Phytic acid doped polyaniline-coupled g-C3N4 nanosheets for synergizing with APP promoting fire safety and waterproof performance of epoxy composites

Eco-Friendly One-Pot Supramolecular-Assembly of P-N Flame Retardant for Fire-Safe Epoxy Resin

Flame retardant treatment of epoxy resins (EP) to reduce their flammability for extending their range of applications attracts considerable attention. However, the synthesis process of conventional flame retardants is complicated and involves organic hazardous solvents. Meanwhile, how to ensure both the flame-retardant and mechanical properties is a long-standing and actual difficult problem. In this work, a supramolecular flame retardant (named ATPFR) is facilely created by one-pot reaction, using cheap and accessible raw materials in an ecologically benign aqueous solvent. ATPFR is applied to improve the fire safety of EP. With only 5 wt% ATPFR addition, EP can reach the limiting oxygen index of 28.5% and the UL-94 V-0 rating with a significant "blow-out effect." The cone calorimetry test reveals that the EP thermoset with 5 wt% ATPFR has a 75.8% reduction in the peak heat release rate (p-HRR) and a 67.3% reduction in the peak smoke production rate (p-SPR), respectively, compared with the pure EP. Additionally, EP composites with the small amount of ATPFR exhibit a slight decrease and maintain good mechanical properties. Therefore, the facile synthesis and application of this supramolecular flame retardant provide a reliable way for the construction of polymer materials with environment-friendly and effective flame-retardant system.

Toward flame-retardant and toughened poly(lactic acid)/cross-linked polyurethane blends via the interfacial reaction with the modified bio-based flame retardants

Incorporating bio-based flame retardants into polylactic acid (PLLA) to improve flame retardancy has always been the focus of research, but the improvement of flame retardancy is usually at the expense of mechanical properties. How to successfully balanced the material's mechanical and combustion properties has puzzled many scholars. Herein, ammonium polyphosphate (APP) and chitosan (CS) were used as acid source and carbon source respectively. Biological flame retardant APP@CS was designed and synthesized by electrostatic self-assembly method. In addition, toughened PLLA composites were prepared by reactive blending with the in-situ formed polyurethane (PU) as toughening phase. The results show that the CS shell not only reduces the hydrophilicity of the flame retardant, but also has good flame retardant property because of its excellent char forming property. The addition of 10 phr APP@CS can endow PLLA/crosslinked PU (CPU) with UL-94 V-2 rating and a LOI value of 24.9 %. Interestingly, CS shell participates in the in-situ reaction, which improves the mechanical properties of the composite with elongation at break of 74 %, which is higher than that of sample doped with the same amount of APP. This work provides guidance for the high performance modification of PLLA and is expected to expand the practical application range.

Anti-Oil-Adhesion Property of Superhydrophilic/Underwater Superoleophobic Phytic Acid-FeIII Complex Coatings

Crude oil adhesion issues are widespread in the petroleum industry, leading to inefficient production and high maintenance costs. Developing efficient antifouling materials and investigating the microscopic adhesion mechanism are of substantial significance. In the present work, a superhydrophilic/underwater superoleophobic PAFC coating with excellent antifouling properties was constructed by the coordination-driven self-assembly of phytic acid (PA) and FeCl₃ (FC). The atomic force microscope (AFM) droplet probe technique was employed to elucidate the underlying mechanism of the anti-oil-adhesion property of the PAFC coating. Results showed that the PAFC modification achieved the optimum effect at a molar ratio of 1:3 between PA and Fe^III. Applying a (3-aminopropyl)triethoxysilane (APTES) interlayer can effectively improve the performance of the PAFC coating on silica substrates. AFM droplet probe experiments indicated that the adhesion force between submerged micrometer-sized oil droplets and PAFC-modified substrates was significantly weaker than that with the untreated substrate. Meanwhile, the adhesion forces between oil droplets and surfaces were inversely proportional to the contact angle of the oil in water and were enhanced by higher salinity, lower collision velocity, and stronger loading force. The oil injection and wall sticking tests also confirmed the effectiveness of the PAFC modification in resisting the adhesion of crude oil.

Co-curing preparation of flame retardant and smoke-suppressive epoxy resin with a novel phosphorus-containing ionic liquid

Phosphorus-containing ionic liquid derivatives have been proven to be effective flame retardants for epoxy resin (EP). Flame retardants can accelerate the curing process and improve flame retardancy and smoke suppression of EP composites, which is challenging. In this paper, a novel phosphorus-containing ionic liquid (TPP-PF₆) was synthesized and used both as a co-curing agent with 4,4'-diaminodiphenylmethane (DDM) and as a highly effective flame retardant for EP. It has been found that TPP-PF₆ was conducive to improve the char formation of EP to inhibit the smoke release at high temperatures. For EP/TPP-PF₆ composites, the flame-retardant performance was enhanced rapidly with the increase of TPP-PF₆. With only 2 wt% of TPP-PF₆, EP/2.0TPP-PF₆ reached a UL-94 V-0 rating and a limiting oxygen index of 30.3%. The peak heat release rate, total heat release, and total smoke production values of EP/2.0TPP-PF₆ were reduced by 36.32%, 45.81%, and 15.1% compared with those of pure EP, respectively. The thermal degradation products and flame retardant mechanism in gas and condensed phases were studied. It was found that TPP-PF₆ had flame retardant effect in the barrier effect of the condensed phase and the quenching effect of the gas phase. This work explores the high-efficiency flame retardant and smoke-suppressive structures with co-curing properties for EP, thus promoting the wide application of EP materials.