Construction And Properties Of Benzoxazine/Epoxy Resin System Based On Phthalocyanine Structure

Polybenzoxazine（PBZ）resin exhibit many excellent characteristics such as:good dimensional stability,good chemical resistance and electrical resistance,high carbon yield,high mechanical strength,high Glass transition temperature（T_g）,and other advantages.The polymer matrix composite radiation shield materials have the characteristics of light weight,excellent physical properties,and good shielding effect,but it also has the disadvantages of poor durability of the polymer matrix.Therefore,benzoxazine resin becomes a potential radiation shield matrix material.However,PBZ still have drawbacks such as high temperature curing,high brittleness,and low molecular weight,which hinders its wide practical application.Epoxy resin（EP）have high strength,very low creep,excellent corrosion and high temperature performance.Due to the brittleness of the cured resin itself,it is extremely susceptible to internal damage caused by low-speed impact,which may cause serious safety and reliability problems.It is very important to improve the damage resistance of benzoxazine and epoxy resin by increasing their impact strength.Phthalocyanine（Pc）is a macrocyclic compound formed by connecting four isoindoles[（C₆H₄）C₂N]units with four N atoms.Its macrocyclic center can coordinate with various metal ions to form a metal complex（MPc）.Their chemistry can be changed by changing the metal ions in the center,by connecting different functional groups to the macrocycle,or by connecting the metal ions to the central ligand.This provides a practical way to meet different requirements.In this paper,through the molecular design and metal phthalocyanine compounds containing an amino group were synthesized,and for the first time,the metal phthalocyanine compounds were used for copolymerization with epoxy resin,benzoxazine,and epoxy-benzoxazine blend resin.The topological structure of copolymer crosslinking network was controlled by adjusting the curing process by adding amount to improve the properties of resin.Differential scanning calorimetry（DSC）,thermogravimetric analysis（TGA）,dynamic mechanical analysis（DMA）,tensile machine,etc.were used to study the polymerization behavior,thermal properties and mechanical properties of the copolymer.Based on the high thermal stability of the phthalocyanine structure and the absorption characteristics of metallic lead and copper elements to high-energy gamma rays,the radiation resistance performance of the benzoxazine-phthalocyanine copolymer were studied using a cobalt-60 irradiation device.3,10,17,24-four amino ethoxy phthalocyanine lead（APbPc）and 3,10,17,24-four amino ethoxy copper phthalocyanine（ACu Pc）ware prepared by liquid phase synthesis method.3,10,17,24-tetramino-substituted phthalocyanine monomer（TAPbPc）was prepared by solid phase melting.Infrared absorption spectroscopy（FT-IR）,nuclear magnetic resonance hydrogen spectroscopy（¹H NMR）,elemental analysis,and ultraviolet-visible absorption spectroscopy（UV-vis）were used to characterize the intermediate monomers and products during the synthesis process.The results showed that the structure of the synthesized three MPcs was consistent with the theoretically designed structure.P-ddm/APbPc copolymer was prepared by using benzoxazine（P-ddm）resin as matrix and 3,10,17,24-tetra-aminoethoxy lead phthalocyanine（APbPc）as additive.The kinetic parameters for the P-ddm/APbPc blend curing processes were examined by utilizing the iso-conversional,Flynn-Wall-Ozawa,and Málek methods.DSC results confirmed that the blending of APbPc monomer can effectively reduce the curing temperature of P-ddm resin.The autocatalytic models also well described the non-isothermal curing reaction rate and the appropriate kinetic parameters of the curing process were obtained.The DMA and impact strength experiments proved that the blending of APbPc monomer can significantly improve the toughness and stiffness of P-ddmresin,the highest enhancements were observed on 25 wt.%addition of APbPc,the recorded values for the storage modulus and impact strength were1003 MPa and 3.60 k J/m² higher,respectively,while a decline of 24.6^οC was observed in the glass transition temperature values.TGA curves indicated that the cured copolymers also exhibit excellent thermal stabilities.Effects of different substituted MPcs on the modification of p-ddm were studied.The results showed that the different metal ions in the central ring of MPc had little effect on the properties of the copolymer,and the substituents on the large ring of MPc were the main factors affecting the properties of the copolymer.A high performance copolymer was prepared by using epoxy（EP）resin as matrix and APbPc as additive with dicyandiamide as curing agent.The experimental results show that APbPc,as a synergistic curing agent,can effectively reduce the curing temperature of epoxy resin.The curing kineticsof the copolymerwas investigated by non-isothermal DSC to determine kinetic data and measurement of the activation energy.DMA,impact,and tensile strength tests proved that phthalocyanine can significantly improve the toughness and stiffness of epoxy resin.Highest values were seen on the 20 wt.%loading of APbPc in the copolymers,energy storage modulus,and impact strength increased respectively 388.5 MPa and 3.60 k J/m²,T_g decreased 19.5°C.TGA curves indicated that the cured copolymers also exhibit excellent thermal properties.The mechanical and dynamic mechanical properties of EP/p-ddm/APbPc ternary curing system were studied.P-ddm can be used as EP curing agent.The best mixing ratio between EP and P-ddm is EP:P-ddm=1:2.The addition of APbPc significantly reduced the curing temperature of the EP/p-ddm/APbPc blend systems.When APbPc mass fraction was 25%,poly（EP/P-ddm/APbPc）system had the best mechanical properties.The mechanical and thermal properties of poly（P-ddm）and poly（P-ddm/APbPc）copolymers radiated with different doses ofγ-rays were studied.FT-IR was used to study the changes of sample groups before and after radiation.The results showed that the mechanical and thermal properties of poly（p-ddm）and poly（p-ddm/APbPc）resins were significantly affected by?-ray radiation at 0～1000KGy.However,radiation had a great influence on the properties of poly（p-ddm）resin,and the flexural strength,flexural modulus and energy storage modulus decreased by more than 10%.However,the mechanical properties of poly（p-ddm/APbPc）remained above 95%after 1000k Gy radiation.FT-IR results showed that the formation and fracture of hydrogen bonds in copolymer cross-linked networks and the main chain fracture of resins were the main factors affecting the mechanical properties of resins.Poly（p-ddm/APbPc）resins with higher network density and heavy metal Pb had good resistance to high-energy rays.