Preparation And Characterization On Acrylate Resin System Based On Thermal-light Two-stage Curing

With the development of science and technology,the two-stage curing method of thermosetting materials,as a sequential staged curing technology,has the superiority of personalized structure design and enhanced performance.It is expected to replace traditional materials in complex scenes such as space expansion structures.However,the current two-stage curing systems show some drawback such as harsh initiation conditions,low storage stability of the first-stage materials,and insignificant properties changes after curing process,which strictly limits the daily use and further application potential.Herien,with the tetrafunctional thiol,difunctional acrylate and hexafunctional acrylate used as monomers,a thiol-acrylate system with thermal-ultraviolet two-stage curing method is introduced by matching the suitable initiators of both stages togther with the non-stoichiometric design of the resin monomers.The first-stage polymer with lower cross-link density is fabricated by the Micheal addition reaction of the thiol and acrylate in ambient environment at the presence of nucleophilic catalyst and a further photo-induced radical polymerization of excessive acrylic groups undergoes to form a robust polymer with higher cross-link density.The influence of the content of hexafunctional acrylate on the crosslinking degree and other properties of the polymers after the first and second stage curing was studied,and the performance of each formula was characterized by Raman spectroscopy and dynamic mechanical analysis test.The test results show that the best formula with the ratio of 1:1:1.5 demonstrates excellent properties,especially with the glass transition temperature(Tg)of the systems increasing to 157 ℃dramatically.Spectral tests show that a sufficient reaction can be achieved after the Michael addition reaction at room temperature for 12 hours in the first stage and the free radical photocuring process for 180s in the second stage.The research result of the prepared best formula show that the material demonstrates outstanding two-stage curing properties.The samples after the first stage curing and second stage curing shows significant difference on mechanical properties and thermal stability.The changes in elastic modulus and tensile strength before and after the second-stage curing process reach 3 and 2 orders of magnitude,respectively.Similarly,the thermogravimetry temperature reaches up to 300 ℃ after second stage curing,which means that the thermal stability shows great enhancement.The first-stage material is flexible with the ability of shape design.Meanwhile,the exposure of common chemical reagents does not affect the feasibility of further curing reaction of the first-stage sample.Besides,the first-stage material exhibits excellent storage stability,and the storage period at room temperature can be more than 5 months.By controlling the two-stage light curing time,an intermediate state polymer with shape memory properties can be obtained.Though the modification of the two-stage curing system or the design of the material preparation process,the thermal-ultraviolet two-stage curing system can be applied to the fields of the surface pattern design and self-healing flexible substrate material preparation,which shows great application potential.