Preparation And Performance Study Of Radiation Protection Flexible Composite Materials Based On Composite Fillers

With the development of nuclear and radiation medicine,the demand of flexible films for radiation protection is increasing.The traditional flexible films for attenuating gamma ray(y-ray),X-ray and neutron,are heavy,toxic,with Pb as a shielding element,and the post-processing is difficult.In this paper,the design and preparation of various films without Pb have been conducted.Multi-element composite avoided the weak absorption area of a single element.The high filling,uniform distribution of filler particles in the rubber latex have been studied.The complementary of elements absorption edge and the influence of gradient structure on the attenuation performance of flexible films have been studied.A wide range of y/X-ray(20-100 keV)were attenuated using an element gradient combination.A comprehensive shielding of the thermal neutron and y/X-ray has been achieved.The main contents and results were listed as following:(1)The compounding and performances of XNBR and NR films were studied.A series of XNBR and NR flexible films were prepared using parallel synthesis,orthogonal design,and uniform design method.An optimal formulation and the process parameters were obtained.The tensile strength,elongation at break,and hardness of XNBR film were 27 MPa,1200%,and 40 HA,respectively.The tensile strength,elongation at break and hardness of NR film were 30 MPa,1170%,and 26 HA,respectively.The tolerance of the flexible films to acid,alkali,oil,and hot air was investigated using high-throughput characterization method.After treated in acid,alkali,oil,and hot air for 120 h,the tensile strength of XNBR film were 18 MPa,19 MPa,15 MPa,24 MPa,respectively,the elongation at break of XNBR film were 900%,900%,860%,1020%,respectively.It indicates that XNBR has a good tolerance to acid,alkali,oil,and hot air.After treated in acid,alkali,and oil for 120 h,the tensile strength and elongation at break of NR film decreased significantly to 5 MPa and less than 100%,respectively.After treated in hot air for 120 h,The tensile strength was 16 MPa,and the elongation at break was 620%.It indicates that NR film has a poor tolerance to acid,alkali and oil,and it has a good tolerance to thermal aging.The laminated films of NR and XNBR were successfully prepared.There was no slice if vulcanized in hot air.The diversified application can be realized by taking the advantages of both NR and XNBR.(2)The composite of shielding filler and flexible matrix were studied.Obtaining a uniform and stable dispersion of high density filler in the rubber latex is a challenge due to the sedimentation problem that is induced by the remarkable density differences.Here,this challenge was approached by reducing the filler particle radius,increasing the viscosity of the latex,and adding a coupling agent.The experimental results confirmed that the filler was well dispersed in the XNBRL in the concentration range from 10-70 wt.%.Compared with the metal filler,oxide filler had a better suspension stability,a better modification property with a coupling agent,and a higher mechanical property.The crosslinking reactions existed in oxide filler and XNBR.A series of latex with different proportions and different filler particle sizes were prepared.The latex viscosity with nano-Gd2O3 was higher than that of micro-Gd2O3.Nano-oxide improved the viscosity of latex resulting in the high filling ratio,and improved the mechanical properties of composite.The mechanical properties of the flexible film with fine fillers were better than that of coarse fillers,and the attenuation efficiencies were also higher.(3)The irradiation aging properties of the flexible composite materials were studied.The irradiation aging properties of NR and XNBR flexible films were investigated before and after subjecting the films to 10-500 kGy ?-ray.The threshold doses of the XNBR and Bi2O3/XNBR films were 300 kGy and 200 kGy,respectively.The threshold doses of the NR and Bi2O3/NR films were 200 kGy and 300 kGy,respectively.The results can be used to predict the service life of the films.It provides a basis for the selection of flexible films for different radiation fields.The mechanism was discussed by analyzing the Fourier Transform Infrared(FT-IR)and X-ray Photo-electron Spectroscopy(XPS)results.The anti-radiation performance of XNBR was better than NR.The main reason may be that the structure of NR molecular chain is simple,the bond energy is low,and it is easy to destroy.The molecular chain structure of XNBR is complex,the bond energy is high,and it is not easy to damage,therefore the anti-radiation performance of XNBR is excellent.After irradiated,NR and Bi2O3/NR became softer,but XNBR and Bi2O3/XNBR became harder.Bi2O3 filled the spaces in the XNBR molecular chain and hindered the cross-linking ofXNBR,therefore,Bi2O3 did not improve the anti-radiation performance of XNBR.After Bi2O3 was added,the anti-radiation performance of NR was enhanced.Although the adding of Bi2O3 was not conducive to the crosslinking of NR,Bi2O3 particles shielded a part of rays,which reduced the destruction of the NR molecular chains.(4)The flexible composite materials for the attenuation of a wide range of y/X-ray(20-100 keV)were studied.The high Z elements(atomic number above 50)and their common compounds for y/X-ray shielding were selected.For y/X-ray in the range of 20-30 keV and 90-100 keV,bismuth oxide(Bi2O3)is the best choice for shielding.For y/X-ray in the range of 30-57 keV,tin oxide(SnO2)is the best choice for shielding.For y/X-ray in the range of 57-90 keV,erbium oxide(Er2O3)is the best choice for shielding.If the energy of the y/X-ray falls within a small known range,a filler/XNBR film can be selected to shield the ray.The weak absorption area of an element can be offset by combining various elements.A wide range of y/X-ray(20-100 keV)can be attenuated using an element gradient combination of SnO2,Er2O3,and Bi2O3.For y/X-ray,the attenuation efficiency of the laminated construction sample was not affected by the film sequence or the incident direction.The attenuation properties of a mixed construction film were the same as those of a laminated construction film,as long as the filler contents were the same.(5)The thermal neutron(n)and n-y/X-ray flexible composite materials were studied.NR was used as the matrix,and 5-70 wt.%B4C/NR flexible films were prepared via a dip-molding method.B4C was well dispersed in NRL according to microscopic observation.Both the inside and outside surfaces of the film were smooth.As the B4C concentration increased,the tensile strength of the B4C/NR films initially increased and thereafter decreased.The addition of 10 wt.%B4C achieved the best reinforcing effect.The tensile strength,elongation at break,and hardness of 70 wt.%B4C/NR were 12 MPa,530%,and 55 HA.The attenuation efficiency of 70 wt.%B4C/NR film with 1 mm for thermal neutrons was 99%.According to different applications of radiation field,through the gradient combination of Gd2O3,WO3,Bi2O3,and B4C,thermal neutrons and?/X-ray shielding flexible films were prepared via multiple dips.The attenuation efficiency for thermal neutrons was 100%.