Adhesion and Suitability of EVA Hot-Melt Adhesives

In actual production, the bonding performance of hot-melt adhesive varies depending on factors such as the heating temperature, the type and quality of the substrate materials, the width and depth of the spine milling, the height of the adhesive application, and the operating speed of the perfect binding machine.

(1) Heating temperature of hot-melt adhesive
The softening point of hot-melt adhesive is generally above 80°C; that is, the adhesive should begin to soften and flow at this temperature. However, this is merely the initial melting point; to achieve a state suitable for binding books, the temperature must be raised to between 130°C and 180°C. At this temperature range, the adhesive's viscosity, fluidity, and tackiness are optimal for bookbinding.

(2) Relationship between paper type and adhesive application temperature
Since the paper used for book production varies in texture, the adhesive application temperature must be adjusted accordingly. This is not only due to differences in paper fibers but, more importantly, because variations in paper type and texture affect thermal conductivity, thereby altering the cooling rate of the adhesive. For instance, when comparing coated paper (such as art paper) with uncoated paper (such as letterpress paper), the adhesive cools more rapidly on the former. This is because coated paper contains approximately ten times the amount of inorganic matter found in uncoated papers (such as letterpress, newsprint, or offset paper); since inorganic matter possesses high thermal conductivity, it accelerates the cooling process of the hot-melt adhesive.