Why can t hot melt adhesive stick firmly? What causes it?

There are many reasons why hot melt adhesive does not stick, depending on what factors affect its performance, and temperature is one of the most common reasons at present. As the weather gets colder, the glue often appears to have cured when the material is bonded. Even if it is not cured, the optimal bonding effect is missed.

Even in some northern regions, the temperature of the material is quite low, resulting in unsatisfactory bonding.

Hot melt adhesive is a kind of plastic adhesive, its physical state changes with temperature within a certain temperature range, and the chemical properties remain unchanged, it is non-toxic and tasteless, and is an environmentally friendly chemical product. Because the product itself is solid, it is easy to package, transport, store, solvent-free, non-polluting and non-toxic; As well as the advantages of simple production process, high added value, high adhesive strength and fast speed, it is favored.

In the process of use, you will encounter "glue non-sticking", "wire drawing problem", "temperature too high bubbles", "cold stickiness" and so on. And in these cases, there is often no problem with the product itself. Taking "glue non-stick" as an example, there are many reasons why hot melt adhesive is not sticky, depending on what factors affect its performance, and temperature is one of the most common reasons at present.

As the weather gets colder, the glue often appears to have cured when the material is bonded. Even if it is not cured, the optimal bonding effect is missed. Even in some northern regions, the temperature of the material is quite low, resulting in unsatisfactory bonding.

The following points should be paid attention to when banding edges:

1) Pay attention to the range of substrates applicable to different types of products.

2) It is best to try to seal it with a discarded small board before each start, so that the problem can be found as soon as possible.

3) When the ambient temperature is too low, the edge banding, the plate can not be too cold, too cold will absorb heat and cool down, affect the bonding of the edge banding strip and the hot melt adhesive, ensure that the plate should be coated with hot melt adhesive, and the glue should be appropriately thicker than in summer in winter.

4) When the ambient temperature is too low, you can make a lampshade on the edge banding machine turntable to heat the edge banding strip, so as not to be too cold and lack of corners or overpower.

5) When the ambient temperature is too low, if the edge banding machine has a preheating device, the preheating temperature should be opened to preheat the plate. At the same time, pay attention to the temperature and speed of use.

6) Due to the large difference in temperature between summer and winter, the opening time of hot melt adhesive is different, pay attention to the temperature change.

7) Inventory products should be based on the principle of first-in, first-out use.

When using pearl cotton packaging, there will be problems such as hot melt adhesive opening or wire drawing, according to their actual situation, why is the pearl cotton hot melt adhesive not firm? And what causes it?

Problem Analysis Situation:

During the heating process of the glue, it is necessary to wait for the glue to boil completely before use, otherwise the following problems are prone to occur:

<> this situation, let the hot melt adhesive boil completely before use.

Everything has its own use, sometimes this kind of hot melt adhesive can only stick some glass, or some plastic, but there are some things he can't use hot melt adhesive, and it can't stick firmly This is one of his characteristics, so some things can have things can't.

You can try the following methods to solve the problem:

1. The dust and oil stains on the surface of the adhesive should also be properly treated in order to make the hot melt adhesive better exert its adhesive effect.

2. Try to speed up when you use it. Fast operation is a major feature of hot melt adhesives, generally about 15 seconds.

3. Try to re-bond at a suitable temperature.

4. Add viscosity regulator appropriately. By adding a viscosity regulator with a low softening point, you can achieve the purpose of good penetration and firm bonding during bonding.

The use of "three elements" of hot melt adhesive film is not well controlled, which is usually the main reason for the poor glue opening and adhesive firmness, namely the pressing temperature, pressing time and pressing pressure. Whether the "three elements" are used reasonably is also the first step in troubleshooting.

The hot-melt adhesive sticks things strongly, and the curing time is short, only 15 seconds of time, and the hot-melt adhesive has low requirements for paste, and the use method is simple, but it is not suitable for the use of plastic products, so as not to damage the surface of the object.

1. Very strong.

The hot melt adhesive sticks to the thing very strong, and the curing time is short, generally dropped on the paste for fifteen seconds, it will gradually solidify, and the item will be pasted firmly, but the hot melt adhesive needs to be heated in the process of use, which will cause damage to plastic products, so it is not suitable for pasting plastic items.

2. Product classification.

According to the use, hot melt adhesive can be divided into book binding, fabric, hot melt pressure sensitive adhesive, furniture edge banding, thermoplastic powder coating and other types, among which hot melt adhesive for book binding often appears in the packaging of food, beverages, instant noodles and other items, and hot melt pressure sensitive adhesive will appear in diapers and hospital mattresses.

3. How to use.

When using hot melt adhesive, it should be inserted into the hot melt glue gun, after turning on the power, the hot melt adhesive will melt into a liquid, at this time it will be applied to the object that needs to be pasted, and then the paste will be pressed on, wait for fifteen seconds, the object will be firmly bonded.

Sometimes the glue does not stick firmly because of the cleaning of the adhesive surface and the selection of bonding materials.

The quality of the adhesive joint and the treatment of the bonding surface are the key factors in the success of the adhesive adhesive. Whether the raw material in the glue can penetrate into the material of the bond determines the strength of the bond.

When the surface of the bonding is accompanied by oil stains, rust, delamination, etc., if it is not treated, it will have a great impact on the adhesive effect. Before bonding this kind of material, we need to use a detergent to clean the stains on the adhesive surface, and the common adhesives can be well removed without increasing the cost.

