Modification of Waterborne PU Finishing Agent with Hydroxyl Silicone

In the present paper, a waterborne polyurethane (PU) finishing agent was synthesized with isophorone diisocyanate (IPDI), polytetrahydrofuran (PTMG), dimethylol propionic acid (DMPA) and n-butylamine, in which hydroxyl-terminated polydimethylsiloxane (OHterminated PDMS) was added in three different ways, i.e., one-step, two-step and as a chain-extension agent. The PU was characterized using FT-IR and DSC and the water resistance and dry/wet rubbing resistance of the PU films were studied and compared. It was found that the chain segments by the reaction with OH-terminated PDMS and IPDI act as hard segments, and the elongation at break and water resistance of PU with OH-terminated PDMS as chain-extension agents are better than those with OH-terminated PDMS in both ways of one-step and two-step. The elongation at break could reach 1300% with the water absorption of only 1/4 of the latter PU films, when the same amount of OH-terminated PDMS is added in the system. It is better that OH-terminated PDMS is added in the top layer than added in the middle layer. The dry rubbing resistance could reach grade 5 with the wet rubbing resistance of grade 4.5.