Effects of NCO/OH molar ratio on structure and properties of graft-interpenetrating polymer networks from polyurethane and nitrolignin

• Published in: Polymer (Guilford) 2002-04, Vol.43 (8), p.2287-2294
• Main Authors: Huang, Jin, Zhang, Lina
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Lignin and derivatives; Natural polymers; Physicochemistry of polymers
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/s0032-3861(02)00028-9

A series of graft-interpenetrating polymer networks (graft-IPNs) with different NCO/OH molar ratio was synthesized from castor oil-based polyurethane (PU) and nitrolignin (NL) by changing the content of 1,4-butanediol as chain-extender. The effects of NCO/OH molar ratio on the morphology and properties of the PU--NL films (UL) were investigated by infrared, wide-angle X-ray diffraction (WAXD), differential scanning calorimetry, dynamic mechanical analysis, and tensile test. WAXD patterns showed that all the UL films were nearly amorphous. With an increase in NCO/OH molar ratio, the glass transition temperature (T sub g ), the stiffness and tensile strength ( sigma sub b ) increased, while the breaking elongation ( epsilon sub b ) and strain recoverability (Re) decreased. The UL films with 1.20 of NCO/OH molar ratio exhibited the maximum value of tensile strength ( sigma sub b =30.2 MPa; epsilon sub b =152%). 2.8 wt% NL plays an important role in the simultaneous enhancement of sigma sub b and epsilon sub b of the UL films. Solid-state exp 13 C nuclear magnetic resonance ( exp 13 C NMR) showed that the introduction of NL into PU restricted the motion of PU molecules, indicating a relatively high cross-link network structure in the UL films. Therefore, a relatively great network structure like a star by grafting with multi-PU networks on a NL molecule as the graft-IPNs model was deduced in this work.