The surface of the bonding is smooth and the effect of bonding cannot be achieved, the surface is too smooth, there is no suitable structure, the surface is not rough, and the adhesive does not produce a chemical reaction on the bonding surface, resulting in insufficient bonding. In such cases, the surface can be dried by sanding the item properly before bonding.

How to remove the glue stuck to your hand.

After the glue accidentally gets on your hands, you can first try to clean it with water, which is a common way to deal with residual glue, because people's **self-cleaning function,** has a certain elasticity, and the glue will slowly detach when stretching, rinse with water when the glue is stained on the hand, and the glue will fall off after a period of time.

Secondly, you can use salt to clean, the glue sticks to the hand and wants to remove it immediately or as soon as possible, you can take some home remedies, after the glue sticks to the hand, first wash it with water to destroy the glue to exert greater viscosity, then you can take some salt and put it on the part of the viscose glue to rub, so that it can also remove the glue well.

The problem can lie in two ways:

First, the selected glue cannot soak the object to be bonded; Second, there was a problem in the curing process, and the glue failed to be transformed into a solid with high strength. If you choose a glue that can soak the surface of the object being bonded, and let the glue cure according to the instructions for use, but the glue still does not stick firmly, it is likely that the strength you require is far beyond the capacity of the glue.

Introduction to the types of glue:

The main ingredient in this common glue is ethyl cyanoacrylate, which is a very low-viscosity, easy-flowing liquid. When we need to glue two objects with all-purpose adhesive, just put a few drops on the surface of one of the objects.

The liquid of ethyl cyanoacrylate is spread on the solid surface to form a thin film, and then another object is covered. As the ethyl cyanoacrylate solidifies into polycyanoacrylate under the action of water vapor, the two objects are firmly glued together.

Glue sometimes doesn't stick well, mainly because glue is also classified, and different glues are used to stick different items.

Glue. It is available in a wide variety of varieties and can be used on most hard materials in the absence of water.

2. Hot melt adhesive. It is mainly a solid adhesive and is usually used for edge banding of furniture such as cabinets and wooden doors.

3. Neoprene. It is a rubber-type glue, usually for flexible film substrates.

The reasons for the weak adhesion of hot melt adhesive are, in general, mainly the following aspects:

1.The temperature is not enough, the glue dries too quickly, and the use temperature needs to be increased to make the glue dry more slowly.

2. After gluing, it is not fixed, the pressure time or pressure is not enough 3, and the type of hot melt adhesive corresponding to different materials is not selected.

4. Look at whether the glued surface or the adhesive surface is not glued well, if the adhesive surface is not glued well, the surface of the adhesive substrate may not be treated well or the material is difficult to penetrate.

5. The temperature is not enough for the glue to dry too quickly, and the use temperature needs to be increased to make the glue dry more slowly.

6. The temperature during the composite does not meet the requirements

The composite temperature does not reach the melting point of the adhesive film or web film, resulting in insufficient melting of the hot melt adhesive and not giving full play to the bonding performance. In this case, it may be that the composite surface of the machine does not reach the melting point of the adhesive film, or the heat permeability of the material is poor. If the machine temperature reaches the upper limit and still cannot be solved, you can choose a low-temperature hot melt adhesive film test.

In addition, on the premise of ensuring that the material is not burned, the surface layer with good heat permeability is selected for pressure heating.

7. Material compatibility issues:

There are also differences in the scope of application of hot melt adhesive films of different materials, and the weak bonding may also be caused by the incompatibility of the selected hot melt adhesive film with the material, as long as the hot melt adhesive film of other materials is replaced!

The hot melt adhesive is not firmly adhered to the following reasons:

Hot melt adhesive needs to be applied according to the material, if the selected hot melt adhesive is not the right type, it is not possible to bond the corresponding material;

The melting temperature is not enough, if the temperature is not enough, the hot melt adhesive is not fully melted, and the connection cannot be well produced;

When bonding, the hot melt adhesive does not apply enough pressure to the bonded object after melting;

When bonding, there is not enough time for the hot melt adhesive to harden;

The surface of the bonded object has not been cleaned, and there are dust or impurities that affect the bonding;

Hot melt adhesive needs to be applied according to the material, if the selected hot melt adhesive is not the right type, it is not possible to bond the corresponding material;

The melting temperature is not enough, if the temperature is not enough, the hot melt adhesive is not fully melted, and the connection cannot be well produced;

When bonding, the hot melt adhesive does not apply enough pressure to the bonded object after melting;

When bonding, there is not enough time for the hot melt adhesive to harden;

The surface of the bonded object has not been cleaned, and there are dust or impurities that affect the bonding;

Reasons why hot melt adhesive plastic doesn't stick firmly:

The melting temperature of the hot melt adhesive is not enough;

Not enough when bonding;

There are debris and dust on the surface of the adhesive material.

1. If the selected hot-melt adhesive is not the right one, it cannot bond the corresponding material;

2. If the temperature is not enough, the hot melt adhesive is not fully melted, and the connection cannot be well generated;

3. During bonding, the hot melt adhesive does not apply enough pressure to the bonded object after melting;

4. When bonding, there is not enough hardening time for the hot melt adhesive;

5. The surface of the bonded object has not been cleaned, and there are dust or impurities that affect the bonding.