Preparation of Cellulose/MWCNTs/TPU Micro-foam Composites

In this work, we dissolved the alpha-cellulose in pre-cooled sodium hydroxide (NaOH) and thiourea solution, and dispersed multi-walled carbon nanotubes (MWCNTs) in solution with the help of cetyltrimethylammonium bromide (CTAB), then cross-linked for 48h to form a gel. The gel was placed in distilled water to displace the sodium hydroxide. After the distilled water was neutral, the gel was freeze-dried to obtain a cellulose/MWCNTs aerogel. We prepared cellulose aerogel with 10 wt% MWCNTs, its density is 139.64 mg/cm(3). Next, using the aerogel as a template, the thermoplastic polyurethane (TPU) was cast into the aerogel by solution method to obtain a cellulose/TPU/MWCNTs composite. The composite is then foamed by supercritical CO2, the pressure was maintained at 13.8 MPa and the temperature was maintained at 100 degrees C. The cell size of TPU is about 10 mu m and the density is 414.79 mg/cm(3). Besides, the compression modulus and compressive strength at 10% compression strain of foaming composite are 0.62 MPa and0.059 MPa.