Bio-based Adhesives: Advantages and Confronting Their Challenges

Due to environmental concerns and considering the petroleum resources, the bio-based materials have recently attracted more attention both in academia and industries. In addition to environmental sustainability and renewability, the bio-based adhesives have shown some competing advantages with respect to fossil-based products. This article covers the advantages and challenges of bio-based adhesives. The main advantages of bio-based adhesives include their less greenhouse gas emission, lower volatile organic compounds (VOC), lower environmental and human toxicity. The bio-based adhesives show higher tendency to biodegradability, which may be considered as their strong aspect compared to fossil-based resources. The bio-based materials may be incorporated in adhesive formulation through direct usage of biopolymer, in the form of building blocks and/or reactive monomer, and in the form of adhesive formulation additives. In bio-based adhesives, the pioneering technologies belong to fabrication of paper and different wooden products using starch and/or protein-based adhesives. The main goal was to remove as much as possible the harmful emitting formaldehyde gases during fabrication and product service life. The modification of bio-resource materials through introduction of new functionalities in the molecular architecture may bring some specific properties. There are many reports on the effect of various vegetable oils on the improved hydrophobicity in epoxy and polyurethane adhesives. The bio-based vegetable oils and cashew nut shell liquids now have acquired reliable position in adhesive and coating market. Recent investigations on some specific bio-resource structures such as lignin and tannin with complex structures have shown promising results for the improved thermal and antibacterial activities in adhesive formulation. In order to make a strong decision on the effectiveness of the bio-based adhesives, much investigations on different biological/economical aspects of bio-based materials are needed to achieve this goal.