Preparation And Application Of Equilibrium Modified Atmosphere Packaging Membrane Based On Sulfonated Poly Ether Ether Ketone / Poly Vinylidene Fluoride

This study was based on Dissolution-Diffusion theory for gas permeation through membrane matrix,and considered that both dissolution and diffusion process of gas molecules through the matrix can be attributed to the gain and the loss of gas molecules among Available Active Site in the membrane matrix.For specific gases,the material with more active sites has better permeation performance for gas,so it can be considerated as Gas Conductor?GC?,while the material with lower performance for gas permeation i.e.Gas Barrier?GB?has fewer active sites.On this basis,Sulfonated Poly Ether Ether Ketone?SPEEK?material was prepared in this study by surface modification as a GC matrix,while Poly Vinylidene Fluoride?PVDF?,which has excellent miscibility with SPEEK in different proportion,was used as GB matrix.A series of GC-GB Blending Membranes?BMs?were prepared.By controlling the ratio of GC and GB,the density of active sites in the BMs can be adjusted.Thus,the gas permeation properties of BMs can be adjusted.Accordingly,BM based Equilibrium Modified Atmosphere Packaging?EMAP?was designed for modified atmosphere of broccoli,and the effects of the EMAPs on the storage quality of broccoli were studied.Some conclusions in this study were detailed as follows:1.The preparation of GC matrix:?1?the sulfonation process of Poly Ether Ether Ketone?PEEK?is related to system temperature and reaction time.Higher system temperature or longer the reaction time can enhance the Degree of Sulfonation?DS?of PEEK.?2?After sulfonation,the Fourier Transform Infrared?FTIR?of SPEEK presented significant characteristic peaks of O=S=O and-OH.The Thermogravimetric Analysis?TGA?of SPEEK displayed a S2 weight-loss stage.The X-ray Diffraction?XRD?showed obvious peaks at 2degrees angle of²0o.Additionally,sulfonation process enhanced the solubility of SPEEK in the organic solution and reduced the viscosity of SPEEK when it was dissolved in organic solution.?3?The surface of SPEEK membrane that was prepared using thermotropic phase method was smooth without obvious sign.Its section was also homogeneous,with no foam hole or perforation hole through it.Sulfonation process can increase the hydrophilicity of SPEEK,slightly increase its internal pore size,and reduce its mechanical strength.Also,sulfonation process can endow the SPEEK membrane with some antibacterial activities.Some obvious inhibition zones agaist different microbial species were presented around the SPEEK disk.2.The preparation of GC-GB BMs:?1?The miscibility between SPEEK and PVDF was outstanding,represented by that they can be uniformly mixed at different ratios.?2?SPEEK content in BM was beneficial to increase the hydrophilicity of BM and endowed BMs with some antibacterial activities.Some obvious inhibition zones toword different microbial species were presented around the BMs disk.?3?PVDF content in BM was beneficial to increase the mechanical strength of BM,and decrease the water absorption and water vapor permeability?WVP?of BM.3.The gas permeation properties of GC-GB BMs:?1?For single gas,the increase of DS in SPEEK membranes can increase the permeability of single pure gas component,as well as the resulting perfect selectivity of CO₂/N₂ and O₂/N₂.The increase can also inhibit the effect of CO₂ plasticization on SPEEK membranes.?2?For single gas,the increase of SPEEK content in BMs can increase the permeability of the single pure gas component,as well as the perfect selectivity of CO₂/N₂ and O₂/N₂.The PVDF content in BMs can avoid the effect of CO₂ plasticization on BMs.For CO₂/N₂ or O₂/N₂ binary mixxed gas,the increase of SPEEK content in BMs can increase the permeability of each gas component,as well as the resulting CO₂/N₂ and O₂/N₂ selectivity.?3?Difference in CO₂ or O₂ selectivity of BMs was unsignificant using ternary mixxed gas that simulated the internal atmosphere in EMAP at different period.4.EMAP for modified atmosphere storage of broccoli.?1?SPEEKcontent in BMs will shorten the balance time of both O₂ and CO₂ components in the internal atmosphere of EMAP.It increased the equilibrium concentration of O₂,and reduced the equilibrium concentration of CO₂ components.Such atmosphere in the EMAP is suitable for the modified atmosphere storage of broccoli.?2?BMs as EMAP to preserve broccoli can maintain sensory quality of the samples.The acceptable storage period was increased from less than 15 d to 30 d.?3?BMs as EMAP to preserve broccoli can maintain the color paramaters of the samples,retard the variations in the hardness and elasticity,inhibit the growth of various microbial species in the sample,slow down the pH change in the sample,inhibit the change of Total Chlorophyll Content?TCC?,Total Phenol?TP?content and Ascorbic Acid?AA?content.In particular,the BM50 packaging showed the best effects.In conclusion,this study used GC-GB theory to design an EMAP based on mixed matrixes.It will show a promissing prospect for the modified atmosphere storage of various fruits and vegetables.