Abstract
Sodium montmorillonite nanoclay (Na+-MMT) was modified by plasma polymerization with methyl methacrylate (MMA) and styrene (St) as monomers and was denominated as Na+-MMT/MMA and Na+-MMT/St, respectively. This plasma modified nanoclay was used as reinforcement for polystyrene (PS) nanocomposites that were prepared by melt mixing. Pristine and modified Na+-MMT nanoclay were analyzed by the dispersion in various solvents, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results confirmed a change in hydrophilicity of the modified Na+-MMT, as well as the presence of a polymeric material over its surface. The pristine PS/Na+-MMT and modified PS/Na+-MMT/MMA and PS/Na+-MMT/St nanocomposites were studied with X-ray diffraction (XRD), differential scanning calorimetry (DSC), and TGA, as well as mechanical properties. It was found that the PS/Na+-MMT/St nanocomposites presented better thermal properties and an improvement in Young’s modulus (YM) in compared to PS/Na+-MMT/MMA nanocomposites.
Highlights
Research and development of polymeric materials with better properties have led to the reinforcement of polymeric matrices with particles at nanometer scale, which facilitates the exchange and transference of properties between the phases [1, 2]
This is a qualitative estimation to the interaction degree between materials, since the organic films deposited on the Na+-MMT using methyl methacrylate (MMA) and St monomers that crosslink due to plasma polymerization cause the modified Na+-MMT to interact in solvents with similar solubility parameter
In samples of PS/Na+-MMT/MMA and PS/Na+-MMT/St nanocomposites, the results indicate that there is no evidence of a significant level of exfoliation or intercalation of Na+-MMT modified by plasma in the PS/Na+-MMT nanocomposites, possibly because the coating formed by plasma on the nanoclay does not allow the introduction of the St or MMA polymer in-between the nanoclay galleries
Summary
Research and development of polymeric materials with better properties have led to the reinforcement of polymeric matrices with particles at nanometer scale, which facilitates the exchange and transference of properties between the phases [1, 2]. Plasma presents certain advantages in this area compared to conventional surface modification methods It is a relatively simple, rapid, dry, and environment-friendly technique that is used to modify the surface of a great variety of materials. If the plasma modification is carried out by using a monomer (plasma polymerization), this can generate a polymeric coating like the specific polymeric matrix over the nanoparticle with a desired increase in surface interaction, promoting an improvement in the adhesion between phases and the transference of properties between them [15, 16]. Reported works using plasma modification of nanoclays and other nanoparticles to prepare polymer composites have presented favorable improvements in particle dispersion as well as thermal, mechanical, and gas barrier properties [5, 15, 16, 39,40,41]. In the reported investigations, there have been no references that include the comparative study of modified Na+-MMT with St (Na+-MMT/St) and with MMA (Na+MMT/MMA) added to PS for the purpose of evaluating the differences between the modifications on the two modified nanoclays and their interaction in the PS matrix
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