二维功能填料尺寸对BN/EPDM柔性中子防护复合材料性能的影响

Effect of two-dimensional functional fillers size on the performance of BN/EPDM flexible neutron protection composite materials

柔性中子防护复合材料对于异形构件和人员防护具有重要意义,其性能与功能填料的性质密切相关,但二维功能填料尺寸对材料性能的影响尚不明确。以性能良好的三元乙丙橡胶(Ethylene Propylene Diene Monomer,EPDM)作为柔性基体,以热中子吸收截面较高的层状氮化硼(Boron Nitride,BN)作为二维功能填料并作表面改性,通过开炼工艺将BN均匀分散于EPDM中,热压硫化后得到BN/EPDM柔性中子防护复合材料,对其微观结构进行表征分析。研究了BN尺寸对复合材料综合性能的影响,结果表明:减小BN尺寸有利于提升复合材料的拉伸强度和热中子屏蔽性能,当材料厚度为2 mm时,其拉伸强度最高可达8.13 MPa,热中子屏蔽率最高可提升约5%。该研究可为聚合物基柔性中子防护复合材料的设计与制备提供基础。

[Background]Flexible neutron protection composite materials are of great significance for the protection of special-shaped components and personnel.Their performances are closely related to the properties of functional fillers,but the effect of size of 2D functional fillers on the performance of composites is not yet clear.[Purpose]This study aims to explore the influence of two-dimensional(2D)functional filler size on the mechanical properties and neutron shielding performance of composite materials.[Methods]Firstly,ethylene propylene diene monomer(EPDM)rubber with good performance such as high temperature resistance,weather resistance,radiation stability,mechanical properties,and high hydrogen content was used as flexible substrate material,and layered boron bitride(BN)with a high thermal neutron absorption cross-section was taken as 2D functional filler,and the surface of BN was modified by mercapto group through two-step chemical grafting.BN/EPDM flexible neutron protection composite materials were prepared by the process of plasticizing,mixing and hot pressing and vulcanization,and the content of BN was controlled at 20~100 phr(parts per hundred parts of rubber),and azodiisobutyronitrile(AIBN)acted as an initiator to promote the interfacial bonding between mercaptylated boron nitride(BN-SH)and EPDM substrate.Then,the microstructures of the materials such as functional group and microscopic morphology were characterized and analyzed using Fourier transform infrared spectrum(FTIR)and scanning electron microscope(SEM).Subsequently,the tensile properties including tensile strength and elongation at break were characterized by universal testing machine,according to GB/T 528―2009 standard.The surface hardness was measured by Shore A hardness tester,according to GB/T 531.1―2008 standard.Finally,the neutron shielding performance was tested based on cadmium sheet difference method,where americium-beryllium source with moderation and collimation was used as narrow beam measurement geometry,and 3He detector was used to count neutrons.[Results]The experimental results indicate that the reduction of BN size is conducive to improving the tensile strength and thermal neutron shielding performance of composite materials.When the thickness of the material is 2 mm,its tensile strength can reach up to 8.13 MPa,and the thermal neutron shielding rate can be increased by up to about 5%,which is related to the amount of nano BN.[Conclusions]This study confirms the size effect of two-dimensional functional fillers in neutron shielding composite materials,and can provide the basis for the design and preparation of polymerbased flexible neutron protection composites.