Paint Wetting Impairment Substances – What are LABS?

Substances that interfere with paint, for short LABS, lead to deficient results when coating materials and workpieces. The effort required for subsequent repairs is enormous. Therefore, it is important to know the sources of LABS in production and to take preventive actions if necessary. In the following, sources of LABS are presented and options for identifying and eliminating LABS are shown.

What are paint wetting impairment substances?

Substances that interfere with paint, in short LABS, lead to errors during the painting process and also during coatings and when using adhesives. These errors become noticeable, for example, through so-called craters or wetting disturbances. The cause of the problem is usually certain contaminants that result in the paint no longer being evenly distributed across all areas of the surface. Contaminants may be, for example: oils, greases or silicones. Physically speaking, a different surface tension is responsible: The contamination has a higher surface tension than the paint and this causes the paint to recede. Craters can, for example, extend to the surface, which means that it remains open and forms an attack surface. In the case of wetting impairments, the disruption in film formation is more extensive and the surface cannot be completely wetted.

Errors caused by LABS must be differentiated from: inclusions, bubbles, residues on the substrate and spray mist.

• (1) Coating
• (2) Surface
• (3) Paint-Wetting Impairment Substances
• (4) Caused Coating Defect

By the way, silicone-free is not the same as LABS-free. Silicone-free refers exclusively to the absence of silicone. There may be other contaminants or other substances that impair paint wetting. Silicone was, however, the first substance that was noticed as impairing wetting. LABS-free includes silicone as well as other substances.

Sources of LABS

Regardless of the material, there are also numerous external sources that can lead to LABS:

• lubricants
• operating and auxiliary materials such as detergents, abrasives, polishing agents
• tubes and sealants
• personal LABS sources such as hand creams, cosmetics, food product, but also plastic bracelets, fitness trackers, smartphone cases

However, it is not possible to generalize which substance impairs paint wetting. The individual interaction between ambient conditions, the surface to be coated and the type of coating must always be observed.

LABS Freedom or LABS Conformity

There are materials, such as plastics, that contain plasticizers or release agents, which are considered to be paint wetting impairment substances. LABS-free means that such substances do not already occur in the material itself. However, this is not automatically mean LABS-conform, just as LABS-conform does not automatically mean LABS-freedom. LABS-conform must always be considered in the context of material and desired coating or painting. LABS conformity is tested according to VDMA 24364. No paint wetting impairment must have occurred during the test. In order to conform to the LABS standards, surfactants, for example, can be modified by eliminating certain components in such a way that they no longer generate LABS. Surfactants are often used in the paint industry as wetting agents or dispersing agents. Therefore, it is not uncommon that a material that is not LABS-free does not show paint wetting impairment in a test according to VDMA 24364 and is thus considered LABS-compliant. It is important to note that this only applies to the procedure used in the test. Other paint systems and test methods may lead to deviating results.

Some materials are easier to make LABS-free or LABS conform. Reasons for this are that they do not contain any LABS that can be released or that they are easier to clean because of their physical properties.

Identify LABS - The Standard VDMA Sheet 24364

The VDMA is an association of experts whose task is to standardize the testing of LABS and to proceed in a way that is independent of the material and tailored to the individual application. These generally valid tests are defined in the standard VDMA Sheet 24364. It is important to understand that it is not possible to provide a comprehensive profile of all LABS.. Rather, the damaging effect should be demonstrated in the specific individual case.

Basically, the following question must always be asked about the product to be assessed:

• Will it come into contact with the paint (or adhesives and other coating substances) in the paint processing plant? Will it come into contact with the surface to be painted?
• What are the general conditions at the place of use? This also includes ambient temperature, humidity, and other parameters.

LABS Zones

The standard VDMA Sheet 24364 also defines three zones that describe the relevance of LABS within a paint shop and then justify different requirements regarding the cleanliness of the products used there.

The direct painting process is located in zone I. Here, the LABS relevance is particularly high and the cleanliness requirements are the strictest: There must be no paint wetting impairment substances.
Zone II is also still in the area of paint processing, but already outside the direct contact zone. In this area, there is a certain degree of contaminants tolerable; however, no noticeable paint defects should occur.
Zone III is no longer counted as area for paint processing, but it is still inside the operation. LABS are no longer relevant here. They would not influence the painting process. If products are used in more than one zone simultaneously, all zone requirements must be met.

Based on the requirements, the products can be divided into five groups, each of which is tested differently. Group A includes, for example, all products with direct contact to paint, solvents or surface; Group B and C includes products with indirect contact to them. Group T products are used at high temperatures and are thus relevant for LABS. Group S contains substances that are applied to the surface to be painted or can be carried over into the first two zones.

LABS conformity tests according to the standard VDMA Sheet 24364

The following steps are required for the LABS conformity test in accordance with standard VDMA Sheet 24364:

• select the product group and test class.
• perform zero test.
• perform the test, evaluate it and document it.

When selecting the product group and test class, both the intended use of the product and the zone classification described above are helpful. The test class is then selected depending on the load when used as intended. Before the actual test, the zero test is essential. This ensures that all testing and work equipment used as well as the work environment itself are LABS-compliant. Otherwise, it cannot be reliably assessed whether any errors are due to the work environment or the test object itself. A zero test can be, for example, to subject the test document to the planned test once.

Subsequently, the actual test is performed. The test specimen is placed on the test document where the test takes place. This can be, for example, the rinsing of the test specimen with solvent. Wait until the solvent has completely evaporated and then carry out the paint process. In the cured state, the paint film is then evaluated. The evaluation consists of a visual inspection without additional aids. Either LABS-compliant or non-LABS-compliant can be considered as a result. Quantification is not the objective of this type of test. It is also important to note that there are LABS-dependent and LABS-independent error patterns, e.g., craters have appeared, but the surface was completely wetted with paint. In this case, the product would still be LABS-compliant.

Avoidance and Elimination Strategies

The sources for LABS are numerous and therefore it is all the more important to ensure in advance that the production is LABS-compliant. Products that are not LABS-compliant should be removed from the corresponding production. Alternatively, there are various methods for LABS cleaning, e.g. wet chemical or with the help of plasma.

If paint defects do occur, the only option is usually to sand them down or, in the worst case, dispose of them. However, every sanding also requires recleaning and the affected part must be repainted. This incurs high costs, which is why cleanliness is the top priority when processing and preparing paints and coatings.