Comparison of additive and reactive phosphorus-based flame retardants in epoxy resins

Abstract

The aim of this work was to investigate the effect of phosphorus-based additive and reactive flame retardants (FR) on the flammability and mechanical properties of a pentaerythritol-based model epoxy resin system cured with a cycloaliphatic diamine hardener. Commercially available ammonium polyphosphate (APP) was used as additive and 9,10-dihydro-9-oxa-10-phosphaphenantrene-10-oxide IntroductionEpoxy resins are extensively used in various industrial application fields as, for example, adhesives, surface coatings, laminates and matrix materials. Despite their exceptional characteristics like prominent adhesion to many substrates; moisture, solvent and chemical resistance; low shrinkage on cure; outstanding mechanical and electronic resistant properties, their flammability can still limit their application. The heat exchange during polymerization is also influences the potential fields of application [1]. The use of structural units made of composites of high mechanical loading capability, being suitable for replacing metallic structures, is rapidly increasing in the aircraft industry [2]. In the newest large commercial airliners the fuselage, the wings and the empennage are also made of carbon fibre reinforced composites. In case of fire, the health risk is not the only danger; also the decrease of mechanical properties can be significant [3]- [5]. Due to environmental reasons, the use of halogencontaining flame retardants needs to be decreased. Their most promising substitutes are the phosphorus-containing flame retardants owing to their extremely wide and versatile range, since the P element exists in various oxidation states [6]- [9]. The fire retarded epoxy resins with conventional additives are usually of poorer physical/mechanical properties than the unmodified ones; therefore the use of reactive comonomers is preferred in many cases. A great advantage of the reactive flame retardants is that they are chemically bound to the matrix, so their release to the environment is blocked, thus we can avoid the formation of FR-containing wastewaters [10]. However, incorporating them into the polymer structure several properties of the material generally decrease. The greatest challenge for the current research works is to create a composite system with optimal balance of mechanical performance and flame retardancy.Ammonium polyphosphate (APP), an additive-type flame retardant, with high phosphorus (31-32 wt%) and nitrogen (14-15 wt%) content, is extensively used in thermoplastic polymers, such as polypropylene [11, 12], ethylene-vinyl-acetate [13], polyurea [14], polylactide [15], etc. The literature deals with the application of APP in aromatic epoxy resins, mainly in diglycidyl ether of bisphenol-A (DGEBA), however

Development of natural fibre reinforced flame retarded epoxy resin composites

“…The P-content of the flame retarded matrix was chosen to be 2.5 mass%, to reach V-0 rating in UL-94 tests, according to previous studies of the authors [19,28] …”

Synthesis of biobased phosphorus-containing flame retardants for epoxy thermosets comparison of additive and reactive approaches

“…The covalent bonding brought by the reactive approach could favor the charring effect. Recently, Szolnoki et al [16] reported a study which compares the additive approach to the reactive one in epoxy thermoset using a phosphorus-containing diamine (curing agent) as reactive P-FR and the ammonium polyphosphate as additive P-FR, showing that a lower phosphorus content is required to reach the V-0 grade at UL-94 test by the reactive approach. However, the P-FR systems used possess different chemical structures which can influence the results.…”

Effect of Particle Size of Additives on the Flammability and Mechanical Properties of Intumescent Flame Retarded Polypropylene Compounds

“…In parallel with the continually increasing use of plastics, the issue of fire safety has come to the forefront. Flame retardancy of polymers has become essential in many application fields such as transportation, construction, and electrical industries [1][2][3][4].…”