Effect of Poly(acrylamide-acrylic acid) on the Fire Resistance and Anti-Aging Properties of Transparent Flame-Retardant Hydrogel Applied in Fireproof Glass

A Pullulan polysaccharide-based flame-retardant polyelectrolyte hydrogel for high-safety flexible zinc ion capacitors

Potential safety hazards such as leakage, flammability and thermal runaway of liquid electrolytes in conventional energy storage devices have seriously hindered their further development. In this work, a flame-retardant polyacrylamide/pullulan/phytic acid (PAM/PUL/PA) hydrogel electrolyte is prepared by using PA as flame-retardant additive, PAM as main polymer chain by one-step radical polymerization method. The PAM/PUL/PA hydrogel shows good flame-retardant properties with limiting oxygen index of up to 58 %, high mechanical performance with stretch up to 1535 % and 92 kPa tensile stress. Zinc ion capacitor (ZIC) assembled with the PAM/PUL/PA hydrogel as electrolyte and separator exhibits high ionic conductivity of 22.54 mS cm-1, high specific capacity of 111.5 mAh g-1 at 0.1 A g-1 and energy density of 97.57 Wh kg-1 at a power density of 49.99 W kg-1, as well as good capacitance retention of 74.6 % even after 10,000 cycles. Furthermore, the ZIC has outstanding flexibility, the capacitance retention rate almost unchanged even after 1000 consecutive bending of deformations. These excellent properties are attributed to the hydrogen bonds easily formed by polar functional groups in hydrogels and the electrostatic interactions with metal ions. This work presented a simple and general pathway to prepare high-safety flexible energy storage devices with multifunctional properties.

Multi-crosslinked gelatin-based composite hydrogel featuring high thermoelectric performance and excellent flame retardancy for intelligent fire-warning system

The frequency occurrence of building fires necessitates response materials with high flame retardancy and temperature sensitivity. Herein, we synthesized a gelatin/poly(acrylamide-co-acrylic acid)/lithium bromide/sodium phytate/glycerol hydrogel (Gly-GAPL) using in situ radical polymerization and solvent exchange techniques. Gly-GAPL exhibits notable thermoelectric performance (the Seebeck coefficient: 8.66 mV/K), temperature sensitivity, commendable mechanical properties and flame retardancy. Remarkably, Gly-GAPL features a rapid response time, triggering an alarm within 2 s upon exposure to flame. Gly-GAPL is highly resistant to ignition and significantly enhances the fire resistance of wood coated with it. Furthermore, its high transparency, impressive water retention and adhesion further underscore its potential as a flame-retardant coating for various inflammable materials. Given its outstanding thermoelectric performance and temperature sensitivity, an early fire-warning system is rapidly activated, promptly sending alerts to smart devices. This work introduces a novel strategy for developing smart flame retardancy materials and advances the applications of ionic hydrogels in early fire-warning systems.

Gelatin-based ionic hydrogel for intelligent fire-alarm system with considerable toughness, flame retardancy, and thermoelectric performance

Temperature-responsive materials with excellent reliability, sensitivity, and flame-retardant properties have always been an urgent need in the field of intelligent fire protection. In this discourse, we introduce a novel thermosensitive ionic hydrogel coating (gelatin/poly(acrylamide-co-acrylic acid)/CaCl2/spindle-shaped aluminum hydroxide nanosheet/glycerol, HCA) synthesized via free radical polymerization. HCA not only demonstrates considerable mechanical properties with a fracture strain of up to 842.5 % and a maximum tensile strength of 0.77 MPa but also exhibits notable flame retardancy and adhesion. It effectively covers combustible surfaces, providing outstanding fire protection. Notably, HCA boasts a Seebeck coefficient of up to 10.1 mV/K, significantly surpassing conventional thermoelectric materials. The well-established linear relationship between the generated voltage and temperature variation enables HCA-based intelligent fire-alarm system to accurately emit continuous alerts during fire incidents and swiftly transmit alarm signals to terminal devices. The development of this intelligent fire-alarm system presents new avenues in intelligent fire-safety technologies.

