Study On The Preparation Of MFC Composite Aerogels And Its Packaging Performance

In this paper,coniferous wood bleached kraft pulp was used as raw material.Cellulose was treated by TEMPO/NaBr/NaClO oxidation system.The cellulose microfiber(MFC)was prepared by high-pressure homogenization.By changing the amount of sodium hypochlorite and homogenization times,MFC prepared under different conditions was obtained,and M-A(8-8)was modified by VTMS.MFC aerogels and silane modified MFC composite aerogels were prepared by freeze drying.The properties of different aerogels such as compression,heat conduction and essential oil slow release were characterized.It was found that with the increase of sodium hypochlorite dosage,the MFC aerogels had the following changes:the density decreased from 12.6mg/cm3 to 10.7mg/cm3,decreased by 15.08%;the volume shrinkage rate was between 12.33%-30.20%and the porosity reached 99.29%;the SEM diagram showed that the MFC aerogels exhibited dense three-dimensional porous structure,and the crystallinity increased from 64.67%to 66.92%,an increase of 3.48%.M-A(8-8)has higher thermal decomposition temperature and better heat resistance.After BET analysis,the pore size of MFC aerogels is mainly mesoporous,with a specific surface area of 43.339m2/g.The compressive strength of aerogels increased,the increase was 28.17%,the thermal conductivity was less than the international standard 0.174Wm-1K-1,and had good thermal insulation performance.The higher the oxidation degree,the less favorable for the release of MFC aerogels,and the slow release effect of M-A(8-6)was better.With the increase of homogenization times,the MFC aerogels had the following changes:the density range was between 10.2mg/cm3-11.5mg/cm3;the volume shrinkage rate was between 12.33%-21.03%;the porosity of M-A(8-8)was the lowest;the crystallinity increased by 4.60%;M-A(8-10)had the best heat resistance,followed by M-A(8-8);the aeration rate of MFC aerogels was the lowest.The specific surface area decreased first and then increased,ranging from 17.643m2/g to 35.171m2/g.The compressive strength of aerogels showed an increasing trend with an increase of 15.35%.MFC aerogels had better thermal insulation properties and homogenization times had little effect on the release properties of MFC aerogels.The change of MFC composite aerogels after M-A(8-8)silane modification is as follows:the density increases by 114.09%,the volume shrinkage rate increases obviously,and the porosity decreases obviously,the lowest is 95.81%,and the reduction is 3.4%.SEM diagram shows that the MFC composite aerogels are denser and even.BET analysis showed that the pores of MFC composite aerogels were mainly mesoporous,but the pore size distribution was smaller.The specific surface area of M-V-A(1:1)(VTMS to pulp dry weight ratio 1:1)was very large,reaching 26.977m2/g.The maximum crystallinity of M-V-A(1:1)was 68.03%,which was 1.7%higher than that before unmodified(66.89%);and the heat resistance of MFC composite aerogels was better.When the strain rate is 80%,the compressive strength of M-V-A(1:1)is increased by 142.4%.The introduction of silane greatly improves the compressive properties of cellulose aerogels.The lowest thermal conductivity of M-V-A(1:0.8)is 0.03217Wm-1K-1,and the highest thermal conductivity of M-V-A(1:1.2)is 0.03496Wm-1K-1,both of which have better thermal insulation performance.The slow release rate of MFC composite aerogels is lower than that of unmodified MFC aerogels,and M-V-A(1:0.8)has better sustained release effect,which may be more suitable for the application of essential oil slow release.