When using hot melt adhesive for edge sealing of sheet materials, it is affected by multiple factors such as material compatibility, equipment parameters, and process operations, and may encounter problems like adhesive detachment, overflow of adhesive, and blackening of the adhesive line.
This article will analyze the causes of the core issues one by one, provide targeted solutions, and also supplement storage and usage precautions to help accurately identify and rectify the problems.
Degumming Problem: The Core Cause of Adhesion Failure and Its Solution
Degumming is the most common problem in hot melt adhesive edge sealing, directly affecting the stability of the product structure. The causes and solutions are as follows:
The main reasons are as follows:
- Firstly, the selection of hot melt adhesive was incorrect. For instance, using a low-temperature specific adhesive in a high-temperature environment led to insufficient bonding strength.
- Secondly, the operation parameters were not in line with the requirements. This includes insufficient heating temperature of the hot melt adhesive, too little glue application, insufficient pressing pressure or too short pressing time, which prevented the formation of a firm bond.
- Thirdly, the surface treatment of the substrate was inadequate. There were contaminants such as oil stains, dust, and impurities on the surface, which hindered the infiltration and penetration of the adhesive into the substrate and reduced the adhesion strength.
Solution:
- Re-select the appropriate hot melt adhesive based on the usage environment and substrate type;
- Precisely calibrate the equipment parameters to ensure that the heating temperature, pressing pressure, glue application volume, and pressing time comply with the process standards;
- Thoroughly clean the substrate surface before edge sealing, removing oil stains and impurities to enhance the adhesive infiltration effect.
Overflow Problem: More likely to occur with EVA glue. Precise control of the amount is crucial.
The phenomenon of glue overflow is more common in the application of EVA hot melt adhesive. It not only affects the appearance neatness of the product, but also may cause material waste. Therefore, adjustments need to be made in terms of parameters and selection.
The main reason:
- Excessive glue application is the primary cause;
- secondly, a too slow edge sealing speed can lead to the accumulation and overflow of glue at the interface;
- moreover, the glue having a too low viscosity and an excessively high heating temperature can also cause glue overflow due to its excessive fluidity.
Solution:
- Reasonably reduce the amount of glue applied. If PUR hot melt glue is used, the amount of glue can be reduced to 1/2 - 1/3 of that of EVA glue, which can both prevent glue overflow and ensure the bonding effect;
- Appropriately increase the edge sealing speed to reduce the time for glue accumulation; adjust the heating temperature according to the properties of the glue, or directly replace with a higher viscosity hot melt glue product to control the fluidity of the glue.
Blackening of Adhesive Lines: Hidden Dangers in the Appearance of Light-Colored Panels and Their Solutions
The blackening of the adhesive lines mainly occurs in the edge sealing scenarios of light-colored materials, seriously affecting the aesthetic appearance of the products. It is mostly related to the performance of the adhesive and the processing temperature.
The main reason:
- The EVA hot melt adhesive has poor heat resistance. When used for a long time or when the heating temperature is too high, the adhesive is prone to aging and carbonization.
- Moreover, the impurities contained in the hot melt adhesive will also be exposed at the adhesive line, causing the problem of discoloration.
Solution:
- Prioritize replacing with high-quality, high-purity, and heat-resistant hot melt adhesives to prevent aging and carbonization at the source;
- Strictly control the heating temperature, ensuring it does not exceed the rated tolerance range of the adhesive;
- For light-colored panels, it is recommended to use PUR hot melt adhesive or laser edge sealing technology to fundamentally solve the problem of blackening of the adhesive lines.
Supplementary Notes: Storage and Aging Prevention Measures
The storage conditions and shelf life of hot melt adhesive directly affect its bonding performance.
If stored improperly or used beyond the expiration date, the adhesive will age and the bonding strength will decrease, indirectly causing various quality problems.
- It is recommended to store the hot melt adhesive in a sealed and moisture-proof manner to avoid moisture and direct exposure to sunlight;
- Strictly follow the expiration date requirements and prohibit the use of expired adhesive; regularly check the condition of the adhesive.
- If there are phenomena such as lumps, color changes, or abnormal fluidity, replace the new product in time.
