Tewarak Parnklang

In this research, shape memory polymers (SMPs) fabricated from bio-based benzoxazine resins, i.e. vanillin-furfurylamine-containing benzoxazine (V-fa) and eugenol-furfurylamine-containing benzoxazine (E-fa) resins, and bio-based epoxy resin, i.e. epoxidized castor oil (ECO), are investigated. Effects of ECO mass concentrations on curing characteristics, thermal stability, dynamic mechanical properties, and shape memory properties are determined by differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, and shape memory tests, respectively. Storage moduli at the glassy state and glass transition temperatures ( T _g ) of V-fa/ECO and E-fa/ECO copolymers decrease with increasing ECO mass concentrations. The bending tests performed with a universal testing machine are employed to evaluate the shape memory properties of the developed bio-based copolymers. V-fa/ECO SMPs show excellent shape fixity of 86%–94% at room temperature and high shape recovery at T _g + 20 °C of 81%–96%. V-fa/ECO SMPs can undergo fold-deploy shape memory cycles without altering the shape memory performances for at least 5 cycles. Good balance between shape memory performances and thermo-mechanical properties in the V-fa/ECO copolymer system is obtained when ECO mass concentration is 40% (w/w).

Smart materials with light-actuated shape memory effects are developed from renewable resources in this work. Bio-based benzoxazine resin is prepared from vanillin, furfurylamine, and paraformaldehyde by utilizing the Mannich-like condensation. Vanillin-furfurylamine-containing benzoxazine resin (V-fa) is subsequently copolymerized with epoxidized castor oil (ECO). When the copolymer is reinforced with multiwalled carbon nanotubes (MWCNTs), the resulting composite exhibits shape memory effects. Molecular characteristics of V-fa resin, ECO, and V-fa/ECO copolymers are obtained from Fourier transform infrared (FT-IR) spectroscopy. Curing behavior of V-fa/ECO copolymers is investigated by differential scanning calorimetry. Dynamic mechanical properties of MWCNT reinforced V-fa/ECO composites are determined by dynamic mechanical analysis. Morphological details and distribution of MWCNTs within the copolymer matrix are characterized by transmission electron microscopy. Shape memory performances of MWCNT reinforced V-fa/ECO composites are studied by shape memory tests performed with a universal testing machine. After a significant deformation to a temporary shape, the composites can be recovered to the original shape by near-infrared (NIR) laser actuation. The shape recovery process can be stimulated at a specific site of the composite simply by focusing NIR laser to that site. The shape recovery time of the composites under NIR actuation is four times faster than the shape recovery process under conventional thermal activation. Furthermore, the composites possess good shape fixity and good shape recovery under NIR actuation.