Effects Of Low Temperature Plasma Modification Technology On Properties Of Eggshell Powder/Corn Starch-Polylactic Acid Bilayer Films

In this research,the ESP,prepared from egg shells,was applied as a reinforcing agent to corn starch?CS?film.The process conditions for preparation of ESP/CS composite films was optimized.Acetyl tributyl citrate?ATBC?was used as a plasticizer to toughen the PLA film.A dielectric barrier?DBD?discharge method was used to generate low-temperature plasma?LTP?.The surface of the PLA film was modified by LTP and the effect of the modification power and processing time on the film properties was syudied.On the basis,ESP/CS-PLA bilayer films were prepared.The effects of LTP and PLA/CS?mass ratio?on the properties of the bilayer films were studied.The main contents and conclusions are as follows:?1?Preparation and characteristics of ESPESP,particle sizes ranging from 0.5 to 100?m,was prepared from egg shells.The average particle size of ESP was 8.12?m.The structure of ESP particles show irregular sheet.The results of X-ray diffraction?XRD?show that the ESP have strongest diffraction peaks at 2?=23.04°.Thermogravimetric analysis?TGA?results show that when the temperature rise to about 305°C,the weight loss rate of ESP is the largest,while the remaining mass percentage is still 98%.?2?Preparation and properties of ESP/CS monolayer filmESP/CS film was prepared with CS as the main film-forming substrate.The optimum process conditions for the preparation of ESP/CS film were optimized through response surface methodology.The concentration of CS was 4.9 g/100 mL,the content of glycerol was 49%,and the content of ESP was 1.9%.The corresponding tensile strength?TS?,elongation at break?EB?,water vapor permeability?WVP?,and oxygen permeability?OP?were 4.97 MPa,109.12%,1.31×10^-12 g·cm^-1·s^-1·Pa^-1 and 1.19×10^-5cm³·m^-2·d^-1·Pa^-1,respectively.The FTIR shows that ESP and CS have good compatibility.XRD and TGA results show that the addition of ESP improves the crystallinity and thermal stability of ESP/CS film.SEM analysis shows that the ESP/CS film have better surface and fracture morphology.?3?Preparation and properties of PLA filmThe effects of PLA concentration and ATBC content on the TS,EB,WVP and OP were studied.According to the results of single-factor test,the PLA film was prepared at a mass concentration of PLA of 6 g/100 mL and an ATBC content of 20%.The TS,EB,WVP,and OP of the film were 203.67%,33.16 MPa,0.95×10^-13 g·cm^-1·s^-1·Pa^-1 and8.32×10^-4 cm³·m^-2·d^-1·Pa^-1,respectively.XRD analysis shows that the addition of ATBC reduced the crystallinity of the PLA film.TGA analysis shows that the PLA film plasticized with 20%ATBC have lower extrapolated onset temperature and maximum degradation temperature than pure PLA film.?4?Study on the surface modification of PLA film by LTPThe surface of PLA film was modified by LTP.The effects of processing power and time on the properties of PLA film were investigated.The results show that the TS and EB of the PLA film gradually decreased with the increase of power and time,but there was no significant effect on WVP and OP.X-ray photoelectron spectroscopy?XPS?,atomic force microscopy?AFM?,and water contact angle?WCA?analysis show that the surface modification of the plasma increased the O/C atomic ratio,roughness,and hydrophilicity on the surface of PLA film.The FTIR results show that the LTP modified PLA film had stronger wave peaks at wavenumbers of 1182 and 1756 cm^-1.XRD results show that the plasma modification of PLA does not affect its crys tal structure.?5?Preparation and properties of ESP/CS-PLA bilayer filmThe effect of LTP modification power,treatment time,and PLA/CS?mass ratio?on the properties of ESP/CS-PLA bilayer films were studied.The experimental results show that the modification of PLA film by LTP resulted in an increase of TS,EB,and peel strength?PS?of the bilayer films,and a decrease of WVP and OP.In addition,as the PLA/CS decreases,the TS,EB,and OP values of the bilayer film decrease,and the WVP value increases.XRD analysis shows that the LTP treatment does not change the crystal structure of the bilayer films.TGA analysis shows that LTP modification technology increases the thermal stability of bilayer films.SEM analysis shows that the PLA film exhibited better compatibility with the ESP/CS film after LTP modification than the control.