Novel star‐shaped and hyperbranched phosphorus‐containing flame retardants in epoxy resins

Abstract

This report presents the synthesis and use of novel derivatives of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO, 1) and 5,5‐dimethyl‐1,3,2‐dioxaphosphorinan‐2‐one (DDPO, 2) as flame retardant additives for epoxy resins. DOPO‐based and DDPO‐based compounds were synthesized via nucleophilic substitution with 1,3,5‐tris‐(2‐hydroxyethyl) isocyanurate (THIC, 3) and subsequent oxidation (Schemes 1 and 2). Another trivalent DOPO derivative recently reported by our group was obtained by transamination followed by a Michaelis–Arbuzov rearrangement (Scheme 1). These products were blended into two epoxy resin systems [DEN 438 and diglycidyl ether of bisphenol A (DGEBA), both cured with dicyandiamide (DICY) and Fenuron] to obtain flame retardant thermosets. The flame retardancy and thermal properties of these epoxy resin systems were examined by UL 94‐V, Thermogravimetric analysis, and differential scanning calorimeter analysis. Furthermore, all reactions with phosphorus‐containing compounds were iterated employing the THIC oligomer, which was prepared via polycondensation of THIC (Scheme 3) using catalytic amounts of p‐toluenesulfonic acid. In addition, Atherton–Todd reaction with the THIC oligomer was studied as a novel synthetic method for phosphorus‐containing flame retardants (Scheme 4). The resulting products were utilized as flame retardants in epoxy resins and compared with the analogous monomeric compounds. Copyright © 2011 John Wiley & Sons, Ltd.

High-performance flame retardancy by char-cage hindering and free radical quenching effects in epoxy thermosets

“…These additives are composed of phosphazene/phosphaphenanthrene [36,37], phosphaphenanthrene/triazene [38,39], phosphaphenanthrene/POSS [40], or other functional groups [41,42]. All of these additives possess excellent flame-retardant efficiencies, which confirms that the methods used in these studies can be employed to obtain high-efficiency flame retardants.…”

Flame-retardant effect of a novel phosphaphenanthrene/triazine-trione bi-group compound on an epoxy thermoset and its pyrolysis behaviour

“…Namely, proper chemical bridge bonds, linking different characteristic structures or groups, potentially benet to endow bi-group or multigroup compound with higher ame-retardant efficiency, resulting from the changed and even optimized pyrolysis route of ame retardant structures or groups. [34][35][36][37][38] In this work, to adjust the pyrolysis route of phosphaphenanthrene and increase additional source of phenoxy derivative radicals, a novel bi-group compound TOD, containing two different chemical bridge bonds (aliphatic and aromatic bridge bonds) between phosphaphenanthrene and triazine-trione groups, was synthesized via the addition reactions between epoxy group/P-H bond and epoxy group/ phenolic hydroxyl group in sequence. The ame-retardant effect and mechanism of TOD were investigated in the diglycidyl ether of bisphenol-A cured with 4,4 0 -diamino-diphenyl methane (EP).…”

Syntheses and Characterization of Four Phosphaphenanthrene and Phosphazene-based Flame Retardants

“…6,7 There has also been great interest from the flame retardant community regarding phosphorus containing molecules (e.g., 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) for epoxy) and nitrogen-phosphorus containing molecules (e.g., Hexa-chloro-cyclotriphosphazene (HCCP) for epoxy, PLA, polybenzoxazines) as environmentally friendly alternatives to the existing, and often used, harmful halogenated flame retardants. [8][9][10][11][12] However, the above-mentioned reactive DOPO, phosphazene compounds and their derivatives could only be introduced to thermosets mainly through chemical reaction, which has restricted their application in many cases. [15][16][17] In this paper, the versatile Atherton-Todd reaction and the Kabachnik-Fields reaction were used to obtain novel derivatives containing phosphaphenanthrene and cyclotriphosphazene double functional groups which can be used as intumescent flame retardant additives.…”