Synthesis and application of aminophenyl-s-triazine derivatives as potential flame retardants in the modification of epoxy resins

Soft Hydroxyapatite Composites Based on Triazine-Trione Systems as Potential Biomedical Engineering Frameworks

Composites of triazine-trione (TATO) thiol-ene networks and hydroxyapatite (HA) have shown great potential as topological fixation materials for complex bone fractures due to their high flexural modulus, biocompatibility, and insusceptibility to forming soft-tissue adhesions. However, the rigid mechanical properties of these composites make them unsuitable for applications requiring softness. The scope of these materials could therefore be widened by the design of new TATO monomers that would lead to composites with a range of mechanical properties. In this work, four novel TATO-based monomers, decorated with either ester or amide linkages as well as alkene or alkyne end groups, have been proposed and synthesized via fluoride-promoted esterification (FPE) chemistry. The ester-modified monomers were then successfully formulated along with the thiol TATO monomer tris [2-(3-mercaptopropionyloxy)ethyl] isocyanurate (TEMPIC) and HA to give soft composites, following the established photo-initiated thiol-ene coupling (TEC) or thiol-yne coupling (TYC) chemistry methodologies. The most promising composite shows excellent softness, with a flexural modulus of 57 (2) MPa and ε_f at maximum σ_f of 11.8 (0.3)%, which are 117 and 10 times softer than the previously developed system containing the commercially available tri-allyl TATO monomer (TATATO). Meanwhile, the surgically convenient viscosity of the composite resins and their excellent cytotoxicity profile allow them to be used in the construction of soft objects in a variety of shapes through drop-casting suitable for biomedical applications.

Fabrication of a bi-hydroxyl-bi-DOPO compound with excellent quenching and charring capacities for lignin-based epoxy resin

In this study, lignin-based epoxy resins (EP) were fabricated using lignin, phenol and glyoxal as crosslinking reagents. For improving the flame retardancy, a bi-DOPO compound with bi-hydroxyl structure was successfully synthesized, containing excellent quenching and charring capacities. Good pyrolysis behaviors of as-synthesized flame retardant resulted in significant quenching effect via structure decomposition to release PO and PO₂ free radicals for capturing reactive H and OH radicals produced from epoxy combustion. With addition of 0.18 wt% phosphorus, epoxy composite (10% LPG-ER-4) passed V-0 rating with high limited oxygen index (LOI) value of 35.2%. Cone calorimeter tests showed that heat release (including heat release rate (HRR) and total heat release (THR)) from combustion was reduced with assistance of flame retardant. Char residue analyses illustrated that bi-hydroxyl structure in DOPO-based flame retardant benefited the formation of char layer with higher compactness and integrity to serve as a protective shell of interior epoxy matrix. Furthermore, exterior pore size of char residue was narrowed or blocked to avoid the release of heat and volatiles generated from combustion. This study provided a feasible method to improve flame retardancy of lignin-based EP and proposed flame-retardant mechanism both in gaseous and solid phases.

DOPO-Decorated Two-Dimensional MXene Nanosheets for Flame-Retardant, Ultraviolet-Protective, and Reinforced Polylactide Composites

This study presents a novel and facile strategy for fabricating fire-resistant, ultraviolet (UV)-shielding, and tensile-enhanced polylactide (PLA) composites using two-dimensional (2D) MXene (Ti₃C₂) flakes chemically modified with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). The thermal and burning performances of PLA composites were demonstrated by the limiting oxygen index, UL-94 test, and cone calorimetry. The UV-shielding and tensile performances were also examined. The results revealed that PLA/Ti₃C₂-DOPO (3 wt %) displayed a V-0 rating in the UL-94 test. The enhancement against fire hazard was reflected by the significant reduction in the peak heat release rate (33.7%), total heat release (47%), peak CO production (58.8%), and total smoke production (41.7%). The improved fire-safety performance of the composites is attributed to the interplay of catalytic, barrier, and condensed effects of the Ti₃C₂-DOPO nanosheets in the PLA matrix. PLA/Ti₃C₂-DOPO also showed an increase (∼9%) in tensile strength and an "Excellent" level (UPF 50+) in the UV-protection assessment. In all, this study introduces a novel chemical modification strategy for 2D MXene flakes to fabricate multifunctional PLA composites, which are promising candidates for next-generation sustainable and protective plastic products.

Synthesis and characterization of PEDMCD as a flame retardant and its application in epoxy resins

In this study, a highly effective flame retardant agent, called polybicyclopentaerythritol phosphate-O-4-imino-p-phenylmethane-4-imino-2-chloro-1,3,5-s-triazine (PEDMCD), has been prepared through a direct polycondensation reaction. PEDMCD was incorporated into epoxy resin (EP) to improve the flame retardancy of EP. The molecular structure and thermal stability of PEDMCD were analyzed by nuclear magnetic resonance spectroscopy. Further, the structural properties, composition, and thermal stability of the PEDMCD/EP composite were characterized by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). PEDMCD exhibited both high thermal stability and high flame-retardant performance; these properties were attributed to the phosphorus-containing structure on the side groups and a triazine structure as the molecular backbone, which played the role of a foaming carbon source. With the addition of PEDMCD, the flame-retardant behavior of PEDMCD/EP composites was gradually enhanced. Furthermore, the amount of char residue of the PEDMCD/EP composite at 500 °C was increased from 21% to 34%. The peak value of the mass loss rate of PEDMCD/EP decreased from 0.52 to 0.35 g s-1. Further, the TSP of the sample decreased from 44.2 m2 to 24.6 m2, and the total oxygen consumption decreased from 64.2 g to 30.4 g. Accordingly, owing to the incorporation of PEDMCD, EP begins to decompose sooner, and the carbon layer formed by decomposition reduces the decomposition rate of the EP matrix. Based on the results of characterization measurements and flame retardancy testing, it is confirmed that PEDMCD exhibits good flame retardancy when applied in EP.

Functionalization of Silica with Triazine Hydrazide to Improve Corrosion Protection and Interfacial Adhesion Properties of Epoxy Coating and Steel Substrate

The chemical bonding of modified filler surfaces with coating networks is an advanced approach for improving the interfacial adhesion force of fillers with coating and substrate surfaces. In this respect, silica gel surfaces were activated and modified by grafting 1,3–dihydrazide-2,4,6-triazine onto hydroxyl groups of activated silica surfaces. The chemical structure, thermal stability and surface morphologies of the modified silica were investigated. The modified silica fillers were blended during the curing of the epoxy resin with the polyamine hardener. The data regarding the chemical structure and thermal stability of the cured epoxy networks in the presence of modified silica elucidated the chemical bonding of amine groups on the silica surfaces cured with the oxirane epoxy resin. Moreover, the incorporation of modified silica in surfaces with epoxy networks improved their adhesion with steel surfaces and enhanced the mechanical, thermal and anticorrosion characteristics of the epoxy to protect steel surfaces against seawater.