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PSA constructions:Manufacturing methods for PSAs |
【author/from】webmanager 【time】2013/7/29 【count】6789 |
There are four popular chemistries resulting in A pressure-sensitive adhesive laminate. One chemistry is achieved through the use of a solvent. With this method, the adhesive components (usually rubber or acrylic) are dissolved in a solvent and then coated onto a web. The solvent is then evaporated using heat and air flow, leaving a dry yet sticky adhesive (pressure-sensitive) that is wound in a roll.
Adhesives made with solvents often provide high performance, but can be expensive and require extra care because of processing restrictions. Special equipment is needed to properly dispose of the solvent, and there must be vigilant awareness of safety issues when dealing with solvents.
Another way to manufacture a PSA is to create an emulsion (water-based). Here, the acrylic polymer and other additives are dispersed, not dissolved, in water and coated onto a web. Again, heat and air flow are used to evaporate the water before winding into a roll. Today’s water-based emulsions can often provide the same high level of performance as solvent-based acrylics and are generally a good choice when lower cost and safety are important, since water-based emulsions don’t require the extra steps that are needed with solvents.
The third method for creating A pressure-sensitive adhesive is developing a hot-melt. Hot melts are typically a mixture of a polymer (such as thermoplastic rubber), tackifying resins and a hydrocarbon diluent (wax or oil plasticizer), which is heated until flowable. The hot-melt adhesive is then coated on a web and cooled before winding into a roll.
Hot-melt adhesives typically exhibit excellent adhesion to substrates and facestocks, have very good coatability, and are less expensive than most solvent-based adhesives. Drawbacks generally include processing and safety challenges, as well as difficulty performing under high temperatures. The major advantage of a hot-melt system is its lack of solvents and water - meaning it doesn't have to be dried in an oven. Hot melts are frequently referred to as 100%-solids (no water or solvent) technology.
Finally, PSAs can be created through the use of a UV-curable adhesive. These adhesives usually require no mixing and cure in seconds when exposed to a UV light source. These environmentally friendly adhesives are reactive compounds that contain no solvents or other volatile substances. Because UV adhesives cure so quickly and at temperatures much lower than thermal heating, they can be used successfully on several heat-sensitive substrates such as plastic films, paper, and synthetic fibers. The quick curing minimizes shrinkage, providing the dimensional accuracy that is often called for in applications such as electronics manufacturing. UV-curable adhesives also offer durability, strength, insulation characteristics, and resistance to chemicals, moisture, and temperature. Like hot melts, UV adhesives do not require an oven.
A decision on which method of adhesive manufacturing technology should be used for a particular application is determined by the performance characteristics needed. |
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