Molecular Design,Preparation And Characterization Of UV-curable Silicon Resin Applied In 3D Printing

Silicone resin is highly crosslinked and organic-inorganic hybride resins with the Si-O-Si skeleton.Due to its advangtages such as good high and low temperature resistance,silicone resin is widely applied in electronic devices,biological medicine,aerospace and other fields,chemical resistance,biological inertia and electrical insulation properties.However,in the past few decades,thermally induced hydrosilane addition or peroxide vulcanization and room temperature vulcanization are the main crosslinking methods of siloxane materials,which have high energy consumption and low efficiency.However,UV-curing technology is widly applied in coatings,inks,photoresist and 3D printing,as its fast,efficient,energy saving and environmental protection characteristics.3D printing technology can construct rapidly and achieve personalized customization with small batch and lowcost production.3D printing silicone materials can be rapidly mold objects in various exquisite and delicate shapes,but currently 3D printing silicone resin generally has the problems such as poor mechanical properties and low printing accuracy.Therefore,this paper proposes to prepare 3D silicone materials with good performance and high precision.The main content and conclusion of this paper is as follows:1.Acrylate modified MTQ silicone resin was obtained by hydrolysis condensation of ethyl orthosilicate(TEOS),?-methylacrylloxypropyl trimethoxy silane(KH570)and hexamethyldisiloxane(MM)under acidic conditions.The effects of the amount of hydrochloric acid,hydrolysis temperature and time,condensation temperature and time on the properties of resin were discussed.The results showed that hydrolysis at 65 ? for 50 min and condensation at 75 ? for 7 h at present of 0.5 wt% catalyst were the best conditions for the synthesis of MTQ resin.MTQ resin is composed of M chain(Monomethoxy siloxane),T chain(Trimethoxy siloxane)and Q chain(Tetramethoxy siloxane).Different ratios of raw materials lead to different properties of the MTQ resin,the results show that the final conversion rate of the double bond can reach 95% under the irradiation of light intensity of 40 m W/cm2 by using 5wt% photoinitiator UV 1173 for the silicone with the ratio of M/T+Q=1 T/Q=1/5.Silicone resin(M/T+Q=1 T/Q=1/5)has high transparency(?=450 nm),good heat resistance and yellowing resistance for visible light transmittance can be kept above 92%(?=450nm)and the yellowing resistance index is only 3.38% after placing in the drum wind drying oven under 200 ? for 144 h.The surface shore hardness grade D reached 56°.M/T+Q=1.4 T/Q=1/3 silicone resin with 3 wt% photoinitiator can print solid objects through 3D printing.2.Polydimethylsiloxane with hydroxyl terminated as soft segment was reacted with isoporone diisocyanate at 60 ? until the residual-NCO content was half of the original,and hydroxyethyl acrylate was added to obtain acrylate double-terminated silicone modified polyurethane resin(SiPUA).The properties of SiPUA were characterized by infrared spectroscopy,1HNMR spectroscopy,infrared spectroscopy,thermogravimetric analyzer machines,etc.The results show that the final conversion rate of the double bond for R=2.0SiPUA added 2.0 wt% TPO-L reaches 90% exposing under 25 m W/cm2 irradiation intensity.3.Due to the high viscosity of SiPUA,it can not be applied to 3D printing alone,so it was modified by MTQ(M/T+Q=1 T/Q=1/1)resin,and study on the thermal stability,yellow resisitance hydrophobicity,mechanical properties of SiPUA with increased added MTQ silicone resin.The results indicate that,adding different contents of MTQ resin,the contact angle of SiPUA increases from 76.6° to 91.0° with the addition of MTQ,changing from hydrophilic to hydrophobic.The tensile strength increased from 1.72 MPa to 3.52 MPa.SIPUA-MTQ 45% resin can be applied to 3D printing with microscale accuracy,resulting in the 3D printed objects contained clear details,complete structure.