Influence of kaolin addition on the dynamics of oxygen mass transport in polyvinyl alcohol dispersion coatings (original) (raw)
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Applied Clay Science, 2016
In this study oxygen permeability in dispersion barriers produced from poly(vinyl alcohol) (PVOH) and kaolin clay blends coated onto polymeric supports was investigated. To determine the oxygen permeability, two measurement methods were used: the oxygen transmission rate (OTR) and the ambient oxygen ingress rate (AOIR). It was found that with increasing kaolin content the oxygen permeability increased, up to about 5 wt% kaolin, whereafter the oxygen permeability decreased, as was expected. The increased (N 5%) kaolin loading lowered the diffusion because of an increased tortuosity. Structural information about the dispersion-barrier coatings, such as kaolin orientation and polymer crystallinity, was obtained from Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Kaolin orientation was influenced by the drying temperature, the thickness of the samples, and the kaolin concentration. The polymer crystallinity increased in thicker samples. The drying temperature did not show any clear effect on the crystallinity of thin samples, while for the thicker barriers, combined with a kaolin concentration lower than 20 wt%, a higher crystallinity was achieved at lower drying temperatures. This study demonstrates the strong influence of chemical and physical structures on the permeability of the investigated coatings.
Modeling of oxygen permeation through filled polymeric layers for barrier coatings
Journal of Applied Polymer Science, 2017
This paper presents an extended model for gas permeation through a filled polymer layer, and it is applied to the case of oxygen permeability through a poly(vinyl alcohol)/kaolin dispersion coating. The model is based on a description of polymer and penetrant properties in a thermodynamically consistent framework. The gradient in chemical potential is considered the driving force for the diffusion of the penetrating gas. The well-established nonequilibrium lattice fluid (NELF) model for the polymer phase is extended in order to account for the additional features of the polymer/filler system, such as the concentration and aspect ratio of the inorganic filler, which enhance the penetrant tortuosity. The model predicts the behavior of penetrant permeability with respect to polymer crystallinity and filler fraction. The calculated results are compared to experimentally obtained data for oxygen permeability through a dispersion coating layer consisting of poly(vinyl alcohol) (PVOH) and two types of kaolin with different aspect ratios. A good agreement is found in terms of the effects of polymer crystallinity, filler concentration, and filler aspect ratio. The experimental results also indicate a complex interplay between the polymer and the filler as the permeability of two differently surface modified kaolin clays was determined, displaying slight deviations from model predictions. Significant differences were observed in the experimental results between the two fillers investigated, and the one characterized by the smaller aspect ratio affects to a minor extent the oxygen permeability, as illustrated by the model. Furthermore, the lower hydrolysis degree of PVOH gives a reduced barrier performance, as expected.
PVOH modified nano-kaolin as barrier coating material for food packaging application
PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS: ICAM 2019
In the present study PVOH (polyvinyl Alcohol) has been used as the modifier for kaolin for its application as the barrier coating on the surface of paper. Food packaging is the essential part of nowadays lifestyle. Food package requires protection from the environmental factors like oxygen, carbon dioxide, temperature and moisture. Synthetic polymers like PVOH, EVOH (ethyl vinyl alchohol) showed high barrier property against the oxygen permeability. Kaolinite (Al 2 Si 2 O 5 (OH) 4) is a 1:1 phyllosilicate clay which consists of an octahedral layer of gibbsite and a tetrahedral layer of silicon oxide. Our study involves the synthesis of nano-kaolin by pre-treatment of native kaolin with DM SO and further modifies with PVOH. M odified nano-kaolin was analyzed using DLS (Dynamic Light Scattering), FTIR (Fourier Transform Infrared Spectra), XRD (X-ray Diffraction) and FESEM (Field Emission Scanning Electron M icroscopy) for the particle size distribution, functional properties, crystalline structure and morphology respectively. PVOH modified kaolin with different size distribution may provide the high barrier against the permeability of oxygen by providing more tortuous pathway to oxygen molecules.
Effect of kaolin content on structure and functional properties of water-based coatings
Progress in Organic Coatings, 2006
The water-based coatings for paperboard were pigmented with a mixture of kaolin and ground calcium carbonate (GCC). The effects of kaolin content on the morphology and gloss of the coatings were determined. Kaolin particle orientation in the coatings was measured with X-ray diffraction (XRD) technique using peak ratio method, which determines the ratio of the integrated peak area intensities of the and reflections. The gloss values and the number of platy kaolin particles oriented parallel to coating surface increased with increasing kaolin content. Moreover, when measured in machine direction, gloss was higher and the orientation index lower compared to measurements in cross-direction. The laser profilometer measurements indicated that the differences in machine and cross-directions are related to the macroroughness of the surface.
