Flame Retardancy in Epoxy: The TDPPI Breakthrough

DSC trace of neat epoxy and epoxy-TDPPI composites
DSC trace of neat epoxy and epoxy-TDPPI composites

A groundbreaking flame retardant has emerged to redefine the performance of epoxy composites. Meet tris[4-(2,5-dioxopyrrol-1-yl)phenyl] phosphite (TDPPI), a phosphorus-based maleimide boasting unparalleled attributes such as moderate transparency, enhanced thermal stability, and improved mechanical strength.

Incorporating TDPPI into epoxy proved to be a game-changer, with SEM studies confirming its uniform dispersion and excellent compatibility with the epoxy matrix. Differential scanning calorimetry showcased that a mere 2.5 wt% of TDPPI led to 100% curing, achieving a glass transition temperature of 43.8°C.

The thermogravimetric study unveiled a remarkable 23% increase in residual mass at 600°C when 2.5 wt% of TDPPI was introduced to the epoxy. Notably, the epoxy thermoset compounded with this minimal TDPPI concentration passed the stringent Underwriter’s Laboratory (UL-94) test with a V-1 classification. Furthermore, it achieved a limiting oxygen index of 30.7%, accompanied by a significant 58.7% reduction in burning rate.

At a conservative 1.5 wt% of TDPPI, the resulting epoxy thermoset exhibited remarkable enhancements across various mechanical properties. Tensile strength saw a notable 23% increase, Young’s modulus soared by 37%, flexural strength showed a 9% improvement, and Izod impact strength experienced an impressive surge of 37%, all in comparison to the neat epoxy.

In conclusion, the addition of 2.5 wt% of TDPPI emerged as the sweet spot for achieving flame retardancy in epoxy composites while simultaneously enhancing mechanical strength. The maleimide-phosphorus synergistic effect showcased TDPPI’s prowess as a promising flame retardant material, marking a significant advancement in the quest for high-performance epoxy formulations in the plastics engineering landscape.

You can read more about this topic in the article “Revolutionizing epoxy performance: A new flame retardant with phosphorus and maleimide for enhanced cure behavior, thermal stability, flame retardancy, and mechanical properties” by Ayyappan RanjithArunjunai Raj MahendranThangamani Rajkumar, published in the September 2023 issue of Polymer Engineering and Science and chosen as the Editor’s Choice article for December 2023.

By Plastics Engineering | December 16, 2023

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