| In this paper,5 types of multistructure and multifunctional paper-based materials were successfully fabricated by using starch particles,starch nanospheres and starchbased polymer particles with various size,microstructures and properties as functional agents via internal sizing and surface modification.The special paper-based material with high sensitivity and absorption activity for formaldehyde;The paper-based package with moisture-proof and antibacterial activity;The paper-based material with radiating cooling ability;The paper-based material for oil/water emulsions breaking and separation;The paper-based material with pH-responsibility for separation of various types of emulsions and removal of dyes.The relation of the microstructures and properties of multifunctional paper-based materials were also systematically researched.The specific contents are as follows:1.A high sensitivity paper-based colorimetric sensor was fabricated through internal-sizing technology using amino-functionalized particles and micro native waxy corn starch as functional additives to realize effective detection of gaseous formaldehyde indoor.The polymer particles were fabricated via the dispersion polymerization of N-vinylformamide(NVF)and acrylonitrile(AN).Furthermore,the morphology,size and primary amine group content of the polymer particles could be regulated by adjusting the synthesis and hydrolysis conditions.In detection process,the amino functionalized polymer particles were used as sensing probes to capture formaldehyde in the paper surface,the waxy corn starch were used to reduce porosity of paper to improve the color uniformity and methyl red was used as pH indicator to express color change before and after contacting with formaldehyde.After exposure to 0.08 mg/m3 formaldehyde for 4 min,the color of the paper-based colorimetric sensor changed from pink to brown,and with the concentration of formaldehyde increasing,the color exhibited gradient change.Due to its easy-to-transport and high sensitivity,the paper-based colorimetric sensor must exhibit great significance for real-time and on-the-spot analysis of formaldehyde.2.A superhydrophobic and lyophobic paper-based materials was obtained through internal-sizing technology using micro S-FAS-PC and Ag@SiO2 composite as functional additives to realize 3D coating of paper fibers for fabricating hydrophobic and antibacterial packaging.Starch was successfully functionalized by(Heptadecafluoro-1,1,2,2-tetradecyl)trimethoxysilane(FAS)and palmitoyl chloride(PC)and named as S-FAS-PC.The hydrophilicity of starch was improved greatly by introducing long carbon chains of PC and low-surface-energy fluorocarbon chain.Then,the Ag@SiO2 composite particles was prepared via in-situ reduction of Ag+on the surface of SiO2.It was found that S-FAS-PC would adhere tightly to every cellulose fiber because of its good compatibility with cellulose fiber which could form a dense coating with low surface energy which decrease the water absorption and Ag@SiO2 composite particles filled in the fiber voids which inhibited the diffusion of water,so the moisture-proof ability would be improved.Furthermore,the superior water repellency ability of obtained multifunctional paper-based materials exhibited outstanding bacteria repellency performance and antibacterial activities.In addition,it also had a good self-cleaning ability.This paper-based materials can meet most requirements for package materials in current market,which is of strategic significance to carry out the policy of "replacing plastic with paper" and alleviate "white pollution".3.Starch was modified by PC and starch nanospheres(SNPs)with particle size of about 80 nm were successfully prepared by nanoprecipitation method.The F-TiO2 particles was prepared using FAS to modify TiO2 particles.A hierarchical micro and nano structure of modified paper-based materials was established via internal-sizing technology using SNPs and F-TiO2 particles as functional additives,which possessed high solar reflectivity(Rsolar)and high infrared thermal emissivity(∈IR).The unique optical characteristics of the obtained paper-based materials could reflect sunlight to the maximum and radiating excessive heat as infrared thermal radiation to the cold outer space through the atmospheric transparent window so that it has great potential to achieve passive daytime radiating cooling.By changing the dosage of F-TiO2 particles,the maximum of Rsolar and ∈IR reached to 0.90 and 0.91,respectively,and the surface temperature drop between the obtained paper-based materials and the original paper could reach to 6.7℃ under the direct sunlight.In addition,the wettability of the obtained paper-based materials could be regulated by adjusting the dosage of F-TiO2 particles and ratio of FAS and TiO2.The materials with proper wettability play a positive role in accelerating water collection under direct sunlight and a maximized water collection rate of 332.09 mg/cm2·h was obtained.Besides,the obtained paperbased material also showed a superior performance in the collection and separation of organic fog.This work provides a new idea for obtaining and relieve pressure of fresh water resources.4.Two kinds of modified paper-based materials(P-C and P-S)were fabricated using SNPs by spraying-coating or internal-sizing technology to compare its oil/water separation performance and put forward corresponding mechanism.It was found that the WCA of P-C and P-S was 130° and 135.1° at beginning,and decreased to 64.7° and 131.8° after 30 minutes,respectively.Compared with P-C,the SNPs evenly distributed on the surface and internal fibers of P-S which could produce a repulsive force to repel water diffusion and showed persistent hydrophilicity.Under the joint effects of structures and wettability,P-S exhibited superior oil/water separation ability for different water in oil(W/O)emulsions with a separation efficiency of 99.9%.As for the separation flux,it related to the density of oils.For heavy oils,its separation flux could reach to 138.2 L/m2·h and for light oils,its separation flux was only 31.91 L/m2·h.5.W/O Pickering emulsions were successfully stabilized using SNPs instead of traditional surfactants.And the modified paper-based materials with raspberry-like hierarchical micro-and nano-structures were fabricated via in-situ W/O Pickering emulsions polymerization using acrylic acid and acrylamide as monomers,N,Ndimethylacrylamide as crosslinker and 2-Hydroxy-4’-(2-hydroxyethoxy)-2methylpropiophenone as initiator.According to the results,the modified paper-based materials exhibited obvious pH-responsibility because of abundant-COOH groups.Under acidic conditions,the modified paper-based materials showed hydrophobicity,oleophilicity and underoil superhydrophobicity,while under basic conditions,it showed hydrophilic,oleophilic and underwater superoleophobicity.Combining its rough hierarchical micro-and nano-structures,the modified paper-based materials can realize W/O and O/W emulsions separation with more than 99.9%of separation efficiency by adjusting pH.Meanwhile,the modified paper-based materials also can achieve dyes removal rapidly and efficiently during the process of oil/water separation because of the electrostatic interaction with abundant carboxyl groups.We believe that this work must have a bright application prospect in treatment of industrial wasteliquid. |
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