Study on properties of flame‐retardant cyanate esters modified with DOPO and triazine compounds

Abstract

Ternary flame-retardant modified cyanate ester blends (CEPG and CEPA) are formed by combining triazine compounds (TGIC or TAIC) and 9,10-dihydro-9-oxa-10phosphaphenanthrene-10-oxide with cyanate ester resin. The curing behaviors, thermal and mechanical properties, and the flame-retardant properties are investigated. The results show that the CEPG and CEPA blends result in lower curing temperatures and glass transition temperatures than those of neat CE. Both of CEPG and CEPA blends significantly improve the flame-retardant properties of CE resins, and UL-94V-0 rate is achieved for CEPG-1.0 and CEPA-0.5. The dielectric constant and loss of CEPA blends are lower than those of CEPG blend with the same phosphors content, and both of them are lower than those of neat CE. Therefore, the ternary flame-retardant modified cyanate ester blends provide 2 ways for composites of producing printed circuit board with high flame-retardant property and low dielectric constant and loss. KEYWORDS cone calorimeter, cyanate esters, dielectric constant and loss, phosphaphenanthrene, triazine compounds 1 | INTRODUCTION Cyanate ester (CE) exhibits high glass transition temperature, 1 low internal stress, 2 good adhesion, 3 low dielectric constant, 4 low toxicity, and high flame-retardant property, 5 due to the formed steady s-triazine ring by the self-curing of CE group. And owing to those advantages, CE offers several advantages over the commercial use high performance epoxy in aircraft field and electronic application. 6 However, as a thermoset resin, its flammability hinders its application which required high fire safety.As investigated in the previous research, the limiting oxygen index (LOI) of CE (26%) is much higher than that of epoxy resin (22%), but it still failed in UL-94 test. To improve the flame-retardant property of CE, many researchers focused on either combining CE with high thermostable resin such as bismaleimide and benzoxazine or modifying CE with flame-retardants such as halogen-containing, 7 phosphoruscontaining, 8,9 sulfur-containing, 10 and silicon-containing compounds. 11

An Effective Method for Preparation of Liquid Phosphoric Anhydride and Its Application in Flame Retardant Epoxy Resin

“…The metaphosphoric acid was polymerized in the combustion and the subsequent formation of a char layer retained on the surface of combustibles prevented further heat transmission. 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) containing biphenyl, phenanthrene ring structures and the side phosphorus group in the form of active O=P-O cyclic bond was considered to be an effective reactive flame retardant substance for epoxy resins [ 16 , 17 , 18 ]. DOPO and their derivatives exhibited good thermal stability, chemical activity and flame retardant performance because of the embedment of a phosphorus atom into the epoxy molecular chain through chemical modification [ 19 , 20 , 21 ].…”

Synergetic effect of thermal conductivity and flame retardancy of cyanate ester composites containing DOPO and BN with great dielectric properties

“…The BN‐DOPO/CE ternary composites were made by solution mixing and casting technology. The CE/DOPO (CEP) prepolymer was synthesized by the following method: add CE resin and DOPO to a three‐neck round‐bottom flask, set the temperature at 125°C for 4 hours, and then cooled to room temperature for standby application. Appropriate amounts of CEP and BN were drastically mixed at 150°C with stirring vigorously to form uniform solution and degassed for 30 minutes before transferred into preheated mold.…”

Cyanate ester composites to improve thermal performance: a review

“…9,10‐Dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) is one of the most promising PFRs studied extensively with various polymeric materials to improve their flame retardance. Several research articles also outline the functionalization of DOPO to improve its compatibility with CE resin 57–60 . Lin modified BADCy monomer by reaction with DOPO at 125 °C with 1–4 wt% phosphorus content.…”