Preparation And Properties Of Nanocellulose-based Composite Films

Cellulose is the most abundant degradable polysaccharide biopolymer.In recent years,the utilization and development of cellulose is not optimistic,and there are still a lot of cellulose raw materials that are wasted and discarded.Therefore,it is of great significance to develop and utilize these raw materials.Nanocellulose,as the nanometer material,has been widely used in the fields of wound dressing,food packaging,drug release and tissue engineering,due to its characteristics of great specific surface area,large amount of active hydroxyl groups,biodegradability and good biocompatibility.Nanocellulose has no antibacterial properties of its own,however,cellulose matrix with antibacterial properties can be obtained by sodium periodate oxidation.Guar gum is a kind of environmentally friendly natural polymer with low cost,biodegradable,non-toxic characteristics.Furthermore,Guar gum has the great water solubility,film formation and good light transmittance.In this paper,guar gum(GG)is mixed with dialdehyde cellulose to prepare biodegradable composite fills with improved properties,which have a broad application prospect in food packaging.Nanocellulose thin films are prepared by vacuum filtration method,and then silver ions are reduced by plasma irradiation to prepare silver nanoparticles loaded nanoceilulose films.Photochemical reduction under plasma irradiation is an environmentally friendly,simple and fast reduction way to produce Ag nanoparticles in the cellulosic matrix,because there is no adding harmful chemical reagents in reduction procedure.Dialdehyde nanocellulose is prepared by sodium periodate oxidation with regenerated nanocellulose as the raw materials.The FTIR results show that the oxidized regenerated cellulose(ORC)have two characteristic peaks near 1728 cm-1 and 889 cm-1,which prove the formation of aldehyde groups.The XRD results reveal that the crystal structure of oxidized nanoceilulose still retains the cellulose ? structure.The TG and DTG results prove that the thermal stability of dialdehyde nanoceilulose is decreased compared with nanocelluose.The results of OD values show that the dialdehyde nanoceilulose has a good inhibition effect on the growth of Staphylococcus aureus.The mechanical properties study of ORC-GG and ORC-glycerol composite films shows that plasticizing effect of glycerol is better than GG.The UV-vis results reveal that dialdehyde nanoceilulose based composite films have good light transmittance.The XRD results prove that the crystal structure of ORC based composite films still retains cellulose ?structure.The FTIR results exhibit that there is good compatibility between GG and ORC.The TG and DTG results prove that the thermal stability of ORC-glycerol films is decreased compared with pure nanocellulose.The SEM results prove that ORC based composite films have a smooth surface.The solvent resistance stUdy shows that the composite films have excellent barrier capacity against N,N-Dimethylacetamide(DMAc),N,N-Dimethylformamide(DMF),tetrahydrofuran(THF),and methanol,their shapes are maintained even after 48 h of soaking in organic solvent.The nanosilver-loaded cellulose films are characterized by FTIR,UV-vis and SEM,the results of characterization confirm that silver nanoparticles are successfully deposited on the cellulose matrix.The XRD results show that the reduction of silver ions on cellulose matrix does not change the crystal structure of cellulose.There are no obvious silver crystal diffraction peaks,which is due to the low content of silver nanoparticles in nanocellulose.The formation of nanosilver particles in the matrix can be proved further by TG and EDS analysis,and the amount of silver loading in nanocellulose films is also determined by both of them.The results show that the silver content is very low.The study of OD values reveals that nanosilver have significantly efficient antibacterial activities against both Staphylococcus aureus and Escherichia coli.Moreover,silver release is observed to be very slow,which confirms the stability of the Ag nanoparticles inside the composite matrix,reducing the risk of toxicity when applied to wound dressing.