How to choose the correct EVA hot melt adhesive in the perfect binding?

It is important to choose a good quality adhesive using the perfect binding process. At present, there are three kinds of adhesives used in the world of wireless perfect binding: the first one is a polyurethane adhesive (ie, PUR adhesive), and the second is an ethylene-vinyl acetate polymer adhesive (ie, EVA hot melt adhesive). The third type is polyvinyl acetate and polypropylene ester adhesive (ie cold glue). These three kinds of adhesives have their own strengths, but the most widely used in China is EVA hot melt adhesive. Below, we will use EVA hot melt adhesive as an example to introduce how to choose the correct adhesive.

Because there are many manufacturers of EVA hot melt adhesives on the market, the quality of the products is not good, and the printing companies should start from the following aspects when choosing EVA hot melt adhesives.

First, the appearance check. Visual inspection of EVA hot melt adhesive, good granular (or sheet) EVA hot melt adhesive should be bright and translucent. The sheet of EVA hot melt adhesive should not be large after folding back and forth with both hands. Deformed, granular EVA hot melt adhesive should not be too deformed after being hit with a small hammer.

Second, the smell is distinguished. The better quality EVA hot melt adhesive smells lighter when it is opened, and there is no pungent smell after heating, no smoke, and it will not turn yellow and black quickly.

Third, elastic identification. EVA hot melt adhesives can be divided into high temperature adhesives, medium temperature adhesives and low temperature adhesives. Printing companies can purchase them according to their equipment. In general, high temperature glue is harder than medium temperature glue, and medium temperature glue is harder than low temperature glue. Good quality high-temperature glue has a certain elasticity when biting with teeth, and the higher the elasticity, the better. However, the difference in elasticity between medium and low temperature adhesives is not obvious and is difficult to distinguish.

Fourth, hot and cold detection. Cold detection is mainly to put EVA hot melt adhesive in the environment of -10 ~ -20 °C. After a period of time, observe the change of toughness and test whether it can adapt to the cold in winter; the heat detection mainly puts it in 40~50 In the environment of °C, see how the degree of solidification changes, and whether it can adapt to the heat of summer.

Fifth, the price comparison. Generally speaking, the quality of EVA hot melt adhesives is relatively high. For EVA hot melt adhesives which are obviously lower than the market price, be careful when purchasing.

In addition, printing companies can also purchase a small amount of materials in conjunction with the operating habits of their own equipment and operators, and conduct rigorous testing. If necessary, do some destructive tests (such as low temperature freezing, high temperature aging test, etc.) ), to see if its stability meets the production needs, and then determine the quality is good, then buy it in large quantities; especially for those printing companies that have used some brand EVA hot melt adhesive, after use, make sure the product is reliable, and don't replace it for price reasons. Otherwise, you must be yourself.

The above content is selected from the third issue of “Printing Technology ·Digital Graphic Arts ” in 2013. For more journal content, please pay attention to the journal channel. The latest journal content clicks into the electronic journal channel of Keyin.com.