Effect Of Free Radical Shielding Agent Regulating Plasma On Structural Characterization, Rheological Behavior Of Chitosan And Preliminary Analysis Of Degradation Mechanism

Pulse discharge plasma technology is an advanced oxidation technology with broad prospects.It forms oxidative degradation by forming a large number of active materials(such as:·OH,·O,H2O2,hydrated electrons,etc.).Studies have shown that pulsed discharge plasma technology has a significant degradation effect on chitosan.However,domestic and foreign scholars emphasized the degradation of OH,but ignored the effects of other active substances.In addition,the controllable degradation of chitosan,as a bottleneck urgently needed to be solved in the industry,has also been extensively studied by scholars at home and abroad.Different types of free-radical shielding agents(tert-butanol,benzoquinone,MnO2,sodium dihydrogen phosphate)can react with corresponding active substances(·OH,·O,H2O2,hydrated electrons),thereby regulating the concentration of corresponding free radicals.effect.Therefore,this paper analyzes the influence of different types of free radical shielding agents on the intrinsic viscosity,rheological behavior,and structural characterization of chitosan,and by analyzing the degradation effect of different active substances on chitosan,the mechanism of pulse discharge plasma degradation of chitosan was elucidated,which provided the experimental basis for exploring the controllable degradation of chitosan by pulse discharge plasma.The test results are as follows:(1)Using the intrinsic viscosity as an index,the effect of different free radical shielding agents on the degradation of chitosan was studied.The test results show that each active substance shielding agent has a reducing effect on the degradation of chitosan.The optimum free radical scavenging concentration was determined to be:210mmol/L of tert-butanol,12mmol/L of benzoquinone,24mmol/L of sodium dihydrogen phosphate,and 91mmol/L of MnO2.(2)Preparation of chitosan degradation products under different free radical shielding agent concentrations,and using the relationship between shear rate-apparent viscosity and angular frequency-modulus as indicators to study the effect of free radical shielding agents on the rheological behavior of chitosan,the test results show:For the steady state rheological test,the apparent viscosity of the degradation products of chitosan was significantly reduced by adding a free radical shielding agent.Moreover,as the shielding agent concentration and shear frequency increase,the Newton platform is significantly damaged,and the phenomenon of shear dilution appears.For the dynamic rheological test,the addition of a free-radical shielding agent reduces the storage modulus of the chitosan degradation products,but the trend is not obvious;the loss modulus of the chitosan degradation products decreases,and the shielding agent concentration and the loss modulus are positive.Correlation relationship:With the decrease of the shielding agent concentration,the decreasing trend of the loss tangent angle(tan8)of the chitosan degradation products is more severe,and the closer it is to the area of tan8<1.(3)Preparation of degradation products of chitosan at different concentrations of free radical shielding agent,and the degradation products were analyzed by ultraviolet spectrum,infrared spectrum,nuclear magnetic resonance spectrum and X-ray diffraction.The test results show that the addition of free radical shielding agent does not The main characteristic structure of chitosan is destroyed;the crystal structure of chitosan is destroyed,the degree of amino weakening of GlcN residues is inversely related to the shielding agent concentration;the amino group on the chitosan molecular chain is grafted by the shielding agent group.The inhibitory effect of MnO2 and benzoquinone on chitosan was better than that of t-butanol,and the inhibitory effect of sodium dihydrogen phosphate was the smallest.(4)Using the intrinsic viscosity as an indicator,under the optimum concentration of the free radical shielding agent,the effect of the free radical shielding agent on the degradation effect of chitosan was studied.The test results show that H2O2,·O,·OH all have significant Degradation,the order of each active substance is:H2O2>·O>·OH>Hydrated electron.In summary,each active substance(·OH,·O,H2O2 and hydrated electrons)in the system all plays a certain role in the degradation effect of chitosan,and it is feasible to control the degradation by adding a free radical shielding agent.