Wax is the most effective regulator of the properties of a hot melt adhesive and the success of a hot melt adhesive often depends on the effect of the wax on the hot melt adhesive.
Adhesion is one of the most important properties of hot melt adhesives. usually EVA, tackifying resin and wax have the greatest influence on the bonding strength of hot melt adhesives. the higher the VA content (or the more tackifying resin, or the less wax), the greater the polarity of the hot melt adhesive, and the significantly higher its bonding strength to polar materials.
Viscosity and fluidity
Viscosity and fluidity are mainly provided by wax and tackifying resin. Usually the melt viscosity of both is low, so the more they are added, the lower the melt viscosity of the hot melt adhesive. However, the amount of wax should not be too much, the general amount between 10%-20%, otherwise it will significantly reduce the adhesive strength of the hot melt adhesive.
The softening point is mainly determined by EVA, viscosity-enhancing resin and wax. the lower the VA content, the higher the softening point of EVA; the softening point of paraffin wax is lower, the softening point of polyethylene wax is higher; the softening point of viscosity-enhancing resin varies from species to species. In the preparation of EVA hot melt adhesive, according to the needs of the selection of similar softening point of EVA, viscous resin and wax, in order to prepare a more suitable hot melt adhesive.
EVA hot melt adhesive softening point and crystallization rate by the EVA, wax softening point and crystallization rate is determined. If both softening point and crystallization rate are higher, the curing rate of the hot melt adhesive is larger. In addition, the higher the softening point of the viscosity-enhancing resin, the more conducive to the improvement of the curing rate of hot melt adhesives.
Glass transition temperature (Tg)
One of the indicators to measure the low temperature resistance of hot melt adhesives. The lower the Tg, the better the cold resistance, such as silicone PDMS; the higher the Tg, the better the temperature resistance, at a certain temperature are in a hard and brittle plastic state, such as PMMA, also known as “acrylic”, “plexiglass “. Common pressure-sensitive adhesives generally have a lower glass transition temperature, because they have to play a role in bonding under room temperature conditions.
Can hot melt adhesives and water-based waxes be mixed? Because wax is the least viscous component of the hot melt adhesive, increasing the amount of wax can significantly reduce the viscosity of the hot melt adhesive and increase its fluidity, as far as possible, choose a wax with low viscosity and low molecular mass, so that you can increase the amount of EVA or use low MI EVA.
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