Nanocomposites from Recycled Polypropylene

Cengiz [53] studied a recycled polypropylene (rPP)/organoclay nanocomposite containing ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) and polypropylene-grafted-maleic anhydride (PP-g-MA) compatibilisers. The rPP/ Cloisite 15A nanocomposite provided the highest improvement in mechanical properties. PP-g-MA was indicated as a better compatibiliser and furthermore, the improvement of both tensile and impact properties were better at a compatibiliser to clay ratio of 3. In addition, a significant enhancement of dispersion level as well 

it was found that the nanoclay loading of 4 wt% and PP-g-MA content of 20 wt% led the best impact and tensile strength [52], Furthermore, the addition of PP-g-MA did not improve the nanocomposite performance due to a portion of PP-g-MA dispersing in the matrix, which disturbs the homogeneity of the nanocomposite. 

The effect of CaCOs nanoparticles on virgin PP and rPP was studied by Elloumi and co-workers [54]. A nonuniform dispersion of nanoparticles in the matrix was shown. Also, the reduction of ductility by CaCOs nanoparticles indicated a decrease in the matrix deformation, attributed to the introduction of mechanical stresses by nondeformable particles 

In addition. Long and co-workers [55] prepared an rPP/CNT nanocomposite by melt mixing, in which the tensile strength and elongation at break increased with increasing CNT content up to 3 wt%. However, a downturn in mechanical properties occurred at 5 wt% of CNT, due to the presence of small bundles of CNT in these samples. Moreover, the thermal degradation of the nanocomposite shifted to higher temperatures as the content of CNT increased. In addition, the additional mass loss was stopped as the temperature of the rPP/CNT nanocomposite was raised from 700 to 1,000 °C. 

In one study, rPP and recycled polyethylene (rPE) were blended with two compatibilisers, polyethylene-grafted-maleic anhydride (PE-g-MA) and ethylene propylene diene monomer (EPDM) copolymer, and OMMT [56]. Scanning electron microscopy (SEM) micrographs showed that the blend with EPDM exhibited a better compatibilisation than PE-g-MA. The presence of OMMT caused an increase of the storage modulus and loss modulus additionally, OMMT improved the thermal stability. 

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