Effect of partial substitution of aluminum hydroxide with colemanite in fire retarded low-density polyethylene

Abstract

Metal hydroxides have long been considered as abundant and low-cost fillers for the development of halogen-free flame-retarded polyolefins. However, large filler loading levels are required in the matrix resin to achieve satisfactory fire retardant performance, which results in deteriorated processing characteristics and poor mechanical properties of compounds. Therefore, this study was aimed at improving the fire retardancy of low-density polyethylene and decreasing the total filler loading in the resin using combinations of aluminum hydroxide and a natural hydrated calcium borate, namely, colemanite mineral. Flame retardancy was studied by the mass loss calorimeter analysis, limiting oxygen index measurements, and UL94 classification. Peak heat release rate and total heat evolved were lowered by around 20% and 15%, respectively, with partial replacement of aluminum hydroxide by colemanite, which facilitated the use of lower total filler loading in the resin. Depending on colemanite content and total filler loading, limiting oxygen index was increased by 1%-4% while maintaining the UL94 V-0 rating. Fire retardant effect of colemanite used in conjunction with aluminum hydroxide was attributed to better protective character of fire residues and more effective fuel trapping in the condensed phase. Lower elastic modulus and higher ductility was obtained due to decreased total filler loading in the matrix.

Thermal Degradation of Particleboards Incorporated with Colemanite and Common Boron-based Fire Retardants

“…Even though the colemanite mineral showed apparently good fire-retardant properties in different sorts of composites and polymers, it was not effective in particleboards without any polymer matrix such as polyethylene, polystyrene, epoxy, or acetate-acrylate-based copolymers (Kaynak and Işitman 2011;Işitman and Kaynak 2012;Guzel et al 2016;Cavodeau et al 2017;Terzi et al 2018). When such polymers and copolymers are exposed to external heat flow, they emit high enough energy to activate the dehydration of the colemanite mineral due to the cleavage of bonds in their structures.…”

“…According to thermal analysis studies, dehydration reactions begin at approximately 80 °C, 130 °C, and 315 °C for borax, boric acid, and zinc borate, respectively. However, significant release of water in colemanite begins at a relatively high temperature at about 390 °C (Waclawska et al 1988;Işitman and Kaynak 2012;Motor Terzi (2018). "Fire-resistant particleboards," BioResources 13(2), 4239-4251.…”

“…In previous studies on various products without wood particles, such as polystyrene-based composites, low-density polyethylene, epoxy composites, ethylene vinyl acetate/ethylene methyl acrylate copolymers, colemanite has been considered as a successful candidate due to its high fire-retardant properties. Colemanite has also showed synergistic effects with common metal hydroxides to increase the fire performance of such materials (Kaynak and Işitman 2011;Işitman and Kaynak 2012;Guzel et al 2016;Cavodeau et al 2017).…”

The use of colemanite and ulexite as novel fillers in epoxy composites: Influences on thermal and physico-mechanical properties

“…This result can be probably explained that higher thermal stability of colemanite than ER. In other words, neat ER degrades initially at around 150 °C and colemanite degrades between 350-440 °C with water formation from hydroxyl groups in the structure, and then hydrogen bonds breaking between water molecules and colemanite chains [29]. Although IDT of the UECs was lower than neat ER, T 50 values exhibited a slightly increase.…”

“…Kaynak et al [28] utilized colemanite as flame retardant in high-impact polystyrene containing brominated epoxy and antimony oxide. Isitman et al [29] purposed to enhance flame retardancy of low-density polyethylene with adding combination of aluminum hydroxide and colemanite. Baştürk et al [30] tried to improve mechanical, thermal and surface properties of bisphenol A dicyanate ester with bisphenol P dicyanate ester and colemanite.…”