Preparation Of Cellulose Nanofibril-based Hydrophobic Composite Film

With the advancement of science and technology,there are increasingly urgent demand for specialty materials,but traditional chemical materials represented by petrochemicals,faced with serious pollution and unsustainable development problems.Therefore,efficient development and utilization of green,environmentally friendly and sustainable biobased materials has become a research hotspot in recent years.As a type of biobased material with abundant reserves and green and sustainable development,nanocellulose affects its high value-added utilization in the field of film materials due to its hydrophilic functional groups.To solve this problem,In this thesis used fiber as raw material,firstly,the preparation of cellulose nanofibrils?CNFs?with mechanical treatment was studied,and then inorganic materials were used to construct micro-nano protrusions and mixed with CNFs to form a film,and chemical vapor deposition was used to modify the low surface energy hydrophobic substance on the film surface,finally,hydrophobic composite films were obtained.Then the prepared hydrophobic composite film materials were analyzed and characterized by functional groups,contact angles,tensile strength and its microstructure,etc.,and the main research results were as follows:?1?Cellulose nanofibrils were prepared by high pressure microfluidizer machine processing fiber raw materials.As the number of mechanical treatments increased,the fibril size became more uniform,but increase in the number of mechanical treatments increased the energy consumption accordingly.The diameter of CNF ranged from 20to 25 nm.As the nanofibrillation progressed,the thermal stability of cellulose nanofibrils had decreased,the temperature of the maximum thermal degradation rate was around 363?.The functional groups of cellulose did not change.The crystallinity of CNF obtained after 15 mechanical treatments was 53%.Increasing the number of mechanical treatments was beneficial to improve the crystallinity,but too many mechanical treatments caused the crystallinity to decrease.?2?PCC-Si O₂ composite with micro-nano bumps was prepared by physical forces?van der Waals force,hydrogen bonding,electrostatic force?,and its particle size was relatively uniform,with a range from 820 to 950 nm,the CNF was mixed with it,and then CNF/PCC film,CNF/Si O₂ film,CNF/PCC-Si O₂ film materials were prepared by casting method,and the size of the micro-nano bumps formed on the surface of the film was relatively uniform.The hydrophobicity from small to large was:CNF/PCC film<CNF film<CNF/Si O₂ film<CNF/PCC-Si O₂ film.?3?The film material was hydrophobically modified with hexadecyl trimethoxysilane,prepared CNF hydrophobic film,CNF/PCC hydrophobic film,CNF/Si O₂ hydrophobic film,CNF/PCC-Si O₂ hydrophobic film.Four hydrophobic film materials were grafted with hydrophobic groups,the results showed that the CNF/PCC-Si O₂ hydrophobic film had the best hydrophobicity,its static contact angle was up to 157°,and the dynamic contact angle after 154 s was still as high as 104°,the dynamic contact angles of CNF hydrophobic film,CNF/PCC hydrophobic film,and CNF/Si O₂ hydrophobic film after 154 s were 57°,70°,and 72°,respectively.And the CNF/PCC-Si O₂ hydrophobic film had the highest tensile strength.