Preparation And Properties Of The Uv/thermal Triggered Silicone Polymers

Polysiloxanes are polymeric materials composed of a Si-O-Si backbone.Due to its unique Si-O bond structure,it has many excellent properties,such as good heat resistance,chemical stability,weather resistance and excellent processability.UV curing is used for the preparation of polysiloxanes due to its high efficiency and low energy consumption.However,UV curing is limited by the lower curing depth.On the basis of UV curing,combining the thermal curing reaction can not only reduce energy consumption,but also deepen the curing degree and improve polymer performance.In this thesis,different UV/thermal triggered polysiloxane systems were constructed based on the dual-activity hyperbranched and linear siloxane with methacryloxy and epoxy groups.Polysiloxanes were cured by two triggering conditions: radical polymerization initiated by UV light and thermally induced epoxy ring-opening polymerization.The construction and performance of different systems of polysiloxane materials were studied.A series of polymerizable photoinitiators were synthesized through molecular structure design.Based on the hyperbranched polysilox ane with methacryloxy and epoxy groups which prepared via the hydrolysis and condensation reaction,a UV/thermal triggered system was constructed by polymerizable photoinitiators and 2-ethyl-4-methylimidazole.And the effects of different photoinitiators o n the photopolymerization behavior of the systems were explored.The polymerizable photoinitiator 4-[(4-maleimido)thiophenyl]benzophenone(MTBP)has the highest initiation efficiency and the final double bond conversion is as high as 96.0%.At the same time,hyperbranched polysiloxanes only containing epoxy groups or methacryloxy groups were synthesized and compared with dual-activity hyperbranched polysiloxane.The effect of terminal groups on the silane hydrolysis condensation process was studied,and the thermal stability and microstructure of different hyperbranched polysiloxanes were analyzed.The methacryloxy groups could accelerate the condensation reaction,producing a more branching sites and a higher molecular weight.However,the structural stability of UV-cured polysiloxane was poor due to the excessive cross-linking and increased internal stress at an elevated temperature.After the epoxy groups were further introduced,epoxy ring opening during thermal curing stage made the system have a better structural stability at an elevated temperature.A linear dual-activity siloxane monomer containing methacryloxy and epoxy groups(MAGETDS)and epoxy-functional linear siloxane monomer(DGETDS)were synthesized via hydrosilylation reaction.A series of polysiloxane systems were then prepared based on MAGETDS via UV/thermal curing reaction.The linear siloxane monomer imparts flexible characteristic to these polysiloxane systems.The mechanical properties,thermal stability,and dynamic thermomechanical pro perties of the systems are affected by the curing time and the linear DGETDS and trimethylolpropane triacrylate(TMPTA)content.The tensile strength of P-030 can reach 9.27 MPa and T5 is 248.3°C.And the system P-030 has a higher modulus and Tg,which are 496.6 MPa and 70.5°C,respectively.In contrast,P-110 has the smallest tensile strength of 0.79 MPa and T5 of 205.8°C.It has a lower modulus and Tg of 10.2 MPa and 1.8°C,respectively.However,P-130 has phase separation due to the largest content of TMPTA and DGETDS.The the double peaks of Tg are 41.6°C and 1.4°C,which represent the DGETDS phase and TMPTA phase,respectively.A double-crosslinked polysiloxane elastomer via UV/thermal curing was constructed combining HPBSi and DGETDS,with adding an aromatic amino compound(AFD)containing dynamic disulfide bonds.The presence of disulfide bonds imparts the self-healing properties to these polysiloxane elastomers.The mechanical properties and self-healing properties of the polysiloxane elastomer are adjusted by adjusting HPBSi and AFD content.When the molar ratio of DGETDS to AFD is 1:1.1,the amount of HPBSi is 5%,the polysiloxane elastomer exhibite s good mechanical properties and elastic recovery properties.The tensile strength and strain are 0.54 MPa and 607%,respectively.The elastomer can still recover its original state within 3 min after 10 times of stretching-release cycle.In addition,the self-healing efficiency could reach 83% after self-healing for 12 hours at room temperature.Then stretchable conductor and strain sensor were prepared based on this UV/thermal cured elastomer.The EGa In/P11-5 strain sensor has excellent sensing performance under bending,different motion frequencies and after self-healing.Hyperbranched and linear siloxanes with methacryloxy and epoxy groups were synthesized herein.And different polysiloxane systems were constructed based on UV/thermal curing reaction.The different structures impart different properties to the polysiloxane systems.The above research content laid the foundation for the application of polysiloxane materials.