Tunable Tannic Acid–Zein Adhesives for Bonding Different Substrates

Abstract

Plant‐based, nontoxic and strong adhesives that can work on different substrates allow for better product recycling. Replacing synthetic adhesives with plant based ones that perform equally well may lead to a more sustainable ecosystem. Adhesives based on zein protein, derived from corn, can be made as strong as Super Glue. Unlike petroleum‐based adhesives, this plant protein is removable and degradable. Here, adhesives from the components zein and tannic acid function well on different substrates such as metals, plastics, and wood. This work presents the properties of selected adhesive formulations including bond strengths when the substrates are changed. To achieve near Super Glue strength, each substrate requires a different adhesive formulation. Temperature‐dependent curing, (potential of hydrogen) changes, and additional variables influence adhesion. Tack testing at room temperature is measured to provide comparisons between initial bonding and that achieved after curing. Adhesion to plastic substrates is less than wood or metal, but still plenty strong to measure. Aging of adhesive solutions as well as water resistance after curing is investigated. Infrared spectroscopy data are correlated with changes in color, age, and pH of adhesives. These new adhesives may lead to a sustainable and cleaner environment.

Underwater Bonding with a Biobased Adhesive from Tannic Acid and Zein Protein

“…For example, here, we found that two metal substrates glued together underwater could hold their weight when taken out of the water about seconds later. For comparison, two substrates glued together on benchtop needed at least 5 min drying time before supporting their own weight . A classic difficulty with achieving underwater bonding is that water usually prevents both formation of polymer–surface adhesion and polymer–polymer cohesive interactions.…”

“…Ethanol, 190 proof, was obtained from Decon Laboratories. Zein formulations were made from zein, tannic acid, and ethanol/water solutions. − The order and addition of individual components influenced the quality of the adhesive as did the age of the zein stock solution once prepared. For example, a translucent and amber-colored zein solution was prepared by vigorously mixing 55.5 g of zein powder with a solution containing 45 g of ethanol (95 or 99%) and 23 g of water (deionized) .…”

“…Substrates were prepared by methods described previously. , Aluminum, stainless steel, and bronze were mirror-polished using buffing wheels (Craftsman) and polishing compounds for metal (Pulidor). Metal substrates were cleaned with water and soap, as well as acetone, ethanol, or methanol before applying the adhesive underwater.…”

“…Metal substrates were cleaned with water and soap, as well as acetone, ethanol, or methanol before applying the adhesive underwater. Pine wood, limestone, polytetrafluoroethylene (PTFE), Teflon, and polypropylene (PP) were used as received. , …”

Dynamic reversible adhesives based on crosslinking network via Schiff base and Michael addition

“…Modern functional adhesives oen face more complex application environments, which means that adhesives need increasingly complex properties and oen require multiple functions. [1][2][3][4][5] Numerous researchers have developed and prepared adhesives with underwater adhesion, [6][7][8][9][10][11] multiple substrate adhesion, [12][13][14][15][16] stretchability, 17,18 self-healing, 19 biosustainability, [20][21][22] moldability, 23 etc. However, this not only requires a more complex structure of the polymer but also means that the conditions and steps required for synthesis become more cumbersome.…”