Study On Protection Performance Of Peelable Coating Against Organophosphorus Chemical Warfare Agent Simulants

The permeation of extremely toxic organophosphorus Chemical Warfare Agents(CWAs)into equipment surfaces has posed a serious threat to the safety of military personnel.Compared to the traditional high-pressure alkaline water flushing method,which typically exihibits highly corrosive and strongly irritant characteristic,the application of peelable coatings can be considered as a more simple,gentle,and costeffective protection measure for these equipment surfaces.However,these existing peelable coatings generally feature poor anti-permeability and short service life in the liquid environment,and some residual toxic agents inside the coatings also bring additional burdens for their subsequent purification treatment.Therefore,to realize the safe,reliabe,simple and efficient protection of the peelable coatings on the equipment surfaces,we chose the two aspects of improving the anti-permeability of existing peelable coatings and accelerating the degradation rate of organophosphorus CWA molecules as the starting points.Subsequently,a series of novel peelable coatings were designed and prepared,and their anti-permeation behaviors as well as mechanical evolution under different solution conditions were explored systematically.At the same time,the catalytic degradation efficiency of these prepared peelable coatings on different simulant molecules of organophosphorus CWAs was also analyzed and compared.The main research contents and results of this study are as follows:(1)To improve the anti-permeability of these existing peelable coatings,a Doublelayer Peelable Coating(DLPC)was designed and prepared by integrating two coatings with complementary properties.First,the basic mechanical properties of DLPC were compared with those of the Mono-layer Peelable coating(MLPC).Then,the antipermeability of both the coatings was evaluated by using the Electrochemical Impedance Spectroscopy(EIS)technology and water uptake test in a conventional inorganic salt solution(3.5 wt.%NaCl).Meanwile,the evolution of peel strength,tensile property,and internal microstructure of the two coatings with immersion time were also tracked.The results showed that the DLPC sample not only maintained the easy removal of the lower peelable layer,but also effectively exerted the antipermeability of the upper dense layer,moreover,the good interfacial combination between the upper and lower layers also endowed the DLPC sample with consistent tensile flexibility.(2)Further verification of the enhanced anti-permeability of the DLPC sample to the organophosphorus solution was conducted by using DMMP(Dimethyl methylphosphonate)as a simulant of organophosphorus CWAs.By changing the DMMP content added into the solution,the effect of DMMP concentration on the antipermeability and mechanical stability of the DLPC sample was systematically investigated,and the failure reasons of the protection performance of this coating were also analyzed.The results showed that the anti-permeability of the DLPC sample to the DMMP molecules was affected by the chemical similarity between the coating and solution as well as the hydrogen bonding interaction between the DMMP and H2O molecules.In addition,the sensitivity of the coating microstructure to the permeated solution also led to the decrease of mechanical properties of the DLPC sample,which showed a positive relation with the DMMP concentration.This study not only revealed the evolution pattern of the anti-permeability and mechanical stability of the DLPC sample in these simulant solutions of organophosphorus CWAs,but also provided a basis and reference for the effective service life evaluation of this peelable coating in a real organophosphorus agent solution.(3)To accelerate the oxidation degradation rate of organophosphorus CWAs,the composite photocatalyst GO@TiO2 as a functional filler was designed and synthesized by in-situ loading TiO2 nanoparticles onto the GO(Graphene Oxide)surfaces.Benefiting from the presence and partial reduction of GO,GO@TiO2 showed a significant improvement in both the light absorption intensity and photoelectric conversion efficiency in the visible wavelengths,thereby achieving the rapid photocatalytic oxidation degradation of the organophosphorus simulant DMMP molecules in the visible light region.Moreover,this functional filler also endowed the peelable coating with satisfactory photocatalytic performance,it was found that the photocatalytic degradation efficiency of DMMP molecules increased by about 4 times by the loading of GO@TiO2filler compared with the direct addition of TiO2 into the peelable coating after 48 h reaction duration.However,due to the weakness of the photoelectric conversion efficiency and the obstruction of the mass transfer process,the overall photocatalytic degradation effect of the composite coating was undesirable.(4)To accelerate the hydrolysis degradation rate of organophosphorus CWAs,the composite hydrolyst GO@UiO-66-NH2 as a functional filler was designed and synthesized by in-situ loading UiO-66-NH2 nanoparticles onto the GO surfaces.The existence of GO carrier significantly eliminated the nanoparticle aggregation phenomena of UiO-66-NH2 within the peelable coating,thereby maintaining the efficient catalytic hydrolysis ability of the prepared peelable coating to the DMNP(Dimethyl methylphosphonate)molecules,another organophosphorus simulant.Moreover,the modification of UiO-66-NH2 on GO surfaces also maintained the intrinsic flakely structure of the latter,and significantly improved its interfacial compatibility with the coating matrix,thus further endowing the peelable coating with great anti-permeability and mechanical stability after exposure to the simulant solutions with different DMMP concentrations.Ultimately,the improvement of the service stability and catalytic degradation ability of the peelable coating was achieved simultaneously in organphosphorus simulant solutions.