Based on bio-based furfural, a phosphorus-containing curing agent (FPD) was successfully synthesized, via the addition reaction between 9,10-dihydro-9-oxa-10 phosphaphenanthrene-10-oxide (DOPO) and furfural-derived Schiff base. Then, as co-curing agent, FPD was used to prepare flame retardant epoxy thermosets (EP) cured by 4, 4′-diaminodiphenyl methane. The incorporated FPD improved the flame retardancy and toughness of epoxy thermoset, simultaneously. When 5 wt% FPD was added into EP, the FPD/EP achieved 35.7% limited oxygen index (LOI) value and passed UL94 V-0 rating, meanwhile. In FPD/EP thermoset, the incorporated FPD reduced the thermal decomposition rate, increased the charring capacity, and inhibited the combustion intensity of epoxy thermoset. Through gas-phase and condensed-phase actions in weakening fuel supply, suppressing volatile combustion, and enhancing charring barrier effect, FPD decreased the heat release of burning epoxy thermoset, significantly. For the outstanding effectiveness on both flame retardancy and toughness, the study on FPD provides a promising way to manufacture high-performance epoxy thermoset.
A flame retardant aluminum 2-carboxyethyl-phenyl-phosphinate (CPA-Al) was synthesized through the salification reaction. The molecular structure of CPA-Al and thermal stability were characterized by solid nuclear magnetic resonance, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Subsequently, CPA-Al mixed in polyurethane was coated on polyester textile to obtain flame-retardant samples. The addition of 14.7 wt.% CPA-Al in textile sample can bring a limited oxygen index (LOI) value of 24.5%, 0 s after flame time, and the vertical burning B1 rating. Meanwhile, the incorporated CPA-Al reduced the peak heat release rate, total heat release, average effective heat of combustion, and increased the charring capacity of polyester textiles in contrast to the samples without CPA-Al. CPA-Al exerted not only its flame inhibition effect in gas phase, but also the charring and barrier effect in the condensed phase. Besides, with an increasing CPA-Al ratio in polyester textile, the contact angle gradually decreased from 123.6° to 75.6°, indicating that the surficial property of coating from hydrophobic to hydrophilic, thereby increasing the moisture permeability of polyester textile.
A novel high phosphorus‐efficiency phosphaphenanthrene curing agent (VND) was synthesized successfully using bio‐based vanillin, N‐phenyl‐p‐phenylenediamine, and 9,10‐dihydro‐9‐oxa‐10 phosphaphenanthrene‐10‐oxide (DOPO). Then, as co‐curing agent, VND combined with 4, 4′‐diaminodiphenyl methane (DDM) to fabricate flame retardant epoxy thermosets (VND/EP/DDM). The VND/EP/DDM thermosets exhibited excellent flame‐retardant performance and toughness, simultaneously. With only 0.35 wt% phosphorus loading, 6%VND/EP/DDM achieved a LOI value of 39.2%, and passed UL94 V‐0 rating. The three reactive functional groups in VND made itself better interpose in the burning process of thermoset matrix, endowing VND with higher efficiency in facilitating matrix carbonization. Meanwhile, the decomposition volatile tracking disclosed the inhibition effect of VND on oxidative cracking. Through gas‐ and condensed‐phased actions, VND decreased the heat release and smoke production of burning epoxy thermosets, efficiently. In addition, three reactive functional groups in VND also brought itself good toughening effect on thermoset matrix, endowing epoxy thermoset with better anti‐impact performance. The flame retarding and toughening behavior of VND provides a new insight to development advanced flame‐retardant epoxy thermosets.
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