Manufacturers often encounter a similar puzzle, when cleaning invisible contaminants from a surface, how do you know when the surface is clean; how clean is clean enough? This is a common question that manufacturers ask when preparing their surfaces for bonding, coating, sealing, printing or painting. Until now, there hasn’t been an objective and reliable way to answer this question. Successfully cleaning a surface directly correlates to the adhesive ability of the surface. In order to get something to stick reliably the surface must be clean. How we define that parameter is different for a variety of materials.

For example, you clean your car differently than you clean your dishes. Why? Because a car rides on the road through rain, smog, dirt, maybe mud, and the other is a vehicle for your food.

At BTG Labs, our answer to the “clean enough” question is, “Depends on what you’re doing.” There are dozens of critical surface preparation processes that exist for a number of different applications. A handful include:

  • Flame treatment on polypropylene bumpers prior to painting
  • Plasma treatment on PET catheters prior to coating
  • Hand sanding and solvent wiping on aircraft nut plates before adhesively bonding to composite
  • Grit-blasting titanium golf clubs in preparation of bonding to composite
  • Corona treatment on film for packaging prior to metallization, lamination, or coating

Surface processes differ depending on the material and the application. The surface of PET used for food packaging is prepared differently than a nut plate for a fighter jet.

One thing all surface preparation processes have in common: they have a range of contact angles that are needed to achieve successful adhesion. Figure 1 exemplifies that for optimum adhesion there exists not one contact angle, but a range of contact angles that can be acceptable in order to properly adhere two surfaces together. The ideal surface is generally a lower contact angle, but not too low.

The Surface Analyst has the ability to set a pass/fail range that falls within the product’s required water contact angles. Thus, the user knows—right on the factory floor—if the desired surface has been created.

Figure 1. Pass range for successful adhesion

Each surface preparation process is specific to its application—its final goal. Surface preparation processes also differ depending on the material. Figure 2 demonstrates general ranges for metals, plastics, and composites after proper preparation. These numbers will change depending on the actual process. But, the Surface Analyst is there to help tailor the process to fit the manufacturer’s needs.

Figure 2. General contact angle ranges for plastics, composites, and metals post preparation.

The Surface Analyst develops a surface preparation process that’s specifically designed to optimize your application. Thanks to state-of-the-art equipment such XPS (X-ray Photoelectron Spectroscopy), FTIR (Fourier Transform Infrared Spectroscopy), and the Instron, BTG Lab’s Materials and Processing Laboratory has the unique ability to dissect your surface preparation process by determining surface chemistry and composition, finding the failure tolerance for your bond, and determining the appropriate contact angle range to get the surface where it needs to be.

This way of honing in a critical surface process results in a more reliable product, reduces waste and time, and eliminates failures. BTG Labs is here to answer your question, “How clean is clean enough?” by breaking down your process and determining a water contact angle range needed to reliably bond your product. So, whether you’re cleaning a bumper for an automobile, or a nut plate for an airplane, you know that you are cleaning it the way it needs to be cleaned to do its job.