Preparation And Properties Of All-Cellulose Composites Based On Dissolution And Regeneration

In order to meet the needs of use performance and environmental performance at the same time,regenerated cellulose(RC)prepared from cellulose as a raw material can be used in daily life and other fields.Because it can control the preparation process and performance.However,the RC still facing some problems,such as high brittleness and poor disperibility.In this regard,all-cellulose composites(ACCs)can alleviate these problems.Using waste kraft paper as raw material and RC prepared by the regeneration system.This thesis studied how different coagulation baths effect the preparation of RC.In order to improve the performance of RC,different types of cellulose were composited to prepare high-performance and environmentally friendly biomass-based composite membranes and cellulose sphere.The specific research contents are as follows:The pulp cellulose was dissolved in Na OH/urea/thiourea/water composite solvent system and regenerated under different types of coagulation baths.It was found that the type of coagulation bath could affect the structure and properties of RC.SEM showed that the defects were easily presented when the cellulose was regenerated in the coagulation bath used.Particle size analysis and Zeta potential showed that the RC regenerated in different coagulation baths were charactered by different sizes and easily agglomerated.Itsζ-potential value was between-10.1 m V and-13.3 m V.The results of XRD and iodine color development indicated that the accessibility and crystal form of cellulose were affected by different coagulation baths.And these could attribute to coagulation baths could effect the surface properties of cellulose.In order to improve the performance of RC,it was reinforced with undissolved cellulose.And ACCs were prepared in a one-step method.FT-IR showed that after the cellulose was dissolved,the crystalline form of cellulose II predominated in ACCs.SEM and mechanical properties showed that when the precooling time was 90 min,a dense structure could be formed between the reinforcement and the matrix,which was conducive to maintaining the mechanical properties.Under this pre-cooling time,the ACCs composite film could reach the highest tensile strength.And the contact angle increased from 23° to 58.5°.The insoluble cellulose could improve the strength of matrix,change the brittleness of the RC,and then affect the performance of ACCs.In order to meet the requirements of mechanical properties,transparency and other properties at the same time,a spherical shape and a crystal structure of type II nanocellulose(QRC)was first prepared.When this QRC matrix was composited with an appropriate amount of oxidized nanocelluloses(TOCNs),the dispersibility of QRC could be improved,which were easily agglomerated by themselves before.However,the content of TOCNs will affect the mechanical strength and transparency of ACCs.XRD analysis results showed that,ACCs with different TOCNs content had different ratios of cellulose I to cellulose II,maintaining the characteristics of mixed crystal form.The dispersion results showed that the ζ-potential value of ACCs was-18.5 m V.The mechanical property analysis more intuitively showed that the QRC and the adjacent TOCNs could maintain good dispersion because there was no interface phase or few interface phases between them.And the highest tensile strength could reach 44.6 MPa.On this basis,cellulose spheres were prepared by using oxidized cellulose,sodium alginate(SA),and RC as raw materials.This kind of cellulose sphere could improve the mechanical properties and maintain its shape.