Fluorescent Sodium Alginate Applied to Papermaking Furnish with Polyamideamine Epichlorohydrin

To explore the distribution of paper strengthening agent polyamideamine epichlorohydrin (PAE)/sodium alginate (SA) binary system in handsheets, SA was labeled by fluorescein isothiocyanate (FITC) to trace the system in paper. 1,6-diaminohexane was used to link SA and FITC to prepare fluorescein isothiocyanate sodium alginate (F-SA), and the optimal synthesis conditions of SA and 1,6-diaminohexane were evaluated. F-SA was identified by ultraviolet (UV) spectral scanning, Fourier transform infrared spectroscopy (FTIR), and fluorescence microscope. The PAE/F-SA binary system in the paper sheet was detected with a fluorescence microscope. The results indicated that FITC could successfully label SA marked as F-SA. The fluorescence substitution degree was 0.89%. Compared with the PAE/SA binary system, the PAE/F-SA binary system produced significant fluorescence in the paper, which indicated that the PAE/SA binary system was evenly distributed and formed a network structure in the handsheets. Furthermore, this method of fluorescence labeling could be employed in papermaking.