Effect Of Hydrothermal Treatment On Morphological Structure And Paper Performance Of Corn Straw

Since the issuance of the waste ban,China’s paper industry has faced the challenge of a shortage of fiber raw materials supply.As a renewable resource rich in cellulose,corn stalk has a large annual output.The development and utilization of corn stalk for pithing and papermaking has attracted widespread attention.At present,people have limited understanding of the changes in the morphology of plant cell walls and the distribution of lignin in corn stalks during hydrothermal treatment.Therefore,it is important to study the effects of hydrothermal treatment on the microstructure of corn stalks and the distribution of lignin in micro regions on subsequent pithing.So,in this study,corn straw was used as raw material and subjected to different degrees of hydrothermal treatment to study the changes in chemical components,cross-sectional microstructure,and especially the distribution of lignin in the cell wall during the treatment process.Finally,the effect of the treatment process on paper performance was explored.Corn straw was divided into four parts:bark,pith,leaf,and sheath,and the differences in chemical components and biological morphology of different parts were studied.The study found that among the four parts,corn straw barkα-cellulose and lignin is the highest,The extract content in the pith is the highest,the ash content in leaves is the highest.The study of biological structure found that the content of vascular bundles in straw bark was high,arranged closely,with an average fiber number length of 1.17 mm and an aspect ratio of 80.41,making it more suitable for papermaking than other parts;The pith contains a large number of spongy miscellaneous cells,with vascular bundles embedded in parenchyma cells,and 89.54%of the fibers have an average length of less than 1.0 mm.Corn straw bark and pith cellulose are bothΙtype structure with relative crystallinity of 51.20%and 30.43%.On this basis,a hydrothermal treatment method that can be tailored to the specific characteristics of raw materials is selected to treat the entire stalk of corn straw.The changes of chemical components and microstructure of corn straw during hydrothermal treatment were studied.The study of chemical components found that the lignin removal rate reached a maximum of 43.28%when the treatment temperature was 190℃ and the holding time was 30minutes.The lignin removal rate decreased when the treatment conditions were further increased.Using scanning electron microscopy and laser confocal microscopy,the microstructure and lignin distribution of corn straw after hydrothermal treatment were studied.The results showed that the cell wall of corn straw was damaged to varying degrees,and the cells collapsed and separated.The intercellular sliding of the cell wall was earlier than the intercellular separation.Spherical particles appeared on the inner wall of the cell,which was determined to be lignin based on energy spectrum analysis of scanning electron microscopy;Laser confocal observation showed that the lignin removal from corn stalks had a sequential order,with the cell wall lignin removed first and then the intercellular layer lignin removed.Finally,the corn stalks subjected to hydrothermal treatment were ground using a vertical pulping machine,and the effects of treatment temperature and holding time on the strength of the pulp into paper were analyzed.The results showed that with the increase of temperature and time,the three showed a trend of first increasing and then decreasing.When the processing temperature was 190℃ and the holding time was 30 minutes,the obtained paper had the highest strength,with a resistance index of 26.99 N·m/g,an annular pressure index of 8.53 N·m/g,and a burst index of 1.01 KPa·m~2/g.The completion of this study further explained the law and mechanism of the dissolution of corn straw lignin during hydrothermal treatment.It lays a theoretical foundation for the hydrothermal treatment and utilization of corn stalks,and provides a possible treatment method for pithing and papermaking,providing theoretical support for large-scale utilization of corn stalks.