die Abnahme ist in PP mit Keimbildner (NA) groBer als in PP ohne NA. Bei DSC-Messungen liegt der Schmelzpunkt (T,) von PP mit NA im ersten Durchlauf deshalb unter dem von PP ohne NA, wogegen es sich im zweiten Durchlauf genau umgekehrt verhalt, da die in PP mit NA nach der Bestrahlung kurzeren Ketten nach dem ersten Durchlauf leichter kristallisieren konnen.