How to Choose the Right Hot Glue?

The hot glue material is adjusted according to its formula, and the difference is still very big. So what do we need to pay attention to when purchasing hot glue? This mainly needs to be judged according to specific needs.

1. Hot glue melting point of the glue

The melting range is usually called the melting point in the hot melt adhesive industry. Calling the melting point is actually not very accurate. Because the melting of hot glue is a temperature range, it is more scientific to call the melting range.

The melting range of hot glue refers to a temperature range from the initial melting point to the final melting point of the hot melt adhesive glue, which is one of the most basic properties of the hot melt adhesive.

Generally, the melting range of all hot melt adhesives will exist between 30°C and 120°C. The melting range of lower temperature hot melt adhesive is about 30℃-50℃, the melting range of medium temperature hot melt adhesive is about 50℃-80℃, and the melting range of high temperature hot melt adhesive is about 80℃-110℃.

2. Melt index of hot glue

Melting is mainly to indicate the fluidity of the hot melt adhesive after it has melted. The larger the melt index, the better the fluidity, and the smaller the melt index, the worse the fluidity.

Melt index is a very important parameter in addition to the melting range of hot glue. It is directly linked to the ease of use of hot melt adhesives.

Because the fluidity of the glue directly affects the sizing process of the glue, the better the fluidity, the faster it will spread and wet out on the bonded surface during sizing. If the fluidity is poor, the speed of spreading and wetting is relatively poor, and relatively speaking, the sizing time will be longer.

So the better the fluidity, the better the hot glue? In fact, this is not the case, it depends on your specific bonding materials and process characteristics to make specific choices.

3. Operating temperature and pressing time of hot glue

The biggest feature of hot melt adhesive is short operating time and high working efficiency. The operating temperature and pressing time of hot melt adhesives are the process parameters that must be mastered when purchasing. The operating temperature and pressing time correspond to the two physical and chemical parameters of hot melt adhesive melting range and melting index.

It should be noted that the operating temperature of the  hot glue is not the value of the melting range, but is generally about 30°C higher than the final melting point in the melting range. Of course, the specific temperature must be adjusted according to the melt index of the hot melt adhesive.

4. High and low temperature resistance of hot glue

Since hot melt adhesive is a kind of thermoplastic material, due to the characteristics of hot melt adhesive, hot melt adhesive generally has poor high temperature resistance. Generally, the hot melt adhesive with the best temperature resistance will not exceed 100°C, but the low temperature resistance performance will vary greatly depending on the material.

When purchasing hot glue, you need to understand the environmental temperature limit of your application, and then choose the right hot melt adhesive. This will save a lot of detours.

5. Water washing resistance of hot glue

Since hot melt adhesives are often used in the bonding of clothing fabrics, it is usually tested for a water-resistant performance.

This is because clothing usually needs to be washed repeatedly. After repeated washing without opening or degumming, the product is qualified. This requires the hot melt adhesive itself to have a certain waterproof performance.

6. Solvent resistance of hot glue

Solvent resistance means that hot melt adhesives can maintain good adhesive strength in environments where they are often exposed to solvents to ensure that they will not open. Solvents refer to organic chemical solvents, usually ethanol, ether, acetone, styrene, etc.

Most  hot glue products have poor solvent resistance, because many organic solvents are themselves macromolecular structures that can dissolve hot melt adhesives.

If you need to purchase solvent-resistant hot-melt adhesives and need to have strong adhesion to the material to be bonded, then you need to screen the solvent-resistant adhesive first, and then test the adhesion. This will save a lot of effort.

7. The aging resistance of hot glue

Aging resistance is a point that needs to be considered when developing many materials, especially in many outdoor applications. For this type of application, hot melt adhesives usually need to be subjected to an aging test that is irradiated by a UV lamp.

The aging resistance of the  hot glue directly reflects the ability of the hot melt adhesive to maintain the bonding strength when exposed to the sun for a long time. You need to pay attention when purchasing hot melt adhesives. If your application needs to be exposed to the outdoors for a long time, don't forget to ask about the performance of the adhesive in this respect.