Solvent- and Catalyst-free Synthesis, Hybridization and Characterization of Biobased Nonisocyanate Polyurethane (NIPU)

Nonisocyanate polyurethane (NIPU) is a research hotspot in polyurethane applications because it does not use phosgene. Herein, a novel method of solvent- and catalyst-free synthesis of a hybrid nonisocyanate polyurethane (HNIPU) is proposed. First, four diamines were used to react with ethylene carbonate to obtain four bis(hydroxyethyloxycarbonylamino)alkane (BHA). Then, BHA reacted with dimer acid under condensation in the melt to prepare four nonisocynate polyurethane prepolymers. Further, the HNIPUs were obtained by crosslinking prepolymers and resin epoxy and cured with the program temperature rise. In addition, four amines and two resin epoxies were employed to study the effects and regularity of HNIPUs. According to the results from thermal and dynamic mechanical analyses, those HNIPUs showed a high degree of thermal stability, and the highest 5% weight loss reached about 350 °C. More importantly, the utilization of these green raw materials accords with the concept of sustainable development. Further, the synthetic method and HNIPUs don’t need isocyanates, catalysts, or solvents.

Effect of hard segments content on the properties, structure and biodegradation of nonisocyanate polyurethane

The present study investigates the biodegradation of synthesized condensation nonisocyanate polyurethanes (NIPUs). It was prepared by reacting phenol sulphonic acid and oligooxypropylene diol and formaldehyde and contained different amounts of hard segments (HSs). Polyurethane samples were submitted to biodegradation with microorganisms R-14 and in garden soil. The tensile strength (TS), relative elongation at break and weight loss of the prepared samples were evaluated and their structure and morphology analysed. It was found that maximum decrease of the TS of all tested NIPU samples occurred only after 7 days of biodegradation. Maximum TS decrease attained was approximately 70% and 75%, respectively, for NIPU based on 0.8-mol and 1-mol HS. Moreover, significant decrease of relative elongation at break and weight loss values after biodegradation in culture R-14 for NIPU samples based on 0.9-mol HS and 1-mol HS was observed. Fourier transform infrared and scanning electron microscopic results confirmed that biodegradation occurred in urea or urethane groups. The glass transition of HSs decreased by at least 20°C due to biodegradation, suggesting that this later took place almost only in the crystalline region of NIPU samples.