Preparation And Properties Of Rice Straw Cellulose Nanofibrils And Their Composite Films

In this study,cellulose microfibrils(CMFs)and cellulose nanofibrils(CNFs)with high aspect ratio were prepared from rice straw.The experimental results showed that after alkali and bleaching treatments,the hemicellulose and lignin of rice straw were removed,and CMFs with a smooth surface and a diameter of 2-5 ?m were obtained,with unchanged crystalline structure but improved crystallinity and thermal stability.After 2,2,6,6-tetramethylpiperidinyl-1-oxyl(TEMPO)-mediated oxidation and mechanical treatment of CMFs,CNFs with high aspect ratio and a diameter of 5-12 nm were obtained,with unchanged crystalline structure and crystallinity but decreased thermal stability.Through solution blending method,the CMFs/PVA and CNFs/PVA composite films were prepared by compounding the rice straw cellulose fibers with different scales and polyvinyl alcohol(PVA),and the structure and properties of these composite films were analyzed by morphology observation and characterization of XRD,TGA,water absorption and mechanical property tests.The experimental results indicated that strong hydrogen bonding interactions were formed between rice straw cellulose fibers and PVA molecules,which results in a more ordered and compact lattice structure of PVA.The incorporation of CMFs and CNFs improved the thermal stability and tensile strength of the composite films,while decreased the water absorption and transmittance of the composite films.Small amounts of CNFs could be uniformly dispersed in the PVA matrix,but obvious CMFs aggregates could be observed in the composite films due to large size of CMFs.Therefore,when the addition of CMFs is higher than 1%,the tensile strength of the composite films begins to decrease,and the transmittance of CMFs/PVA composite films is lower at the same cellulose fiber content.Through melt blending method,the CNFs/PCL composite films were prepared by compounding CNFs and poly(?-caprolactone)(PCL),and the structure and properties of these composite films were analyzed by morphology observation and the characterization of XRD,DSC,TGA,water absorption and mechanical property tests.The experimental results revealed that small amounts of CNFs could be uniformly dispersed in PCL matrix,but partial agglomeration occurred when the content of CNFs reached 5%.After the addition of CNFs,the crystal structure and phase transition temperatures of PCL did not change,the water absorption and modulus of the composite films were increasesd,and the thermal stability of the composite films were decreased.