As we all know, the binding quality of wireless binding books is related to the quality of the selected EVA hot melt adhesive, and also directly related to the working environment, the material and characteristics of the paper, the adjustment of the binding equipment, and the processing conditions of the processing. Normally, the bond strength of a Binder book is tested by a tensile test. The higher the required pull, the better the bond strength. But how to test the bonding strength and what the testing standard is is always a problem that bothers us. In this paper, the author discusses the bonding strength detection of wireless binding books.
Factors affecting bond strength
1. Relationship between EVA hot melt adhesive quality and bond strength
EVA hot melt adhesive is solid at normal temperature, and when heated to a certain extent, it becomes a liquid that can flow and has a certain viscosity. The main component of EVA hot melt adhesive is resin, and the resin is copolymerized with ethylene and vinyl acetate under high pressure. The main ingredients of EVA hot melt adhesive include tackifier, viscosity modifier and antioxidant.
Among them, the resin is the main component of EVA hot melt adhesive, accounting for more than 50% of the total amount of EVA hot melt adhesive; the tackifier is one of the main additives of EVA hot melt adhesive, and its main component is rosin or terpene resin. The main function is to improve the fluidity and wettability of the colloid, thereby improving the bonding strength; the viscosity modifier is also one of the main additives of EVA hot melt adhesive, and its main component is paraffin-like substance, which acts to reduce the melt viscosity and increase the flow. Sex, wettability, adjust the solidification speed, in order to achieve the purpose of fast bonding. Otherwise, EVA hot melt adhesive is too sticky, easy to flow, difficult to penetrate into the pages of the book, can not stick the pages; antioxidants are added To prevent premature oxidation and deterioration of EVA hot melt adhesive, it is generally selected from di-tert-butyl-p-methylphenol.
The bonding strength of the wireless binding book has a great relationship with the quality of the selected EVA hot melt adhesive. Therefore, tracking and testing the selected EVA hot melt adhesive is an essential part of the use of EVA hot melt adhesive. Under normal circumstances, the curing time of EVA hot melt adhesive should be 7 to 13 seconds, and the cooling time should be about 2 minutes.
2.Effect of EVA hot melt temperature on bond strength
The temperature of EVA hot melt adhesive has a great influence on the bond strength. The glue temperature is too high. Although the fluidity and permeability of the colloid will increase (thin), the viscosity and bond strength will decrease significantly. Otherwise, the glue temperature will be too low. Although the colloidal viscosity will rise (thickness), its fluidity, wettability and permeability will decrease, and it will also reduce the bond strength, consistency, toughness, etc. of the colloid, and even the cover after colloid coating There is no sticking or sticking between the back of the book. Therefore, the temperature of the EVA hot melt adhesive must be strictly controlled within an optimal and appropriate range to achieve a certain bond strength requirement.
Under normal circumstances, the softening point of EVA hot melt adhesive should be above 80 °C, so that it should be melted to the extent that it can bond books, and the heating temperature should rise to 130-180 °C.
3. Relationship between paper texture and glue temperature and bond strength
Different paper textures, sizing temperature and bonding strength will be different, not only because of different paper fibers, but more importantly because of the different curing and cooling rates of EVA hot melt adhesive on different papers. For example, coated paper, light coated paper, and book paper, because the inorganic material contained in the coated paper is about 10 times higher than the book paper, and the inorganic material has good thermal conductivity, which can accelerate the curing of the EVA hot melt adhesive. And cooling rate, so EVA hot melt adhesive on the coated paper, the fastest curing, cooling speed, the last time in the light coated paper, the slowest on the book paper.
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