Synthesis of DOPO-based spiroorthocarbonate and its application in epoxy resin

Abstract

In this work, a novel DOPO-based spiroorthocarbonate (DSOC), 6,6ʹ-((3,9-diethyl-1,5,7,11-tetraoxaspiro[5.5]undecane-3,9-diyl)bis(hydroxymethylene))bis(6H-dibenzo[c,e][1,2]oxaphosphinine 6-oxide) was synthesized and confirmed with 1 H, 31 P, 13 C NMR, and FT-IR spectra. It was used as anti-shrinkage additive and flame retardant in the cationic polymerization of epoxy resin. The shrinkage of the cured epoxy resin containing DSOC was investigated by measuring the density of the system before and after curing. It was found that the shrinkage of epoxy resin changed from −1.49 to 1.43% with the content of DSOC increased to 20 wt%, not only the shrinkage of epoxy resin was eliminated, but also a slight expansion was achieved. The flame retardancy and thermal stability of the cured epoxy resins were tested by limiting oxygen index (LOI), vertical burning test (UL-94), and thermogravimetric analysis (TGA). LOI values increased from 19.9% for pure E-51 to 30.9% for modified epoxy resins, UL-94 V-0 rating can be obtained with 15 wt% DSOC. The mechanical properties of the modified epoxy resin were also investigated. The results showed that DSOC was a promising anti-shrinkage additive and flame retardant for epoxy resins.

Improving thermal and flame‐retardant properties of epoxy resins by a new imine linkage phosphorous‐containing curing agent

“…Reduction in combustibility of the epoxy resins by using phosphorus‐containing retardants has become a pivotal part of the development and application especially in aerospace industries and electrical/electronic fields . Among these phosphorus‐containing retardants, 9, 10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) derivatives are attractive because of their relatively high thermal stability and flame‐retarding efficiency. Furthermore, phosphorus‐containing reactive imine can be used as curing agent and flame retardant in epoxy resins .…”

Development of Low‐Shrinkage Polymers by Using Expanding Monomers

“…The synthesis of a DOPO‐based SOC (XVI) was performed by Wang et al This SOC was evaluated as an anti‐shrinkage additive and flame‐retardant in the epoxy monomer DGEBA. It was found that an expansion of 1.43% was achieved when 20% w/w of the SOC was copolymerized with the epoxy monomer.…”

Effect of oligo(spiroorthocarbonate)s on the volume shrinkage of epoxides during crosslinking by sulfonium salt‐initiated cationic polymerization of epoxides

“…Their cationic ring‐opening polymerization accompanies volume expansion or no volume shrinkage as a result of the double ring‐opening reaction involved in the polymerization mechanism . Based on this volume expanding nature, copolymerization of epoxides with SOCs has been investigated with the hypothesis that the volume expansion arisen by the double ring‐opening reaction of SOCs would compensate the shrinkage caused by the polymerization of epoxides (Scheme ) . As expected, the addition of SOCs resulted in remarkable suppression of the volume shrinkage; however, the use of SOCs as comonomers often gives polymers with seriously deteriorated thermal stability because of the decrease in crosslinking degree as well as the incorporation of the flexibility of the SOC‐derived units in the main chains …”

“…2,3 Based on this volume expanding nature, copolymerization of epoxides with SOCs has been investigated with the hypothesis that the volume expansion arisen by the double ring-opening reaction of SOCs would compensate the shrinkage caused by the polymerization of epoxides (Scheme 1). [4][5][6][7][8][9][10][11][12][13][14][15][16][17] As expected, the addition of SOCs resulted in remarkable suppression of the volume shrinkage; however, the use of SOCs as comonomers often gives polymers with seriously deteriorated thermal stability because of the decrease in crosslinking degree as well as the incorporation of the flexibility of the SOC-derived units in the main chains. [5][6][7][8][9][10][11][12][13] Recently, we reported a facile synthesis of oligo(spiroorthocarbonate)s 1, a new series of multifunctional SOCs, by polycondensation of tetraethylorthocarbonate with pentaerythritol or its derivatives.…”