Atactic Polypropylene Grafted With Maleic Anhydride As A Compatibilizer and Crystallizing Agent for Polypropylene Polyamide Blends

Both polypropylene (PP) and polyamide (PA) are widely used polymeric materials, but both have their own advantages and disadvantages that limit the scope of use. In recent years, blends of PP and PA have attracted attention because they can combine the advantages of both and eliminate their disadvantages, and the key to achieving these goals lies in solving the compatibility of PP with PA.
In this paper, the random polyethylene grafted maleic anhydride (aPP-g-MAH) is used as a compatibilizer for PP and PA6 blends, which can improve the crystallinity of PP and the compatibility of PP/PA6.

Figure 1 shows the SEM photos of PP/PA6 blends with different ratios and after the addition of 5% aPP-g-MAH. It can be found that the PP/PA6 blends without the addition of aPP-g-MAH, regardless of their proportions, the minor phase is dispersed in the major phase in a spherical shape, the size increases with its proportion, the interface between the two phases is clear and there are voids, indicating that the force between the two phases is weak and the compatibility is poor; after the addition of aPP-g-MAH, it is difficult to distinguish the two phases at low PA6 fraction, and with the PA6 ratio increased, PP became a minor phase and started to disperse in PA6 in a spherical shape, which indicated that aPP-g-MAH could promote the compatibility between PA6 and PP when the PA6 content was low, and aPP-g-MAH was difficult to achieve the improvement of two-phase compatibility when the PA6 content was too high, which might be related to the grafting rate of aPP-g-MAH.

Figures 2 and 3 show the heating and cooling DSC curves of PP/PA6 blends with different ratios and after the addition of 5% aPP-g-MAH, respectively. At low PA6 fraction, the crystalline peaks of PA6 disappeared after the addition of aPP-g-MAH, indicating the good compatibility of the two phases. In addition, the crystalline peaks of PP became stronger and the peak shapes narrower, indicating that the addition of aPP-g-MAH improved the crystallinity of PP; while the crystalline peaks of PP moved to lower temperatures and became less crystalline when the proportion of PP phase was very low, which was due to the fact that the aPP-g MAH is too high for PP at this time, while there is no significant change for PA6, indicating that aPP-g-MAH has little effect on the crystallinity of PA6.

DOI号：10.1016/j.polymer.2020.122386