Abstract
A series of samples of Mg/Zn/Al LDHs (layered double hydroxides) materials was prepared by the co-precipitation and urea hydrolysis methods. They were modified with organic surfactants (acrylate and oleate anions) and characterized by X-ray diffraction, which corroborated the intercalation of anionic species into the interlayer space. The hydrophobized materials were incorporated at low contents (10 and 15 wt.%) to polystyrene, which was synthesized by emulsion polymerization techniques. The polymeric composites were analyzed by thermogravimetry to determine the decomposition temperature. The results demonstrated that the materials with Zn presented the greatest increment in the degradation temperature (7 °C < T < 54 °C). Moreover, the Friedman, Flynn–Wall–Ozawa, and Coats–Redfern models were compared to obtain the kinetic parameters of degradation process. The obtained order of decomposition of the Coats–Redfern model showed that the decomposition process occurs in at least two stages. Finally, the addition of environmentally friendly modified Layered Double Hydroxides (LDH) nanomaterials to the polystyrene (PS) matrix allowed for obtaining polymeric composites with higher thermal stability, retarding the decomposition process of PS.
Highlights
Flame retardants (FRs) are additives that have been incorporated into polymers to reduce their flammability [1]
A variety of multicationic Layered Double Hydroxides (LDH) were synthesized by the co-precipitation and urea hydrolysis methods. These materials were modified with oleate and acrylate anions, so that they could be dispersed into polystyrene (PS) matrix, because they are short-chain organic compounds and they have a good hydrophobic-lipophilic balance (HLB ≈ 1); to be precise, the lipophilic part has almost the same size of the hydrophilic part. This characteristic allows for the inorganic materials, such as LDH, to be hydrophobized [25,26] the incorporation of modified LDH materials was carried out and their thermal stability was studied in order to increase the thermal stability of the PS matrix, generating environmentally friendly composite materials
Mg/Zn/Al LDH nanomaterials were prepared by coprecipitation and urea hydrolysis and their structures were hydrophobized with the acrylate and oleate anions
Summary
Flame retardants (FRs) are additives that have been incorporated into polymers to reduce their flammability [1]. A good dispersion of flame retardants within a polymeric matrix is an important parameter for increasing the decomposition temperature, modifying the ignition point, and providing greater thermal stability [7,8,9] This can be accomplished by the organophilization of the inorganic nano-additive, which forms a barrier that minimizes the mass transfer that is associated with polymer degradation [1,10]. A variety of multicationic LDHs (containing Mg, Zn, and Al) were synthesized by the co-precipitation and urea hydrolysis methods These materials were modified with oleate and acrylate anions, so that they could be dispersed into polystyrene (PS) matrix, because they are short-chain organic compounds and they have a good hydrophobic-lipophilic balance (HLB ≈ 1); to be precise, the lipophilic part has almost the same size of the hydrophilic part. This characteristic allows for the inorganic materials, such as LDH, to be hydrophobized [25,26] the incorporation of modified LDH materials was carried out and their thermal stability was studied in order to increase the thermal stability of the PS matrix, generating environmentally friendly composite materials
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