Structure and solvent-resistant property of fluorinated polyurethane elastomer

A series of main-chain fluorinated casting polyurethane elastomer (CFPU) based on fluoropoly(oxyalkylene)diol (FPOA) were prepared via bulk polymerization and prepolymer process. Polybutylene adipate glycol (PBA) was combined with FPOA as a soft-segment. It was found that the significant difference of solubility parameters of PBA soft-segment and FPOA soft-segment, and two detectable peaks corresponding to the Tg of these two segments from DMA analysis indicated that the two blocks were immiscible and formed the phase separation structure. By SEM analysis, three types of micro-structure of CFPU can be observed. With increasing FPOA/PBA mass ratio, the size of the spherical dispersion phase formed by PBA soft-segment block embedded in FPOA soft-segment block declined, and the more uniform dispersion and the more clear interface indicated the increasing phase separation. With increasing FPOA/PBA mass ratio, the equilibrium swelling ratio and the swelling rate constant k in cyclohexanone and xylene decreased, while for the sample after etching in cyclohexanone, the matrix folds almost disappeared, and the “worm like” structure became unobvious, resulting in an enhanced solvent resistance of CFPU by a shield protective effect of FPOA soft segment on the hydrocarbon chain segment. Moreover, the migration of fluorine atoms to the surface of the sample of CFPU resulted in a decrease of surface polarity and the surface tension. With increasing FPOA/PBA mass ratio, the tensile strength and elongation at break, hardness and storage modulus all decreased.