Borja Fernández-d’Arlas

Comparison between exfoliated graphite, graphene oxide and multiwalled carbon nanotubes as reinforcing agents of a polyurethane elastomer

A highly crystalline aliphatic segmented polyurethane (PU) elastomer with 40 wt% hard segment (HS) content, based on 1,6-hexamethylene diisocyanate and 1,4-butanediol as the HS, and a block copolymer of hexamethylene carbonate and polycaprolactone as the soft segment (SS), has been used as the matrix to prepare carbon nanofiller/PU composites by solution casting. Composite films with different loadings of solvent-exfoliated graphene (G)/nanographite, graphene oxide (GO) obtained by the so-called modified Hummers method, and acid-treated multiwalled carbon nanotubes (MWCNT) were obtained and characterised. Tensile test results show that the effectiveness of increasing PU strength follows the trend MWCNT > GO > G. The ductility reduction in all the cases is related to the large sizes of nanofillers in relation to PU hard domains and the hindrance to allow plastic flow of PU SSs by larger fillers.

Effect of Diisocyanate Structure on Thermal Properties and Microstructure of Polyurethanes Based on Polyols Derived from Renewable Resources

Polyols derived from renewables resources are good candidates to obtaining segmented polyurethane elastomers. Diisocyanates with different chemical structure, aliphatic and aromatic, have been used to synthesize by a two step polymerization procedure polyurethane elastomers with different hard segment content. Microphase separation and thermal stability have been studied using attenuated total reflection Fourier transform infrared spectroscopy (ATR‐FTIR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The analysis of the H‐bonded and non H‐bonded urethane carbonyl stretching vibration in the amide I region, the glass transition temperature of the soft and hard segments and the melting temperature and enthalpies of hard segment reveal that aliphatic diisocyanate based polyurethanes present higher phase separation degree and harder segment crystallinity and also superior thermal stability than aromatic diisocyanate‐based polyurethanes.