Preparation And Properties Of Lead Borate/PET Composite

Lead borate has received wide attention for shielding neutrons and gamma rays simultaneously.It can be synthesized by hydrothermal method,solid phase sintering method and chemical precipitation method.Among them,hydrothermal method is the most common.In actual production,hydrothermal methods often require some harsh reaction conditions（such as high temperature and high pressure）as well as extremely low yields,which limits development.On the other hand,in the existing lead borate structure,the content of boron and lead cannot be adjusted,and it is difficult to deal with radiation fields with different radiation doses.In view of this,heavy element Pb and light element B were assembled by chemical precipitation method to form lead borate amorphous with complex structure and Pb₂B₅O₉[OH]·H₂O crystals and uniform morphology,which can shield both neutron andγrays.In the process of synthesizing lead borate amorphous,by adjusting the ratio of boric acid and lead acetate in the reaction raw materials,lead borate amorphous with different boron content can be synthesized.Among them,the boron content can reach up to 48.41%,which can be applied to different types of radiation fields.In addition,Pb₂B₅O₉[OH]·H₂O crystals was synthesized by another chemical precipitation method,and characterized by SEM,XRD,and TG-DTG.The results show that it possesses a uniform morphology and size,high crystallinity,and thermodynamic properties.By modification of lead borate,a special structure is designed on the surface,so that it can be in close contact with the hydroxyl group in EG,and lead hydrogen borate is used to break up lead borate into single molecules to prepare lead borate/EG dispersion.In order to verify that this modification method did not inactivate the hydroxyl groups in EG,the dispersion was used as a raw material and reacted with PTA to successfully prepare two low-content lead borate/PET composites of 4wt%and 8wt%.The SEM characterization results show that the lead borate particles in the composite are about 100-200nm and uniformly dispersed.The XRD characterization results show that lead borate has preferentially grown during the polymerization.The results fully prove that this modification method does not cause the hydroxyl groups in EG to lose activity and facilitate the dispersion of lead borate particles in PET.In order to meet the requirements of shielding performance,three different mass fractions of lead borate/PET composite materials of 10wt%,15wt%,and 20wt%were prepared by the esterification method and the PTA method.The results show that the size of lead borate in PET borate/PET composites synthesized by the esterification method is about 50 nm,and there is obvious agglomeration.It is worth noting that acicular lead borate appeared in the15%wt lead borate/PET composite prepared by the PTA method,and the lead borate dispersion was generally better than that of the esterification method.In addition,tests on the viscosity,melting point,diethylene glycol,carboxyl end groups,and L/b value of the composite materials show that the composites has excellent processing properties.In order to test the shielding performance of the composite material,lead borate/PET composite materials with three mass fractions of 10wt%,15wt%,and 20wt%were pressed into 2mm-thick sheets,which were tested forγrays at three energy points of 143kev,163kev and186kev.The results show that the 15%composite material has the highest shielding rate toγ-rays,which can reach to 10.98%.