Preparation And Properties Of High Performance Graphene Natural Rubber Composites

With the rapid development of economy,the application of rubber in the automotive industry has grown steadily and China has become the world’s largest consumer of rubber.The preparation of green tire rubber materials with low rolling resistance,high wear resistance and wet-slip resistance has received wide attention from researchers.Traditionally,rubber reinforced with carbon black,silica,montmorillonite,etc.is still focused on improving the mechanical properties of rubber materials.However,relatively little attention has been paid to the control of dynamic temperature of rubber materials.At present,for the study of temperature control of rubber materials during the dynamic environment,the focus is divided into two aspects:Firstly,to reduce the heat generation of the rubber composites by adjusting the filler-filler and filler-matrix interaction through process improvement and filler modification.Secondly,to increase the thermal conductivity of rubber composites by regulating the formation of thermally conductive fillers in the rubber matrix to form thermally conductive paths and reducing the interface thermal resistance between the filler and the matrix.The application of new functional nanomaterials,such as graphene oxide（GO）,carbon nanotubes（CNTs）and so on in rubber has brought new possibilities for the development of rubber functionality.In response to the current research status and problems of carbon black,silica and graphene oxide reinforced natural rubber,this paper discusses how to balance the thermal conductivity,heat generation and mechanical properties of natural rubber composites for tires.Research has been carried out on the basis of graphene-reinforced rubber to regulate the dynamic performance of natural rubber for tires.The main contents and conclusions are as follows:（1）The effects of graphene oxide and reduced graphene oxide on the static mechanical properties,compression fatigue heat generation and thermal conductivity of rubber were explored when the latex co-precipitation method was used.On the basis of this work,a mild reducing agent gelatin（Gel）was used to modify and reduce graphene oxide to prepare G-r GO.The G-r GO filler was prepared using Gel modified GO and grafted onto the surface of GO through chemical bonds.And GO was modified with Gel,which could enhance the interaction between GO and NR.So the influence of the interaction between filler and matrix on rubber performance was mainly explored.And the qualitative influence on the temperature field distribution of rubber tires were studied.When the content of G-r GO was 1 phr,the tensile strength reached a maximum value of 29.3 MPa and the elongation at break was greater than 600%.Compared with pure NR,the tensile strength of NR/G-r GO-1 was increased by about 56%.When the content of G-r GO was 1 phr,the compressive fatigue heat generation of the rubber composites was reduced to 1.9°C,which was 45.8%lower than that of NR/GO.When the G-r GO was 4 phr,the thermal conductivity of the rubber composite could reach 0.375 Wm^-1K^-1,which was 90.3%higher than that of pure NR.（2）The rubber vulcanization accelerator NS was used to modify and reduce GO to prepare NS-r GO.It mainly explored the chemical bond connection between the filler and the matrix,and the influence of the interaction between the filler and the matrix on the properties of rubber.GO was modified with NS,which could enhance the interaction between GO and NR.When the content of NS-r GO was 1 phr,the tensile strength of the NR/NS-r GO composite could reach 30.3 MPa,which was about 57.9%higher than pure NR,and the elongation at break was greater than 600%.When 1 phr NS-r GO was added,the heat generation of the rubber composite was 2.6℃,which was much smaller than the 4.8℃of the NR/VC-r GO composite.Compared with pure NR,the heat generation of NR/NS-r GO was also reduced by 0.9℃.When the content of NS-r GO was 4 phr,the thermal conductivity of NR/NS-r GO could reach 0.397 Wm^-1K^-1,which was 105%higher than that of unfilled NR.（3）The ANSYS finite element software was used to predict the temperature distribution of rolling solid tires,and the influence of thermal conductivity and loss factor on tire temperature rise was quantitatively analyzed.The established finite element model of the solid tire temperature field could be used to predict the internal temperature field distribution of solid tires made of different rubber materials under rolling conditions.It was found that as the thermal conductivity of the rubber material increased,the maximum temperature gradually decreased exponentially.And as the loss factor of the tread rubber increased,the temperature gradually increased linearly.It was found through simulation that when the thermal conductivity of the rubber material reaches 0.45 Wm^-1K^-1,further improving the thermal conductivity of the rubber material would reduce the effect of reducing the maximum temperature in the rubber tire.Therefore,when the thermal conductivity of the rubber material is lower than 0.45 Wm^-1K^-1,increasing the thermal conductivity of the material is more important for controlling the temperature field of the rubber tire;while reducing the loss factor of the rubber material is always important for controlling the temperature field of the rubber tire.（4）On the basis of NR/NS-r GO,silica（SiO₂） and SiO₂ modified with KH550 were used as reinforcing particles,and a mechanical blending method was used to prepare rubber composites.The effect of SiO₂surface modification on its dispersibility in the rubber matrix was mainly analyzed,and the mechanical properties,thermal conductivity and heat generation properties of rubber materials with different filler contents were studied.KH550 could be effectively grafted on the surface of SiO₂through chemical bonds to produce SiO₂-NH₂.SiO₂-NH₂could accelerate the vulcanization of rubber filler.When the content was 20 phr,the tensile strength of the NR-r GO/SiO₂-NH₂composite was 18 MPa and the elongation at break was 550%.When adding 50 phr of SiO₂-NH₂,the heat generation of NR-r GO/SiO₂-NH₂was30℃,but compared to that of NR-r GO/SiO₂（42℃）,it was still 12℃lower.It showed that improving the dispersibility of the filler could help reduce the heat generation of the rubber composites,especially when the content of the filler was relatively high.When the filler content of SiO₂-NH₂was 50 phr,the thermal conductivity of NR-r GO/SiO₂-NH₂was 0.415Wm^-1K^-1.（5）The GO-SiO₂ filler was obtained by reacting SiO₂-NH₂ with GO.Furthermore,KH580 was used to modify the GO-SiO₂fillers to realize the sulfhydrylization and obtain the GO-SiO₂-SH filler.Then the rubber composites were prepared by the latex co-precipitation method.Here,the effect of filler dispersion and filler-matrix interaction on the overall performance of rubber was mainly explored.And the mechanical properties,thermal conductivity and heat build-up properties of rubber materials with different filler content were studied.Compared with GO-SiO₂filler,the agglomeration phenomenon of GO-SiO₂-SH in the rubber matrix was weakened,and the vulcanization speed of the rubber material was faster.Compared with NR/GO-SiO₂,NR/GO-SiO₂-SH had stronger tensile strength,tear strength,hardness and tensile stress,and at the same time,had a more stable elongation at break.When the filler content was 40 phr,the tensile strength of the NR/GO-SiO₂-SH composite was 30MPa,the elongation at break was greater than 530%,the tear strength was greater than 50N/mm,and the shore hardness was greater than 58.When 50 phr of GO-SiO₂-SH was added,the heat generation of NR/GO-SiO₂-SH was 19℃,and the thermal conductivity of NR/GO-SiO₂-SH was 0.55 Wm^-1K^-1.