| Polymer nanocomposites(PNCs)refers to a polymer matrix filled with one or more nanoparticles to form a composite material.These nano-fillers can enhance the physical and chemical properties several times or even dozens of times on the premise that the volume ratio is small,and the processing performance is not reduced.Therefore,this field has received extensive attention and research from scholars.Boron nitride nanosheets are often used to develop thermally conductive and anti-corrosion materials due to their ultra-high in-plane thermal conductivity and barrier properties.However,due to the subversive difference between the boron atom and the nitrogen atom in boron nitride,a strong ionic bond is formed after the bond is formed.The strong interlayer force makes the peeling process very difficult and hinders the development of the nanomaterials.The efficient preparation of boron nitride nanomaterials has become an important topic.In this paper,two cationic surfactants with similar structures are selected:Hexagonal boron nitride(h-BN)was modified by cetyltrimethyl ammonium bromide(CTAB)and N,N-bis(cetyldimethyl)-2-ethylenediamine bromide(GS16),respectively.The h-BN was effectively separated by liquid phase ultrasonic treatment to obtain a large area of two-dimensional lamellar boron nitride(CBNNS and G-BNNS).The method is simple to operate,environmentally friendly,pollution-free,and the finished product is of high quality.The nano boron nitride material and polyvinyl alcohol(PVA)composite preparation of high thermal conductivity polymer composites;High anti-corrosive coatings were prepared by nano boron nitride with waterborne polyurethane(WPU)using existing composite technology.The morphology and dispersion stability of C-BNNS and G-BNNS were characterized by various testing methods to determine the optimal amount of surfactant,and the properties of the synthesized polymer nanocomposites were tested.The specific work is as follows:(1)First,GS-16 with the same carbon chain length as CTAB is prepared by the chemical principle of quaternization reaction.This paper chooses to prepare high-quality boron nitride nano-sheet materials by liquid-phase ultrasonic peeling and surfactant-assisted modification.The influence of CTAB and GS-16 addition on the quality of nano-sheets is mainly discussed.The product quality of three peeling processes was compared:pure solvent ultrasonic peeling,CTAB modified ultrasonic peeling,and GS-16 modified ultrasonic peeling.The results show that GS-16 has the best modification and dispersion effect on h-BN;in the deionized water solvent,the stripping time is 8 hours,and the ratio of h-BN to GS-16 is 10:3.The quality of the nanosheets has been significantly improved.Through the observation results of the scanning electron microscope and transmission electron microscope,the lateral dimensions of C-BNNS and G-BNNS are both 50～200nm.The Turbiscan Stability Index(TSI)of the G-BNNS solution is the lowest(p=1.38),which is 45 times lower than the TSI value of h-BN,which proves that the solution stability of G-BNNS nanosheets is the best.(2)Disperse the prepared C-BNNS and G-BNNS powders in a small amount of deionized water,and then compound them with water-based polymer polyvinyl alcohol to prepare thermal management materials,which are used in the field of flexible electronics.The mixing process adopts a simple magnetic stirring operation.During the mixing process,ultrasound is used to help dispersion every hour,so that the nano boron nitride can be uniformly dispersed to the greatest extent.The amount of C-BNNS and G-BNNS added is a key factor that affects the performance of polymer composites.Therefore,the amount of nano-filler is fully discussed in the third chapter.The performance test results prove that when the content of G-BNNS is 30wt%,the thermal and mechanical properties of the composite material are the best.This phenomenon can be attributed to the significant enhancement effect of the nano-filler on the polymer material.When the addition amount is 30%,G-BNNS forms an effective heat conduction path in PVA,and has the best compatibility,without obvious accumulation and agglomeration.(3)Water-based polyurethane(WPU)was prepared by a simple synthesis method.The c-BNNS and G-BNNS dispersions prepared above were combined with WPU to prepare high-performance anticorrosive coatings(C-BNNS/WPU and G-BNNS/WPU).The corrosion resistance of the two coatings was studied by electrochemical impedance test,and the influence of the contents of C-BNNS and G-BNNS dispersions on corrosion resistance,mechanical,and water resistance was discussed.By atomic mechanics microscope observation,it was found that the addition of 0.3wt%C-BNNs and G-BNNS could produce a compact and robust WPU coating with fewer defects.The testing results of water resistance also prove this,and the introduction of Boron nitride nanosheets can effectively improve the waterproof effect and prevent corrosive media from entering the surface of the substrate.EIS test results show that the impedance modulus of G-BNNS/WPU(4)coating is the highest,reaching 1.18×109Ω·cm2,indicating that the sample has the best anti-corrosion performance.The enhancement of corrosion resistance,water resistance,thermal stability,and mechanical properties is mainly attributed to the excellent barrier properties,chemical inertia,and electrical insulation of boron nitride nanosheets.The small size of nanomaterials can fill in the defects and holes in the WPU matrix and improve the shielding effect of the coating.Its good dispersion in the matrix can not only increase the tortuous path of the corrosive medium into the metal surface but also enhance the overall rigidity of the coating.Therefore,boron nitride nanosheets have become a promising reinforcement material,and their enhancement effect on WPU is obvious. |
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