Cone calorimeter study of polyethylene flame retarded with expandable graphite and intumescent fire-retardant additives

Abstract

Polyethylene was flame retarded with an intumescent flame retardant at 27 wt.% and expandable graphite at 10 wt.% either on its own or in combination with 10 wt.% or 20 wt.% of the intumescent. Two grades of each flame retardant type were used. They differed primarily with respect to the onset temperature for exfoliation (commercially sourced expandable graphite types) or decomposition (intumescents). The latter were the highdecomposition-onset-temperature intumescent 3,5-diaminobenzoic acid phosphate and the commercially available low-decomposition-onset-temperature ethylenediamine phosphate. The fire performance of pressed sheets with a nominal thickness of 3.2 mm was tested in a cone calorimeter at a radiant flux of 35 kW m 2 . The best char yields were obtained with compositions containing 3,5-diaminobenzoic acid phosphate. Despite this, the best fire overall performance was realized using ethylenediamine phosphate, together with the lowexfoliation-onset-temperature expandable graphite. Formulations based on this intumescent compound ignited later, reached the peak heat release rate earlier, and also burned longer irrespective of the expandable graphite grade used. This can be attributed to the formation, at the burning surface, of a more cohesive char with better thermal and mass transfer barrier properties. This explains why compositions based on ethylenediamine phosphate as intumescent outperformed those containing 3,5-diaminobenzoic acid phosphate in terms of the peak heat release rate and other important fire indices.

A macromolecular halogen‐free flame retardant and its effect on the properties of thermoplastic polyesters

“…20,21 It should be noted that a shortened ignition time has been observed on other phosphor-containing flame retardants before. 22 Second, the total heat evolved is reduced from 68.6 to 61.2 MJ m 2 .…”

Characterization of commercial expandable graphite fire retardants

“…This investigation and its associated projects aim to explore the use of these additives in a variety of applications ranging from flame retardants to heat storage materials [27][28][29][30]. The objective of this particular study in particular was to perform a comprehensive characterization of two commercial expandable graphite grades used in industrial polymer applications.…”

Thermal properties of polyethylene flame retarded with expandable graphite and intumescent fire retardant additives

“…Very good bonding of loose EG strings was observed with both EDAP and DABAP present. The EDAP binary systems showed the best cohesive thermal barrier formation thus yielding excellent fire retardation as a result . All flame‐retarded samples prevented polymer flow.…”

“…The d 10 , d 50 , and d 90 particle sizes of this low expansion onset temperature grade were 313, 533 and 807 µm, respectively (Mastersizer 2000, Malvern Instruments, Malvern, UK), and the density was 2.23 ± 0.01 g cm −3 . The phosphate salts of ethylenediamine phosphate (EDAP) and of 3,5‐diaminobenzoic acid phosphate (DABAP) were synthesized using the procedures previously described . The structural formulas for these two compounds are presented in Scheme .…”