Bio-Based Alkali Lignin Cooperative Systems for Improving the Flame Retardant and Mechanical Properties of Rigid Polyurethane Foam.

Lignin was utilized as an environmentally friendly synergistic agent to augment the fire resistance and mechanical characteristics of rigid polyurethane foam (PUF)/melamine-formaldehyde resin ammonium polyphosphate (MFAPP). The incorporation of lignin significantly enhanced the charring capability and flame retardancy of PUF/MFAPP. Specifically, PUF/MFAPP12/A-lignin3 exhibited a charring residue of 23.1% at 800 °C, accompanied by an increase in the limiting oxygen index (LOI) to 23.1%, resulting in a UL-94 V-0 rating. The cone calorimeter test (CCT) revealed that the peak heat release rate (PHRR), total heat release (THR), smoke production rate (SPR), and total smoke production (TSP) values of PUF/MFAPP12/A-lignin3 were all lower than for pure PUF. MFAPP and alkali lignin exerted a noticeable influence on the physical and mechanical properties, leading to increases in density (35.4 kg/m3), thermal conductivity (32.68 mW/(m·K)), and compressive strength (160.5 kPa). Observations of the morphology and elemental composition of char residues after combustion indicated the formation of an intact, thick, and continuous char layer enriched with nitrogen and phosphorus elements, which acted as a protective shield for the underlying foam.

Rapid Preparation of Antifreezing Conductive Hydrogels for Flexible Strain Sensors and Supercapacitors.

Conductive hydrogels have shown great promise in flexible electronics, but their practical applications may be impeded by the time-consuming and energy-consuming polymerization process. We proposed a sodium lignosulfonate-Fe (SLS-Fe) strategy to address this challenge and took advantage of carboxymethyl cellulose (CMC) and poly(acrylic acid) to prepare the CMC/PAA/Fe3+/LiCl interpenetrating conductive hydrogels with good self-healing properties, antifreezing properties, and a 6-fold increase in conductivity in this study. The hydrogel-based flexible strain sensors demonstrated a broad detection range (400%), high sensitivity (GF = 6.19 at 200-400%), and human motion detection capability. The hydrogel-based supercapacitor exhibited a single-electrode specific capacitance of 122.36 F g-1 which successfully powered LEDs. Furthermore, the supercapacitor showed a single-electrode specific capacitance of 83.16 F g-1 at -23 °C (68% of the one exhibited at 25 °C). Therefore, the multifunctional performance of the CMC/PAA/Fe3+/LiCl hydrogel is anticipated to play an exemplary role in a new generation of flexible electronics.