Functionalization Of Boron Nitride And The Construction High-performance Polymeric Nanocomposites

Boron nitride nanosheets have broad application prospects in enhancing polymer properties due to their unique two-dimensional layered structure and excellent mechanical properties.In addition to the role of Van der Waals forces,the interlayers also have the characteristics of ion bonds,and the interaction between the layers is strong,making the hexagonal boron nitride stripping more difficult than graphene,which greatly limits its application.In this paper,boron nitride nanosheets,functionalized boron nitride and boron nitride nanocomposites were prepared by solution stripping,ball milling,and chemical reduction methods,respectively.The prepared boron nitride nanosheets were characterized to study their effects on the properties of LDPE.It mainly includes the following aspects:(1)In this chapter,boron nitride nanoplates were successfully prepared by stripping hexagonal boron nitride in N-methylpyrrolidone(NMP)using commercial hexagonal boron nitride as a raw material and ultrasonic comminution technology.The structure and morphology of boron nitride nanosheets were measured by FTIR,X-ray diffraction(XRD),transmission electron microscopy(TEM)and Raman spectroscopy(Raman).The results show that a small amount of boron nitride nanosheets with complete crystal structure and large size can be prepared by solution stripping.(2)Boron nitride nanosheets were prepared by ball milling method.Boron nitride nanosheets were prepared by adding p-chloroaniline,p-fluoroaniline and aniline as the ball-grinding agent under the same rotation speed,ball-to-material ratio,and ball milling time.The structure and morphology of the prepared nanosheets were tested by FTIR,X-RD,TEM and electron diffraction.The results show that the exposed layers of the boron nitride nanosheets are exposed,which makes the Out-of-plane bending vibration peak of the B-N-B bond significantly enhanced.After the addition of the ball-grinding agent,the degree of peeling of the boron nitride nano-sheets increased,and the sheets were not damaged.It can stably disperse in water,ethanol,NMP for a long time,and the dispersion concentration can reach up to 2.58 mg/ml.(3)Hexagonal boron nitride is negatively electronized by a sodium-naphthalene solution formed from naphthalene/sodium and THF,followed by the addition of 1-bromobutane,1-bromododecane,1-bromooctadecane to produce alkyl functionalized nitrides.boron.The functionalized boron nitride crystals were characterized by XRD and TEM.X-ray photoelectron spectroscopy(XPS),FTIR and thermogravimetric analysis(TGA)were used to characterize the functionalization and calculate the alkyl grafting ratio.The results showed that after the negative electronization of naphthalene sodium reagent,the grafting rate of the alkyl group was significantly increased and the grafting ratio was 0.121 to 0.131.The increase in the length of the carbon chain in the alkyl reagent used for the growth,the graft density increases significantly,due to the steric hindrance effect of the carbon chain,the number of moles of alkyl groups grafted on the boron nitride is reduced.The number of functionalized boron nitride layers is reduced,and they are more easily peeled off under the action of ultrasound to generate boron nitride nanosheets.Using the prepared alkylated boron nitride and low density polyethylene as raw materials,a composite material with different percentages of boron nitride was prepared by solvent blending.The composite material was tested for its mechanical properties.The results show that the mechanical strength of the composite material is significantly improved with the content of functionalized boron nitride increases,and the functionalized boron nitride nanosheet is uniformly dispersed in the polymer.