Gamma irradiated LDPE in presence of oxygen. Part I. Non-isothermal crystallization

V.A. ALVAREZ; C. J. PÉREZ

THERMOCHIMICA ACTA

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 vol. 570 p. 64 - 73

0040-6031

Non isothermal crystallization of low density polyethylene (LDPE) samples, irradiated under three different atmospheres were analyzed. The used doses were between 33 and 222 kGy. At a given radiation dose the amount of gel produced is higher the lower is oxygen content present in the radiation process. The temperature and the enthalpy of crystallization of the modified polymer decreased almost linearly with the radiation dose. Different classic models were used to predict the relative degree of crystallinity (in the range 0.01-0.3 crystallinity fraction) and several parameters were analyzed. The values of half-time of crystallization (t1/2) and the parameter Zc in the Avrami method which characterize the kinetics of non-isothermal crystallization, show that the crystallization rates decreases with increasing radiation dose at the same cooling rate, and with the decrease in oxygen content (at the same dose). Crystallization rates of all samples increase as the cooling rate increases. The activation energy for crystallization increased with the radiation dose indicating that the increment in molecular crosslinking restricts the crystallization process