Improving thermal and flame-retardant properties of epoxy resins by a novel reactive phosphorous-containing curing agent

• Published in: Polymer engineering and science Vol. 54; no. 5; pp. 1192 - 1200
• Main Authors: Xie, Cong, Zeng, Birong, Gao, Hui, Xu, Yiting, Luo, Weiang, Liu, Xinyu, Dai, Lizong
• Format: Journal Article
• Language: English
• Published: Hoboken, NJ Blackwell Publishing Ltd 01.05.2014; Wiley; Society of Plastics Engineers, Inc
• Subjects: Applied sciences; Chemical properties; Compounding ingredients; Curing agents; Dynamic mechanical properties; Dynamic tests; Dynamics; Epoxy resins; Exact sciences and technology; Fireproof agents; Methane; Oxygen; Phosphorus; Phosphorus content; Polymer industry, paints, wood; Polymers; Production processes; Properties and testing; Resins; Technology of polymers; Thermal properties; Thermogravimetric analysis; China; Molecular structure; Curing agent; Epoxy resin; Organic phosphinate; Flame retardant; Curing (plastics); Experimental study; Oxygen index; Thermal stability; Phosphorus polymer; Thermal properties; Diamine; Additive; Preparation; Concentration effect; Reaction mechanism; Property structure relationship; Organo non metallic polymer
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.23642

In an attempt to improve thermal and flame‐retardant properties of epoxy resins efficiently, a new reactive phosphorus‐containing curing agent called 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐yl‐(phenylimino)‐(4‐hydroxyphenyl)me‐thane (DOPO‐PHM) was synthesized and was combined with 4,4′‐diaminodiphenyl methane (DDM) to co‐cure epoxy resins (E51), which covalently incorporated halogen‐free DOPO organ groups into the epoxy networks. The chemical structure of this curing agent was confirmed by FTIR, 1D, and 2D NMR spectra. A reaction mechanism during the preparation was proposed, and the electron effect on the stabilization of the carbocation was discussed. Various DDM/DOPO‐PHM molar ratios were used to get the materials with different phosphorus contents. Their dynamic mechanical, thermal, and flame‐retardant properties were evaluated by dynamic mechanical thermal analysis, thermogravimetric analysis, and limiting oxygen index (LOI) respectively. All samples had a single Tg, showing that these epoxy resins were homogeneous phase for long‐term use in spite of adding DOPO‐PHM. Both char yields (under nitrogen and air atmospheres) increased with the increasing of phosphorus content and the LOI values increased from 24.5 for standard resin to 33.5 for phosphorus‐containing resins, indicating the significant enhancement of thermal stability and flame retardancy. POLYM. ENG. SCI., 54:1192–1200, 2014. © 2013 Society of Plastics Engineers