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ABSTRACT:The surface structure and physical properties of polyethylene glycol series polyurethane (PEG-PU) membranes, in which were introduced hydrophobic polydimethylsiloxane (PDMS) component by the procedure of PU blending or of soft-segment copolymerization, were studied in this investigation. In the case of the blending process, the synthesized waterborne polyurethanes (WBPUs) of PEG-PU and of polydimethylsiloxane series polyurethane (PDMS-PU) were combined, whereas in the copolymerization process PEG and PDMS were taken as mixed soft segments to polymerize the WBPU. For the blending method, glass-transition and melting temperatures increased rapidly when a small amount of PDMS-PU was added to PEG-PU and reached a maximum with 5% PDM-S-PU mixed in. However, in the case of the copolymer method, thermal properties closely followed predicted values. From dynamic mechanical analysis studies it was found that a low PDMS-PU content ratio could increase the rubbery elasticity of PEG-PU membrane and improve its strength simultaneously in the blending method, and the copolymer method only caused PU to gain some natural complementary strength and elasticity. Electron spectroscopy for chemical analysis studies indicated that PDMS migrated to the surface much more easily in the blending method than in the copolymer method. The SEM studies also found that, in the blending method, the numbers of pores were less than those in the copolymer method.

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Polydimethylsiloxane polyurethane (PDMS-PU), which was synthesized from PDMS as the soft segment, was blended into a variety of ester-or ether-based softsegment waterborne polyurethanes with different concentrations to investigate the crystallization, thermal, and physical properties of the membrane formations. According to X-ray analysis, the ether-based PUs, synthesized from soft segments of poly(propylene glycol) (PPG1000) or poly(ethylene glycol) (PEG2000), were found to have maximum crystallinity at a 5% blending ratio of PDMS-PU, but the ester-based PU, synthesized from soft segments of polycaprolactone (PCL1250), had decreased crystallinity at a 5% blending ratio. Differential scanning calorimetric analysis revealed that the T g,s values of PUs were highest when the blending ratio of PDMS-PU was 5%-10%, except for PU from PCL1250. Moreover, ether-based PUs showed maximum T m,h values, but the T m,h of the ester-based PU was greatly reduced when PU with PCL1250 was blended with PDMS-PU. In addition, the PU from PEG2000 had the highest melting entropy. Mechanical property analysis showed that the stress of ether-based PUs would be increased when PUs were blended with a small amount of PDMS-PU and that the stress of PU from poly(tetramethylene glycol) (PTMG1000) increased to its greatest value (20 -30 MPa). On the other hand, the ester-based PU, from PCL1250 blended with PDMS-PU, would have reduced stress. On the whole, the stress and strain of PU from PEG1000 had excellent balance.

This study of waterborne polyurethane prepolymer blends was done to investigate the effects of different types of soft segments on the dispersion properties and other properties of treated nylon fabrics. The particle size of the dispersion increased, the surface tension of the dispersion decreased, and the contact angle of the nylon fabric with the dispersion decreased when the blending amount of the polydimethylsiloxane polyurethane prepolymer increased. The add-on of ether-type polyurethane increased rapidly when the ether-type polyurethane was blended with a small amount of the polydimethylsiloxane polyurethane prepolymer, whereas the add-on of the ether-type polyurethane reached a maximum at a blending content of 10%. The add-on of the ester-type polyurethane prepolymer constantly decreased with increasing blending amount of the polydimethylsiloxane polyurethane prepolymer. The vertical wicking height of the treated nylon fabrics decreased slightly when the treating agent contained a small amount of the polydimethylsiloxane polyurethane prepolymer. For the treated nylon fabrics with blended prepolymers, the drying time was faster than for the untreated fabric, and the moisture ratio reached about 10% in 15 min