Novel organo-modifier for thermally-stable polymer-layered silicate nanocomposites

Abstract

A new novel approach for the stabilisation of polymer-clay nanocomposites has been investigated based on reacting chemically an antioxidant function, a hindered phenol moiety, with an organic modifier based on a quaternary ammonium salt. The chemically linked antioxidant-containing organic modifier (AO-OM) was then introduced into natural montmorillonite (MMt) through a cation-exchange reaction resulting in antioxidant-containing organo-modified clay (AO-OM-MMt). The new antioxidant-containing modified clay, along with other organo-modified clays having a similar organo-modifier but without the reacted antioxidant, were characterised by spectroscopic, thermogravimetric and x-ray diffraction techniques and tested for their thermo-oxidative stability. PA11-based clay nanocomposites samples containing the AO-OM-MMt and the other organo-modified clays, both without and with an added (i.e. not chemically reacted) hindered phenol antioxidant (similar to the one used in the AO-OM) were prepared by melt processing and examined for their processing and long-term thermal-oxidative stability at high temperatures. It was shown that although the new organo-modifier, AO-OM, was also susceptible to the Hoffman elimination reaction, the nanocomposites containing this newly modified clay (PA11/AO-OM-MMt) showed higher melt processing and long-term thermo-oxidative stability, along with excellent clay dispersion and exfoliation, compared to the other PA11-nanocomposites examined here (with and without the conventionally added antioxidant). It is suggested here that the excellent overall performance observed for the PA11/AO-OM-MMt nanocomposites is due to an in-situ partial release of low molecular weight antioxidant species having stabilising functionalities that are capable of acting locally at the interface between the inorganic clay platelets and the polymeric matrix which is a critical area for the onset of degradation processes

Thermo‐oxidative stabilization of poly(lactic acid)‐based nanocomposites through the incorporation of clay with in‐built antioxidant activity

“…The antioxidant‐organo‐modified clay [(AO)OM‐Mt] was produced (see below) by cation‐exchange reaction between the commercial natural unmodified Mt and an ammonium salt of the antioxidant‐containing organic modifier, named here (AO)OM, synthesized according to procedure reported earlier . Briefly, to produce (AO)OM, a reactive antioxidant molecule (a hindered phenol) was grafted onto a quaternary ammonium salt (2‐hydroxyethyl)oleylmethylbis ammonium chloride, molecular weight of 370.64 g/mol, and formula: C 23 H 48 NO 2 , supplied by Akzo Nobel ® under the trade name ETHOQUAD ® O/12 PG This ammonium salt which was used to produce the (AO)OM product is the same as that present in the commercial Cloisite ® 30B.…”

“…Briefly, to produce (AO)OM, a reactive antioxidant molecule (a hindered phenol) was grafted onto a quaternary ammonium salt (2‐hydroxyethyl)oleylmethylbis ammonium chloride, molecular weight of 370.64 g/mol, and formula: C 23 H 48 NO 2 , supplied by Akzo Nobel ® under the trade name ETHOQUAD ® O/12 PG This ammonium salt which was used to produce the (AO)OM product is the same as that present in the commercial Cloisite ® 30B. As was shown previously, the (AO)OM is a mixture of mono‐ and disubstituted compounds containing one and two Irganox acid molecules, respectively, at a ratio of approximately 2:3.…”

Effect of Graphene on Flame Retardancy of Graphite Doped Intumescent Flame Retardant (IFR) Coatings: Synergy or Antagonism

“…Flame retardancy of polymeric materials is a subject of major concern due to the need to minimize fire risk and meet fire safety requirements [1], especially for timber structures (plywood, density board, and fiberboard), which are widely used as interiorly decorative materials. Construction materials have long been required to resist burn through or sudden loss of mechanical properties, and maintain structural integrity, whilst continuing to stay intact when exposed to fire or heat [2,3]. Consequently, surface coating with flame retardant paints or varnishes emerges as an available, effective, and efficient surface-treatment method.…”

“…Consequently, surface coating with flame retardant paints or varnishes emerges as an available, effective, and efficient surface-treatment method. Intumescent flame retardant (IFR) coatings have been employed as ecologically-friendly substitutes for halogen-containing flame retardant additives [4], which favor the formation of shielding char layers, providing adequate fire suppression and/or thermal insulation [2,3], due to their facile, cost-effective, and energy-efficient synthesis. IFR coatings can be used not only for wood fire protection, but also (especially) for thermal insulation protection of steel, which prevents the loss of mechanical properties in case of fires, and allows for more effective evacuation and fire extinguishing [3].…”

Influence of the chemical structure of para‐bridged group on the antioxidant behavior of hindered phenol antioxidants in HDPE resin

“…[10] In order to reduce the physical loss of the antioxidants during the processing of the HDPE resin, some hindered phenol antioxidants with different chemical structures were developed, such as macromolecular antioxidants, polymerbound antioxidants, immobilized antioxidant. [11][12][13] Gyorgy Kasza synthesized hyperbranched poly(ethyleneimine) based macromolecular antioxidants with hyperbranched poly(ethyleneimine) as p-substituent of the phenolic hydroxyl and found that these antioxidants had the best stabilizing efficiency in both thermo oxidative and photooxidation in polypropylene films . [14] Cuiqin Li synthesized a series of hyperbranched macromolecule bridged hindered phenol antioxidants using hyperbranched macromolecules as p-substituent of the phenolic hydroxyl and the results of antioxidant activities showed that the antioxidant activities increased with increasing of the alkyl-chain length of psubstituent .…”