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Direct answer:Hot melt adhesive pelletsThe most direct consequence of high moisture content is the formation of bubbles, intermittent glue lines, and decreased bonding strength during the melting process. In severe cases, the glue layer may turn white and the spine may become hollow. EVA rubber particles themselves do not have strong moisture absorption, but after packaging damage, warehouse moisture regain, or outdoor stacking, the surface adsorbed moisture will also vaporize instantly in a glue pot above 160 ℃.
From March to May every year in southern China, printing and packaging factories are most likely to have a concentration of “the same batch of glue, good last week, problems this week”. In most cases, it’s not that the formula has changed, but rather that the rubber particles have been left open in the workshop for a few days, or the warehouse floor has become damp, causing the bottom of the packaging bag to become damp first.
| link | method | key points |
|---|---|---|
| warehousing | Stacking off the ground and wall | The height of the pad should not be less than 10cm and should be kept away from the exterior wall |
| Warehousing | Control relative humidity | Suggest below 65%, avoid storing with water-based adhesive in the same warehouse |
| unpack | Ready to use and dismantle | After opening the bag, use it up on duty, and seal the remaining materials by tying the mouth |
| transfer | Use covered material bucket | Prevent open turnover boxes from staying overnight in the workshop |
| computer operation | Preheating exhaust | Let it sit for a few minutes after the first glue is melted before dispensing |
| Exception | Suspected of moisture, please spread and dry first | Spread thinly on a clean tray, hang in a ventilated area, and do not bake at high temperatures |
When bubbles and broken glue appear, the most common reaction on the front line is to raise the temperature and increase the amount of glue produced. As a result, as the temperature increases, the glue is more prone to oxidation and yellowing, and the problem is compounded. The correct sequence should be: first remove the moisture, then check the temperature, and finally adjust the amount of glue. The judgment method is also simple – take a small handful of adhesive particles and place them on a clean heating plate. If there is a cracking sound and obvious bubbles, it can be basically confirmed that they are damp.
The Sunlife hot melt adhesive produced by Guangzhou Sunlife Trading is packaged with a moisture-proof film lining, and both 25kg bags and ton bags have undergone inner bag treatment. When supplying to customers for book binding, packaging and sealing, and quick printing of graphics and text, we will also provide storage suggestions and moisture identification methods to reduce rework during the rainy season.
Slightly damp and not clumped, most of them can be used normally after being spread and dried; If there are obvious lumps or adhesions, it is recommended not to use the machine to avoid clogging the nozzle and pipeline.
Not recommended. The softening point of rubber particles is generally between 80-110 ℃. If the oven temperature is slightly higher, they will stick together into blocks. Ventilation and drying are more reliable methods.
Hot melt adhesive is a 100% solid content product and usually does not have a separate moisture index. The actual control is mainly based on intact packaging and dry storage. If necessary, suppliers may be required to provide batch volatile matter data.
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