Study On Structure And Properties Of Polypropylene/Polystyrene And POE Elastomer Blend Prepared Via Reactive Extrusion

Polypropylene/polystyrene(PP/PS)blend are typical immiscible polymer system.The addition of PS could improve the strength of PP matrix.However,as the poor compatibility between PP and PS,the PS phase will damage the toughness of PP.In this paper,the highly compatible PP/PS blend was developed by reactive extrusion method.The main achievements are as follows.In this study,the dicumyl peroxide(DCP)and benzoyl peroxide(BPO)were employed as the initiator of the PP/styrene(St)monomer for reactive extruding,the torque curves of the content of different initiators show the suitable initiator was DCP at 1.5 wt%.The extrusion product was characterized by FT-IR after extracting by ethyl acetate,the result shows the St has been grafted on the PP chain during the reactive extrusion process,and the polypropylene-grafted-polystyrene(PP-g-PS)has been generated in blending systems.The calculation of grafting rate proves grafting rate is increasing with rise of St content,the highest grafting rate is 90 %.The morphology of PP/PS blends were observed by SEM,the more uniform morphology was obtained in in-situ PP/PS blends.The calculation of particles size shows the diameter of PS dispersion in in-situ blend is only 80.23 nm,which could refer as a nano-blend.The mechanical properties show the tensile strength and flexural modulus are increasing with the rise of PS content,the elongation at break and impact strength are decreasing with the rise of PS content.The mechanical properties of in-situ PP/PS blends are preceding than simple blend PP/PS blends,especially for the elongation at break when the PS content is lower than 15 %,the elongation at break of in-situ PP/PS could exceed 400%,which is no differ from the pure PP.The rheology properties were characterized by Haake capillary rheometer.The results show the PP-g-PS generated in reactive extrusion has changed the rheology behavior of PP/PS blend.It leads to a higher flow activation energy,a stronger interaction between polymer chains,a larger shear viscosity of blends and a lower dependence of temperature.The crystal properties were characterized by XRD and DSC.The results show the PP-g-PS can increase the crystal temperature of blends,which means it is a heterogeneous nucleation agent.And it leads to the beta-form crystal has been generated in blend.The addition of POE can improve the elongation at break and impact strength of binary PP/PS blend,but it also drops the tensile strength and flexural modulus of blends.The SEM observation shows the size of POE is declining in in-situ PP/PS/POE blends,which could bring a better mechanical property.The results of DMA show the loss peak is appear at low temperature,and the glass transform peaks of PP and PS close to each other,indicated a better compatibility between each phase in blend.