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ABSTRACT:Broad line NMR and spin-lattice relaxation times T1 have been used to study glass transition phenomena in isotactic polypropylene modified and blended with an ethylene aminoalkylacrylate copolymer. By means of decomposition of spectra into elementary components corresponding to the chains with different mobility a softening due to the polymer modifier was observed. The modification results in an increase of fractions of amorphous and intermediate chains, respectively, gives rise to the enhancement of the chain mobility in amorphous regions, but the higher amount of the polymer modifier, which was used in the range up to I 5 wt%, the lower chain mobility in intermediate regions was found out. From the temperature dependences of the spin-lattice relaxation times T1 measured over the temperature range 290--430 K, a broadening of correlation time distribution on the side of the shorter correlation times has been found out to be and it was ascribed to overlapping of relaxation processes in amorphous regions. The sample containing the highest amount of the polymer modifier, in contrast to others, was shown to blend not only on the molecular level but also on the overmolecular.KEY WORDS In many of the previous works it was shown that isotactic polypropylene (PP) has a complex structure with regions of the different chain arrangement and different chain mobility. A heterogeneity, which may be studied by means of the broad line NMR spectra 1 -7 (ref I is to see the earlier papers) gives rise to the multiple transitions occuring in the temperature range around and above the glass transition ofPP. 8 Three components of the rotating frame spin-lattice relaxation times T 1 P with several relaxation minima in their temperature dependences also confirmed such relaxation behaviour. 9 · 10 On the other hand, due to spin diffusion only one relaxation time T1, a value of which is obviously determined by the most quickly relaxing, i.e., amorphous chains, may usually be measured. The minimum being appeared in the temperature range above the glass transition of PP corresponds to the f3 relaxation which was assigned to the glass transition phenomena. 9 · 11 -15In the precedent paper a considerable effect of the polymer modifier PFDA 522 on relaxation processes in PP was found out by the rotating frame spin-lattice relaxation times T 1P. 10 By the modification two temperature shifts towards the low temperatures were provoked in the amorphous regions of modified PP. They were the small shift only of the f3 relaxation corresponding to the segmental motion and the marked shift of the a. process, which was ascribed to the motion of the whole amorphous chains. This behaviour produced an overlapping of both discussed relaxations. It is reasonable to expect that this effect will also be observable by the spin-lattice relaxation times T1. But on the score of the spin diffusion only averaged parameters can be drawn from the T 1 measurements, an interpretation of which is not always unambiguos. On the other hand, it turns out that the b...

The structure of fibres prepared from a polypropylene‐polycaproamide mixture is studied. The blend fibres possess a matrix‐fibril structure. The presence of a dispersed polycaproamide component in the form of fibrils in the polypropylene matrix, affects the macrostructure created inthe fibres under the dynamic fibre‐forming conditions.

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SYNOPSISThe effect of the addition of polyamide on the structure and properties of polypropylene fiber has been studied. Although a good fiber is obtained with a composition containing only a very low concentration of polycaproamide in polypropylene, the increase in polyamide content decreases the drawing strength of the mixed polymer melt due to sudden lowering of melt viscosity and strength. The poor melt strength of the studied polymer mixture is attributed to increased heterogeneity induced in the system with increased concentration of polyamide. Use of an effective interphase modifier, maleic anhydride-grafted polypropylene, however, was found to improve fiber properties of the studied polymer mixtures even with a very high concentration of polyamide as the dispersed phase. Thus, addition of a 1-4 wt % interphase modifier facilitates the formation of good fiber even with 30 wt % polycaproamide in the blend. This improvement is attributed to the improved dispersity of polyamide in the polypropylene matrix as well as improved phase compatibility due to the formation of a chemically modified polyamide during melt extrusion in the presence of maleic anhydride-grafted polypropylene.