What should I do if the hot melt adhesive has a strong odor? Sources and reduction methods of melting odor

When hot melt adhesive is melted and coated at 160-180 ℃, there may be a slight odor – this is a normal physical manifestation of EVA hot melt adhesive. But if the odor suddenly becomes strong, stuffy, or even pungent, it is usually not a problem with the glue itself, but rather a mismatch in temperature, equipment status, or selection. Below, we will explain the sources and methods of handling the odors that Sunlife has repeatedly encountered during training and on-site activities.

1、 First distinguish: normal odor vs abnormal odor

EVA hot melt adhesive itself has a low odor, with only a faint wax/resin smell when melted, and it is basically not disturbing people under ventilation. Abnormal odors are mostly caused by the following situations:

• High temperature or out of controlAfter the melt adhesive exceeds 180 ℃, EVA will begin to thermally disintegrate, the odor will significantly increase, and the colloid will turn yellow, brittle, and even carbonized;
• The adhesive groove has not been cleaned for a long timeResidual glue is repeatedly heated and carbonized, accumulating on the groove wall and continuously emitting odor; In the training, it is required to clean the glue tank about once every two weeks to prevent this;
• Mixing different brands/modelsPouring two batches of glue with different ingredients together for melting may result in abnormal reactions and odors, so “not mixing different brands and models” is a mandatory rule;
• The temperature control of the glue pot is malfunctioningSunlife training repeatedly emphasizes that,90% of after-sales service actually stems from equipment temperature control failure——It shows 160 ℃, but in reality it may only be 100 ℃ (the glue is not sticky), or it may be too high (the glue is carbonized and has a strong odor). Calibrating the actual temperature of the glue pot with a thermometer is often more effective than changing the glue.

2、 How to reduce the odor

1. First calibrate the temperature to within the window
The suitable melting range for book and magazine glue is 160-180 ℃, and it is most dangerous to stick to the upper limit of temperature. Measure the actual temperature of the glue pot with a thermometer, align the set value with the measured value, and the abnormal odor often immediately decreases.

2. Regularly clean the glue tank and avoid mixing glue
Clean the residual glue in the glue groove every two weeks to avoid the carbonization layer from continuing to emit odor; Before applying glue, confirm that no other brand/model has been mixed into the glue pot.

3. For odor sensitive scenes, choose a low odor formula
Priority should be given to odor sensitive applications such as food contact packaging, stationery, children’s products, and interior decorationPolyolefinsHot melt adhesive – This type of system has a lower odor and does not draw (Sunlife pearl cotton thread chooses polyolefin based on the principle of “no odor, no drawing”). Directly informing Sunlife of the ‘low odor requirement’ and matching the model according to the scene is more convenient than post odor removal.

4. Workshop ventilation
The melting station is equipped with exhaust to promptly remove normal odors and avoid aggregation.

3、 When should the glue be replaced instead of deodorizing

If the groove has been cleaned, the temperature has been adjusted, and the ventilation has been carried out, but the odor is still significantly strong, accompanied by yellowing of the gel, increased wire drawing, and weak adhesion, it may be due to the wrong batch or model (such as using ordinary glue in high-temperature or high-sensitivity scenarios). At this momentSample book/sample, measured temperature of glue pot, current modelTell Sunlife that it is more stable to have the technology reconfigure according to “material+machine speed+odor requirements” than to repeatedly adjust the temperature by oneself.

Frequently Asked Questions

Is it possible that hot melt adhesive has no odor at all?

EVA can hardly achieve “completely odorless” during melting, only low odor and non pungent. For scenarios that are highly sensitive to odors, choosing low odor systems such as polyolefins is a more realistic solution, rather than expecting a certain adhesive to have “zero odor”.

Does a strong odor indicate toxicity?

The size of the odor is mainly related to temperature, carbonization, and formula, and cannot be directly equated with “toxic”. But the pungent/burnt smell often means that the temperature is too high and has carbonized, which affects both the bonding and the workshop environment, so it should be treated accordingly. The specific safety and compliance shall be subject to the accompanying MSDS and testing report.

The odor of hot melt adhesive is likely due to poor temperature/equipment management, rather than adhesive issues. The idea of “first calibrating the temperature, then cleaning the tank, and selecting a low odor formula according to the scene” has been repeatedly verified by Sunlife on site. If you can’t pick it up on time, give Sunlife the measured temperature and samples of the glue pot, and match the model and process card according to the purpose, which is much more stable than repeatedly testing the glue based on feeling.

Related Reading:Hot melt safety and preventive measures