Polypropylene (PP) is one of the most commonly used synthetic resins. PP has a very good overall performance so that it is widely used in all aspects of the national economy. But there are also some obvious defects that limit the use of polypropylene in certain areas. Therefore, in order to overcome the shortcomings of performance, as well as improve its application, many researchers have focused on the investigation of polypropylene. In the present paper, in order to cope with the lack of toughness (that is one of the most important drawbacks of polypropylene) and poor rigid-tough balance in modification for PP, these problems are studied and discussed in detail. Firstly, the effect of nano-CaCO₃ on the mechanical properties of PP was also studied. It was found that nano-CaCO...[ Read more ]

Polypropylene (PP) is one of the most commonly used synthetic resins. PP has a very good overall performance so that it is widely used in all aspects of the national economy. But there are also some obvious defects that limit the use of polypropylene in certain areas. Therefore, in order to overcome the shortcomings of performance, as well as improve its application, many researchers have focused on the investigation of polypropylene. In the present paper, in order to cope with the lack of toughness (that is one of the most important drawbacks of polypropylene) and poor rigid-tough balance in modification for PP, these problems are studied and discussed in detail. Firstly, the effect of nano-CaCO₃ on the mechanical properties of PP was also studied. It was found that nano-CaCO₃ had a better toughening effect on PP. When the content of nano-CaCO₃ were 35wt% and 30wt%, the impact strength attained the maximum value at room temperature (23℃) and low temperature (-20℃) respectively. When the content of nano-CaCO₃ was over a certain value, the impact strength drops dramatically due to the nanoparticles get into agglomeration. Meanwhile, the effects of the SPF179-g-GMA addition on the mechanical properties of PP and toughening effect of EPR on PP matrix were also investigated. In this paper, the PP/nano-CaCO₃/grafted impact co-PP (SPF179-g-GMA) system was studied and characterized in detail. Through the test of the mechanical properties, thermal properties, dimensional stability and processing properties of PP/nano-CaCO₃/grafted impact co-PP, the effect of each component on the various properties of the composites and microstructure were studied. It was found that the presence of ethylene-propylene rubber with polar functional groups in the three-phase system containing 40wt% calcium carbonate showed that the calcium carbonate did not appear as a dry powder agglomeration state in the two phases, but a large part entered the EPR to form a rubber nanoparticle composite ball.

The microstructures of binary blends and ternary composites were characterized by SEM, TEM and AFM. And the relationship between the microstructure of the material and the change of the impact strength is studied in depth. The synergistic effects of PP/nano-CaCO₃/ grafted impact co-PP three-phase composite system at room temperature (23℃) and low temperature (-20℃) were successfully explained by energy absorption mechanism. The effects of temperature and particle concentration on the molecular chain motion of rubber were studied. The different phenomena of the three-phase system under room temperature and low temperature were explained and confirmed by DMA characterization.

Through the study, under the guidance of the mechanism, a comprehensive performance of a good formula is obtained: composite material contains 30wt%PP, 30wt%nano-CaCO₃, 40wt% grafted impact co-PP. Compared with pure PP, the impact strength of composited increased by nearly 6 times, but the modulus did not decrease. And both mechanical properties and heat resistance are not reduced, while the material showed excellent isotropic (lateral shrinkage 0.85%, vertical shrinkage 0.85%). Above good results will provide us good theoretical basis and practical formula to further improve performance, expand the application of PP.