Study On The Properties Of Red Mud/phosphogypsum/polyethylene Composite

As a highly crystalline thermoplastic resin,high density polyethylene（HDPE）has good physical and chemical properties such as corrosion resistance,chemical stability and good processability,thus is widely used in fields such as pipes,wires and cables.In order to expand the range of applications of HDPE materials,traditional inorganic fillers such as silica,calcium carbonate,mica,etc.are usually added during the processing of HDPE composites to improve the overall performance of HDPE composites.However,the cost of using the above mentioned traditional inorganic fillers to improve the performance of HDPE composite materials is high.In recent years,it has been found that solid waste red mud（RM）and phosphogypsum（PG）can be used as new inorganic fillers to replace the traditional inorganic fillers due to their wide natural sources,high yield and low cost.Therefore,in this thesis,the neutral red mud/phosphogypsum（RP）prepared by our group previously was chosen as the inorganic filler to study the effect of RP on the performance of HDPE materials.The main findings are as follows:（1）RP was selected as inorganic filler reinforcement material,and the effect of RP on the properties of HDPE materials was systematically studied.The results showed that RP can promote crystallization of the composites,improve the thermal stability and heat deflection temperature of the composites;RP was added to the composites as rigid inorganic filler to increase the intermolecular friction,increase the resistance to melt flow and impede the movement of the molecular chains of the composites,thus improving the complex viscosity,energy storage modulus and loss modulus of the composites;and as increased of RP contents,the tensile strength and flexural properties of the composites increased.The tensile strength and bending properties of the composites increase with increasing RP content.（2）RP was employed as inorganic filler reinforcement material,titanate coupling agent（TMC-114）,aluminium-titanium composite coupling agent（TL-TA-1618）and silane coupling agent（KH550）were used as RP surface modifiers,and the optimum modification conditions of the coupling agents were studied.The results showed that when the content,reaction temperature,stirring speed and reaction time of TMC-114 were 4%of RP,80°C,600 r/min and 2 h,respectively,the modification effect of RP was the best;when the content,reaction temperature,stirring speed and reaction time of TL-TA-1618 were 3%of RP,80°C,800 r/min and 3 h respectively,the modification effect of RP was the best;when the content,reaction temperature,stirring speed and reaction time of KH550 were 3%of RP,80°C,800 r/min and 3 h respectively,the modification effect of RP was the best.The three coupling agents modified RP all improved the water contact angle TMC-114-RP>TL-TA-1618>KH550,causing a molecular layer to form on the surface of RP,thus improving the compatibility of RP in HDPE and increasing the interfacial bonding between RP and HDPE,impeding the movement of molecular chains,and improving the overall performance of the composites TMC-114-RP/HDPE>TL-TA-1618-RP/HDPE>KH550-RP/HDPE.When TMC-114and RP content were 4%and 30%,respectively,the T_max of TMC-114-RP/HDPE composite was476.09°C,HDT was 84.15°C,notched impact strength was 21.4 KJ/M²,tensile strength was 26.62MPa,bending strength was 29.59 MPa and bending modulus was 1489.05 MPa.The best thermal stability performance and mechanical properties of the composites were achieved.（3）Diisopropyl peroxide（DCP）was selected as the cross-linking agent to study the effect of DCP content on the properties of TMC-114-RP/HDPE composites.The results showed that as DCP content increased,the molecular chains of HDPE matrix underwent cross-linking reaction to form three-dimensional network junctions and the degree of cross-linking increased,which hindered the movement of HDPE molecular chains and improved the thermal stability properties,heat deflection temperature,rheological properties and mechanical properties.When the DCP content was 0.4%,the TMC-114-RP/cross-linked HDPE composite exhibited the best overall performance with T_maxof 485.86°C,HDT of 87°C,notched impact strength of 21.98 KJ/M²,tensile strength of 38.4 MPa,bending strength of 36.02 MPa and bending modulus of 1681.03 MPa.