Polyvinyl Alcohol and Nano-Clay Based Solution Processed Packaging Coatings
Coatings
Cost-effective, clean, highly transparent, and flexible as well as a coatable packaging material is envisioned to solve or at least mitigate quality preservation issues of organic materials, originating from moisture interaction under ambient conditions. Liquid phase processing of packaging coatings using nano-clay and polyvinyl alcohol (PVOH) has been developed and reported. Detailed analysis of the developed coating revealed moisture permeability of 2.8 × 10−2 g·cm/m2·day at 40 °C and 85% relative humidity (RH), which is in close accordance with Bharadwaj’s theoretical permeability model. Moreover, the developed coatings are not only more than 90% transparent, when exposed to white light, but also exhibit excellent flexibility and even after going through 10,000 bending cycles maintained the same blocking effect against moisture.
Development and characterization of unmodified kaolinite/EVOH nanocomposites by melt compounding
Applied Clay Science, 2017
12 13 Nanocomposites of unmodified kaolinite (Kaol) / ethylene-vinyl alcohol copolymer 14 (EVOH) with different Kaol contents have been obtained by a two-step process: melt 15 blending in an internal mixer and film processing by co-extruding the obtained clay 16 polymer nanocomposites pellets in between two low-density polyethylene (LDPE) 17 layers. The addition of the clay mineral to the molten polymer has been carried out by 18 using a Kaol/EVOH masterbatch containing 15mass% Kaol. The so-obtained samples 19 have been analysed by means of WAXS, SEM, TEM, DMA and tensile tests. Finally, 20 barrier properties to water vapour and oxygen at two relative humidities have been 21 assessed. Morphological analysis has revealed high degree of dispersion and 22 distribution of the Kaol within the EVOH matrix. A considerable increase in the 23 mechanical and in the barrier properties has been found. The present work puts forward 24 the effectiveness of an unmodified kaolinite for obtaining ultra-high barrier clay mineral 25 / polymer nanocomposites. 26 27 Ethylene-vinyl alcohol (EVOH) copolymers are a family of semi-crystalline random 30 copolymers widely used in the food-packaging sector due to their outstanding gas 31 barrier properties to oxygen and organic compounds (solvents and food aromas); as well 32 as their considerable chemical resistance and high transparency(Lagaron et al., 2001). 33 The major drawback of these materials is their moisture sensitivity that causes a 34 significant decrease in their gas barrier properties at high relative humidities(Lagarón et 35
Preparation and Characterization of Polymer Blends/ Kaolinite Nanoclay
Iraqi journal of science, 2020
In this research, we prepared a polymer blend of polyvinylalcohol (PVA)/carrageenan/kaolinite by means of the solution cast approach. The composition of the blend was PVA in 1 gm by weight with 0.2 gm carrageenan as a plasticizer. The ratio of nanoclay varied between 1 and 5 wt%. Different properties were investigated in this study such as water vapor permeability, hardness, tear strength, color stability, thermal stability, and antibacterial activity. Water vapor permeability was decreased with increasing the ratio of nanoclay, while the values of hardness, tear strength, color stability, and thermal stability were increased. Also, the antibacterial activity examination with two types of bacteria, e.g. Gram positive (Staphylococcus aureus) and Gram negative (Klebsiella pneumonia), showed inhibition zone diameter which was increased with increasing nanoclay ratio. Moreover, it was found that nanoclay has the ability to kill both Gram positive and negative kinds of bacteria. It was found that the preparation of such films is suitable for food packaging.
Oxygen Diffusion into Polymer-Clay Composite Films as a Function of Clay Content and Temperature
Macromolecular Symposia, 2009
A simple fluorescence technique is proposed for the measurement of the diffusion coefficient of oxygen into polystyrene-clay composite films as a function of clay content and temperature. The composite films were prepared from a mixture of surfactant-free pyrene-labeled polystyrene latexes and modified Na-montmorillonite clay of various compositions at room temperature. Diffusion measurements were performed with films at room temperature for seven different clay contents (0, 5, 10, 20, 30, 50 and 60 wt.%). The diffusion coefficients of oxygen increased from 7.4 Â 10 À10 to 26.9 Â 10 À10 cm 2 s À1 with increasing clay content. On the other hand, diffusion measurements were performed over a temperature range of 25-70 8C for 0, 5 and 20 wt.% clay content films. The calculated diffusion activation energies decreased from 2.44 to 0.44 kcal/mol with increasing clay content. No clay content and temperature effects were observed on quenching rate constant and mutual diffusion coefficient values. The results showed that the diffusion coefficients are strongly dependent on both the temperature and clay content in the film.