Effect Of Rare Earth Oxides On The Reaction Extrusion Of Polypropylene-graft-Cardanol

Polypropylene was one of the five general-purpose plastics, because it had many advantages, which was widely used in social life. However, PP was non-polar and semi-crystalline polymers, which had low surface energy, poor compatibility with polar polymers or inorganic powders, so it was necessary to modify PP. At present, it was the most commonly used method to graft a polar monomer onto PP to improve the surface energy of PP. The grafting reaction was often accompanied by side reactions which resulted to a low grafting degree and affected the performance of the grafted products greatly. The electronic structure of the rare earth elements was unique, expecially for the 4f orbitals which were located in the inner space. During the grafting reaction,4f orbitals could stabilize primary radicals generated by an initiator, which not only improved the grafting degree, but also inhibited the degradation of PP to some extent.In this study, the rare earth oxides (REO) particles, as La2O3, CeO2, Sm2O3,Gd2O3, Er2O3, modified with titanate coupling agent of TCA-401 were used as co-initiator in the reactive extrusion of polypropylene-graft-cardanol (CAPP). The grafting degree, crystallization behavior, mechanical properties, rheological behavior and aging resistance of CAPP extruded assisted with REO particles (CAPPRE) were studied.Results showed that:Metastable complex composed of DCP and REO was formed, which could prolong the life span of the free radicals. This could be explained by the synergistic effect between DCP and REO particles. In 5 kinds of REO particles, Sm2O3 and Er2O3 particles could increase the grafting degree of CAPPRE remarkably. REO particles could be used as crystal nucleating agent which resuled that the crystallization temperature, the crystallization rate and the density of nuclei of CAPPRE raised. Meanwhile, the size of the spherulites decreased and the boundary of the spherulites became indistinct. As a result, the accumulation of PP molecular chains became tightly. The influence of REO on the crystal structure of PP was beneficial for the polymer processing and the mechanical properties of CAPPRE. Attributed to the plasticization of REO particles on CAPP matrix, the mechanical properties of CAPPRE were significantly better than those of CAPP. The tensile strength, the impact strength of CAPPRE increased first and reached a maximum value when the rare earth element content was 9 mmol%, and then, dropped gradually when the rare earth element content was too high. The elongation at break showed a descending tendency with the increasing of rare earth element content. The storage modula of CAPPRE was higher than that of CAPP. In contract, the loss modulus and the mechanical loss factor of CAPPRE were lower than those of CAPP. CAPPRE showed good toughness even at low temperature, which was consistent with the results of SEM fractographs. CAPP and CAPPRE were typically pseudoplastic fluid and showed a shear-thinning behavior. Most of REO particles could absorb UV radiation. CAPPRE possessed more perfect anti-aging performance than CAPP.