Research On The Molecule Design Of Bifunctional Initiators And The Dual Curing Behavior Of Organic Silicone

Silicone resin has been widely used in aerospace materials as the superior materials due to the high temperature resistence property and UV resistence property.Usually,the curing of organic silicone resins is heat-curing,while heat-curing has the disadvantages,such as high energy dissipation,time-wasted and cost much resource,which limit the application of silicone resins.At the same time,UV cured silicone has many disadvantages including lower hardness and adhesion force.The superficial curing depth limits the application of UV-cured silicone.In this paper,in order to overcome the drawbacks of single curing,the scheme of UV-heat curing was designed and the UV-heat bifunctional initiator possessing C-S bonds and other bifunctional intiator was synthesized.The machanism and heat resistence of dual-cured silicone were studied.In order to cure the silicone,the key is bifucntional initiator.Firstly,the benzophenone initiators including(4-aminophenyl)(4-((4-aminophenyl)thio)phenyl)-methanone(NH2-S-BP)or have latent imidazole group(i-S-BP)have been synthesized.FT-IR and 1H-NMR were taken to characterize the structure.The Ultraviolet absorption of the different initiators were measured by Ultraviolet absorption spectrum,it was concluded that the UV maximal absorbtion was redshifted with the introduction of imidazlole group and sulfer atom.The photoinitiator with sulfer atom was significant redshifted,70 nm higher than BP.The introduction of imidazlole group and sulfer atom enhanced the UV absorbtion.Secondly,silane coupling agent ?-(2,3-epoxypropoxy)propytrimethoxysilane,?-(methacryloxypropyl)trimethoxy silane were chose as raw material to synthesize a new type of curable silicone resin by a two-step process,and the resin structure was chacterized and analyzed by FT-IR and 1H-NMR.The silicone resin was cured by three different initiating system,including benzophenone imidazole system(i-BP),NH2-S-BP system and i-S-BP,dimethylaminoethyl methacrylate as the co-initiator,then the curing reaction was carried under high-pressure Hg lamp.The results showed that the i-S-BP initiating system possessed the fastest curing speed,only 65 s when the concentration is 0.2 mmol/g.The thermal property of the cured resin was characterized by Thermogravimetric analysis and Differential S canning Calorimetry,the results showed that the resin cured by the i-S-BP initiating system possess the best thermal behavior,the temperature of initial decomposition was 200 oC,the final quality retention rate was 34.2%.Comparing the different initiators,it can be concluded that,the latent initiator i-S-BP can not only overcomes the shortcomings of single photoinitiator,but also remains the superiority of high efficiency and energy saving.Above all,latent initiator i-S-BP settles a matter of uncontrollable temperature in heating-curing reaction,endowing the process curing of bifunctional silicone resin stimuli responsive property.