They are ‘facilitators’ between the adhesive and the surface of the material to be bonded. They generally serve two purposes.
The first is related to the liquid component, which serves to clean and prepare the surface of the target material before the functional polymer is applied.
The latter performs the ‘second function’ and is optimally coordinated to the adhesive.
Many plastics and metals do not have glue-friendly surfaces due to the composition of the materials and the pre-manufacturing processes involved. Sometimes the surfaces still have lubricants or separating agents on them, which need to be removed for the functional polymer (and consequently, the adhesive) to be able to work properly.
Primers are most effective when applied in a very thin and even layer over the whole surface. This also enables fast drying, which is good for short cycle times in automated production processes.
Solvent-based primers are classic products that have been used for decades. They are suitable for pre-treating a variety of plastics, such as PVC or ABS, as well as metals. They are usually applied with felt or roller systems, but can also be sprayed on. Their benefit is that they dry quickly without any additional heat supplied.
These are the newest type of primer on the market. They are low-emission and have a lower proportion of volatile components, depending on and customized to individual requirements. VOC-reduced primers can be used on the same surfaces as solvent primers, but need more contact time and additional heat to dry. They can generally be applied with the sames tools, making it easy for users to switch to these primers. Due to the low content of volatile components, VOC-reduced primers are very suitable for using with vacuum application systems, which are considered to be very efficient. Classic solvent-based primers cannot be used with such equipment.