Study On Sorbic Acid Modified Layered Clay Filler And Its Reinforcement Of HNBR Performance

With the rapid development of economy,the requirements for rubber properties are also increasing.In order to meet the high requirements for the performance of rubber materials,it is necessary to use one or more fillers to strengthen rubber in order to improve the properties of rubber.As a two-dimensional nano-filler,layered clay has a large aspect ratio and can effectively improve the mechanical properties,flame retardant performance,gas barrier performance and aging resistance of rubber composites.However,layered clay is inorganic filler and has much hydroxyl groups,resulting in terrible dispersion in rubber matrix.In order to enhance the dispersion of layered clay and prepare composites with excellent mechanical properties,sorbic acid(SA)was used to modify layered clay.The main work contents are as follows:1.MMT/SA/HNBR composites were prepared by using SA in-situ modified montmorillonite(MMT)and reinforced into HNBR.As an unsaturated carboxylic acid,SA has carbon-carbon double bonds,which can form free radicals under the initiation of DCP and graft itself onto HNBR rubber chain.At the same time,the carboxyl group in SA can form hydrogen bonds with the hydroxyl groups which between MMT layers and on the surface of MMT,which can effectively improve the interaction between MMT and HNBR and significantly improve the dispersion of MMT in rubber.In addition,SA and vulcanization assistant ZnO can react in the vulcanization stage to produce zinc sorbate(ZDS).On the one hand,consume excessive ZnO makes the rubber composite show transparency.On the other hand,ZDS is self-polymerized under the initiation of DCP to produce poly-zinc sorbate(poly-ZDS)to further strengthen the rubber.When the MMT content is 10phr and the SA content is15 phr,the comprehensive mechanical properties of MMT/SA/HNBR composite are the best.The tensile strength reaches 43.65 MPa,the tear strength reaches 53.52 kN/m,the hardness is 71.4°,and the elastic modulus is 12.12 MPa,which is obviously better than MMT/HNBR composite.2.LDH was modified in situ by SA and reinforced into HNBR to prepare LDH/SA/HNBR composites.The carbon-carbon double bond in SA can be grafted onto the HNBR rubber chain.At the same time,the carboxyl group in SA can form a bridge coordination bond with the metal ions in LDH,which can effectively improve the interaction between LDH and HNBR and significantly improve the dispersion of LDH in rubber.In addition,SA and ZnO can react in the vulcanization stage to produce ZDS.On the one hand,consume excessive ZnO makes the rubber composite show transparency.On the other hand,ZDS is self-polymerized under the initiation of DCP to produce poly-ZDS to further strengthen the rubber.When add LDH with 30phr and SA with 20 phr,the comprehensive mechanical properties of LDH/SA/HNBR composite are the best,the tensile strength reaches 39.31 MPa,tear strength reaches 62.38 kN/m,hardness is 85.1°and elastic modulus is 20.14 MPa,which is obviously better than LDH/HNBR composite.3.SA-LDH was prepared by SA intercalation modified LDH and reinforced into HNBR to prepare SA-LDH/HNBR composite.SA~-has carbon-carbon double bonds,which can form chemical cross-linking reaction with rubber matrix and be grafted onto the HNBR rubber chain.At the same time,there is ionic bond between SA~-and LDH lamellar,which can effectively improve the interaction between LDH lamella and rubber matrix.In addition,SA~-intercalation into LDH interlayer can change LDH from hydrophilic to lipophilic,besides,it can effectively expand the layer spacing of LDH,which is conducive to the dispersion of LDH in rubber matrix.When the SA-LDH content is 40phr,the comprehensive mechanical properties of SA-LDH/HNBR rubber composite are the best,the tensile strength is 29.73 MPa,tear strength is40.12 kN/m,shore A hardness is 73.6°,elastic modulus is 13.03 MPa,which is obviously better than LDH/HNBR composite,but the reinforcing effect of SA intercalation modification method on rubber is worse than SA in-situ modification method.SA-LDH and SA were used to reinforce HNBR to prepare SA-LDH/SA/HNBR composite.The results show that the combination of the two can significantly improve the tear strength,hardness and elastic modulus of rubber composites,especially the elastic modulus.When 30 phr SA is added,the elastic modulus can reach 37.2 MPa.However,joint addition of SA-LDH and SA greatly reduces the elongation at break of the rubber composite.The elongation at break of the rubber composite with 40 phr SA-LDH and 30 phr SA is only 159.67%.