Crystallization and thermal properties in waterborne polyurethane elastomers: Influence of mixed soft segment block
Abstract
A series of nontoxic biodegradable waterborne polyurethane (WBPUs) elastomers were synthesized by two-step polymerization, using isophorone diisocyanate (IPDI), 1,4-butandiol (BDO) and L-lysine as a chain extender and a range of soft segments with various macrodiols composition. The soft segment was formed by replacing polycaprolactone diol (PCL) as a polyester type polyol with hydrophilic polyether type polyol.
Hydrophilic poly(ethylene glycol) (PEG) or poly(propylene glycol) (PPG) different block lengths were used to this purpose. Fourier-transformed infrared spectroscopy (FTIR) was used for evaluation of degree of phase separation.
The effect of the soft segment composition on the thermal properties of polyurethane elastomeric films was investigated by means of thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). The thermal stability of materials is influenced by composition of soft segments and it was explained by the effect of oxygen content of polyether polyols, the length polyether block and interaction between the soft and hard segment.
The wide-angle X-ray scattering (WAXS) is used to investigate the degree of crystallinity of PCL in soft segment of WBPUs. It was found that the polyether polyol length in the soft segment had a significant influence on degree of microphase separation in the soft and hard segment and crystallization behaviour of the materials.
The restriction of the crystallization of the PCL soft segment depends on the hard segment content and length of the polyether polyol. The results show that the properties of polyurethanes prepared are directly related to the soft segment composition and can be varied easily for a different set of properties that are significant for biomaterial application.