| Epoxy resin as being the most widely used in structural engineering applications of thermosetting resin,has excellent adhesive properties,outstanding physical and mechanical properties,electrical insulating performance and has good corrosion resistance and other characteristics,for which is widely used in such as electronic electrician,adhesive coating,aerospace,auto mechanics etc.However,the brittleness of epoxy resin and poor resistance to crack propagation,restrain the application of epoxy resin.Therefore,how to toughen epoxy resin has become a research focus currently.In this thesis,on the basis of the combination of the methods and mechanisms of toughening epoxy,the new approach is the modification of epoxy resin by the homogeneous and non-homogeneous toughening with in-situ polymerization oligomers,which improve the toughness of epoxy resin and do not decrease the strength?the modulus and the thermal stability of the cured epoxy resin.Poly(butyl acrylate-glycidyl methacrylate)(PBG)and poly(butyl acrylate-styrene)(PBS)were used to toughen epoxy resin respectively,it is investigated how preparation methods(in situ polymerization,physical blending method),composition,molecular weight of PBG and PBS influence toughening epoxy resin performance behavior.The modified resin curing kinetics and curing mechanisms were analyzed and researched,so as to formulate a suitable curing process;Based on modified epoxy resin curing the impact strength,bending strength,fracture toughness,glass transition temperature,dynamic mechanical behavior and microstructure of area of test and characterization,the results was used to analyze the effect of modified epoxy resin toughening behavior.Main conclusion of this dissertation are as follows:The curing process of the modified epoxy resin with the copolymer PBG by different weight ratios composition of butyl acrylate(nBA): glycidyl methacrylate(GMA)?preparation methods?molecular weights reacted with MeTHPA are studied by non-isothermal differential scanning calorimetry(DSC).Studies have shown that: the curing reaction of modified epoxy resin modified by PBG is proceeding in nth cure mechanism,the same as unmodified epox resin;the activation energy of the modified epoxy resin by PBG were higher than the unmodified epoxy system;with the decrease of the molecular weight of PBG,the activation energy of modified epoxy resin curing system decreased,so was the curing temperature.In the process of the PBG in situ polymerization toughening epoxy resin,the weight ratio composition of the copolymer in the nBA-GMA was 7.5:7.5,the best comprehensive performance modified epoxy resin was obtained.the impact strength of modified curing system was increased by 78.6%,the fracture toughness was increased by 60%;Meanwhile,the bending strength didn't decrease obviously,and the glass transition temperature is 123?.In the process of the PBG with different molecular weight toughening epoxy resin,the impact strength and fracture toughness of the modified networks exhibit first increased then decreased as the molecular weight of PBG decrease.When the number average molecular weight of PBG in situ polymerization was 2684,the impact strength was increased by 111.1%,the fracture toughness was increased by 55.1%;In the process of the PBG by physical blending toughening epoxy resin,when the number average molecular weight of PBG was 2703,the impact strength was increased by 77.8%,the fracture toughness was increased by 50.2%;Bending strength and the glass transition temperature decreased with the decrease of the molecular weight.The thermal properties and phase transition behavior of the modified epoxy resin curing system with the copolymer PBG by different composition,preparation methods,molecular weights are studied by dynamic mechanical analysis(DMA).The modified epoxy by PBG exhibited single relaxation peak,indicative of homogeneous microstructure and of absence of phase separation in the curing systems;The tan? peak temperatures and storage modulus(E')were lower than the pure epoxy resin cured system,and the tan? peak temperature decreased with the decrease of the molecular weight of PBG;storage modulus(E')decreased as nBA content increased in PBG,and decreased with the decrease of the molecular weight of PBG.The curing process of the modified epoxy resin with the copolymer PBG by different weight ratios composition of butyl acrylate(nBA): styrene(St),preparation methods,molecular weights reacted with MeTHPA are studied by non-isothermal differential scanning calorimetry(DSC).Studies have shown that: the curing reaction of modified epoxy resin modified by PBS is proceeding in nth cure mechanism,the same as unmodified epoxy resin;the activation energy of the modified epoxy resin by PBG were lower than the unmodified epoxy system;with the decrease of the molecular weight of PBG,the activation energy of modified epoxy resin curing system increased,so was the curing temperature.In the process of the PBS in situ polymerization toughening epoxy resin,the weight ratio composition of the copolymer in the nBA-St was 7.5:7.5,the best comprehensive performance modified epoxy resin was obtained.the impact strength of modified curing system was increased by 111.1%,the fracture toughness was increased by 45.3%;Meanwhile,the bending strength didn't decrease obviously,and the glass transition temperature is 116?.In the process of the PBG with different molecular weight toughening epoxy resin,the impact strength and fracture toughness of the modified networks exhibit first increased then decreased as the molecular weight of BPG decrease.When the number average molecular weight of PBG in situ polymerization was 3651,the impact strength was increased by 110.6%,the fracture toughness was increased by 54.6%;In the process of the PBG by physical blending toughening epoxy resin,when the number average molecular weight of PBG was 2841,the impact strength was increased by 86.5%,the fracture toughness was increased by 46.2%;Bending strength and the glass transition temperature decreased with the decrease of the molecular weight.The thermal properties and phase transition behavior of the modified epoxy resin curing system with the copolymer PBS by different composition ? preparation methods?molecular weights are studied by dynamic mechanical analysis(DMA).The modified epoxy by PBS exhibited two relaxation peaks,indicative of heterogeneous microstructure and phase separation in the curing systems;The tan ? peak temperatures and storage modulus(E')were lower than the pure epoxy resin cured system,and the tan? peak temperature decreased with the decrease of the molecular weight of PBS.The cured impact section of the epoxy resin modified by PBG was homogeneous structure.With the increase of nBA content,phase separation was more obvious.PBG in situ polymerization with epoxy resin curing system formed full-interpenetrating network structure,the interfacial interaction was enhanced.The toughness mechanism of PBG modified epoxy resin are summarized in the following: the bridge-link anchor between PBG and the crack in front of the gap?crazing shear yielding and plastic deformation in matrix.In the epoxy resin modified by physical blending,the molecular weight of PBG were too large and too small,the surfaces roughness of these surfaces were not high.The cured impact section of the epoxy resin modified by PBG was heterogeneous structure,PBS in situ polymerization with epoxy resin curing system formed semi-interpenetrating network structure,The toughness mechanism of PBS modified epoxy resin are summarized in the following:the crazing shear yielding and plastic deformation of the matrix?the tearing stretching effec,PBS particles dispersed in epoxy resin,which fromed the bridge in the cracks.With the decrease of the molecular weight of the copolymer PBS,the size of the dispersed phase of PBS particle in the process of curing decreased in turn.Compare the in-situ polymerization with the physical blending,the former roughness of epoxy curing cross-sections was significantly higher than the latter;Meanwhile,in the same ratio of initiator and chain transfer agent,the cross section of silver grain shear yielding,polymer matrix plastic deformation of the matrix,torn stretching of the polymer,the bridge-link anchor are much stronger than the latter. |
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