Preparation And Properties Of Silicone Elastomer Based On Dynamic Chemical Bondings

Polysiloxane elastomer is a general term for a polymer with a silicon-oxygen bond repeating structure in its backbone.Because of its many unique and valuable properties,such as high and low temperature resistance,electrical insulation,ozone resistance,flame resistance,physiological inertia,for other organic polymer materials can not compare and replace,so in aerospace,electronic and electrical,light industry,transportation,medical health,People’s Daily life and other aspects have been widely used.With the sustainable development of society,people have put forward the urgent demand for high performance,functional and green polysiloxane elastomers.Therefore,in this paper,a new type of polysiloxane elastomer with dynamic chemical bonds on the main chain was prepared by using hydroxy-terminated polysiloxane as raw material,and the recyclable and self-healing polysiloxane elastomer was studied by focusing on the structure design and molecular chain assembly of the polymer network.The elastomer with acyl-arbazone bond was synthesized by using hydroxypolydimethylsiloxane(PDMS-OH)as the material and isophorone diisocyanate(IPDI)as the terminal.Then,the elastomer was extended with dihydrazine adipate(AD)and cross-linked with triethanolamine(TEA).By adjusting the molar ratio of diacylhydrazine adipate,a series of elastomers with different properties were obtained.Due to the highly flexible Si-O chain and a large number of hydrogen bonds formed by dynamic acylarbazone(ASC)groups,the elastomers have good mechanical properties,the maximum stress is 4.1 MPa,the average elongation at break is 1145%,and the elastomers can repair themselves.The repair efficiency reached more than 90%.It is noteworthy that under the dynamic action of hydrogen bonds,the elastomer can be completely recovered without chemical treatment and can still reach 91% of its initial mechanical strength even after ten dissolution recoveries.And through three times of hot pressing recovery,but also maintain 86% mechanical properties.In addition,selfhealing flexible electronic devices were fabricated by composite multi-walled carbon nanotubes(MWCNTs)to monitor the subtle movements of the human body.Elastomers with phenol carbamate bond were prepared using hydroxy-poly(dimethylsiloxane)as soft chain segment,biotannic acid(TA)as crosslinking agent and2,2-bis(hydroxymethyl)propionic acid(DMPA)as intermediate chain extender.The optimal stress-strain of the elastomer is 7.5 MPa and the elongation at break is 1540%.Based on the interaction between phenol carbamate bond and hydrogen bond,the elastomer has high self-healing ability,and the self-healing efficiency is more than 85%.The elastomer can achieve dynamic dissociation at 120℃,complete recovery and reuse,the mechanical efficiency after recovery is 90% of the original,the performance of the elastomer after recovery only slightly decreased.Due to the natural antibacterial and flame retardant properties of tannic acid,the antibacterial ability and flame retardant properties of silicone elastomer are greatly improved,and the antibacterial efficiency reaches more than 90%,and the final oxygen index reaches 25.5%.Elastomers based on phenol carbamate bond have great application potential in recyclable refractory and antibacterial materials.