Adhesion is the bond strength measurement of a coating to a substrate. When an adhesive is bonded to an item or surface, numerous physical, mechanical and chemical forces come into play, which may have an effect on each other. These need to be tested before a product can be used.
Determination of the failure point can be critical for the final use of the material and the adhesive. There are a large number of different adhesive products, which require different testing methods to characterise the properties of the material. Some examples include substrates, glue, creams, gels, paints and varnishes and bonding of different materials together in layers, which all require different adhesive test methods.
Determination of the failure point can be critical for the final use of the materials, depending on the final product they have been designed for. Tests can also be done at different temperatures to simulate real world use for the materials. Material characteristics can change at high or low temperatures due to expansion and contraction.
Adhesion testing is often associated with adhesives, tape, sealants, laminates, electronics,cosmetics, medical device packaging, general packaging seal strength and applications where bond strength measurement is critical for research and quality control applications. Stud pull coating adhesion testing, for instance, is a very common test used in micro-electronic coatings or other forms of “thin film” application on rigid substrates.
Typical graph showing a test performed on adhesives, paints or varnishes:
Typical test measurements include:
– 180 degree and 90 degree peel tests
– Lap shear tests for evaluating the shear strength of adhesives for bonding two surfaces together and welds such as metal and plastic welds
– Coating cohesion – adhesion or bond strength of a coating to substrates such as paints or varnishes
– Cure behaviour
– Tensile strength
– Seal strength, peel strength and adhesion strength tests to determine adhesion strength of flexible plastic packaging