Study On Synthesis Of Acrylate Terminated Polyfluoropolyetherty And Its Property

Photocuring is a new curing technology relies on light stimulation for the achievement of rapid curing of materials.And it has advantages of no solvent,high curing efficiency,and green environmental protection.In recent years,in order to realize the rapid prototyping of energetic materials,researchers have gradually tried to apply photocuring technology to the molding of energetic materials,and have made some progress.Photocuring ink is the most commonly used material in photocuring.It is composed of diluents,prepolymers,photoinitiators and other auxiliaries composed of monomers.But common prepolymers do not contain energy-containing groups like-N₃,-NF₂,-NO₃,-NO₂-and-NNO₂-and so on.For the improvement of energy of the energetic material formula,a large amount of aluminum powder and boron powder are often added as combustion aids.Studies^[1-4]have shown that fluorine-containing resin as a binder for energetic materials can promote the combustion of aluminum powder and boron powder in the formulation of energetic materials,thereby obtaining greater energy.To meet the requirements of energetic ink and photocuring at the same time,in this study,five acrylate terminated polyfluoropolyether prepolymer suitable for photocuring were prepared using different fluoroethylene oxide monomers as raw materials.Besides,infrared spectroscopy（FTIR）,nuclear magnetic analysis（NMR）and gel permeation chromatography（GPC）was used to characterized the polymers.Furthermore,by adding different diluents and adjusting the ratio of diluent and prepolymer,a variety of photocurable inks were prepared and cured.In addition,the properties of the cured splines were studied by mechanical testing,differential scanning calorimetry（DSC）and thermogravimetric analysis（TG）.Inks were selected according to their mechanical properties.The details are as follows:（1）Synthesis of acrylate terminated polyfluoropolyether prepolymer.Poly-2-（（2,2,2-Tri-fluoroethoxy）methyl）ethylene oxide（P3F）,poly-2-（（2,2,2-pentafluoropropoxy）methyl）ethy-lene oxide（P5F）,poly-2-（2,2,3,3,4,4,4-heptafluorobutoxy）methyl ethylene oxide（P7F）,tri-functional poly-2-（（2,2,2-trifluoroethoxy）methyl base）ethylene oxide(P3F_f-3)and trifuncti-onal poly-2-（（2,2,2-pentafluoropropoxy）methyl）ethylene oxide(P5F_f-3)were prepared by cationic ring-opening reaction of 2-（（2,2,2-trifluoroethoxy）methyl）oxirane,2-（（2,2,3,3,3-pentafluoropropoxy）me-thyl）oxyethane and 2-（2,2,3,3,4,4,4-heptafluorobutoxy）methyl ox-irane.Then,five prepolymers were esterified and capped with acrylic acid.And poly-2-（（2,2,2-trifluoroethoxy）-methyl）ethylene oxide（P3F-AA）,acrylated poly-2-（（2,2,3,3,3-pentafluoro-propoxy）-methyl）ethylene oxide（P5F-AA）,acrylated poly-2-（2,2,3,3,4,4,4-heptafluoro-butoxy）methyl ethylene oxide（P7F-AA）,acrylated trifunctional poly-2-(（2,2,2-trifluo-roethoxy）(P3F_f-3-AA)and trifunctional poly-2-（（2,2,3,3,3-pentafluoropropoxy）methyl）-oxirane(P5F_f=3-AA)were obtained.The structure,hydroxyl value,molecular weight and molecular weight distribution,glass transition temperature,density and viscosity of five hydroxyl-terminated polyfluoropolyether prepolymers were characterized by modern test methods such as FTIR,NMR,GPC,and DSC.Besides,the structure,glass transition temperature,carbon-carbon double bond content and viscosity of the acrylate-terminated polyfluoropolyether prepolymer were confirmed.（2）P3F-AA system and P5F-AA system ink formulation design and curing performance research.Diphenyl（2,4,6-trimethylbenzoyl）phosphine oxide（TPO）was used as the photoinitiator,and ethyl acrylate（Et-AA）,trifluoroethyl acrylate（3F-AA）and penta-fluoropropyl acrylate（5F-AA）were used as monofunctional diluents,and were mixed with P3F-AA and P5F-AA respectively to obtain different ink formulations.The cured samples were characterized by mechanical test and DSC.To further improve the mechanical properties of the cured splines,1,6-hexanediol diacrylate（HDDA）and trimethylolpropane triacrylate（TMPA）were added as multifunctional diluents to the selected P3F-AA and P5F-AA system ink formulation.The mechanical test and DSC test were carried out.Finally,P3F-AA/3F-AA/HDDA=2/2/1 and P5F-AA/3F-AA/HDDA=2/2/1 were selected as the best formulas.（3）P7F-AA system,P3F_f-3-AA system and P5F_f-3-AA system ink formulation design and curing performance research.According to the curing results of P3F-AA,P5F-AA and different monofunctional diluents,3F-AA is selected as monofunctional diluent.HDDA and TMPA are used as multifunctional diluents.P7F-AA and P3F_f-3-AA and P5F_f-3-AA are mixed with diluents above to obtain different curing inks.Besides,the mechanical test and DSC test were used to characterized the cured sample.Finally,P7F-AA/3F-AA/TMPA=5/5/1,P3F_f-3-AA/3F-AA/HDDA=2/2/1,P5F_f-3-AA/3F-AA/HDDA=2/2/1 are selected as the best ink formulations of P7F-AA system,P3F_f-3-AA system and P5F_f-3-AA system respectively.On this basis,the cured samples with moderate mechanical properties were tested by thermogravimetric analysis,and it was found that the thermal decomposition of the cured samples was roughly divided into two stages.The second stage starts at 500°C and stops around 550°C.