Mechanical & Chemical

Flexibility, Hardness and Impact Resistance

Not every coating will have the same flexibility or toughness.  Sometimes these attributes are not important in the final requirement of the coating, however on occasion these properties are vital, for example in a post-forming context.  Mechanical tests are often carried out as part of QC process as an indicator of cure and include many testing procedures, from falling weight impact, to pencil hardness, to scratch or abrasion testing.

Processing Issues

The coating has a lower flexibility, hardness and/or impact resistance than expected directly after application

  • Potential Cause

    A change has been made in the substrate or pre-treatment system without making changes in the process.

  • Solution

    Contact suppliers to ensure no changes to the substrate have been made.  Ensure that the pre-treatment system is appropriate to the substrate.

  • Potential Cause

    Under cured films will have lower flexibility, hardness and impact resistance

  • Solution

    Modify cure conditions by increasing temperature and/or dwell time.

  • Potential Cause

    The film thickness is too high

  • Solution

    Optimise the thickness of the film.  Most coatings are designed for application between 60 and 100 microns; consult the technical data sheet for the coating.

  • Potential Cause

    Different resin chemistries will have different physical properties.  Many standard coatings are a balance of properties to achieve a recognised standard such as Qualicoat.  Often, improving one coating attribute will have a negativel impact on another attribute.  For example, increasing the UV-weathering resistance of a polyester coating will reduce its flexibility and impact resistance.

  • Solution

    Contact us to discuss your specific requirements.  We may have an off-the-shelf alternative, or we can custom build a product to your requirements.

Post Process

The coating has a lower flexibility and/or impact resistance than expected some days or months after application.

  • Potential Cause

    Flexibility deteriorates over time.  Powder coatings will naturally lose a little flexibility and become more brittle over time.  This can be confirmed using a reverse impact test (falling weight) and is is a consequence of the binder system becoming more crystalline.

  • Solution

    If long term flexibility is an issue for post-forming work, we can tailor-make coatings that are more flexible and retain their flexibility for longer.

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