| Using the technologically modified twin-screw extruder and applying the controlled degradation principle of reactive extrusion,the equipment requirements,process conditions,formula,the continuity of reaction and the properties of reactive extrusion products were studied systematically in this paper.Firstly,the existing twin-extruder is modified and the processing technic is optimized to meet the requirement of extrusion controllable degradation reaction.We design a series of mechanism which contains extruder cylinder connecter,middle feeding component,guide component,automatic feeder,feeder placed platform,as well as other relevant subsidiary accessories.Adjusting and testing the temperature control method of twin screw extruder screw barrel.The problem that the intermediate feeding port is easy to feed back during extrusion stage is solved.Secondly,we develop two new testing methods which is featured as accurate and timesaving to applied in the Melt Flow Rate(MFR)testing of high fluidity polypropylene(PP).The comparative experiment between those two methods shows that the best way to test the MFR of high fluidity PP is the one named as half die port method.This method holds such characteristic: easy to operate,short measurement,relative smaller error and the data multiplied by coefficient of 10 can be converted to standard values directly.Experiments also show that traditional standard method take more time and show higher relative error,325 g method failed to get a liner relationship to transfer the measuring value to the standard when MFR of high-fluidity PP is measured.Thirdly,the influence of various factors on the extrusion reaction,such as the temperature condition.the feeding position of initiator and antioxidant,the screw speed,the initiator types,the amount of initiator and so on,is systematically studying.It shows that the temperature holds a slight impact on MFR;The speed of screws have a notable influence on MFR,The MFR of the product increases by about 20g/10 min when the screw speed is increased by 50 rpm;The addition of a little amount peroxide enhance significantly the melt flow rate(MFR)of the reactive extrusion products,The MFR of the product increases by about 20g/10 min with the increase of 0.02% of the initiator peroxide dosage;The induction of 2,5-Dimethyl-2,5-di(tertbutylperoxy)hexane(Double 25)is more efficient than that of dicumyl peroxide(DCP);A high-fluidity and long period stability of PP is produced and revealed with oxidant induction time(OIT)testing,although its MFR decreases a bit when antioxidant1010 masterbatch is fed into the middle position of extruder.Fourthly,the mechanical properties of the high fluidity polypropylene products are studied.The stress-strain test,no-notch test and notch impact test at different temperatures show that high MFR will decrease the tensile and impact resistance of the product.On this basis,linear low density polyethylene(LLDPE)is added into the extrusion reaction product in the middle position of the extruder to make PP/LLDPE composite material.The stress-strain test and the impact strength test of simply supported beam notched/notched at different temperatures show that the addition of LLDPE have a significant toughening effect on the high fluidity polypropylene product. |
