| In order to understand the influence of pre-polymers of polyurethane which have different hard segments/soft segments ratio on paper properties, the effect of molecule weight of polyethylene glycol was investigated. A series of pre-polymers were synthesized with imidazole, 2,4-diisocyanate (TDI) and six homologues of PEG, including PEG200, PEG400, PEG600, PEG800, PEG1000 and PEG1500. The application of the polyurethanes in paper coating was also investigated. Coating weights were 3 g/m2, 5 g/m2, 8 g/m2 and 10 g/m2 respectively. The physical properties of the coated paper were tested. It was found that different hard segments/soft segments ratio did not significantly affect wet tensile index, tear index and folding endurance of the paper. With the increase of the soft segment ratio, the dry tensile index and the stiffness decrease. The surface treatment can enhance the physical strength of paper significantly. Take imidazole-TDI-PEG (LTP400) as example, when the coating weight of LTP400 was 8 g/m2, the wet tensile index of the treated paper was increased by 10.7 times. Dry tensile index of the paper increased by 2.1 times. The folding endurance increased by 53.6 times. Moreover, the tear index and stiffness were also increased by 1.5 times and 1.3 times respectively. |
