Preparation And Application Research Of Biomass-based Waterproof Coating Materials

Biomass resources are of great significance in coping with climate change and solving environmental pollution problems,especially in the packaging industry.The release of the"Plastic Restriction Policy"has brought significant attention to paper-based materials as a green and biodegradable packaging material.However,the hydroxyl groups and porous structure on the surface of the paper-based materials restrict their water resistance,which remains a key limitation for their widespread application.Compared with traditional waterproof paper preparation technologies such as lamination and chemical modification,waterproof coating can effectively improve the surface properties of paper-based materials,and does not require complex chemical reactions,which is a simple and efficient method.However,the preparation of waterproof coatings still has the following problems.First,fluorides,which are commonly used to reduce the surface energy of paper,have biotoxicity and bioaccumulation that are harmful to human health and the environment.Then,the low reaction efficiency forces most of the current research to use toxic organic solvents.In addition,the durability and stability are poor,and the raw materials are usually non-renewable.Based on these,the paper focuses on the selection of low surface energy materials,the construction of water-based systems,the design of microstructures,and the improvement of coating durability.The preparation and application performance of environmentally friendly paper-based waterproof coatings were investigated through the following research:（1）From the perspective of the selection of low surface energy materials,natural fatty acids（oleic acid,OA）were selected as low surface energy modifiers to realize the application of renewable raw materials in waterproof coatings.Firstly,the hydrolysis reaction of3-（mercaptopropyl）trimethoxysilane（MTS）produces silicon hydroxyl group（Si-OH）and forms hydrogen bond with hydroxyl group（-OH）of the paper surface,and then uses thiol-ene click chemical reaction to successfully grafting OA to achieve low surface energy modification of paper-based materials,and finally obtain biomass-based waterproof coated paper.The surface energy of the paper modified by the waterproof coating was significantly reduced,only 10.35±0.76 m N/m.The finally obtained waterproof coated paper has a water contact angle of 133°,and the water absorption rate and Cobb（60）value are significantly reduced,showing excellent water resistance.In addition,the waterproof paper is biocompatible and can be completely degraded in soil within 70 days,showing green and environmentally friendly properties.（2）From the perspectives of the selection of low surface energy materials and the design of the water-based system,the Pickering beeswax emulsion with stable dispersion in water was prepared by using hemicellulose-grafted lauric acid（H-LA）micelles as the nano-stabilizer,and it was used as a low surface energy modification substance to act on the surface of the paper-based material by simple spraying,and an all-biomass-based water-based waterproof coated paper was successfully prepared.The uniform dispersion of beeswax in water benefits from the H-LA micelle nano-stabilizer,which is an important guarantee for the successful introduction of long-chain alkanes on the surface of paper to achieve low surface energy.In addition,the wax emulsion modifies the paper fibers while filling the fiber pores,forming a dense waterproof layer on the surface of the paper.The final waterproof paper has a water contact angle of 130°,an effective waterproof time of up to 6 hours,and excellent moisture-proof performance,with a water vapor transmission rate of less than 5.05g·mm/m²/d.In addition,the all-biomass coating system is non-toxic,environmentally friendly,and biocompatible,and the waterproof paper can be completely degraded in soil within 2months.This work provides an alternative solution for sustainable paper-based packaging materials to replace single-use plastics.（3）On the basis of low surface energy modification,the microstructure of the coating was designed,and the water-based biomass-based superhydrophobic coated paper was developed.Using cellulose nanocrystals（CNC）as a nano-stabilizer,low surface energy hexadecyltrimethoxysilane（HDTMS）was stably dispersed in water in the form of Pickering emulsion,and passed through 3-aminopropyltriethoxy silane（AS）further promoted the long-chain silane modification of CNC,and finally,a water-based biomass-based superhydrophobic coating was prepared in one step.The results of FTIR and XPS showed that the nanoemulsification of CNC promoted the dispersion of HDTMS in water and improved the reaction efficiency of HDTMS.The Si-OH produced by the hydrolysis of AS binds to the-OH of the CNC through hydrogen bonding,and further forms Si-O-Si bonds through the hydrolysis condensation between silanes,realizing the hydrophobic modification of CNC.At the same time,the CNC embedded AS-HDTMS polymer successfully constructed the micro/nano hierarchical rough structure of the coating.The surface energy of the superhydrophobic transparent coated paper obtained by spraying the water-based coating is reduced to 0.79±0.02 m N/m,and the surface roughness is about 10 times that of the base paper.The coated paper exhibits excellent superhydrophobicity,the water contact angle reaches 155°,the sliding angle is only 1°,and its Cobb（60）value is close to 0 g/m²,the water absorption rate is less than 10%,and hot water does not seep within 30 minutes.The composite structure of CNC and polymer forms a stable and strong coating surface,and the-NH₂of AS promotes the combination of paper and coating,making the waterproof coating of paper have excellent mechanical durability.In addition,the coated paper is biocompatible,degradable,and recyclable（pulp recovery rate>90%）,and does not use any organic solvents in the preparation process,which has guiding significance for the preparation of water-based green superhydrophobic coatings.（4）Based on the design of the waterproof coating,a multifunctional water-based superhydrophobic coating was designed to promote the high-value application of paper-based materials.Using functional graphene oxide（GO）and high aspect ratio bacterial cellulose（BC）as Pickering emulsion stabilizers to emulsify HDTMS and react with AS,a functional superhydrophobic coating was prepared by one step in aqueous medium.And it was sprayed on the paper,and the multifunctional superhydrophobic coated paper was successfully prepared.During this process,AS and HDTMS were hydrolyzed and condensed to generate hydrogen bonds with the hydroxyl groups on the surface of GO and BC to realize the hydrophobic modification of GO and BC.The water-based coating is used to modify the paper by spraying,and the-NH₂ functional group of AS provides a good combination between the paper and the coating.The surface energy of the obtained coated paper was0.93±0.09 m N/m,and the roughness increased to about 20 times that of the base paper.The addition of BC facilitated the homogeneous dispersion of GO within the coating.BC and GO combined to form a three-dimensional micro/nano hierarchical rough structure,resulting in a superhydrophobic coating with outstanding mechanical durability.The coated paper,with the addition of 10%BC,exhibits a contact angle of 154°and a sliding angle of 1.5°,indicating its superhydrophobic properties.It also demonstrates low Cobb（60）value and water absorption,effectively blocking hot water.Additionally,the coated paper shows multifunctionality,including photothermal conversion,antibacterial properties,and flame retardancy.Furthermore,this superhydrophobic paper is biodegradable and recyclable.The preparation process is environmentally friendly,devoid of organic solvents,and the reaction is simple,allowing for large-scale production.These features highlight its exceptional practical value and promising applications.