Abstract
The most common polymeric nanocomposites are constituted of organically-modified clays. Generally, these organic modifiers are based on quaternary ammonium salts. These systems have as disadvantage the low thermal resistance of its modifiers under processing. Ionic liquids (IL) with different molecular structures can be used as organic modifier in lamellar clays-based polymeric nanocomposites, being promising not only to increase interactions between the nanoclay and the matrix, but also to increase the thermal resistance. In this study, polypropylene-based/montmorillonite nanocomposites were compared from two different organic modifiers. The use of short alkyl chain length imidazolium-based IL as montmorillonite modifier was investigated in terms of the thermal stability when compared to the usual quaternary ammonium salt surfactant. Integral procedure decomposition temperature was employed to determine the effect of these two different organoclay modifiers in PP-nanocomposites. The activation energy for these samples was calculated using Flynn–Wall–Ozawa (FWO) method. It was also used the multiple linear regression analysis to calculate the activation energy in order to evaluate the accuracy of this method when applied to nanocomposites.Article HighlightsShort length alkyl group in ionic liquid was able to improve the thermal stability of PP-based nanocomposite.IPDT methodology is more realistic to evaluate the thermal stability of ionic liquid-based nanocomposite.MLR methodology was efficient to assess the entropic contribution associated to polymer-clay interactions, inter-lamellae spaces and interface morphology.
Highlights
Nanocomposites based on organically modified clays especially montmorillonite (MMT) have been attracting great interest to be used in polymeric matrices due to significant influences on the mechanical properties, gases and liquids permeability, barrier properties and thermal resistance [1,2,3,4,5]
Due to its molecular volume the quaternary ammonium salt present in MMT-20A clay contributes to increase the d spacing of the clay galleries when compared to the [BMMIM] Cl modifier present in MMT-Ionic liquids (IL) clay
In order to evaluate the thermal stability of the nanocomposites it was used the integral procedure decomposition temperature (IPDT) proposed by Doyle [28]
Summary
Nanocomposites based on organically modified clays especially montmorillonite (MMT) have been attracting great interest to be used in polymeric matrices due to significant influences on the mechanical properties, gases and liquids permeability, barrier properties and thermal resistance [1,2,3,4,5]. To obtain a successful preparation of polyolefinbased nanocomposites, ions can be exchanged by a wide variety of hydrated inorganic or organic cations, including those of amines, quaternary ammonium salts or alkylphosphonium cations [3, 5, 7, 10,11,12,13] It is well-known that the miscibility between layered clay nanoparticles and olefins polymers is low. How the effect of the alkyl length in IL on the thermal stability of polymeric nanocomposites when compared to the traditional quaternary ammonium salts remains as an important question In this investigation, organoclays based on IL obtained from the modification of 1,2-dimethyl imidazole was prepared. Systematic evaluation of the thermal stability of the samples was conducted using non-conventional methodology, as integral procedure decomposition temperature (IPDT) and multiple linear regression (MLR) differential method
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