Sol–Gel Treatments to Flame Retard PA11/Flax Composites

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.

Organic–inorganic hybrids having a talc-like structure as suitable hosts to guest a wide range of species

The sol–gel process involving hydrolysis and condensation reactions is an attractive way to form siloxane based hybrid materials since it is a one-step method performed under mild conditions.

Modification of Talc@TiO2 toward high-performance nitrile rubber application

To improve the dispersion of talcum powder (Talc) for polymer applications, modified nano-titania powders (TiO₂) using a silane coupling agent (KH550), a titanate coupling agent (NDZ201) and sodium polyacrylate (PAAS) were well adhered to the surface of Talc with a ball milling method, thereby preparing a series of mixed Talc@TiO₂ particles to realize good dispersion in carboxylated acrylonitrile–butadiene rubber (XNBR). Note that Talc@TiO₂ particles modified by PAAS and NDZ201 show better colloidal dispersion in anhydrous ethanol due to organification and repulsion of charge, with original Talc and NDZ201 modified Talc@TiO₂ powders as a comparison. Modified Talc@TiO₂ hybrid XNBR shows good performance characteristics, including damping capacity and impact resistance, depending mainly on the excellent mechanical property of Talc, good dispersion and the high adhesive force between modified Talc@TiO₂ and XNBR.

Modified nano-titania powders (TiO₂) with KH550, NDZ201 and PAAS were adhered to the surface of talcum powder (Talc) using a ball milling method.