Water-Resistant Zein-Based Adhesives

Abstract

Protein-based adhesives have gained considerable interest, due to their unique ecofriendliness and abundant functional groups. However, the presence of polar groups results in poor water resistance and unsatisfactory bonding strength of protein-based adhesives, limiting their practical applications. In addition, the complicated preparation process also made the production of protein-based adhesives time-consuming and costly. In this work, a hydrophobic protein zein, which lacks polar groups, was chosen as a basic ingredient for the preparation of protein-based adhesive. Sodium dodecyl sulfate (SDS) with a concentration of 200 mmol/L was added to promote the dissolution of zein and also render it negatively charged. The cations in metal chloride solution effectively cross-linked with SDS modified zein molecular chains, resulting in the formation of final zein-based adhesives. Results showed that a zein-based adhesive formed after treatment with 5 wt % FeCl3 aqueous solution (Fe­(III)@zein/SDS adhesive) showed the best performance. It indicates that Fe­(III)@zein/SDS adhesive could bond a wide range of materials. Four common substrates were chosen to test the adhesive properties of Fe­(III)@zein/SDS adhesive at 25 °C, including one inorganic material glass, one metal material copper, and two organic polymer materials polyvinyl chloride (PVC) and polyimide (PI). The adhesive strength of Fe­(III)@zein/SDS adhesive was found from 125 kPa (PI) to 586 kPa (copper) in dry conditions, while from 12 kPa (copper) to 33 kPa (PI) in the wet state, displaying a promising adhesive strength in both dry and wet conditions. Meanwhile, the Fe­(III)@zein/SDS adhesive can be easily removed from the attached surfaces without nonchemical contamination by immersing in 70% ethanol aqueous solution. Therefore, such an environmentally friendly protein-based adhesive has great potential for practical use in various fields.

Bio-based and bio-inspired adhesives from animals and plants for biomedical applications

“…, sodium dodecyl sulfate) are added to a zein solution, they trigger a conformational change in the zein structure; as a consequence, polar groups become accessible and can engage in hydrogen bonds – a mechanism that boosts the adhesion behavior of zein ( Fig. 4 b) [ 179 ]. Up to now, studies leveraging the sticky properties of zein-based formulations were mostly limited to industrial applications such as glass and wood binding [ 182 , 183 ].…”

“…Although their potential use in drug delivery [ 185 ] and tissue engineering [ 186 ] has been tested recently, employing zein-based formulations as an inexpensive, antibacterial, and biocompatible medical adhesive is an underexplored area. Yet, recent studies make use of phenolic components [ 106 ], chelating ions [ 179 ], and nanocomposite formulations [ 187 ] to improve the bonding strength of zein-based materials. A zein modification conducted by Schmidt et al.…”

Recent Advances on the Development of Protein-Based Adhesives for Wood Composite Materials—A Review

“…For this reason, zein was chosen as one of the primary ingredients that can be used to prepare protein-based adhesives. Previous work reported an easy strategy for manufacturing a zein-based adhesive induced by chelation with metal cations [130], using different metal chloride solutions. It was found that the processing with five wt.% FeCl 3 aqueous solutions (Fe(III)@zein/SDS adhesive) conduced to the best performance, ensuring good adhesive strength and water resistance.…”

Tunable Tannic Acid–Zein Adhesives for Bonding Different Substrates

“…[ 10 ] Zein protein is resistant to heat, humidity and abrasion. [ 11 ] Coatings can be fast and easy to prepare. [ 12 ] Zein protein is not soluble in pure water, but soluble in alcohols, in solutions containing urea, surfactants and in aqueous solutions at high pH.…”