Preparation Of SNPEEK/PVC Gas Blended Film For Red Grapes Preservation

In this paper,the polymer material polyether ether ketone(PEEK)was modified,and nitrated/sulfonated polyether ether ketone(SNPEEK)and nitrated polyether ether ketone(NPEEK)were synthesized.The chemical structure and physical properties of the two substances were determined through characterization tests.Solvent evaporation method was used,SNPEEK/PVC blended films with different SNPEEK content were prepared,and the performance of the blended films were tested and analyzed.Finally,1%SN1/PVC and1%SN5/PVC films were selected to study the fresh-keeping effect of red grapes.The main research contents of this paper were as follows:Study on nitrification and sulfonation of PEEK.A nitrate-sulfur mixed acid reaction system was used in reaction,a single factor experiment was used to explore the effects of different time,temperature,and mixed acid ratio conditions on the product.The results showed that within a certain range,the change of time and temperature had no effect on the reaction system.SNPEEK with different contents of nitric acid and sulfonic acid groups can be synthesized by controlling the change of the mixed acid ratio.The structures of SNPEEK and NPPEK were determined by FTIR,elemental analysis,and ¹H NMR.XRD confirmed that the original crystal structure of PEEK was destroyed by the introduction of groups.TGA and DTG showed that the introduction of groups reduced the thermal stability of the material.At the same time,the solubility analysis found that the introduction of high-content nitric acid groups improved the solubility of SNPEEK,making it dissolvable at room temperature,and reducing the difficulty of film formation.Preparation and performance test of SNPEEK/PVC blended film.Different types of fruits and vegetables have different requirements for membrane gas selective permeability.Different sulfonic acid group content will affect the membrane gas selective permeability.Therefore,SN1 and SN5 materials with different sulfonic acid group content were selected to make SN1/PVC films and SN5/PVC films with different proportions,and explored the specific influence of sulfonic acid groups'content on the selective permeability of the membrane.With the increase of SNPEEK,the surface and cross section of the SN1/PVC and SN5/PVC films had micron-level pores,the O₂permeability of blended films increased less than CO₂,and the solubility coefficient also increased,resulting in the gas separation coefficients of 2.5%SN1/PVC and 2.5%SN5/PVC films increased by 2 times and 2.5 times,respectively.With the increase of SNPEEK content,the hydrophilicity of the blend films increased,while the light transmittance decreased,and the tensile strength and elongation at break of blended films increased first and then decreased.Compared with PVC,the comprehensive performance of the two sets of blended films had been improved to varying degrees.Study on SNPEEK/PVC blended film for red grapes preservation.After testing the performance of the two groups of blended films with different proportions,it is found that1.0%SN1/PVC and 1.0%SN5/PVC films have better mechanical properties and light transmittance and good gas selective permeability.1.0%SN1/PVC film and 1.0%SN5/PVC film were selected for the application of red grapes fresh-keeping,and the sensory and physical and chemical index changes of red grapes were tested within 32 days of storage.CO₂and O₂content in the two sets of blend film packaging reached equilibrium gas concentration on the 4th day,the packages retained a certain CO₂concentration and reduces the O₂concentration.The osmotic system method was used to calculate the respiratory intensity of three groups of packages,among them,the 1%SN1/PVC group<1%SN5/PVC group<PVC group,and 1%SN1/PVC and 1%SN5/PVC groups kept the red grapes at a low respiratory intensity.On the 32nd day,the good fruit rates of the 1%SN1/PVC and 1%SN5/PVC groups were 85.7%and 82.5%,respectively,while the good fruit rates of the PVC group and the blank group were only 72.9%and 12.0%.Compared with the blank group and the PVC group,the blend film group prolonged the preservation period of red grapes by 16 days and more than 8 days.Therefore,During the storage of time,1.0%SN1/PVC film and 1.0%SN5/PVC film packaging can effectively maintain the fresh quality of red grapes.