| In many application fields,such as tire inner liners,chemical protection equipments,aerospace high vacuum systems etc.,there are extremely high requirements for the barrier properties of rubber composites.However,raw rubbers are highly permeable to most gases and liquids,since large free volumes exist among the rubber molecules caused by the extremely low glass transition temperature of rubbers and weak interaction between rubber molecules.In order to efficiently improve the barrier propertie of rubber composites to meet the requirements,nanoparticles are routinely filled into rubber matrix.In this study,the influence of the topology of fillers,the dispersion of fillers in rubber matrix,filler-rubber interfaces,and three-dimensional filler networks on the barrier performance of rubber composites were studied.The correlations between the microstructure and barrier properties of rubber composites are correlated,which provided theoretical supports for the design and preparation of high barrier rubber composites.The main research contents and results are as follows.(1)The influences of the filler networks formed by three types of nanofillers with different topologies,including spherical carbon black(CB),fibrous carbon nanotubes(CNTs),and layered graphene(GE),on the gas barrier properties of styrene-butadiene rubber(SBR)were investigated.The results showed that CNTs or GE could construct a strong filler network easily in SBR composites at low filler contents,while CB filler networks only constructed altering filling higher filler contents.When the filling content of CB,CNTs or GE was 35 phr,8 phr or 4 phr respectively,the strength of filler network of CB/SBR,CNT/SBR and GE/SBR composites was basically the same.However,compared with CNT/SBR and CB/SBR composites,GE/SBR composites possessed more excellent gas barrier properties,indicating that two-dimensional layered GE had unique advantages in improving the gas barrier properties of rubber composites.Combining with the analysis of Sorrentino theoretical model,it is concluded that the dispersion of the layered fillers,the interface interactions between layered fillers and rubber molecules,and the construction of oriented filler networks were of three key factors for the preparation of high barrier rubber composites.(2)In order to improve the dispersion state of the layered fillers in rubber matrix and enhance the interfacial interactions between the layered fillers and the rubber molecules,graphene oxide(GO)with abundant active oxygen groups was chosen as the reinforcing filler,then sulfur nanoparticles were generated and in situ grew on the surface of GO to produce GO-supported sulfur(S-GO)hybrids.Subquently,S-GO hybrids were introduced into SBR matrix by the latex compounding method to prepare the S-GO/SBR composites.It’s found that the sulfur on the surface of S-GO could not only crosslink the SBR molecules,but also chemically react with GO,thereby constructing a strong chemical interface between GO and SBR.More importantly,sulfur could also effectively prevent the aggregation of GO,thus improving the dispersion of GO in SBR matrix.The special microstructure made S-GO/SBR composites show excellent gas barrier properties and mechanical properties.When the filling content was 3 phr,the gas barrier properties of S-GO/SBR composites were improved by 50.7%and 23.3%,respectively,when compared with pure SBR and traditional GO/SBR composites.In addition,the tensile strength of SGO/SBR composites was also increased by 66.2%compared with GO/SBR composites.(3)Functionalized graphene oxide/silicone rubber(SCGO/SiR)composites with two different filler network structures(oriented filler network and random distributed filler network)were prepared by the Pickering emulsion template method.Then the effect of these two type of filler nwtworks on the gas barrier properties of SCGO/SiR composites was sdudied.The results showed that the oriented filler networks could significantly enhance the gas barrier properties of SiR composites.When the content of SCGO was 3 phr,the gas barrier properties of SCGO/SiR composites were increased by 85.7%when compared to pure SiR composites.Meanwhile,under the same filler contents,the improvement effect on the gas barrier properties of SCGO/SiR composites with oriented networks were 20-30%higher than those of the SCGO/SiR composites with random distributed filler networks.(4)GO/butyl rubber(GO/IIR)composites were prepared by the latex compounding method,and the protective performance of the composites on the chemical poison(sulfur mustard)was studied.The results showed that the diffusion behavior of sulfur mustard in GO/IIR composites was closely related to the filler networks formed by GO sheets,and the filler network structure could be controlled by changing the content of GO.When the filler content was 2 phr,GO formed a uniformly dispersed filler network in the GO/IIR composites,resulting into 38.2%improvement in barrier properties against sulfur mustard of GO/IIR when compared with pure IIR.When the filler content was up to 3 phr,GO layers could overlap each other to form a three-dimensional interconnected network,which made the barrier properties of GO/IIR composies 45.8%higher than that of pure IIR. |
