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The adhesion of the spine cloth (gauze/mull) in hardcover books is the most technically advanced part of the binding process: the spine cloth should stick to the back of the book, adhere to the shell surface, and ensure that the spine cloth does not come off or shift when flipping pages. choose wronghot melt adhesive pelletsIt can cause fatal quality problems such as blistering, delamination, and cracking of the spine fabric and book cover.
This guide starts with three core parameters to teach you how to choose the right hot-melt adhesive particles for spine fabric bonding.
Ridge fabric is a loose fabric, and if the viscosity of the glue is too low, it will penetrate into the book core and cause “glue leakage”; If the viscosity is too high, the infiltration will be insufficient and the bonding surface will be insufficient. It is recommended to choose a formula with a melt viscosity of 8000-15000 mPa · s (170 ℃).
There is a time window between the application of adhesive and the pressing of the spine cloth adhesive. The opening time of the machine assembly line is 30-40 seconds (the glue cannot solidify before pressing), and the hand assembly line needs more than 60 seconds. Adhesive particles with too short an opening time can cause them to solidify before applying the adhesive to the spine.
When flipping through hardcover books, the spine of the book repeatedly bends, and the adhesive layer must be soft and elastic. Hard and brittle adhesive particles can cause the spine fabric to crack after flipping hundreds of pages. It is recommended to choose a flexible formula with a Shore hardness lower than 65A.
Sunlife’s hot-melt adhesive granules for high-end spine fabric have been balanced and optimized in these three parameters, with an opening time of 35 seconds, viscosity of 12000mPa · s, and Shore hardness of 58A.
Q: Can we use sealing adhesive particles instead of ridge fabric bonding?
A: Not recommended. The sealing rubber particles are relatively hard and brittle, with a short opening time, and the spine cloth is prone to cracking when flipping pages after bonding. The specialized formula is more suitable for flexibility and opening time.
Q: Is foaming on the spine necessarily a problem with the adhesive particles?
A: Not necessarily. Low glue temperature can cause bubbles in the glue solution and insufficient pressure to form bubbles. First check the process parameters before considering changing the adhesive.
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