Eco-Composites of Polyurethane and Luffa Aegyptiaca Modified by Mercerisation and Benzylation
New eco-composites were prepared from castor oil polyurethane reinforced with Luffa cylindrica fibres. These fibres were used without treatment as well as after mercerisation and mercerisation/benzylation surface treatments. TG curves of mercerised Luffa showed a small increase in thermal stability, associated with the removal of polyoses and soluble lignin. TG curves of benzylated fibres showed a decrease in thermal stability (Tonset and Tmax.) and an increase in residual carbon due to aromatic ring insertion. FTIR spectra and elemental analysis also confirmed benzylation, and X-ray diffractograms showed a decrease in cellulose crystallinity. The eco-composite (crude fibre) absorbed more water (14% after 4 – weeks' exposure) than the resin, because of the hydrophilic character of natural fibres, but mercerisation and benzylation reduced this value by about 50%. Tensile moduli of composites reinforced with untreated and mercerised fibres were comparable, but increased by 33% with the use of mercerised/benzylated Luffa cylindrica. SEMs of the fibres and fibres-matrix interfaces are presented.