The Effects of Halogen-Free Flame Retardant Additives in Epoxidized Natural Rubber (ENR)

Abstract

Legislation on fire safety requirements especially in the USA and UK has been the driving force behind the use of halogen-free flame retardants (FR) in recent years. The present study describes the effect of inorganic fillers, namely aluminium hydroxides (ATH) on epoxidized natural rubber (ENR) in order to increase its flame retardant capability. Two different types of ATH, a standard type Apyral 60 CD (ATH 60) and a submicron sized Apyral 200 SM (ATH 200) were used. The flame-retardant ENR composite was characterized by limiting oxygen index (LOI), UL-94V, and thermogravimetric analysis (TGA) to study the combustion behavior and thermal stability. The finer particles size (ATH 200) as expected produced better flame retardant properties (measured by LOI) compared to ATH 60; however, the difference between the values is marginal. It was also observed that a combination of 100 pphr ATH 200 and 60 pphr ATH 60 gave the highest LOI value (29.4%) in ENR compounds. The compound was V0 rated in UL-94V burn test. Even at the higher loading, it was also found that the compound exhibited lower viscosity indicating its easier processability.