Broad line 1 h nmr study of polymer blend composed of isotactic polypropylene and ethylene-propylene-diene terpolymer

The study of the polymer blend composed of isotactic polypropylene (i-PP) and ethylene-propylene-diene terpolymer and of the components of this blend was made with the use of the broad line H nuclear magnetic resonance technique. Experiments were carried out within the broad temperature range of 160 – 370 K that covers the glass transition regions of all investigated polymers. Interpretation of the experimental results is based on analysis of the variation of the second moments M2 with temperature and on decomposition of the NMR spectra into elementary components related to the amorphous, intermediate and crystalline regions of partially crystalline polymers. The temperature dependences of the second moment of the spectra measured on the terpolymer and iPP show drops in the temperature ranges 200 – 250 K and 270 – 320 K, respectively, which are related to the glass transitions of the particular polymers. A double glass transition was revealed on the blend by means of the second moment temperature dependence whereby the observed transitions are located in the glass transition temperature regions of the components of the blend. A chain penetration of one polymer into the region of the second one and mutual restriction of the chain mobility were concluded from the fact that the second moment M2 of the measured spectra differs from that calculated using the additivity principle. Some conclusions concerning the relaxation processes in the particular phases of the PP and blend were drawn from the temperature dependences of the mass fractions of the structural phases. The relaxation process related to the lower glass transition was found to be associated with activation of the hindered chain motion and then with its transformation into “free” motion. The lower crystallinity and the higher fraction of intermediate regions of the blend, compared with those of neat i-PP, were found.