Research On Synthesis Of Functional Siloxane And Its Modified Epoxy Resin

Epoxy resin is a kind of thermosetting polymer with excellent moisture resistance,temperature resistance,medium resistance and dimensional stability.It is widely used in coatings,adhesives,composites,as well as electronic and electrical seals.However,cured epoxy resin is high brittleness,low ductility and easy cracking.Because the epoxy resin is easy to form high crosslinking structure.In order to overcome these shortcomings,scholars at home and abroad have proposed a variety of modified methods,such as polyurethane modification,acrylic modification,nanomaterial modification,organosilicon modification and composite modification to improve the comprehensive properties of epoxy resin.Among them,silicone modified epoxy resin can significantly improve the weatherability,solvent resistance,hydrophobicity,high and low temperature resistance and toughness of the epoxy resin,and its modification mechanism is mainly based on the hydrolysis and condensation reaction of siloxane.At present,there are some problems in organosilicon modified epoxy resin:(1)The polarity of the epoxy resin and polysiloxane is different,the compatibility is poor,and the phase separation is easy to affect the properties of the organosilicon modified epoxy resin;(2)The epoxy resin system often uses the toxic organic volatile solvent as the organosilicon dispersant.There are environmental risks.(3)At room temperature,the hydrolysis rate of siloxane is slow,resulting in low curing rate and poor construction efficiency.Therefore,in order to solve the above problems,a silicoxane oligomer with-NH2 functional group was designed by the hydrolysis and condensation reaction of siloxane to study the silicone modified epoxy resin with good compatibility,low VOC and controllable crosslinking speed to meet the construction requirements of high efficiency and environmental protection composite coating.The amino silane oligomers with narrow molecular weight distribution and low viscosity are synthesized by controlling the molar ratio of water,reaction temperature and concentration of monomers by the control of the hydrolysis and condensation reaction of the triethoxy silane as monomer and anhydrous ethanol as the solvent.Further,amino siloxane oligomers are usd as curing agent of bisphenol A epoxy resin,the curing rate of epoxy resin and the comprehensive performance of the film were improved.The curing rate of epoxy resin at room temperature is slow,which leads to poor compatibility,high VOC,uncontrollable crosslinking speed and poor construction efficiency.The contents of this study are as follows:APTES oligomers with uniform molecular weight distribution and low viscosity are synthesized by controlling water,reaction temperature and concentration of monomers at the same time by controlling the amount of water,reaction temperature and monomer concentration by controlling the water amount,reaction temperature and monomer concentration.It is used as curing agent to solidify the modified bisphenol A epoxy resin,which greatly improves the curing rate and after curing performance of epoxy resin,and solves the problems of inconvenience in construction and environmental protection at the slow curing rate at room temperature at the room temperature at home.First,the hydrolysis and condensation reaction of ammonia propyl triethoxy silane is systematically tracked by Fourier transform infrared spectroscopy(FT-IR)and nuclear magnetic resonance(NMR),It is found that the condensation reaction rate of ammonia propyl triethoxy silane is greater than the hydrolysis rate under the alkaline autocatalytic reaction.NMR is used to characterize the polycondensation products.The technological conditions are determined by the rotational viscosity tester and the matrix assisted laser desorption ionization time of flight mass spectrometry(MALDI-TOF MS),which are water:aminopropyl triethoxysilane =0.9500,20℃ hydrolysis temperature,and aminopropyl triethoxysilane:ethanol(w/w)＝1:1(w/w)concentration of ammol triethoxy siloxane.The molar ratio of-NH2 to-OEt is 1:1,the viscosity of 32mPa·s,and the number average molecular weight is about 1047g/mol in the synthesized aminopropyl triethoxysilane oligomer.With the increase of water molar ratio,the increase of reaction temperature,the increase of the concentration of the triethoxy silane monomer,the viscosity of the oligomer and the molecular weight are increased,and the molecular weight distribution of the oligomer products obtained by the vacuum distillation process is narrower,and the number of the formation of the ring is the lowest.Secondly,in order to study the kinetics of the curing of bisphenol A epoxy resin with ammonia propyl triethoxy silane oligomer,the molecular structure-NH2 and-OEt molar ratio is 1:1,the molecular weight 1047g/mol of the triethoxy siloxane oligomer is cured epoxy resin,and the two crosslinking curing system is constructed,and the differential scanning calorimeter(DSC)is used.The curing reaction activation energy(E alpha)of the system is 54.61kJ/mol,the pre finger factor A is 1.897×107 and the reaction series n is 0.86,which shows that the curing process is complex.The gel time of the synthesized oligomer cured epoxy resin is measured by the dynamic rotating rheometer(DHR)with different water molar ratio,reaction temperature and monomer concentration,and the time of curing(48h above)is significantly higher than that of 4.30～6.62h.By regulating the synthesis process of the oligomeric triethoxy silane oligomer,the gelation time can be further shortened,so that the cured epoxy resin is far higher than the amino propyl triethoxy siloxane monomer.Finally,through the analysis of the thermal weight loss analysis(TGA)and the impact test instrument on the thermodynamic properties of the epoxy resin after the crosslinking curing,it is found that the thermal stability of the epoxy resin crosslinked by the amino propyl triethyl silane oligomer is good,and the thermal weightlessness begins at 200℃,and the weight loss rate is the fastest at 300℃ and 450℃,respectively,which is obviously improved than non amino siloxane oligomers modified epoxy resin.In addition,the impact resistance of the modified epoxy resin is also improved significantly,reaching 11kJ/m2.