| In recent years,acrylic resin has been widespread concern due to its good weather resistance,corrosion resistance,durability and flexibility,etc,as well as its low price and abundant resources.Thus,much attention has been paid to its application researches,including coating,adhesive,printing ink,textile auxiliaries,pharmaceutical,aerospace and other fields.However,the phenomenon that it’s sticky while hot and fragile while cold,and the poor thermal stability limits its application.Therefore,its modification has become an effective means to improve its physical mechanical properties and endow it new functions.Polysilsesquioxane(POSS)as an organic/inorganic nano-hybrid material has both properties of organic and inorganic.After acrylic resin is modified using POSS,which can not only improve the heat resistance,corrosion resistance and mechanical properties of acrylic resin,but also participate in the polymerization reaction to increase the solubility of acrylic resin.Therefore,in order to investigate the polymerization mechanism and application of POSS modifying acrylic resin,the properties and polymerization kinetics of acrylic resin modified by POSS and its derivatives were studied.Based on this,the following work was done in this paper.(1)Study on the properties of copolymer of PMMA modified by MA7iBu-POSS.Adopting secondary polymerization forming process,a series of copolymers PMAPS were prepared through bulk polymerization of MA7iBu-POSS and MMA.The structure,morphology and properties of PMAPS were systematically studied and characterized by FT-IR、1H-NMR、XRD、XPS、AFM and DSC.The results show that introducing ofMA7iBu-POSS into PMMA system significantly improved the thermal stability and fracture brittleness of PMMA and increased the surface roughness of polymer.Interior structure of the Polymer PMAPS changed from lamellar brittle fracture to flexible fracture,indicating that polymer flexibility increased.The research on thermal properties of polymer PMAPS showed that the heat stability of the modified polymer PMAPS increased with the increase of the amount of MA7iBu-POSS.When MA7iBu-POSS dosage increased from 0 to 12%,the glass transition temperature(Tg)of PMAPS would go up from 102.87℃ to 117.24℃,and Tg increased by 14℃.Again,the Tg of the copolymer PMAPS could reach 129.58℃ when MA7iBu-POSS and 8MA-POSS were both used for modification,27℃ higher than that of unmodified PMMA.Moreover,the introduction of MA7iBu-POSSreduce the light transmittance of polymer and the polymer PMAPS with 9%MA7iBu-POSS content had better mechanical properties.(2)The polymerization kinetics study of MA7iBu-POSS and MMA.The polymerization kinetics of MA7iBu-POSS and MMA was studied by bulk polymerization and emulsion polymerization under the condition of low conversion rate<10%.The effects of reaction temperature,raw material and initiator dosage on the conversion rate and polymerization rate(Rp)of polymer PMAPS was studied,meanwhile,reactivity ratio and monomers distribution of bulk polymerization also studied.First,the bulk polymerization reaction of MA7iBu-POSS and MMA was conducted,the results showed that Rp increased with the increase of reaction temperature and initiator dosage,but decreased with the increase of MMA dosage.In addition,Rp first increased and then decreased with the increase of MA7iBu-POSS dosage.The activation energy Ea of the reaction is 87.297 kJ/mol,and reaction order I(initiator)=0.617.When the concentration of MA7iBu-POSS(CN)is less than 0.1239mol/L,the reaction order is 0.217;when CN is greater than it,the reaction order is-0.202.Secondly,the kinetics study of emulsion polymerization of MA7iBu-POSS and MMA showed that the emulsion polymerization rate Rp increased with the increase of temperature,MMA and initiation dose,and decreased with the increase of MA7iBu-POSS and emulsion dosage.And MA7iBu-POSS had a synergistic effect with emulsifier,and they can put off the reaction rate of emulsion polymerization.At the same time,it was also found that there was an inflection point in the reaction rate curve of MA7iBu-POSS and emulsifier,the reaction rate was fast and the emulsion was stable when its dosage was less than the key point.Rp dropped sharply and the induction period of emulsion polymerization was prolonged when the amount of MA7iBu-POSS and emulsifier was higher than the inflection point.The result was that when the addition amount of MA7iBu-POSS is less than 13.7wt%(0.01314mol/L),and the addition amount of emulsifier is less than 5.3wt%(0.01652mol/L),the emulsion polymerization is stable.For the emulsion polymerization of MA7iBu-POSS and MMA,the activation energy Ea=215.54 kJ/mol,and the reaction order m(MMA)=1.291,n(MA7iBu-POSS)=-0.0150,I(initiator)=0.399,e(emulsifier)=-0.033.The reaction rate equation of polymerization can be expressed as:Rp=k×CE-0.033×[MMA]1.291 ×[MA7iBu-POSS]-0.0150×[K2S2O8]0.399.Finally,the reactivity ratio of polymerization was also determined using 1H NMR,r1=1.212,r2=0.567 and r1r2=0.687,respectively.It was inferred that the auto-polymerization of MMA was greater than the copolymerization,while the copolymerization of MA7iBu-POSS was greater than the auto-polymerization.MMA and MA7iBu-POSS were randomly distributed in the polymer.By comparing the reaction kinetics of bulk copolymerization and emulsion copolymerization of two monomers,it is found that because of the difference in the polymerization mechanism the influence of various factors on the conversion rate is different and the activation energy is also different.The results are helpful for us to understand the polymerization mechanism of POSS hybrid acrylic resin and provide some theoretical guidance for its polymerization process.