Preparation And Study On Functionalization Of Nano-fibrillar PP/ABS Composite

At present,the methods of in situ fibrillation are mainly based on the deformation of molten droplet of dispersed phase in stretching flow field,which is so-called fibrillation of polymer on fluid phase.However,strategy in this way can not get nanofibrils,because of limited draw ratio and aggregation of polymer droplet during process.A new strategy of in situ fibrillation was found by choosing unentangled semi-crystal polymer as fibrillar phase which has good deformable ability in solid state.The nanofibril can be obtained by shear unentangled semi-crystal polymer in molten polymer matrix which had occurred plastic deformation during compounding.But gain a lot of unentangled semi-crystal polymer is so difficult that limited application of nanofibrillar composite.Amorphous polymer has good deformable ability and easy to functionaliztion in high-elastic state,which can take place of unentangled semi-crystal polymer as fibrillar phase.Thus,ABS was selected as fibrillar phase to compound with molten polypropylene for preparation of PP/ABS microfibrillar composite.SEM,rheometer,XRD,and electronic tensile testing machine were used to analyze micro-morphology,rheological,crystal structure,and mechanical property of PP/ABS microfibrillar composite.The factors such as screw rotation,process temperature,content of ABS,shear time,facilities were effect on fibrillation of ABS has been studied.Then,the carbon black was added in PP/ABS microfibrillar composite,which produced PP/ABS/CB conductive microfibrillar composite with low percolation threshold.The results showed that morphology of ABS phase is micro-particles by normal condition of compounding at 230 ^oC.The process temperature?190 ^oC?is higher than melt point of PP but lower than process temperature of ABS,10wt%inclusion of ABS phase was in situ deformed to fibrils in molten PP matrix with low screw rotation?50rpm?during compounding,the diameter of majority fibrils are about 100nm,but it was disadvantage for fibrillation of ABS at such high screw rotation?200 rpm,300rpm?.While lower and higher inclusions of ABS?5wt%and 15wt%,20wt%?were still bad for fibrillation.In the condition of temperature of 185 ^oC,ABS was deformed as microfibrillar network structure in torque rheometer with compounding time of 15minutes,but fibril thickness is only about 230 nm on average,which is larger than the fibril thickness prepared by twin-screw extruder.The better fibrillar structure can be got easily by using of more time in compounding.When process temperature higher than 190 ^oC,which is disadvantage for deformation of ABS.The results of rheological test demonstrated that big elasticity of ABS and long relaxation time at 185 ^oC,which were helpful for fibrillation of ABS and stable for the fibrillar structure.The relaxation time was reduced obviously when process temperature exceeds over 190 ^oC and caused decline of elasticity of ABS molecular chain,which was disadvantage for fibrilltion of ABS.Mechanical property of PP/ABS microfibrillar composite is better than normal PP/ABS blend,especially for bending strength and modulus,each of which was 13.7%and 9.2%higher than the latter by contrast.The results of XRD test showed that no difference between crystal structure of PP/ABS microfibrillar composite and PP/ABS blend,because ABS can induce formation of?crystal in both the composite and blend.Therefore,enhancement mechanism of PP/ABS microfibrillar composite was only attributed to ABS microfibrillar network structure.Firstly,CB was filled into molten ABS for preparation of ABS/CB conductive master batch.Then the ABS/CB conductive master batch was compounded with molten PP by weight ratio of 1/9 under the method of above-mentioned in torque rheometer for preparation of PP/ABS/CB conductive composite.SEM images showed that ABS/CB master batch was generated in situ microfibrillar structure in molten PP matrix,thus the low percolation threshold composite has been prepared successfully.By contrast to normal PP/ABS/CB composite,the volume resistivity of PP/ABS/CB conductive microfibrillar composite is 3.8×10¹²??cm which has 5 order of magnitudes lower than the former.The volume resistivity of PP/ABS/CB condutive microfibrillar composite was further decreased to 6.9×10¹⁰??cm when inclusion of CB reached to 1wt%in the composite.