UV Curing 3D Printing Silicone Elastomer

Over the past few decades,thermally-induced hydrosilylation or peroxide vulcanization and room temperature vulcanization?polycondensation?are the overwhelming crosslinking chemistries for silicone materials.Nevertheless,it is well-known that these conventional crosslinking techniques not only seriously consume time and dissipate energy,but also involve in the transition metal catalyst induced biotoxic ity.In view of this,UV curing technology is used for more rapid and efficient crosslinking of silicone elastomers.In this paper,the two mechanisms of free radicals and thiol-e ne photopolymerization are used to form the crosslinke networks of polysiloxane.The effects of various factors on the cross-linking point distribution and cross-linking density of the network structure were investigated.The cross-linking processes and their kinetics in a broader range of molecular weight of siloxane polymer and the impact of such structure on mechanical properties were also studied.Finally,these photosensitive polysiloxa nes are applied to lithography-based 3D printing to promote the development of elastomer ic consumables in SLA materials.1.A novel UV-curable acrylate functionalized polysiloxane with fast cure rate is successfully synthesized by hydrolysis-condensation.The synthesis conditions of acryla te functionalized polysiloxane,such as hydrolysis temperature,hydrolysis time,catalyst dosage,condensation temperature,the molar ration and the phenyl content were optimized.And its molecular structure is characterized by FTIR and ¹H NMR.The photopolymerization kinetics of the acrylate functionalized polysiloxane and the properties of the UV-cured silicone elastomer are then investigated.2.A side-chain thiol-functionalised poly?dimethylsiloxane?crosslinker?PDMS-SH?synthesized by hydrolysis-condensation and its molecular structure is characterized by FTIR,¹H NMR,²⁹H NMR and GPC.We explore the use of the photo-initiated thiol–e ne reaction to cross-link?PDMS-SH?with different molecular structure of telechelic vinyl-PDMS chains at ambient temperature.We also investigate the impact of different curing parameters,such as functional group conversion,critical exposure amount and photoinitiator dosage,reaction rate,curing heat and gelation kinetics,on the cross-link ing processes,using real-time FTIR,Photo-DSC and in situ photo-rheology.The structur a l morphology,crosslink density and macroscopic properties of the UV-cured silic o ne elastomer were investigated by TGA,DMA and tensile machines.Finally,the use of thio l–ene photochemistry enabled for the stereolithography of siloxane elastomers possessing a wide range of mechanical properties.