A thermally stimulated depolarization current technique has been used to deduce the compensation law in low density polyethylene β and γ relaxations. The linear relationship between the activation energy and the logarithm of the preexponential factor of the relaxation time has been discussed in terms of compensation temperature and variation of the thermal expansion coefficient through the β and γ processes.

The poor im oact strength of isotactic polyprooylene ( P.P) is one of the major deficiencies of this p oly m er for many aonlications. Its toughness can be im proved by incoroorating a propylene-ethylene rubber (EPR) by "in situ" block co polyme ri�ation techniques. A oolypropylene copoly m er is thus obtai ned w hose pro p erties deoend on the molecular motions allo w ed in its phase separated m ophology.W he have studied the chain motions in the amor p hous regions of the polyprooylene cODoly m er using ther m ostim ulated depo larization comDlex soectra (TSD) cou p led with thermal sam pling (T .5) techniques (1, 2). EXPERIMENTALThe experiments have been carried out in a com mon LN2cryostat. The T.S.D cell has been designed to avoid thermal gradients in the sa m pIes and has been described else w hEl't'(3).Sa m pIe preoaration is an im portant sten towards obtaining noiseless and reproducible results. The noly m ers under conside ration have been melt pressed between two stainless steel circular electrodes (28 m m in dia meter) in order to obtain a film of about 220 Ii m thick. To extract all tra p ped charges, the films needed to be melted again between the electrodes.T he crystallization conditions were 10 K / m n cooling rate and have been the sa m e for all sa moles.In T 5 D and T 5 exoeri m ents cooling and heating rates were 10K / m n. 454