Halloysite silanization in polyethylene terephthalate composites for bottling and packaging applications

Fernando Garcia-Escobar,Adriana Berenice Espinoza-Martinez,Jaime Bonilla-Rios,Patricia Cerda-Hurtado

doi:10.1007/s10853-021-06337-8

Fernando Garcia-Escobar, Adriana Berenice Espinoza-Martinez + Show 2 more

Open Access

https://doi.org/10.1007/s10853-021-06337-8

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Abstract

Composite materials of polyethylene terephthalate with silanized halloysite nanoclay were prepared and characterized. Halloysite was first functionalized with benzoyloxypropyltrimethoxysilane and then incorporated it into the polymer matrix via melt extrusion at 0.5, 1, and 2 wt% clay load ratios. The modified clay was characterized by means of elemental carbon quantification, thermogravimetric analysis, X-ray diffraction, and nitrogen adsorption–desorption. The silanization was confirmed to have taken place with an approximate reaction yield of 5%. While the silanization did not significantly affect the crystal structure or the morphological properties of the clay, a mass loss starting from 190 °C attributed to the organosilane compound used to modify the clay was observed in the reacted samples, along with increased thermal stability. The composite materials exhibited an increase in Young’s modulus and a decrease in the ultimate strain, but not a significant change in the oxygen permeability of the composites with respect to the neat PET.Graphical abstract

Highlights

The development of polymeric composite materials with lower gas permeability than the matrix has garnered attention in recent years, as a lower gas permeability can increase the shelf life of food products by delaying the inward diffusion of oxygen that can spoil the freshness of the contained product or the outward diffusion of CO2 in carbonated beverages
To the best of our knowledge, the only work on Polyethylene terephthalate (PET)/ HNT composites was reported by Gorrasi et al [21]. Who studied these materials intended for bottling applications and concluded that the incorporation of the clay in the PET matrix reinforces the mechanical properties of the material, the agglomerated clay particles act as nucleation centers when the material is cooled after melt compounding, making the material overall prone to crystallization and to be brittle and opaque: properties not desirable in bottles. To address this area of opportunity, we studied the silanization of halloysite nanoclay with benzoyloxypropyltrimethoxysilane (BOPTMS) to improve the clay’s compatibility with the polymer matrix and its dispersion in the material
Halloysite clay was functionalized with BOPTMS, and PET composites were prepared at clay loadings of 0.5, 1, and 2% with the objective to improve the gas barrier properties of the material while conserving the same mechanical properties of the neat polymer

Summary

Introduction

The development of polymeric composite materials with lower gas permeability than the matrix has garnered attention in recent years, as a lower gas permeability can increase the shelf life of food products by delaying the inward diffusion of oxygen that can spoil the freshness of the contained product or the outward diffusion of CO2 in carbonated beverages. The chemical modification of halloysite with an organosilane coupling agent with specific functional groups can lead to better dispersion of the clay in the polymer matrix [6, 7]. Variables such as the chemical structure of the organosilane, or the reaction conditions of the functionalization reaction, can affect the way the organosilane attaches to the nanotubes, and the way the modified clay interacts with the matrix [8, 9]

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