Scratches are made in the printed/painted surface in two perpendicular
directions and an adhesive tape is then stuck to the surface. The tape is
pulled off and the ratio between the area of the undamaged surface and the
area where the paint/ink layer has peeled off with the tape is established
visually.
Depending on the specific application, additional exposure tests may be
requested, like:
- Humidity exposure
- Water soak
- Heat aging
-
Thermal shock
- Steam jet
- Stone chipping
Chemical resistance testing
The stress crack resistance of the substrate to a particular paint/ink system
can be tested by coating tensile bars while they are subjected to a strain of
up to 1%. Uncoated tensile bars and tensile bars that are coated without an
applied strain are used as a reference. The tensile bars are subjected to a
tensile test after the coating process and the stress-strain curves of the
test bars are compared with the curve of the reference bars.
Impact testing
Impact performance after painting/printing can be tested with several impact
tests, like a puncture test or a falling dart test.
Scratch resistance
The scratch resistance can be established e.g. in the Taber abrasion test,
where the amount of haze is established after a number of abrasive cycles. The
scratch resistance can also be determined quantitatively by measuring the
weight loss after a number of sanding cycles (see DIN 53754). The pen test
according ISO 1518 determines the indentation caused by a sharp pencil applied
with a defined force.
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