Properties of Adhesives
This handbook contains information about the classification, types, form, properties, bonding process of adhesives.
TABLE OF CONTENTS Properties of Adhesives
Classifying Adhesives
Adhesives are classified into thermosetting synthetic resins, thermoplastic synthetic resins, and natural resin additives based on their chemical and physical natures.
Thermosetting Synthetic Resins
Thermosetting synthetic resins undergo chemical changes and convert into an infusible, insoluble mass on heating. These adhesives possess good resistance to moisture, heat, insects, and fungi.
Phenol formaldehyde resins, urea-formaldehyde resins, and epoxy resins are examples of thermosetting synthetic resins.
| Note | to view a Microsoft Excel sheet listing the properties of Thermosetting synthetic resins adhesives. |
Phenol Formaldehyde Resins
Phenol formaldehyde resins are formed by poly condensation between phenol and formaldehyde in the presence of a catalyst, such as acids or bases. With an excess of formaldehyde, a cross-linked, three-dimensional resin is formed ultimately. This resin possesses great adhesive properties. Paper, fabric, and asbestos cloth are impregnated with resol, which are hardening resins or thermoset resins. Many layers of the impregnated material are pressed together in a hydraulic press and heated at around 150 C. The resin cures under pressure and bonds the various layers firmly to form one sheet of greater thickness.
These adhesives are used as core binders in foundries, waterproof plywood, laminates, coating compositions, and electrical circuits.
Urea-Formaldehyde Resin
Urea can condense with formaldehyde to form urea formaldehyde (UF) resins. This resin is colorless and clearer. As a result, objects of lighter shades can be made with them. Tensile strength and hardness are also much greater, but their heat and moisture resistance are lower than those of phenol formaldehyde resins.
These adhesives...
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