6 things you need to know about plastic primer.

Plastic materials have been progressively introduced in the manufacture of vehicles. That's why there are certain things you need to keep in mind when working with a plastic primer.

Plastic materials have been progressively introduced in the manufacture of vehicles until reaching very important percentages in the order of around 50% in total. This marked prominence is due to the multitude of advantages offered by this material.

However, when it comes to repairing or replacing them, the work processes used differ from those traditionally employed in steel repair. In this sense, the workshop professional must be more meticulous when carrying out the repair and use a series of specific products that are adjusted to the particularities and behavior of this material.

Within this set of new products, today we want to discuss in detail an essential material in the plastic repair process: the primer or adhesion promoter for plastics. Do you know about them? I’m sure you do, but are you really using them as indicated by the manufacturer? Be that as it may, we are going to analyze in detail this essential consumable both in the area of body repair and paint.

General characteristics of plastic materials

The widespread use of plastics in the configuration of a vehicle responds mainly to the need to contribute to the reduction of its weight, with the aim of reducing motorization and, with it, the polluting emissions that allow manufacturers to comply with the increasingly strict EURO standards. On the other hand, plastics show other particularities such as the following that define their behavior and that must be taken into account when repairing them:

  • They can be repaired quite easily and reliably, as long as the most suitable process for the type of plastic in question is strictly followed. During this process, it is also important to use specific products for this type of material, such as fillers for plastics, paint elasticizers or special cleaners, among others.
  • Its degree of flexibility depends on the nature of the plastic. This aspect is taken into consideration in order to apply the repair method that best reproduces this degree of flexibility. As a general rule, thermoplastic (more flexible) plastics are repaired with methods that reproduce this flexibility, while the more rigid versions of plastics (mainly thermosets) require corresponding repair methods.
  • They have low adhesion, so before applying any type of paint, whether primer or finish, they must be treated to ensure adhesion.
  • Their oxidation process is slow and they never corrode, so they can be manufactured without any type of coating.
  • It is a recyclable material, although composite plastics (composites, tires, etc.) are more difficult to recycle.
  • They are good electrical, thermal and acoustic insulators. In addition, they have the capacity to absorb part of the energy generated in a collision.

What is a plastic primer and when is it used?

A plastic primer, also known as an adhesion promoter, is a one-component primer designed to treat bare plastic to increase the adhesion of the various layers of paint applied during the repair and/or painting process. Thanks to its use, any adhesion failure and the risk of cracking or peeling is eliminated, providing the repair with quality and durability.

The most frequent work situations that require the use of a plastic primers are the following:

  • New plastic body parts that are not factory primed.
  • Worn patches that appear during the repair process of a plastic in which its coating layers have been removed. This generally occurs during the sanding of surface anomalies such as small scratches, paint chipping, etc.

Precautions to be taken when using a plastic primer.

As with any type of paint, the use of a plastic primer is carried out according to the guidelines established by the manufacturer in the corresponding product data sheet. However, we can establish a series of application considerations that under no circumstances must be overlooked, as doing so would drastically reduce the final level of adhesion achieved. The most relevant aspects to be taken into account are the following:

  • Identify the plastic to determine the need to use plastic primer, since there are currently primers for direct adhesion on this type of substrate, such as Roberlo’s MULTYFILLER GRIP, which adhere perfectly on ABS, PP-EPDM and PP-PE-EPDM variants.
  • The preparation of the plastic substrate must be carried out so that the surface is completely sanded or matted, free of dust and decontaminated. Decontamination is carried out with specific plastic cleaners, such as Disolac degreaser 226, as they are designed to reduce the static charge of the substrate and, therefore, the attraction of dust particles to the substrate surface.
  • Choose the most suitable primer format for the surface to be treated. As a general rule, aerosol formats are used for the treatment of smaller surfaces, such as spot repairs or patches, while spray formats are used whenever it is necessary to prime large surfaces, such as new bumpers or plastic parts with a lot of damage. An example of these primers are Roberlo’s Primerplast variants, with both spray and aerosol
  • Shake the primer can to homogenize its content. In the case of aerosol formats, this step is of vital importance and usually requires a couple of minutes of shaking to ensure its function.
  • Apply the plastic primer maintaining an application distance of about 20 cm. The application is made in one coat, making sure that the deposited layer is thin and perfectly homogeneous, ensuring that all the bare plastic surface is covered.
  • Respect the evaporation time indicated in the product data sheet before applying the subsequent coat of paint.

Plastic primer, the great ally of repairs on plastic materials

The repair and painting of plastics are jobs that are performed on a daily basis in a body shop. However, the particularities of these materials require that the repair processes used be applied strictly and precisely. Similarly, the use of certain products, such as plastic primers cannot be overlooked when the body shop’s aim is to offer quality and long-lasting repairs. Therefore, knowing the characteristics of plastics and the specific products for these types of substrates, achieving this goal is not at all complicated.

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