Study On The Structure And Properties Of Carboxymethyl Cellulose Rare Earth Composite Film And Its Application In Anti-counterfeiting Paper

Carboxymethyl cellulose?CMC?has attracted attention because of its advantages of being renewable and biologically non-toxic.The preparation of ionic metal-polymer composite films based on CMC is conducive that could fix the traditional composite films.Traditional films are expensive and difficult to degrade within low strength and modulus.This study is not only developing the high-value utilization of cellulose,but also improving the economic efficiency and environment.In this paper,CMC/Tb-Eu and CMC/Eu???composite films were prepared by using CMC and rare earth metal ions Tb³⁺and Eu³⁺.The entanglement model between CMC and CMC/Tb-Eu macromolecules was established to study the structure-performance relationship of the composite film.In addition,CMC/Tb-Eu and CMC/Eu???anti-counterfeiting paper were prepared by calendering the composite film.The main conclusions of this article are as follows:?1?The entanglement model between CMC and CMC/Tb-Eu macromolecules was confirmed by studying the changes of rheological behaves during the drying process of the film forming solutions.The dynamic modulus showed that the rheological properties of film forming solutions with different CMC/Tb-Eu contents changed significantly during the drying process.The Han curves of all initial film forming solutions could overlap well.According to the XRD data of the composite films,the crystallinity of the composite film was 23.1%,23.0%,18.6%and 15.8%with the increase of CMC/Tb-Eu content.These results confirmed that there were interactions between CMC and CMC/Tb-Eu macromolecules.And the interactions were not hydrogen bonding but random entanglements.Combined with the complex viscosity and relaxation time spectrum of the film forming solutions,it also confirmed that the degree of macromolecular entanglements in the model increased with the increase of the CMC/Tb-Eu content,and the entanglements were not uniform in the film forming solution with a CMC/Tb-Eu content of 0.3 g.Addition of CMC/Tb-Eu could decrease the interactions between CMC chains.The AFM graphs showed that the average roughness of the composite films increased due to the increase of entanglements,which was1.42,3.79,5.03,and 5.60 nm,respectively.Combined with the SEM image,it could be seen that the surface of the composite film was flat and smooth,and the cracks were disappeared as the degree of entanglements increased.It could be seen from the cross-sectional view that the composite film had a dense cellulose aggregation structure.Due to the uneven entanglements of the composite film with a CMC/Tb-Eu content of 0.3 g,the phenomenon of uneven thickness of the sheet was also observed.As a result,its tensile strength decreased compared with the composite film with CMC/Tb-Eu content of 0.2 g,from 78.76MPa to 59.25MPa.At the same time,the fluorescence intensity of the composite film decreased due to the concentration quenching caused by the uneven entanglement.The above results showed that the model established through rheological studies during the film drying process could effectively explain how the interaction between macromolecules affected the structure and properties of the composite films.?2?Using the J-O theory to quantitatively calculate the optical transition intensity parameters of the characteristic ⁵D₀?⁷F₁magnetic dipole transition and ⁵D₀?⁷F₂,⁵D₀?⁷F₄electrical dipole transition of Eu³⁺in CMC/Eu???composite films.Its?₂with increasing CMC/Eu???content was 9.1676,7.1672 and 5.9842,and?₄with increasing CMC/Eu???content was 0.0838,0.1135 and 0.0314,respectively.The trend of?₂being greater than?₄indicated that there was a covalent bond between Eu³⁺and the ligand CMC and asymmetry around the Eu³⁺site.Further calculations showed that the fluorescence branching ratios of⁵D₀?⁷F₂transitions of all samples were 87.01%,83.69%,and 81.54%,and the radiation lifetimes were 3.0895,3.8193,and 4.4567 ms,which meant that no concentration quenching phenomenon of CMC/Eu???composite films was observed within the scope of this experiment.?3?The anti-counterfeiting paper,prepared by a simple and effective method,could display neatly arranged circular fluorescence under the ultraviolet lamp.It indicated that the anti-counterfeiting paper prepared in this paper could control the shape,quantity and position of fluorescent substances more effectivdely.The fluorescence spectrum showed that the emission peak of the⁵D₄?⁷F₅characteristic transition of Tb³⁺located at 545nm was the highest in the emission spectrum of the anti-counterfeit paper.The emission peak at 593nm emission peak at 615nm was composed of the ⁵D₄?⁷F₃transition of Tb³⁺and the ⁵D₀?⁷F₂transition of Eu³⁺,indicating that the anti-counterfeiting paper retained the characteristic fluorescence emission of rare earth ions.By comparing the structure and properties of CTE anti-counterfeiting paper and CE anti-counterfeiting paper,it was found that only fluorescence performed a large difference,while the difference in other aspects could be neglected.It showed that our purpose of color control could be achieved by adjusting the ratio of rare earth ions in anti-counterfeiting paper.Above results indicated that the anti-counterfeiting paper prepared in this paper could be completed by using traditional paper-making equipments.The lab-made anti-counterfeiting paper had fluorescent substance which was hard to stack and break.As a result,it had certain potential in anti-counterfeiting applications.