Active Bio-Based Pressure-Sensitive Adhesive Based Natural Rubber for Food Antimicrobial Applications: Effect of Processing Parameters on Its Adhesion Properties

Abstract

A novel active bio-based pressure-sensitive adhesive incorporating cinnamon oil (Bio-PSA/CO) obtained from the mixture of natural rubber (NR), xyloglucan (XG), and cinnamon oil (CO) for food antimicrobial applications were successfully developed by using a two-roll mill mixer. The effect of the main process factors (i.e., nip gap and mastication time) and XG content on the adhesion properties of the obtained PSA were investigated with different coated substrates including kraft paper, nylon film, polypropylene (PP) film, and aluminum foil (Al). The results suggested that the developed NR-PSA/CO could be applied well to all types of substrate materials. Peel strength and shear strength of the NR-PSA/CO with all substrate types were in the ranges of ~0.03 × 10²-5.64 × 10² N/m and ~0.24 × 10⁴-9.50 × 10⁴ N/m², respectively. The proper processed condition of the NR-PSA/CO was represented with a nip gap of 2 mm and a mastication time of 15 min. An increase in XG content up to 40-60 phr can improve the adhesion properties of the adhesive. The resulting material could be used as an active sticky patch to extend the shelf-life of food in a closed packaging system. The shelf-life of the food samples (banana cupcake) could be extended from 4 to 9 days with NR-PSA/CO patch.

Keywords: antimicrobial packaging; bio-based pressure-sensitive adhesive; cinnamon oil; natural rubber; processing parameters; xyloglucan.

Figure 1

Physical appearance and antimicrobial activity of banana cupcake samples in a polypropylene (PP) bag with and without the natural rubber (NR)-PSA/CO patch at days 9 under 30 °C, 75% room humidity (RH).

Figure 2

The Mw, Mn and polydispersity index (PDI) of NR obtained from NR-PSA/CO with 20 phr of XG + 0.06 phr of CO with a mastication time of 10 min for different nip gaps (1 and 2 mm).

Figure 3

Adhesion model of mechanical interlocking in case of NR-PSA/CO with smooth and non-smooth surfaces along with the physical appearance of the substrate surfaces after peeling. NR-PSA/CO was produced using 20 phr of XG + 0.06 phr of CO with a mastication time of 10 min for 1 and 2 mm nip gaps.

Figure 4

SEM micrographs of the substrate surfaces: (a) kraft paper; (b) nylon film; (c) PP film, and (d) Al foil.

Figure 5

Physical appearance of NR-PSA/CO produced with 20 phr of XG + 0.06 phr of CO by using 2 mm nip gap with different mastication time (5–15 min).

Figure 6

(a) Physical appearance of the NR-PSA/CO produced with 2 mm nip gap at a mastication time of 15 min with different XG content (20–80 phr); (b) proposed model of intermolecular interaction among cellulose molecules and XG of PSA.