Preparation and characterization of high-strength elastomers with high poly(trifluoropropylmethyl)siloxane content into polyurethane urea

A series of poly(trifluoropropylmethyl)siloxane-block-polyurethane urea (PUUFS) films containing over 30 wt% poly(trifluoropropylmethyl) siloxane (PFS) were prepared via the three-step process that the prepolymer was synthesized from poly(tetramethylene oxide) (PTMO) and toluene diisocyanate (TDI), chain-extended with alpha,omega-bis(3-aminopropyldiethoxylsilane) poly(trifluoropropylmethyl) siloxane (APFS), and then with 3,3'-dichloro-4,4'-diaminodiphenylmethane (DDDPM). The films were formed through moisture curing and they were characterized using Fourier transform infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy, X-ray Diffraction, dynamic mechanical analysis, thermogravimetric analysis, mechanical testing, and so on. The influence of the concentration ratios between hard and soft segments (C-HS/C-SS) on the microstructure and properties of the materials was investigated. Higher crosslink densities or extent of hydrogen bonding that result from higher hard segment concentrations enhanced the mechanical properties of the materials. The extent of the phase separation of materials initially decreased and then increased as the C-HS/C-SS elevated from 1.85 to 4.13. The material with a C-HS/C-SS of 3.01 exhibited the lowest phase separation and the highest crystallinity and tensile strength. In addition, the trend of the surface properties of the materials was similar to the change in tensile strength and associated with phase separation, hydrogen bonding, and crosslinkage. Moreover, the copolymer may have practical applications in coatings and adhesions.