Design And Preparation Of High Strength And Fatigue Resistant Graphene/rubber Nanocomposites

Rubber composites have important applications in the fields of transportation,sealing protection,shock absorption and damping,due to their unique viscoelasticity,low elastic modulus and reversible deformation.In actual use,rubber products need to endure quasi-static or periodic dynamic load for a long time.During this process,rubber composites will be gradually damaged and broken,which will bring about severe security risks or cause huge economic losses.Therefore,studying and evaluating the fatigue properties of rubber composites is of great significance for the preparation and pratical use of the rubber products.In this study,the effects of filler type,filler dispersion,filler network structure,and filler-rubber interface on the mechanical strength and fatigue performance of rubber composites were explored and revealed.Through the investigation,a new strategy for the design and preparation of rubber composites with high strength and excellent fatigue resistance was provided.The research contents of this study are as follows:(1)The effects of three kinds of different fillers,including spherical silica(SiO2),tubular carbon nanotubes(CNT)and lamellar graphene oxide(GO),on the microstructure,mechanical strength,crack growth behavior,fracture surface morphology and zinc oxide(ZnO)dispersion of SBR composites were studied.The results showed that the type of fillers had great influence on the microstructure,mechanical strength and fatigue properties of the SBR composites.CNT or GO formed overlapping filler network at low contents,which could significantly improve the tensile stress of SBR composites.Also,the fatigue crack growth rate and fracture morphology were closely related to the filler type and filler contents.When the SBR composites filled with these three different fillers had the same hardness,the crack growth rate of SiO2/SBR and GO/SBR composites were almost equivalent,while the crack growth rate of CNT/SBR composites was the largest.In addition,the elemental analysis of fatigue fracture surfaces revealed that ZnO was also one of the important factors that caused crack propagation in rubber composites.It can be obtained from the research in this part that the filler network,filler-rubber interface,and ZnO dispersion were the three key factors that affected the fatigue performance of the rubber composites.(2)In order to investigate the influence of filler networks on the properties of the rubber composites,SBR composites were reinforced by three different filler systems(SiO2,CNT-SiO2,GO-SiO2).The results showed that the interpenetrating isolation network formed by CNT-SiO2 or GO-SiO2 was beneficial to improve the tensile stress and tear strength of rubber composites.For uniaxial fatigue test,GO-SiO2 filler network in SBR composites was more stable under dynamic strain.The GO sheets comprised in the filler networks could undertake the stress,making the crack more prone to deflection and generating secondary cracks,thus reducing the crack growth rate.For multiaxial fatigue test,the maximum engineering stress(?max)and stress amplitude had a certain effect on the fatigue life of SBR composites.At the same ?max or stress amplitude,GO-SiO2/SBR composites had the longest fatigue life.Moreover,?max was found to have a good correspondence with fatigue life,which could be used as a reliable fatigue life predictor for SBR composites.(3)In order to improve the interfacial compatibility between GO and non-polar SBR,low-cost sodium lignosulfonate(SLS)as stabilizer and ascorbic acid(VC)as green reducing agent were used together to prepare functionalized graphene(SRGO)which could be stably dispersed in aqueous solution for several weeks.Then the SRGO aqueous dispersion and SBR latex were mixed by latex compounding method.The co-coagulated products were directly processed to obtain SRGO/SBR composites or combined with SiO2 to prepare SRGO-SiO2/SBR composites.The results showed that the SRGO/SBR composites not only possessed high tensile stress and excellent tensile strength,but also maintained large elongation at break.When the content of SRGO was up to 3 phr,the crack fracture surface of SRGO/SBR composites exhibited a rough morphology with less defect structure,and the crack growth rate also decreased significantly.Meanwhile,the synergistic filler network constructed by SRGO-SiO2 also exhibited excellent crack growth resistance.It was found that the SBR composites filled with 1 phr SRGO for SRGO-SiO2 system had almost the same crack growth rate with the SBR composites filled 3 phr GO for GO-SiO2 filler system.The homogenous dispersion of SRGO and strong interfacial interaction between SRGO and SBR molecules played a key role in achieving excellent fatigue resistance.(4)GO supported zinc oxide(ZG)hybrids were prepared by electrostatic adsorption and in situ growth methods.Subsequently,ZG/chloroprene rubber(CR)composites was prepared by mechanical blending of ZG hybrid with polar CR,and ZG/SBR composites was prepared by latex compounding of ZG hybrid with non-polar SBR.In ZG/CR composites,the strong interfacial interaction was constructed owing to the formation of hydrogen bonds and metal coordination bonds between the ZG hybrids and CR molecules.The ZG hybrids not only accelerated the crosslinking rate,increased the crosslinking density and mechanical strength,but also improved the ZnO dispersion and enhanced the crack growth resistance of CR composites.When the GO content was 3 phr,the vulcanization rate of ZG/CR composites was 2.6 times higher than that of ZnO-GO/CR composites,and the 300%tensile stress and tensile strength were increased by 31%and 60%,respectively.In ZG/SBR composites,carboxylated styrene butadiene rubber(XSBR)was used as interface agent.The-COO-/Zn3+ionic bonds and hydrogen bonds were formed between ZG hybrids and XSBR molecules.Meanwhile,covalent bonds could be formed between XSBR and SBR through sulfur crosslinking.Under multiple bond interactions,ZG/SBR composites exhibited higher mechanical strength than that of ZnO-GO/SBR.Since ionic bonds and hydrogen bonds could preferentially break and dissipate energy under dynamic deformation,and the ZnO dispersion was significantly improved,ZG/SBR composites had more significant advantages in crack growth resistance and fatigue performance.The ZG hybrids not only acted as crosslinking agents but also exhibited excellent reinforcement effect.The simple and effective method provides new insights into the design of multifunctional rubber additives and fabrication of rubber composites with high performance.