Study On The Optical Security Features Of NCC Based Ink

Nanocrystal cellulose(NCC) is a natural nano-material owning superior properties, and particularly suitable as a filler in high-performance composite materials. It can be given more characteristic through the functional modification on its surface, showing great application prospects in many fields.NCC suspension was prepared by the method of acid hydrolysis with 60% sulfuric acid at 35℃. The structures and properties of NCC were characterized and investigated. The results showed that the products belonged to be cellulosic substances and had the rod-like structures. The NCC had dimensions varying from 10-30 nm in diameter and 100～500 nm in length. The NCC had good thermal stability.Graft polymerization could not only reduce the content of hydroxyl groups on the NCC surface, but also introduce new functional groups, which could further improve the functionality of NCC without changing their intrinsic properties. Nanocellulose whiskers’ modification by the sodium chloroacetate were investigated, respectively, in this thesis.Based on the mechanism. NCC was conducted the etherification reaction, before mercerized. The carboxymethyl nano-cellulose whiskers(CMNCC) was prepared by modification of sodium chloroacetate, analyzed by single factor experimental method. It was showed that the DS at 0.11 was obtained when the alkalization time and etherification time were 30 and 60 min, the alkalization temperature and etherification temperature were 25 and 60℃. respectively. CMNCC were characterized by FT-IR, SEM, DSC, laser particle size analyzer and Zeta potential testing. The FT-IR spectrum showed that the modified product owning the basic structure of the cellulose molecule is a cellulosic-1 substance. While the product is carboxyl group absorption peak at about 1608 cm-1 indicating that the carboxyl group is connected to the NCC structure. TEM analysis showed that the CMNCC owns the same rod-like structure with NCC and the morphology didn’t change significanly. The particle diameter is sbout 10-30 nm. and the length is about 100-400 nm. The dispersibility has been significantly improved. DSC analysis shows that the stability of NCC modified is improved. The laser particle size analysis also showed that the modification can reduce the particle size and improve the stability of the suspension system.To CMNCC as the carner, the cationic fluorescent yellow 40 was assembled to the surface of CMNCC by electrostatic self-assembly technique. It was showed that the greatest degree of self-assembly was obtained when the quality ratio of fluorescent yellow of 40 and CMNCC reached 1:1.54 × 103.Fluorescent Yellow 40 owns a significant absorption peaks at the wavelength of 441 nm, and excitation wavelength of the single photon fluorescence is 450 nm, the maximum emission wavelength is 495 nm, same as fluorescent yellow 40, but the fluorescence intensity has significantly increased compared with fluorescent yellow 40. The fluorescence intensity of fluorescent ink is evidently decreased under different aging time, and the change of fluorescence intensity presents a gentle trend after 160 h, substantially reduced to 0. This water-based fluorescent ink is most suitable for screen printing.