A natural adhesive is a bonding agent derived from organic or inorganic materials found in nature, including those from plant, animal, and mineral sources. These materials are utilized for their inherent ability to stick surfaces together.
Composition and Types of Natural Adhesives
The term "natural adhesives" broadly encompasses vegetable-based, animal-based, and natural gums. They are primarily composed of organic materials, but some inorganic substances also fall under this classification.
Organic Natural Adhesives are derived from living organisms and their byproducts. These include:
- Casein: A protein obtained from milk, widely used in various applications like wood glues and labeling.
- Blood and Albumin: Protein-based adhesives historically employed in different industrial and artistic contexts.
- Hide, Bone, and Fish Glues: These are collagen-based adhesives sourced from animal byproducts, traditionally valued in woodworking, bookbinding, and musical instrument manufacturing.
- Starch: Derived from plant sources such as corn, wheat, or potatoes, commonly utilized in the paper, corrugated board, and textile industries.
- Resin: Natural tree saps, which can act as adhesives or components within adhesive formulations.
- Shellac: A natural resin secreted by the female lac bug, known for its use in finishes and as an adhesive.
- Asphalt: A naturally occurring petroleum substance, used not only in paving and roofing but also as an adhesive in construction.
- Chitosan: A linear polysaccharide extracted from the shells of crustaceans, increasingly recognized for its adhesive properties in biomedical and industrial fields.
Inorganic Natural Adhesives are derived from mineral sources. A significant example is:
- Sodium Silicate: Often referred to as "water glass," this inorganic compound serves as an effective binder and adhesive in diverse applications, from paperboard manufacturing to refractory materials.
Applications and Significance
Natural adhesives have been integral to human endeavors for millennia, predating the advent of synthetic alternatives. Their applications remain diverse today, particularly in sectors prioritizing sustainability and biodegradability. They are valued for their specific characteristics, such as being biodegradable, often non-toxic, and compatible with various natural substrates. While some natural adhesives have seen their roles diminished by high-performance synthetic polymers, they continue to be crucial in niche markets, traditional crafts, and the development of emerging bio-based technologies.
