Design,Preparation And Properties Of Self-Healing Silicone Elastomers Fabricated By Side Chain Groups

Silicone elastomers possess many properties such as high and low temperature resistance,electrical insulation,and excellent biocompatibility,which can be widely used in aerospace,chemical industry,and medical science.At the same time,owing to the dynamic bond structure,some elastomer with the self-healing ability can prolong the service life of the material,and can solve the problem of recycling in some aspects.As a result,it is urgent to prepare the self-healing elastomers based on the silicone materials.Considering that the molecular structure of the silicone possesses both an inorganic Si-O backbone and organic side groups,some functional groups such as amino groups,vinyl groups,and methoxy groups could be introduced on to the main chain of silicone in addition to the methyl group.Moreover,the dynamic covalent bond can also be introduced into the structure with these functional groups,and then the silicone material can be self-healed and repossessed,thereby saving resources.Thus,this thesis discusses the preparation of self-healing silicone elastomers via the reaction of functional groups in organosilicon side chain to design dynamic reversible crosslinking networks.(1)Self-healing silicone elastomers based on metal coordination-hydrogen bond crosslinking.Silicone oil with 10%amino side groups were prepared,and pyridine groups were introduced,and then silicone elastomers were formed after the addition of Fe3+ via the metal coordination crosslinking networks.In the preliminary exploration,it is obvious that self-healing silicone elastomers with higher grafting rate is obtained by melt grafting modification,which was with high self-healing efficiency and stability.As a result,the samples obtained via melt modification can facilitate the formation of more dynamic bond crosslinking networks and are chosen in the following self-healing test.Moreover,the mechanical and self-healing properties of the silicone elastomers with different molar ratio of Fe3+:Py(pyridine ring)are also investigated.It indicates that the healing efficiency of the products with different molar ratios of Fe3+:Py is all above 90%,and even reaches 91.7%when Fe3+:Py=1:2,after 20 hours of healing at 80?.Besides,these silicone elastomers exhibit excellent dielectric properties as the presence of polar groups picolinic acid and amide,which are potentially used as dielectric elastomers.(2)Self-healing silicone elastomers based on disulfide-hydrogen bond crosslinkingIn the preliminary exploration stage,first,the methyl vinyl silicone rubber is graft modified via the thiol-ene click chemical reaction after the addition of mercaptopropionic acid.Then the disulfide-hydrogen bond crosslinking silicone elastomers with different crosslinking degree were obtained by the reaction between aromatic disulfide bond crosslinker and mercaptopropionic acid-modified silicone rubber.The degree of cross-linking,self-healing properties,and reprocess ability of the obtained silicone elastomers were characterized,and it is indicated that there are many factors can induce the permanent cross-linking in the system.Consequently,the silicone elastomers with different crosslinking degrees of disulfide-hydrogen bond were fabricated by an improved experimental route,in which the silicone oil with amino side groups was directly reacted with the aliphatic acid with disulfide bonds.It not only avoids the permanent cross-linking,but also can be completed in two steps,which is more simple and easy.Moreover,the elongation of the products is obviously improved.However,as a result of not triggering the disulfide-hydrogen bond cross-linking network,the self-healing and reprocess ability of the silicone elastomers should be optimized from other parameters,such as the molecular weight of side amino silicone oil,crosslinking degree,molding temperature/time,as well as introduction of catalyst.