Analyses of structures for a synthetic leather made of polyurethane and microfiber

Abstract A gradient extraction method was developed and used for a synthetic leather made of polyurethane (PU) and microfiber polycaprolactam (PA‐6), by which the two components were separated using DMF and formic acid as solvents, respectively. Their chemical structure was confirmed by FTIR spectra, and the result showed that the PU is a kind of polyester polyurethane with phenylene rings in the molecule. The condensed phase structure was analyzed using X‐ray diffraction (XRD). The crystallinity of the PA‐6 is about 65.6%, and for the PU, there was not distinct crystalline character shown in the XRD pattern but a phase separation structure of hard block‐soft block with the hard domains content about 58.7%. SEM images showed that the PA‐6 microfibers transfixing the PU matrix form a net bundle structure, and there are two kinds of porous structures in the synthetic leather, with one type of pore sized 5–80 μm between the components of PU and PA‐6, and the other in PU matrix with a size of 0.1–2 μm. The multipores run through the synthetic leather as three‐dimensional channels, benefit for transportation of air, water, dyes, and so on. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 903–908, 2007