Preparation, Characterization and Photostability of Nanocomposite Films Based on Poly(acrylic acid) and Montmorillonite

Virgínia De Alencar Muniz Gonzaga,Alessandra Lima Poli,Bruno Alvim Chrisostomo,Carla Cristina Schmitt

doi:10.1590/1980-5373-mr-2017-1024

Virgínia De Alencar Muniz Gonzaga, Alessandra Lima Poli + Show 2 more

Open Access

https://doi.org/10.1590/1980-5373-mr-2017-1024

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Abstract

Polyacrylic acid (PAA)/clay mineral (SWy-1) nanocomposites were prepared by intercalation in solution and their photostability was evaluated. For the nanocomposite films containing 5, 10 and 20 wt % in SWy-1 mass occurred intercalation along with some clay exfoliation, while for PAA/30%SWy-1, the intercalation of PAA chains into the clay interlayers was observed. Scanning Electron Microscopy (SEM) images of the films suggested that nanocomposite films are homogeneous, indicating efficient dispersion of the polymer matrix into the SWy-1 clay. The thermal degradation temperatures of depolymerisation for the nanocomposite films were higher (362-370 °C) than pure PAA (361 °C), which means that the presence of SWy-1 clay promotes thermal stabilization.The photooxidative degradation of pure PAA and nanocomposite films was followed using Size Exclusion Chromatography (SEC). The degradation rate constant for pure PAA was higher than nanocomposite films; therefore, the increase of SWy-1concentration detained the degradation of PAA. The presence of SWy-1 clay contributes for the photostabilization of the material. SWy-1 has ability to disperse the incident light as well as also to absorb part of the UV light instead of PAA, hence minimizing the degradation rate.

Highlights

In recent years, polymer layered silicate nanocomposites have attracted attention in many fields, e.g., in industry exploitation and fundamental research[1,2]
The 001 reflection peak for Polyacrylic acid (PAA)/30%SWy-1 has been shifted toward lower angles, which is an indication of the lower regularity and large basal spacing as a result of the intercalation of PAA chains into the clay galleries[26]
Fourier transform infrared spectroscopy (FTIR)-attenuated total reflectance (ATR) spectrum of PAA/5%SWy-1 is the combination of the characteristics bands of the spectra of both components, the band at 1700 cm-1 is connected with the stretching vibrations of C = O in carboxyl group

Summary

Introduction

Polymer layered silicate nanocomposites have attracted attention in many fields, e.g., in industry exploitation and fundamental research[1,2]. These materials exhibit excellent mechanical and thermal properties, decrease in gas/vapor permeability, and reduced flammability in the presence of a small amount of the silicate, as compared with the polymer itself[2,3,4]. Montmorillonite (Mt) is one of the most commonly used and extensively studied of clay mineral polymer nanocomposites[5,6] It pertains to the general family of 2:1 layered silicates made up of two silica tetrahedral sheets merged to an edge-shared octahedral sheet of magnesia or alumina. The stacking of these layers occurs in a parallel way, leading to a regular van der Waals gap between the layers called the interlayer region[7,8]

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