Flame Retardancy of Dicyandiamide-Crosslinked Epoxy Resins Containing Phenolphthalein Structures and/or a Phosphorus- Containing Additive

Abstract

The feasibility of producing halogen-free epoxy moldings having a UL-94 V-0 flammability rating has been further supported. We have shown that the fire retarding properties (OI and UL-94) of the cured epoxy were strongly im proved by using the commercial additive resorcinol bis(diphenyl phosphate) (FYROLFLEX RDP) but not improved merely by reacting phenolphthalein into the resin as a chain extender. However, a combination of the phosphate with the phenolphthalein as a chain extender gave substantially enhanced flame retar dant results. A related system where the phenolphthalein structure was built into the phosphate additive rather than into the polymer backbone gave inferior re sults. Thermogravimetric analysis in N2 showed that the system of the phosphate ad ditive in the phenolphthalein-extended resin gave an increased char yield. Infrared studies on the system at different pyrolysis temperatures showed that the lactone carbonyl of the phenolphthalein structure underwent reaction during decomposition of the cured resin in the presence of the phosphate. Infrared evi dence suggested that this lactone group may be involved in a crosslinking reac tion forming amide links, which may lead to char enhancement. The phosphate depressed somewhat both the Tg and thermal stability but the presence of the phenolphthalein structure partially overcame the Tg depression.

Thermal decomposition, combustion and flame‐retardancy of epoxy resins—a review of the recent literature

“…Liu et al 91 showed that the fire‐retarding properties (OI and UL‐94) of a cured epoxy were strongly improved by using the commercial additive resorcinol bis(diphenyl phosphate) (RDP). Moreover, a combination of the phosphate with phenolphthalein, used as a chain extender, gave substantially enhanced flame‐retardant results.…”

The effect of chemically reactive type flame retardant additives on flammability of PES toughened epoxy resin and carbon fiber‐reinforced composites

“…The control composite laminate had T g at 205°C, which is lowered in the presence of flame retardants. This may be due to plasticizing effect of FR additives in the resin 30. The higher T g values of the control C1 composite may also be due to slightly higher resin content (Table 6) and hence, higher number of sulphone groups which affect the toughening of the resin31 compared to samples C2 and C3, where resin content is lowered due to additional FR chemicals presence.…”

Influence of organic-modified iron–montmorillonite on smoke-suppression properties and combustion behavior of intumescent flame-retardant epoxy composites

“…The slope of THR curve can be assumed as representative of fire spread. 17 From Figure 3, the THR of samples with Fe-OMT is decreased with increasing contents of Fe-OMT. It is very clear that the flame spread of samples with IFR and Fe-OMT decreases, and the flame spread of EP-3 is comparatively the lowest among all samples.…”

“…Several approaches for modification of the EP backbone to enhance the thermal properties of EP resins have been reported. [14][15][16][17] Flame retardants such as tetrabromobisphenol-A, phosphorus-halogen mixtures, ammonium phosphate, and organophosphorus compounds have been used to impart flame retardancy to EP resins. [18][19][20][21] In a fire, halogens (such as bromine or chlorine) lead to problems of smoke and possibly enhanced toxicity and corrosion.…”