Researchers at the Queen Mary University of London and Mae Fah Luang University in Thailand have created a shellac-based coating to enhance the gas barrier properties of a sustainably sourced, recyclable, and compostable packaging material.
More than 30% of all paper-based packaging materials are produced using molded pulp manufactured from sustainable resources like sugarcane bagasse or eucalyptus wood, which can be recycled and composted. However, the materials’ low gas barrier capabilities and inadequate water and oil resistance make it unsuitable for preserving the quality and shelf-life of many products.
The study, which was published on February 7th, 2023 in the SCI journal Polymer International, aimed to create a new coating made of eco-friendly, renewable, and biodegradable materials that could improve the molded pulp’s barrier properties and surface resistance while maintaining its sustainability.
Shellac has been manufactured from a resin excreted by lac bugs and used to make everything from furniture lacquer to nail polish to different colors. Due to its nontoxic nature, thermoplastic behavior, oil resistance, and effective moisture barrier qualities, it is a biopolymer of the polyester group that is widely employed in the pharmaceutical and food sectors.
Pure shellac, due to its high oxygen permeability and brittleness, is not frequently utilized as a covering. In this study, a molded pulp’s barrier and surface resistance performance were enhanced by coating it with a nanocomposite layer made of shellac and nanofibrillated cellulose (NFC). Modified nanofibrillated cellulose (mNFC) was created to improve NFC’s compatibility with the shellac phase and boost its water resistance.
The effects of the nanocomposite coating formulation on the morphology, barrier properties, water vapor transmission rate (WVTR), oil transmission rate (OTR), water and oil resistance, thermal stability, and mechanical properties of the fabricated specimens were systematically investigated.
“According to tests on the water contact angle, oil contact angle, and oil absorption rate, the nanocomposite coating layer gave the molded pulp sheet outstanding water resistance and a potentially greaseproof surface” said Azo Materials.
The coating layer improved the sheet samples’ tensile qualities as well, particularly for the sample coated with mNFC and shellac. After adding the shellac layer with reduced thermal degradation temperature, the samples acquired good thermal stability (about 250 °C), demonstrating its potential for packaging applications. The material is now ideal for instant, dehydrated, frozen, and chilled foods.
However, the expense of commercialization is now a hindrance, according to author Professor Soykeabkaew, who thinks that it is three to ten times more expensive than materials already in use. The coating could, according to Professor Soykeabkaew, “be applied on other eco-materials to decrease the water/moisture sensitivity.”
