Study On Structure And Properties Of Silicone And Crosslinked Double Modified Waterborne Polyurethane-Acrylate

Waterborne polyurethane(WPU)exhibited many distinctive properties and advantages,including excellent mechanical strength,flexibility,adhesion,chemical resistance,durability,nontoxicity,harmless and environmentally friendly.However,due to using water as a dispersing agent,the hydrophilic groups(such as-COOH,-OH etc.)need to be introduced to polyurethane to improve the poor hydrophilicity,which greatly weaken the water resistance.In order to avoiding the erosion of water on structures of polyurethane,the reasonable strategy should be designed to fabricate water-resistant waterborne coatings based on the effective modification of molecular structure for polyurethane.Herein,we prepared a waterborne polyurethane coating with excellent combination property though molecular modification of polyurethane using silicone(PDMS),cross-linking agent and acrylate.Waterborne polyurethane is synthesized using polytetrahydrofuran diol(PTMG),isophorone diisocyanate(IPDI),dimethylolpropionic acid(DMPA),hydroxyl terminated polydimethylsiloxane(PDMS).The introduction of cross-linking agents of castor oil(C.O.)and trimethylolpropane(TMP)was used to prepare a series of cross-linked waterborne polyurethane emulsions.And the mechanical properties and water resistance of WPU were systematically studied.WPU crosslinked by TMP exhibited excellent mechanical performance and heating resistance,comparing to that crosslinked by C.O..However,the WPU modified by C.O.presented a better water-resistant behavior.The polyurethane film with 2w% TMP presented the largest contact angle 88.8°,and the best mechanical properties with 31.27MPa;the film with 12w% C.O.possess the largest contact angle 94.3°,the lowest water absorption and the best water resistance.As for the WPU modified by CO and PDMS,the WPUA emulsion and performance of the film with different kinds of acrylate monomers(MA,EA,BA,EHA,IBMOA)were discussed based on the emulsion particle size,FTIR,TG,TEM and water resistance test.Moreover,the emulsion particle size test,scanning electron microscopy,infrared spectroscopy,dynamic mechanical testing and water resistance tests were used to explore the effects of acrylate monomer on polyurethane properties.The water absorption ratios of polyurethane with different acrylate monomers decreased with the increase of molecular chain flexibility,The lowest water absorption rate is 6.78%.It was because that the improvement of flexibility significantly increases the molecular gap,leading to the increase of water absorption ratio.Based on the results of dynamic mechanical analysis,the peaks of the hard segment and the soft segment of the WPU film modified by EHA are closest,and the WPU exhibited the better compatibility comparing to that of MA.The WPU films modified by EHA demonstrated the remarkable optical properties with largest transmittance and the lowest haze in a series of samples.