Effect Of Regulatory Pretreatment On The Packaging Performance Of MFC Film

During the preparation of microfibrillated cellulose(MFC)by cellulase pretreatment,the endo-cellulase is mainly used in the amorphous region of cellulose,so the pretreatment of endo-cellulase has a unique advantage and practical application value in reduction of energy consumption of MFC,improvement of product yield and enhancement of product performance,however,there is a problem that the pretreatment time is too long and the production efficiency is low.Therefore,it is necessary to carry out in-depth study on the regulation of endo-cellulase adsorption-pretreatment,improvement of the pretreatment efficiency,and the mechanism of its correlation.In this paper,the bleached eucalyptus sulpfate pulp was adopted as the raw material,and on basis of the principle of charge adsorption,the pretreatment efficiency of the endo-cellulase(R cellulase)and the performance of the MFC films were improved by adding the cationic polymer,such as polydimethyldiallylammonium chloride(PDADMAC)and polyacrylamide(CPAM).The results of enzymatic studies have shown that:With the increase of PD ADM AC(Ⅰ),the activity of FPA was increasing,and when the dosage of PDADMAC(Ⅱ),CPAM(Ⅰ),CPAM(Ⅱ)was 0.6mg/g,1.Omg/g,1.2mg/g,the corresponding changes of FPA activity were increased by 6.87%,decreased by 15.78%,desreased by 15.90%,respectively.When the dosage of PDADMAC(Ⅰ),PDADMAC(Ⅱ),CPAM(Ⅰ)and CPAM(Ⅱ)was 2.5mg/g,1.2mg/g,2.0mg/g,2.4mg/g,respectively,the corresponding changes of Cx activity were decreased by 21.03%,increased by 5.26%,decreased by 29.90%and decreased by 21.65%,respectively.The results showed that the high charge of PDADMAC was beneficial to the increase of cellulase activity;For CPAM,the cellulase activity would be decrease.The analysis of MFC and its film performance have shown that:When the pulp concentration of 10%,cellulase dosage of 6u/g,processing time of 16h,comparing with cellulase dosage of 4u/g,the specific surfae area of MFC increased by 2.52%,the crystallinity increased by 5.96%,the viscosity increased by 14.63%,and the water retention value decreased by 17.85%;The tensile strength of the MFC film was 29.96MPa,the elongation at break was 2.288%,the oxygen permeability was 1.362×10-15cm3·cm/(cm2·s·Pa),and the transmittance was 71.90%,which could match up to the performance requirements of the packaging film.For PDADMAC,compared to PDADMAC(Ⅱ)with low molecular weight and high charge,the specific surface area of the MFC prepared by adding the amount of PDADMAC(Ⅰ),which hold on high molecular weight and low charge increased by 2.75%,the crystallinity increased by 2.25%,the viscosity increased by 13.44mpa·s,and the range of particle size becomes larger;The tensile strength of MFC film increased by 34.24%,the elongation at break increased by 0.897%,the oxygen permeability coefficient increased by 0.146×10-15cm3·cm/(cm2·s·Pa),and the barrier property was slightly reduced,the amount of PDADMAC(Ⅰ)addition was about 360ppm.PDADMAC with high charge has a great effect on the promotion of enzyme activity,the pretreatment efficiency of the cellulase was improved,and the performance of MFC and its film mechanical properties have declined.For CPAM,compared to CPAM(Ⅱ)with low molecular weight and low charge,the specific surface area of MFC prepared by adding CPAM(Ⅰ)including high molecular weight and high charge increased by 1.72%,the water retention value increased 2.79%,the viscosity increased by 9.78mpa·s;The tensile strength of the film increased by 14.49MPa,the elongation at break increased by 2.175%,the oxygen permeability coefficient decreased by 6.32%,which indicated the blocking performance was excellent,the amount of CPAM(Ⅰ)addition was about 250ppm.The aaddition of CPAM had a reduction on the activity of the cellulase,however,it has taken the effective control of the excessive hydrolysis of cellulase in the amorphous area to some extent,which was gainful to the improvement of mechanical and barrier properties for MFC films.Therefore,the specific surface area and viscosity of MFC,the tensile strength and elongation at break of MFC films,which prepared by adding cationic polymer with high molecular weight are better,moreover,the high charge of cationic polymer is favorable for increase of MFC’crystallinity,and the preparation of MFC films with better barrier properties is achieved.