Structure-property relationships of novel fluorinated polycarbonate polyurethane films with high transparency and thermal stability

Novel polycarbonate diol (PCDL) was synthesized using dimethyl carbonate, 1,5-pentanediol (1,5-PD), 1,6-hexanediol (1,6-HD) and 1,4-cyclohexanedimethanol (1,4-CD) by a two-step method. Fluorinated thermoplastic polycarbonate polyurethanes (FPCUs) have been synthesized with novel PCDL as the soft segment and 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate and compound chain extenders [1,4-butanediol (BDO), 1,2-propanediol (PG) and 2,2-bis (4-hydroxyphenyl) hexafluoropropane (BPAF)] as the hard segment. A series of FPCU films was prepared and investigated to elucidate the effect of the different chain extenders on the structure and properties. Morphological, optical performance, thermostability and mechanical properties of FPCU films have been studied by Fourier transform infrared (FTIR) spectrometry, wide-angle X-ray diffraction (WXRD), atomic force microscopy (AFM), UV-visible (UV-Vis) spectrometry, thermogravimetric analysis (TGA) and mechanical tests. As the increase of thefluorine chain content, the increase of immiscibility between soft and hard microdomains has been obtained from the FTIR, AFM and WXRD measurements. UV-Vis tests showed that the transmittance of FPCU films decreased with the increase of crystallization, which resulted in superior mechanical properties such as higher tensile stress and tear strength. TGA tests indicated that the thermal stability of FPCU films was improved significantly with the introduction of BPAF.