Effect of clay and clay/essential oil in packaging films

Abstract

The influence of the different contents of organo‐modified montmorillonite clay (1 and 3%wt.) and two essential oils (Carvacrol and Eugenol ‐ 2 and 6%wt.) when incorporated into low‐density polyethylene films (LDPE) was characterized by X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). This study shows the potential of montmorillonite clay as a carrier of carvacrol and eugenol essential oils, ClayC and ClayE, respectively, into LDPE nanocomposites. To prepare the nanocomposites, oils and clay hybrid were mixed and added to polyethylene using a homogenizer. The clay increased the thermal stability of the essential oils. PE/ClayC and PE/ClayE nanocomposites showed increased crystallinity as a function of the amount of hybrid; this was more significant for the PE/ClayC system. Increased crystallinity suggests that clay acts as nucleating agent, due its intercalated/exfoliated configuration. The results contribute to obtaining a more efficient nanocomposite system for subsequent applications, such as active packaging. POLYM. COMPOS., 39:4034–4040, 2018. © 2017 Society of Plastics Engineers

Antimicrobial films containing hybrid systems aiming at packaging applications

“…Another point considered from the results described in Table 2 is that the CI/C MMT-EO and CI/C EO ratios showed reduced CI with an increase in hybrids and EOs present, less expressive for nanocomposites with eugenol. This behaviour occurred due to the presence of the alkyl radicals of the eugenol molecules, which probably showed a high interaction with hydrocarbon chains present in the polyethylene, as seen by Torin et al 29 Compared to LDPE, the high crystallinity in the nanocomposite films possibly affected the EO migration from the bulk of material to the surface. This could occur due to the high crystallinity and partial exfoliation of the nanoclay, which creates tortuous paths and delays diffusion of the oil.…”

“…Structural and antimicrobial characterization of nanocomposite films X-ray diffraction (XRD) The CI values are given in Table 2 for samples LDPE, LDPE/ MMT-C3, LDPE/MMT-C9, LDPE/MMT-E3 and LDPE/MMT-E9, as presented in previous work. 29 Ratios between the CI and hybrid concentrations (C MMT-EO ), clay (C MMT ) and EOs (C EO ) present in the samples were calculated and are given in Table 2.…”

“…Both EOs fulfil the interlayer spacing (d-spacing) between the clay and the polymer bulk, as identified in previous work. 29 From the point of view of nanocomposites as delivery systems for active compounds, the intermediate crystallinities of nanocomposites are more promising to ensure the effectiveness of the EO migration and its antibacterial action. For this study, the best system that could improve antimicrobial action was for hybrids containing eugenol EO.…”

“…The planes used for the crystallinity index calculation were planes (001) and (002), as described in previous work. 29 The crystallinity index (CI %) of the LDPE and nanocomposite films was estimated using Antimicrobial films containing hybrid systems www.soci.org…”

“…where I c is the crystalline peak and I a is the amorphous halo. 29,30 Tensile tests (mechanical properties) Mechanical tests characterizing tensile properties were conducted to determine the nanocomposite strength, maximum elongation, tensile strength at break and Young's modulus, in a Universal Machine Instron, Model 3369 (Instron Brasil Equipamentos Científicos, São José dos Pinhais, PR, Brazil), with an optical strain gauge for displacement control. The tests were carried out according to ASTM D-638-14, comprising type IV, specified in the standard, with a test speed of 50 mm min −1 , a load cell of 50 kN and the following specimen dimensions: length overall 115 mm, width overall 20 mm and thickness 1.4 mm, approaching the minimum required.…”