Study On The Influence Of Supercritical CO₂on The Assisted Processing And Extrusion Foaming Of PP/Inorganic Fillers System

The functionality and the mechanical property of polymer can be improved when thepolymer is modified by inorganic fillers. And this modification method can reduce the cost ofthe raw material. So it is widely used in the polymer industry. But if we want to get thepolymer with our expected requirements, there are high standard demands for the assistedprocessing. And this is the important and the difficult points for the modification of polymerwith inorganic fillers. With the internal mixer, the single screw extruder and the twin-screwextruder, this paper studied the influence of supercritical CO₂, the varieties and contents of theinorganic fillers, the equipment and the processing condition （temperature and rotate speed）for the assisted processing of PP/inorganic filler system’s.The results of the study show that supercritical CO₂play an active role in the assistedprocessing of PP/inorganic filler system’s. For the PP/talc system, the products can be in agood dispersion and well-defined morphology with the supercritical CO₂.The more thesupercritical CO₂, the more obvious effect can be seen. The dissipation of the single screwextruder with the supercritical CO₂can be almost equivalent with the twin-screw extruder,and it can avoid the severe damage of the laminated structure of talc. In addition, the higherthe temperature, the better-distributed of talc and its laminated structure can be saved better.The higher the rotate speed, the better-distributed of talc but its laminated structure will bedamaged more severely. The more contents of talc, it can not be equably distributed and therewill be large reunite in PP, and the friction of PP/talc system will be enlarged, as a result, thelaminated structure will be damaged more severely. For the PP/OMMT system, supercriticalCO₂can promote the polymer intercalation, the more content of supercritical CO₂, the moreobvious effect can be seen. The processing condition （temperature and rotate speed） has aneffect upon the polymer intercalation, but it isn’t obvious.PP foam is widely used today as it save original material, reduce the weight of materialand it has a good property of toughness, heat endurance, insulating quality, heat preservation,chemical resistance and biodegradable recovery. Nevertheless, the traditional intermittentfoam molding method has a low productivity. It is unsuited for industrial production. Thechemical foaming agent used in the traditional extrusion foaming is expensive, not in the bestinterests of the environment and the foam effect is not ideal. For these reasons, this paperstudied the performance of the extrusion foaming with supercritical CO₂of PP/inorganicfillers. We studied the effect of the content of the supercritical CO₂, the varieties and contentsof the inorganic fillers, the equipment and the processing condition （temperature, rotate speedand die pressure） for the extrusion foaming performance of PP/inorganic fillers system. The results of the study show that inorganic fillers can promote the heterogeneousnucleation. But the content of inorganic fillers can’t be too much, otherwise the viscosity willincreases and it can’t be evenly distributed. The shearing action well be increased when therotate speed is increased, it will be beneficial to the formation of the homogeneous system ofPP/inorganic fillers, and the cell distributed more evenly. But the higher the rotate speed willreduce the contact time of polymer melt and supercritical CO₂. This is not beneficial to theformation of the homogeneous system. When the temperature is low, the die pressure is high,but the die will be easily closed. When the temperature is high, the die pressure is low. This isnot beneficial to the bubble nucleation and bubble expansion. In the allowing experimentalconditions range, the bubble density will increase and the distribution will be more evenlywhen the die pressure is high. As for the extrusion foaming of PP/inorganic fillers system inthis paper, when the content of supercritical CO₂is0.05ml/min, the content of talc is10%wtor the content of OMMT is3%wt, the temperature is about160℃, the rotate speed is about10HZ, the die pressure is between14MPa and17MPa, we can obtain the ideal foam products.And the foam effect of HMSPP/inorganic fillers system’s is better than PP/inorganic fillerssystem’s.