Study On Nano-CaCO₃/Polypropylene Composite With Ultra-high-speed Mixer

Preparation of polymer composites is one of the important methods to realize high performance of polymer materials. Polymer/nano-CaCOs composite have been rapidly developed recently because of their excellent comprehensive properties, in particular, the composite prepared with melt dispersion technology have great commercial value as consequence of convenient and economical technology. Using the ultra-high-speed mixer we designed , the key problems of PP/nano-CaCO3 were studied in detail on the paper, including the design of ultra-high-speed mixer, nano-CaCO3 surface modification and dispersion law of nano-CaCO3 in polymeric melt base on finite passivation theory of nano-CaCO3 surface and the rheological and crystallization behaviors of PP/nano- CaCO3 blends. The goal of the paper was to find whys of these problems and how to solve these problems, in order to promote development of nano material industry in the field of theory and practice. The key works and conclusions were listed as follows:1.According to the aggregation law of nano-particle and mixing theory of high-speed mixer, a kind of ultra-high speed mixer was designed by us to treat inorganic nano-particle, which has obtained a new type patent and is applying inventive patent. Structure and technologic parameters of the ultra-high speed mixer has been designed or chosen, such as the clearance between vane and wall, shape of vane, obliquity of vane, shear blade of side wall, atomization muzzle, rotate speed of impeller and shear blade, etc.2.For the first time dynamic shear bearing nano-particle was mathematics simulated in the clearance between the most circumgyrate radius of underside vaneand inside chamber of mixer. Physics model of stress of nano-particle in the clearance bearing was build, and on the basis of physics model elementary mathematics model was build. Aim at actual case to estimate and calculate the most shear stress of nano-particle in the clearance, and achieve the most shear stress of nano-particle in the difference clearance and rotate speed of impeller, which combining with calculation of aggregation intension of nano-particle offer evidence to design rotate speed of the ultra-high speed mixer. The result shows that when the clearance is designed as 0.5mm and rotate speed exceed 4000r/min, the ablation request of nano-particle could be satisfied whose diameter exceeds 70nm. This result approves the possibility, namely nano-CaCO3 agglomerate was treated effectively and break inhigh speed mixer. In order to treat smaller diameter nano-CaCO3, rotate speed of the ultra-high speed mixer is designed as 6000r/min and the clearance is designed as 0.5mm.3.The magnifition of the ultra-high speed mixer is studied. According to geometry analogical arithmetic, the magnifition of the ultra-high speed mixer that applied to industry is discussed and calculated, and effect of shear and blend are acted as amplificatory foundation. On the basis of 1OL lab machine, the ultra-high speed mixer with volume 500L is magnify and manufacture successfully that can be applied to industry. The magnifition calculation of the high-speed mixer has not been reported at present.4.In the study of preparation nano-CaCO3/PP composite using high-speed mixer treating nano-particle, the phenomenon is found that the new ultra-high speed mixer (6000r/min) is more effective than traditional high-speed mixer (1000-2000r/min) to treat surface of nano-CaCO3. Using SEM find that nano-CaCO3 treated by the ultra-high speed mixer can disperse mostly with crude nano-particle state in matrix PP, even if its content is very high (about 35%). So excellent performance nano-CaCO3/PP composite could be gained, and impact strength is higher 150% than one of composite treated by normal high-speed mixer, and 370% than pure PP. When the content of nano-CaCO3 is 35wt%, the peak of impact strength of composite appears. Content of nano-CaCO3 increase largely than one of prevenient report, aswell as mechanic performance of composite could be kept.5.The new ultra-high speed mixe...