Design And Preparation Of High Barrier Butyl Rubber Composites

Rubber composites with high barrier properties are needed in many application fields that require sealing and air preservation,such as tire inner tubes,medical rubber plugs,chemical protective equipment,aerospace high vacuum systems,etc.With the continuous expansion of the application field,the traditional barrier rubber is also put forward higher requirements.The factors affecting rubber air barrier are complex,including the structure of matrix molecular chain,filler,crosslinking network and so on.In order to meet the requirements of various working conditions,the barrier and other properties of rubber composites can be improved from many aspects.In this paper,the relationship between the microstructure and barrier properties of rubber composites was studied from three aspects:the construction of entangling network filled with liquid rubber,the filling of layered filler and the modification of rubber molecular chain.A variety of high barrier butyl rubber composite were designed and prepared.The main research contents of this thesis are as follows:（1）The effects of liquid nitrile butadiene rubber（LNBR）,hindered phenol AO80 and C5 hydrogenated resin on the damping properties and gas barrier properties of brominated butyl rubber（BIIR）were studied,and damping sheet with excellent properties were designed and prepared.The results show that LNBR can improve the damping performance of the material at low temperature,AO80 and C5 can improve the damping performance at high temperature.LNBR can form a high entangling network and produce hydrogen bond with AO80 at the same time,hydrogen bond will fracture and dissipation,C5 through the strong van der Waals force to improve the viscosity of the system,making the movement of molecular chains more difficult.The effective damping temperature range of BIIR/LNBR-AO80-C5 composites is 49.2%higher than that of BIIR,and the glass transition temperature moves to high temperature by about 20℃.With the addition of 30 phr LNBR and AO80,the nitrogen permeability coefficient of BIIR/LNBR and BIIR/LNBR-AO80 decreased by 23.6%and 38.9%,respectively,compared with that of BIIR.And the permeability coefficient of BIIR/LNBR-AO80-C5 has increased,but still better than BIIR.（2）The effects of molecular chain structure,molecular weight and polarity of liquid rubber on the free volume and airtight properties of rubber composites were investigated.Five kinds of liquid rubber（EPDM with 30,000 and 50,000 molecular weight,PIB with 680 and 2400molecular weight and NBR with 5,000 molecular weight,respectively）were mixed with IIR to prepare composites and characterized accordingly.The results show that the high molecular weight EPDM and the PIB 680have no obvious effect on the free volume and air barrier of the composites at the addition of 10 phr.PIB 2400 was able to introduce additional molecular chain relaxation as a suspension chain,reducing the nitrogen permeability of the composite by 13.2%,while NBR 5000 was able to reconstruct the entangling network and enhance the chain interaction,reducing the permeability of the composite by 14.3%.（3）In order to improve the interface between graphene oxide（GO）and rubber matrix,vinyl silane coupling agent KH570 was used to graft the GO to obtain modified graphene oxide（m GO）.m GO and IIR latex were prepared masterbatch by latex compounding method,and IIR-m GO composite was prepared by mixing with IIR raw rubber.m GO can produce chemical crosslinking with molecular chains through double bonds,thus building strong chemical interfacial interaction.The results showed that the tensile strength and tear strength of IIR-m GO increased by 39.1 and14.8%compared with IIR when the m GO was 1.5 phr.On this basis,the addition of 10 phr NBR 5000 can further improve the tear strength of the composite material,and helps m GO achieve good dispersion in the matrix,so that the lowest gas permeability of IIR/NBR 5000-m GO can reach 1.984×10^-14 cm³·cm/cm²·s·Pa.It is 44.0%lower than IIR.（4）In order to explore the influence of in-chain modification on the gas barrier properties of IIR,the double bond of IIR was epoxidized to obtain epoxidized butyl rubber（EIIR）.After the epoxy group was looped into hydroxylated butyl rubber（OH-IIR）,a section of unsaturated fatty acid was further grafting on the side chain of IIR through esterification reaction.The grafted unsaturated side chain butyl rubber（GIIR）was obtained.The degree of epoxidation（relative to the content of double bond）and the degree of hydroxylation is close to 100%by regulating the dosage of the drug.Docosahexaenoic Acid（DHA）was selected as graft monomers to investigate the possibility of grafting reaction.The performance and application of the product still need further experimental investigation.