EFFECT AND MECHANISM OF POLYURETHANE TREATMENT ON PAPER

The methods of synthesizing polyurethane (Toluene, 2, 4-diisocyanate TDI and Isophorone diisocyanate IPDI) with paper of cotton pulp were investigated. The combination of multimedia microscope and IR analysis were used to analyze the chemical and physical characteristics and forming mechanism of the polyurethane derived from paper. On the conditions of dosage of TDI 10%, reaction time 10min and temperature 60 degrees C, facture length is elevated by 21.55%, folding strength is raised by 1.6times, and wet strength / dry strength by 41.61%; when dosage of IPDI 12%, time 10min and temperature 60 degrees C, the fracture length is heightened by 54.88%, the folding strength is enhanced by 4.1 times, and the wet strength/dry strength is raised by 41.19%. It was found that carbonate bond was formed between TDI and IPDI with cellulose in fibers when the paper was treated with TDI or IPDI. The treatment can change hydrogen bonds into chemical bonds and enhance the paper's physical strength. The hydroxyl of cellulose and - N=C=O produced the structure of amino formic acid ester, which formed as a bridge between the fibers. The hydrogen combining was transformed to chemical combining, which strengthened the intensity of single fiber and reinforced the combination of fibers. The treatment could change hydrogen bond into chemical bond and improve the paper's physical strength, especially the wet strength.