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The multiple-sample approach by means of centrifugal adhesion testing (CAT-technology) allows the determination of bonding strength of adhesive-bonded joints on a statistical basis of up to eight samples. Therefore, it is obvious to ensure the continuous handling and identical processing of an octet of samples within the entire process chain of wet-chemical cleaning, plasma-chemical pre-treatment, bonding of samples, and testing of bonding strength. Within the multiple-sample bonding set-up (MPKV-technology) a defined bonding pressure can be adjusted regardless the actual number of samples. A comparison of single- and multiple-sample approach is made for bonding strength of selected adhesives, double-sided adhesive tapes and different material combinations [stainless steel (V2A) vs. stainless steel, polyamide (PA), or polypropylene (PP)]. It is shown that both technologies improve reliability of results
The quality and durability of bonded joints, coated systems and composites depend on various factors. Therefore effective quantitative tests to determine adhesive, bonding or composite strength are of great need for R&D and QC. In this paper a new measuring principle is described which uses the centrifugal force to generate the test load. By the geometry of the whole measurement set-up, the test specimen are supported from only one side, the influence of shear forces is avoided. The possibility to test up to eight samples in one measurement under identical testing conditions allows a high sample throughput.
A detailed description of the whole sample preparation procedure including pre-treatment is followed by the specification of the measuring protocol as well as result analysis. For each application area bonding strength of joints, adhesive strength of coated systems and internal strength of composite materials examples are presented.
Multiple-sample approach: reliable ranking and validated statistics of bonding and adhesive strength
(2014)
Bonding strength of adhesive-bonded joints and adhesive strength of coatings have been exclusively determined in single-sample tests using a tensile testing machine. Necessarily, the single-sample approach was also applied to the corresponding bonding procedure. As a consequence, reliability and reproducibility of results were restricted. By applying the newly introduced centrifuge technology, the multiple-sample approach was realized for simultaneous tensile testing of up to eight samples under identical conditions without any disturbing shear-force effects. In order to introduce the multiple-sample approach into the bonding procedure, a hydraulic bonding set-up was developed which enables identical bonding pressure also for slightly different heights of sample assemblies. Both sample approaches were compared for various application examples: ranking of different classes of adhesives, validated statistics of adhesive-bonded joints using one particular adhesive and effects of cleaning and plasma-treatment on the adhesive strength of coatings. The investigated systems included glass, metals and polymer substrates, different adhesives, metallic and dielectric coatings on polymers.