Preparation Of 1,7-Bis[(3-Ethyl-3-Methoxyoxetane) Propyl] Octamethyltetrasiloxane And Its Application In Stereolithography 3D Printing

UV curing is a process in which liquid photosensitive materials undergo photopolymerization and cross-link curing under ultraviolet light irradiation.Oxetane derivatives are common UV-curable prepolymers with low viscosity,good flow properties,and its cured film has good flexibility.However,oxetane derivatives have the problem of insufficient photosensitivity for UV-curing,which limits its application in UV curing technology and 3D printing.A new type of photosensitive resin was synthesized with epoxy resin and siloxane,which fully enrich the types of photosensitive resins and promote the development of this field.In this paper,3-ethyl-3-allylmethoxyoxetane(Ally EHO)was synthesized with diethyl carbonate,trihydroxypropane and allyl bromide as main raw materials.1,7-bis[(3-ethyl-3-methoxyoxetane)propyl]octamethyltetrasiloxane(BEMOPOMTS)was synthesized with EHO and 1,1,3,3,5,5,7,7-octamethyltetrasiloxane by silylation reaction.New type of photosensitive resins were prepared by using BEMOPOMTS as raw material,studied its UV-curing properties and applied it to 3D printing stereolithography technology to make the printing experiments of molds and parts.The specific research contents are as follows:The precursor 3-ethyl-3-hydroxymethyloxetane(EHO)was synthesized with diethyl carbonate and trihydroxypropane as the main raw materials in an alkaline environment;The intermediate Ally EHO was synthesized with EHO and allyl bromide;finally,using Karstedt reagent as a catalyst,prepolymer BEMOPOMTS was synthesized with Ally EHO and 1,1,3,3,5,5,7,7-octamethyltetrasiloxane as raw materials.In the experiment,the influence factors such as raw material ratio,reaction temperature,reaction time,catalyst content were studied,and the the best synthetic scheme of 1,7-bis[(3-ethyl-3-methoxyoxetane)propyl]octamethyltetrasiloxane was determined: the ratio of raw material 1,1,3,3,5,5,7,7-octamethyltetrasiloxane and3-ethyl-3-allylmethoxyoxetane is 1:2.3,the content of Karstedt catalyst was 1.5% and the temperature was 90°C,and the reaction time was 12 h.The self-made BEMOPOMTS and E-51 were mixed in different proportions,then added 3% photoinitiator(UVI-6976)to obtain a new type of photosensitive resin,and its performance was tested.When the mass ratio of E-51 and BEMOPOMTS is1:1,the performance of photosensitive resin is the best.The tensile strength of the tensile spline was 30.65 MPa,the elongation at break was 10.01%,the impact strength of the cured film was 30 kg.cm and the flexibility was 2mm,besides,it had good alkali resistance and water resistance.Through the Photo-DSC test,it could be found that the photosensitivity of BEMOPOMTS had reached the level of first-class products in the market,far exceeding the commonly used E-51;TGA test also proved that BEMOPOMTS had good thermal stability.A photosensitive resin formulation for 3D printing was obtained by using self-made BEMOPOMTS,2021 P,specialty polyether polyols,cationic initiator UVI-6976 and other additives,and its parameters for 3D printing were determined.The laser power was set as 150 m W,the scanning speed is set to 2000 mm/s,the layer thickness is 0.10 mm,and the scanning spacing is 0.08 mm;besides,the viscosity of the resin was 142 m Pa · s at 30°C,the viscosity is moderate,so the system temperature was set to 30℃.