Sol–Gel Treatments to Flame Retard PA11/Flax Composites

Abstract

This work investigates the efficiency of sol–gel treatments to flame retard flax fabric/PA11 composites. Different sol–gel treatments applied to the flax fabrics were prepared using TEOS in combination with phosphorus and/or nitrogen containing co-precursors (DEPTES, APTES) or additives (OP1230, OP1311). When the nitrogen and the phosphorus co-precursors were used, two coating methods were studied: a ‘one-pot’ route and a successive layer deposition method. For the “one-pot” method, the three precursors (TEOS, DEPTES, and APTES) were mixed together in the same solutions whereas for the different layers deposition method, the three different treatments were deposited on the fibers successively, first the TEOS, then a mix of TEOS/DEPTES, and finally a mix of TEOS/APTES. After deposition, the sol–gel coatings were characterized using scanning electron microscope, electron probe microanalyzer, and 29Si and 31P solid-state NMR. When only TEOS or a mix of TEOS and DEPTES is used, homogeneous coatings are obtained presenting well-condensed Si units (mainly Q units). When APTES is added, the coatings are less homogenous and agglomerates are present. A lower condensation rate of the Si network is also noticed by solid-state NMR. When additives are used in combination with TEOS, the TEOS forms a homogenous and continuous film at the surface of the fibers, but the flame retardants are not well distributed and form aggregates. The flame retardant (FR) efficiency of the different treatments on flax fabrics was evaluated using horizontal flame spread test. The following ranking of the different systems is obtained: TEOS + Additives > TEOS > TEOS + DEPTES ~ TEOS + DEPTES + APTES > multilayers. All the sol–gel coatings improve the flame retardant properties of the flax fabric, except the multilayer treatment. Based on these results, the three most efficient sol–gels were selected to prepare sol–gel-modified flax/PA11 composites. The composite modified with only TEOS showed the best FR properties. Surprisingly, the composite modified with the phosphorus-based flame retardant (AlPi) did not exhibit improved FR properties. This effect was attributed to the fact that the amount of the FR additive deposited on the fabrics was too low.

Thin coatings for fire protection: An overview of the existing strategies, with an emphasis on layer-by-layer surface treatments and promising new solutions

“…[44], [45] Other strategies to use P and Si synergism is to treat the cotton by phosphorylation [34] or phenylphosphonic acid padding. [36] More commonly, phosphorouscontaining molecules are added in the sol, such as aluminum phosphinate, [46], [47] phytic acid, [48]- [50] diethylphosphite, [33] ammonium polyphosphate, [51], [52] ammonium hexametaphosphate, [53] phenylphosphonic dichloride, [54] triphenylphosphate [55] or 9,10dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). [56] The combination reduces the pHRR and THR in MLC and brings self-extinguishment behavior, which can be further enhanced by the addition of a molecule containing nitrogen, in order to obtain a P-Si-N synergism.…”

“…[56] The combination reduces the pHRR and THR in MLC and brings self-extinguishment behavior, which can be further enhanced by the addition of a molecule containing nitrogen, in order to obtain a P-Si-N synergism. [33], [34], [47], [49], [57] For example, DPTES on cotton mixed with monoethanolamine rises the LOI of the fabric up to 29 %. [58] Phosphoramidate siloxane (DTSP) on cotton increases the LOI up to 30 %.…”

Flame Retardancy of Biobased Composites—Research Development

“…Flame retardancy can be provided by the reinforcement fibers or fabric, or by using a protective coating of fibers. Flax fabric used for the polyamide 11 composite application (Flax/PA11) can be treated with silane precursors, such as tetraethoxysilane (TEOS), diethylphosphatoethyltriethoxysilane (DEPTES), and (3-aminopropyl)triethoxysilane (APTES) ( Figure 3) using two various sol-gel methods differing by the water content in order to increase the concentration of precursors in the media [68]. Various formulations of silane precursors alone and mixtures, with or without flame retardant additives in a form of aluminium phosphinate and mixture of aluminium phosphinate and melamine polyphosphate (AlPiMPP) were hydrolyzed using 0.1 M HCl in a mix of ethanol and deionized water.…”

“…Flame retardancy can be provided by the reinforcement fibers or fabric, or by using a protective coating of fibers. Flax fabric used for the polyamide 11 composite application (Flax/PA11) can be treated with silane precursors, such as tetraethoxysilane (TEOS), diethylphosphatoethyltriethoxysilane (DEPTES), and (3-aminopropyl)triethoxysilane (APTES) ( Figure 3 ) using two various sol-gel methods differing by the water content in order to increase the concentration of precursors in the media [ 68 ].…”

Sustainable Flame-Retardant Flax Fabrics by Engineered Layer-by-Layer Surface Functionalization with Phytic Acid and Polyethylenimine

“…Flax fabric is an attractive natural material, but it is highly flammable. Several reports have addressed treatment of flax fibers/fabrics with different chemicals such as tetraethoxysilane (TEOS), diethylphosphatoethyltriethoxysilane (DEPTES), and (3-aminopropyl) triethoxysilane (APTES) [ 20 ], polydopamine [ 21 ], and extracellular polymeric substances [ 22 ] to improve flame retardancy. In a previous work, we a non-biobased flame retardant of ammonium polyphosphate (APP) and a conductive polyaniline to modify flax fabric and succeed to obtain bifunctional (flame retardant and electrical conductive) flax fabrics [ 23 ].…”