Kaolin-embedded cellulose hydrogel with tunable properties as a green fire retardant

This study reports the synthesis of methylene bisacrylamide (MBA) crosslinked cellulose-kaolin (CMK) composite hydrogels. The internal structures of hydrogels were deduced using network parameters, viz. elastic modulus, average molecular weight, mesh size, and effective crosslink. Meanwhile, combustion behavior was investigated using the cone calorimeter test (CCT), limiting oxygen index (LOI) test, vertical flammability test (VFT), and open fire test (OFT). Our results revealed that kaolin addition improves the fire retardancy of hydrogels but reduces their swelling ability. Hydrogel having cellulose to MBA ratio of 1:2 and 2 % w/v kaolin (CM2K2) produced 63 % wt. char residue and the hydrogel-coated cotton fabric exhibited the lowest heat release rate (HRR) of 26.60 kJ/m² and total heat release (THR) of 0.9 MJ/m². The LOI of the cotton fabric surged from 20 % to 34.37 % after hydrogel coating. Kinetic analysis using the isoconversional model yielded the highest activation energy (216 kJ/mol) for the CM2K2 hydrogel, corroborating the increased LOI after kaolin addition. VFT and OFT validated the delay in the burning process and the formation of a char layer, which protected the underlying layer of cotton from burning. Overall, cellulose-kaolin hydrogels developed in this study are effective green fire retardant coatings for flammable materials.

Preparation and Characterization of a Novel Cassava Starch-Based Phosphorus Releasing Super-Absorbent Polymer, and Optimization of the Performance of Water Absorption and Phosphorus Release

To prepare a novel cassava starch-based phosphorus releasing super-absorbent polymer (CST-PRP-SAP), the single factor and orthogonal experiment were applied to analyze the effects of different reaction conditions on the absorption and phosphorus release capacities of CST-PRP-SAP samples. The structural and morphological characteristics of the cassava starch (CST), powdered rock phosphate (PRP), cassava starch-based super-absorbent polymer (CST-SAP) and CST-PRP-SAP samples were all compared with various technologies, such as the Fourier transform infrared spectroscopy and X-ray diffraction pattern, etc. The results showed that the CST-PRP-SAP samples had good performances of water retention and phosphorus release which were synthesized, such as the reaction temperature, starch content, P2O5 content, crosslinking agent, initiator, neutralization degree, and acrylamide content, which were 60 °C, 20% w/w, 10% w/w, 0.02% w/w, 0.6% w/w, 70% w/w, and 15% w/w, respectively. The water absorbency of CST-PRP-SAP was almost larger than that of the CST-SAP sample with a P2O5 content of 5.0% and 7.5%, and they all gradually decreased after three consecutive water absorption cycles. The CST-PRP-SAP sample could maintain about 50% of the initial water content after 24 h, even at the temperature of 40 °C. The swelling process of CST-PRP-SAP conformed to the non-Fickian diffusion, which was determined by the diffusion of water molecules and the relaxation process of polymer chain segments. The cumulative phosphorus release amount and release rate of the CST-PRP-SAP samples were increased with the increasing PRP content and the decreasing neutralization degree. After a 216 h immersion, the cumulative phosphorus release amount and release rate of the CST-PRP-SAP samples with different PRP contents were increased by 17.4 and 3.7 times, respectively. The rough surface of the CST-PRP-SAP sample after swelling was beneficial to the performance of water absorption and phosphorus release. The crystallization degree of PRP in the CST-PRP-SAP system was decreased and most of the PRP existed in the form of physical filling, and the available phosphorus content was increased to a certain extent. It was concluded that the CST-PRP-SAP synthesized in this study has excellent properties of continuous water absorption and retention with functions of promotion and the slow-release phosphorus.

Facile Fabrication of Multifunctional Transparent Flame-Retarded Hydrogel for Fire-Resistant Glass with Excellent Transparency, Fire Resistance and Anti-Ageing Property

Acrylamide-methacrylic acid copolymer named P (AM-co-MAA) was synthesized via aqueous solution polymerization, and then mixed with crosslinker, flame retardants and initiators to prepare multifunctional transparent flame-retarded hydrogels with transparency, fire resistance and anti-ageing property. The results show that the application of multifunctional transparent flame-retarded hydrogel imparts high level of transparency and excellent fire resistance to the fire-resistant glass, and the light transmittance and fire resistance of the flame-retarded hydrogel increases with the increasing mass ratio of AM to MAA in P(AM-co-MAA). When the mass ratio of AM to MAA is 4:1, the obtained P(AM-co-MAA) imparts the lowest backside temperature of 130 °C at 3600 s and highest light transmittance of 86.1% to the transparent flame-retarded hydrogel. TG and DSC analysis show that the addition of P(AM-co-MAA) increases the thermal stability of the transparent flame-retarded hydrogels due to the formation of numerous hydrogen bonds via the complexation between amide and carboxyl groups. Accelerated ageing test indicates that the transparent flame-retarded hydrogel containing P(AM-co-MAA) exerts durable fire resistance and transparency, and the ageing resistance of the transparent flame-retarded hydrogel depends on the mass ratio of AM to MAA in P(AM-co-MAA). Therefore, this study provides a promising strategy to prepare a novel multifunctional transparent flame-retarded hydrogel with excellent light transmittance, fire resistance and anti-ageing properties.