Interfacial Interactions and Flammability of Flame-Retarded and Short Fiber-Reinforced Polyamides

Abstract

Interfacial properties, crystallinity and flammability of short fiber reinforced and flame retarded polyamide 6 and polyamide 66 compounds are investigated, emphasizing the influence of flame retardant fillers on the resistance of fiber/matrix interface to shear. Interfacial shear strengths are derived through a micromechanical approach by determining the tensile properties and residual fiber length distributions. Validated by fracture morphologies, interfacial strengths are found to be governed by filler -induced apparent crystallinities and fractional occurrence of polyamide polymorphs, obtained via peak deconvolution of X-Ray diffraction patterns. Although flame retardant additives based on Br/Sb synergism are found to impart excellent flammability reductions regarding oxygen index and UL94 classifications (V-0 rating), degree of crystallinity; thus, interfacial properties are deteriorated due to lowered thermal expansion and increased cooling rates. Red phosphorus as a flame retardant also induces a UL94 V-0 and significant reduction in flammability together with the facts that crystallinity is not altered and a strong fiber/matrix interface is maintained. Use of melamine cyanurate in an unreinforced polyamide improves the limiting oxygen index considerably; however, the UL94 rating remains unchanged as V-2 as a consequence of increased level of melt dripping. Melamine cyanurate additionally increases the degree of crystallinity through promotion of heterogeneous nucleation.

A phosphorus‐containing inorganic compound as an effective flame retardant for glass‐fiber‐reinforced polyamide 6

“…1–3 However, both PA6 and GF–PA6 are flammable; this restricts their applications in some fields. The flame retardation of GF–PA6 is much more difficult than that of PA6 because of the candlewick effect caused by the glass fibers (GFs) 3–5. Thus, the flame retardation of GF–PA6 used in electrical and electronic equipment has been a topical challenge for a long time 3.…”

“…Thus, the flame retardation of GF–PA6 used in electrical and electronic equipment has been a topical challenge for a long time 3. Many attempts to flame‐retard GF–PA6 with some halogen‐containing and nonhalogen flame retardants have been reported 3–6. Inorganic compounds such as M g (OH) 2 and Al(OH) 3 are the most environmentally friendly and cost‐effective.…”

Micro-intumescent flame retardant polyamide 6 based on cyclic phosphate grafting phenol formaldehyde

“…Lots of these applications require flame retardancy, and hence developing PA6 with good flame retardant performance has attracted much attention. [1,2] The flame retardancy of PA6 was achieved by the incorporation of halogen-containing compounds formerly; however, for the sake of safety and environmental concerns, [3] more and more applications have resorted to non-halogenated flame retardants. So far the majority of the non-halogenated alternatives are based on nitrogen, phosphorus, silicon and metal hydroxides and nanoparticles etc., [4][5][6][7][8][9][10][11][12][13][14][15] for example, melamine cyanurate (MCA), [4] Mg(OH) 2 , [5] red phosphorus, [6,7] melamine polyphosphate (MPP) [8,9] and metal dialkyl-phosphinates (MDAP).…”

Effects of ammonium polyphosphate and triphenyl phosphate on the flame retardancy, thermal, and mechanical properties of glass fiber–reinforced PLA/PC composites

“…So the different modifications were carried out to enhance the low mechanical properties. Besides, it is also known fiber reinforcement improves mechanical properties of polymers . The most common reinforcing fibers are glass, carbon, polyethylene terephthalate (PET), and Kevlar fiber .…”