XRD studies of chitin-based polyurethane elastomers

Chitin-based polyurethane elastomers (PUEs) were synthesized by step growth polymerization techniques using poly(ɛ-caprolactone) (PCL) varying diisocyanate and chain extender structures. The viscosity average molecular weight (Mv) of chitin was deduced from the intrinsic viscosity and found; Mv = 6.067 × 105. The conventional spectroscopic characterization of the samples with FTIR, 1H NMR and 13C NMR were in accordance with proposed PUEs structure. The crystalline behavior of the synthesized polymers were investigated by X-ray diffraction (XRD), differential scanning calorimetery (DSC) and loss tangent curves (tan δ peaks). The observed patterns of the crystalline peaks for the lower angle for chitin in the 2θ range were indexed as 9.39°, 19.72°, 20.73°, 23.41° and 26.39°. Results showed that crystallinity of the synthesized PUEs samples was affected by varying the structure of the diisocyanate and chain extender. Crystallinity decreased from aliphatic to aromatic characters of the diisocyanates used in the final PU. The presence of chitin also favors the formation of more ordered structure, as higher peak intensities was obtained from the PU extended with chitin than 1,4-butane diol (BDO). The value of peak enthalpy (ΔH) of chitin was found to be 47.13 J g−1. The higher ΔH value of 46.35 J g−1 was found in the samples extended with chitin than BDO (39.73 J g−1).