Abstract

The great concern about the use of hazardous additives in food packaging materials has shown the way to new bio-based materials, such as nanoclays incorporating bioactive essential oils (EO). One of the still unresolved issues is the proper incorporation of these materials into a polymeric matrix. The in situ polymerization seems to be a promising technique, not requiring high temperatures or toxic solvents. Therefore, in this study, the bulk radical polymerization of styrene was investigated in the presence of sodium montmorillonite (NaMMT) and organo-modified montmorillonite (orgMMT) including thyme (TO), oregano (OO), and basil (BO) essential oil. It was found that the hydroxyl groups present in the main ingredients of TO and OO may participate in side retardation reactions leading to lower polymerization rates (measured gravimetrically by the variation of monomer conversion with time) accompanied by higher polymer average molecular weight (measured via GPC). The use of BO did not seem to affect significantly the polymerization kinetics and polymer MWD. These results were verified from independent experiments using model compounds, thymol, carvacrol and estragol instead of the clays. Partially intercalated structures were revealed from XRD scans. The glass transition temperature (from DSC) and the thermal stability (from TGA) of the nanocomposites formed were slightly increased from 95 to 98 °C and from 435 to 445 °C, respectively. Finally, better dispersion was observed when orgMMT was added instead of NaMMT.

Highlights

  • Introduction published maps and institutional affilIn recent years, the great concern about the use of hazardous and/or toxic additives in food packaging materials has led the scientific community to search for new bio-based compounds to be used in active plastic packaging

  • The in situ bulk polymerization was investigated as a promising technique, not requiring high temperatures or toxic solvents, in order to incorporate additives containing possibly volatile materials into a polymer matrix

  • The radical polymerization of styrene was investigated in the presence of sodium montmorillonite (NaMMT) and organo-modified montmorillonite including thyme (TO), oregano (OO), and basil (BO) essential oil at nominal composition 60% and

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Summary

Introduction

Introduction published maps and institutional affilIn recent years, the great concern about the use of hazardous and/or toxic additives in food packaging materials has led the scientific community to search for new bio-based compounds to be used in active plastic packaging. Essential oils are the most widely used materials in the food packaging industry [1]. To this direction, hybrids of montmorillonite (MMT) with essential oils (EO) have been prepared recently in order to be used in active packaging because of their controllable and long-life antioxidant activity [2,3,4,5,6,7,8,9]. The large bioactivity of EOs has being confirmed by several studies and includes antibacterial, anti-inflammatory, antifungal, antimutagenic, antineoplasmatic and antioxidant activities, along with other miscellaneous activities [12]

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