(3)Synthesis of the bridged double POSS polyether(DPPE)and its preparation of modified acrylic resin.The following three aspect work was done in this chapter:①Using phenyl triethoxysilane[Ph-Si(OC2H5)3]as raw material,the semi-closed cage of heptylphenyl trisilanol[Ph-T7(OH)3]was first prepared by the hydrolyzed polycondensation.It was then polycondensed with a homemade double(trimethoxysilane)polyether(DTPE),and then a new type of bridged double POSS polyether(DPPE)that has never been reported was attained and its structure was determined through characterization.Finally,DPPE was ready for applying to the subsequent modification of acrylic resin.②)Using DPPE as hybrid modifier to modify PMMA,a new polymethacrylate resin(DPPMA)was prepared by physical modifying.The structure and properties of the modified resin were studied using instruments of FT-IR,XPS,AFM,DSC,TGA,etc.The results showed that DPPE was introduced into PMMA by physical blending,which increased the surface roughness and material flexibility of PMMA.It was found that with the increase of DPPE dosage,the thermal stability of polymer DPPMA increased and the glass transition temperature Tg first increases and then decreases.When the DPPE dosage was 4%(measured by the mass of monomer MMA),Tg reached the maximum at 118.92℃.It was also found that the mechanical properties of polymer DPPMA was best when the dosage of DPPE was 8%.It can be seen that an appropriate amount of DPPE can improve the surface roughness,heat resistance stability and mechanical properties of DPPMA resin according to the performance requirements of the material.③The prepolymer of fluorinated polyacrylate(FAAO)containing reactive hydroxyl functional groups was prepared by copolymerizing Methyl methacrylate(MMA),butyl acrylate(BA),hydroxypropyl acrylate(HPAA)and Dodecafluoroheptyl methacrylate(DFMA).Then,DPPE was mixed with FAAO,and cured by polyisocyanate curing agent N3390 to produce a water-repellent and oil-repellent acrylic resin coating(FPAPUA),and the morphology and properties of the coating were studied.The results showed that the introduction of DPPE into coatings can significantly increase the surface roughness and thermal stability of FPAPUA coatings that increased with the increase of DPPE dosage.Then,the study on the hydrophobicity of the FPAPUA coating found that both FAAO and DPPE had effect on the hydrophobicity of FPAPUA coating.The contact Angle of FPAPUA coating increased with the increase of DFMA,and firstly increased and then decreased with the increase of DPPE dosage.When the DFMA dosage was 18%,DPPE dosage was 8 wt%of the total mass,the maximum contact angle was 117.5° and the hydrophobicity of FPAPUA coating significantly improved.Subsequently,a study on the effect of DPPE usage on the mechanical properties of FPAPUA coating found that the mechanical properties of FPAPUA coating were optimized when DPPE usage was 8wt%.(4)Construction,preparation and application of UV-curable POSS modified fluorinated polyurethane polyacrylate coating(UV-PFPUA)Ph-T7(OH)3 was used as trifunctional chain extender to modify PUA to prepared the PUA prepolymer(T7@PUA).A high-performance POSS hybrid fluorinated polyurethane polyacrylate coating(UV-PFPUA)was then ultimately prepared under UV light after the T7@PUA was mixed with DFMA,8MA-POSS,photoinitiator,etc.Its structure,morphology and properties were test by FT-IR,XPS,AFM and DSC,and so on.The results showed that the UV-PFPUA coating modified by POSS had high thermal stability that increased with the increase of 8MA-POSS dosage.The study on hydrophobicity of UV-PFPUA coating found that with the increase of DFMA dosage in the coating,the contact Angle of UV-PFPUA coating increased and the maximum contact Angle was 110°.The contact Angle slowly decreased with the dosage of 8MA-POSS increased.Meanwhile,the UV-PFPUA coating containing 6%8MA-POSS had displayed the best mechanical properties.Therefore,an appropriate amount of 8MA-POSS is beneficial to the overall properties of UV-PFPUA coating in case of without affecting its hydrophobicity.Based on the above research results,it can be seen that the UV-PFPUA coating prepared by photocuring possessed the better hydrophobicity,thermal stability,mechanical properties and durability,which can provide an excellent protection for the iron substrate. |
