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Direct answer: For adhesive PP woven bags, APAO or POE based ones should be preferredHot melt adhesive pelletsDo not use regular EVA. The reason is that PP belongs to low surface energy materials (about 30 mN/m), and the EVA adhesive layer is almost unable to effectively wet it. When it sticks on, it does not fall off and can be peeled off as soon as it is pulled. The difference between the three types of glue in this scenario is very obvious.
Woven bags are widely used in industries such as feed, fertilizer, rice, and cement, and the efficiency of sealing and labeling directly determines the production line speed. Many factories use sewing for sealing, which results in slow speed, dust leakage, and poor appearance; After switching to hot melt adhesive, it is often found that it cannot stick, leading to the conclusion that “woven bags can only be sewn”. The problem actually lies not in the craftsmanship, but in the wrong category of adhesive selection.
| Comparison item | EVA type | APAO type | POE type |
|---|---|---|---|
| Wettability of PP | poor | Excellent | good |
| Stripping performance | Whole interface peeling off | Substrate tearing (qualified) | Substrate tearing or partial interface |
| low temperature resistance | General | Excellent, still resilient at -20 ℃ | good |
| Heat resistance (stacking) | General | Moderate, attention should be paid to summer | Excellent, with a higher softening point |
| Opening hours | short | Longer, suitable for slow speed lines | moderate |
| Ton price reference | minimum | upper middle | high |
There is a huge difference in the results between PP woven bags and those that have undergone corona treatment. The surface energy of the bag that has undergone corona discharge can be increased to over 38 mN/m, and ordinary adhesive can barely stick to it; Untreated bags must rely on the wetting ability of the adhesive itself. Asking before purchasing whether the bag has been corona treated can save a lot of trial and error.
When handling such demands, Guangzhou Sunlife Trading will require customers to send two pieces of actual bag materials for peeling tests, rather than recommending the model based on the four words “PP woven bag”. The judgment criteria for Sunlife hot melt adhesive are simple: if the bag material fibers are torn instead of the adhesive layer falling off completely after tearing, it is considered qualified. If it does not meet the requirements, the formula will be changed and the product will be tried again.
Raising the temperature can only improve fluidity, but cannot change the nature of surface energy mismatch. Moreover, high temperature can accelerate carbonization, which is not worth the loss.
Conduct a 180 degree peel test and observe the form of damage. Substrate tearing is considered qualified, while interface peeling is considered unqualified, which is more intuitive than looking at the peeling force value.
In most cases, it is possible, but labeling requires a shorter opening time. If the label is prone to displacement, choose a model with higher initial adhesion separately.
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