What role does polyethylene wax play in hot melt adhesive? Wax is the most effective regulator of hot melt adhesive performance. The melting viscosity of wax itself is very low, which can reduce the melt viscosity and surface tension of hot melt adhesive. It is used to improve the surface wettability and adhesion of hot melt adhesive when bonding metal and plastic, so as to improve the bonding performance of hot melt adhesive to these materials within a certain limit.

Main components of EVA hot melt adhesive:

EVA hot melt adhesive is mainly composed of the following four components: basic resin, namely EVA resin, tackifying resin, wax and antioxidant. In some cases, a small amount of filler can be added to increase the gap filling and reduce the cost.

1.  Performance adjustment and adhesion of hot melt adhesive:

Adhesion is one of the most important properties of hot melt adhesive, and the influencing factors are also the most.

Firstly, EVA is the main determinant of the bonding performance of hot melt adhesive. As mentioned earlier, when the VA content in EVA increases, the adhesion of hot melt adhesive is greatly improved. EVA with high VA content can be used to bond non-polar non porous materials, such as polyethylene and polypropylene films.

Firstly, EVA is the main determinant of the bonding performance of hot melt adhesive. As mentioned earlier, when the VA content in EVA increases, the adhesion of hot melt adhesive is greatly improved. EVA with high VA content can be used to bond non-polar non porous materials, such as polyethylene and polypropylene films.

Secondly, the effect of tackifying resin and wax on adhesion mainly depends on their melt viscosity and chemical structure. The lower the viscosity, the easier it is for the hot melt adhesive to penetrate into the porous substrate, so as to form mechanical bonding. The surface energy of wax is low. When the amount of wax increases, the wettability of hot melt adhesive improves and the adhesion can be increased. Using microcrystalline wax instead of paraffin can improve the adhesion caused by valence bond force, which is due to the low modulus and long setting time of microcrystalline wax hot melt adhesive.

For polar substrates, the use of waxes with polar groups (such as hydroxyl wax or natural wax) can improve the adhesion. The adhesion of hot melt adhesive is affected by the compatibility of the whole adhesive system. Taking wax and EVA as an example, the compatibility between wax and EVA with VA content of 18% ～ 28% is the best, it is easy to form co crystallization and has good adhesion. However, when VA content is less than 9%, EVA crystallizes before wax and becomes the filler of wax, and the adhesion of glue is very poor.

2.  Performance adjustment and fluidity of hot melt adhesive:

The viscosity and fluidity of hot melt adhesive are closely related to the sizing performance. EVA with high MI and tackifying resin with low melt viscosity can reduce the viscosity of hot melt adhesive. EVA with different MI can also be used together to adjust the construction viscosity of hot melt adhesive.

However, wax has the greatest impact, because wax is the component with the lowest viscosity in hot melt adhesive. Increasing the amount of wax can significantly reduce the viscosity of hot melt adhesive and increase its fluidity. Wax with low viscosity and low molecular weight can be selected as far as possible, so that the amount of EVA can be increased or EVA with low MI can be used.

When bonding porous materials (paperboard and corrugated board), generally speaking, the smaller the viscosity of hot melt adhesive, the better. If the viscosity is too high, it may have consolidated when the adhesive does not fully penetrate the substrate, resulting in poor bonding; Too low viscosity may lead to excessive penetration of glue into porous substrate, resulting in glue shortage, which should be paid special attention in the packaging of mechanized quantitative sizing.

In short, the viscosity of hot melt adhesive is mainly adjusted by the type and amount of wax and the MI of EVA. The melting point of wax and the softening point of hot melt adhesive have no corresponding relationship with the viscosity of hot melt adhesive.

3. Performance adjustment and flexibility of hot melt adhesive:

Wax also has a great influence on the flexibility of hot melt adhesive. Using microcrystalline wax instead of paraffin, or using narrow distribution synthetic wax instead of ordinary synthetic wax, can increase the flexibility of hot melt adhesive. This is because microcrystalline wax has better flexibility than paraffin, and narrow distribution synthetic wax is more compatible with the ethylene chain segment in EVA. In addition, the greater the polarity of rosin ester and terpene resin tackifier, the better the compatibility with EVA with high VA content, which can also improve the toughness of hot-melt adhesive. The amount of isomeric and cyclized alkanes in wax molecules is high, and the elongation of hot melt adhesive is high.

4. Performance adjustment of hot melt adhesive, opening time:

The opening time refers to the time interval that can still be used after sizing without dewetting due to coagulation or crystallization. The opening time of hot melt adhesive is often measured in seconds. For polymer tackifying resin system, the addition of wax always shortens the opening time, and the degree of influence varies with the properties of wax. Generally speaking, the greater the amount of wax, the higher the melting point and crystallinity, the shorter the opening time of hot melt adhesive. Hot melt adhesives for different purposes require different opening times. For example, the opening time of glue for handicrafts should be longer to facilitate manual operation and adjustment, while the opening time of high-speed paperboard sealant is very short, which is conducive to shortening the construction period.

5.  Performance adjustment of hot melt adhesive, setting time:

The setting time is the positioning time of the adhesive, which is related to the melting point and ambient temperature of the hot melt adhesive. In winter, the temperature is low, the heat dissipation is fast, and the setting time is short. Wax can be used to adjust the setting time in formula design. Wax with high crystallinity and high melting point can shorten the setting time, while microcrystalline wax can prolong the setting time.

Performance adjustment of hot melt adhesive, uncured strength and initial viscosity:

The adhesive strength before curing directly affects the pressure time after sizing, and thus also affects the bonding process. The uncured strength is related to the polarity and wettability of the adhesive. The selection of components with high cohesive strength and tensile strength is conducive to improve the uncured strength of the adhesive. The type and amount of wax also have a great influence on the uncured strength.

6. Performance adjustment of hot melt adhesive, heat resistance:

It is related to the melting point and molecular weight distribution of components. The hot melt adhesive made of high melting point components has high heat resistance, while the addition of wax often reduces the heat resistance.

7.  Performance adjustment and adhesion resistance of hot melt adhesive:

The adhesion resistance of hot melt adhesive particles is directly related to the storage of hot melt adhesive. The glue with poor adhesion resistance is easy to agglomerate when stored under high temperature and humidity. The adhesion of rubber particles can be prevented by using a hard wax, such as polyethylene wax. In addition to selecting the appropriate wax, the amount of wax can also control adhesion. In addition, in some cases, powder such as talc powder can be mixed into the rubber particles to prevent adhesion.

Qingdao Sainuo Chemical Co.,Ltd. We are manufacturer for PE wax, PP wax, OPE wax, EVA wax, PEMA, EBS,Zinc/Calcium Stearate…. Our products have passed the REACH, ROHS, PAHS, FDA testing. Sainuo rest assured wax, welcome your inquiry!

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