Influence of Interfacial Parameters on the Adhesion of Aluminium on Mild Steel using Pressure Sensitive Adhesives

Abstract

The influence of interfacial parameters on the adhesion of pressure sensitive adhesives was investigated. Study on effect of
adhesive rheology, interface parameters, surface modification and adhesion strength prediction from correlation between fracture
energy/ thermodynamic work of adhesion was done. Research analysis was carried out using concept of physical and practical
adhesion approaches. Test liquids Ethylene glycol, Glycerol and Ethanol were used to derive contact angle. Contact angles
snapshots for both substrates and adhesives were done using high definition Nikon D80 camera. Low Bond Axisymmetric Drop
Shape Analysis with Image J software was used to measure contact angle values. Fowkes law was used to calculate surface free
energy for both adhesives and substrates. Owendts-Wendt law was employed to calculate thermodynamic work of adhesion.
Surface roughness of substrate was evaluated using SRT-6100 surface roughness tester. Characterization of the substrates was
done with XMET 700XRF spectrometer. Analytical tools such as SPSS, Excel, Minitab 3D surface plot plot were used for data
analysis. Correlation evaluation for fracture energy and thermodynamic work of adhesion showed an inverse relation measured
across adhesives used. As follows, Epoxy (-0.387), Natural rubber (- 0.6), Acrylic (-0.345), Silicon (-0336). 3D Surface Plot
showed linear, inverse and partial relation for polar and dispersive component of substrates and adhesives. A novel way of
evaluating adhesion strength without breaking of bond was put forward. This involves deriving the Adhesion Ratio across the
bonds. Additionally, interfacial attraction between substrates and adhesives along the lines of dispersive and polar components of
surface free energy were used to evaluate adhesion strength. Hence, this work established that when substrate and pressure
sensitive adhesives of opposite polarities are bonded at interface, stronger work of adhesion is achieved. This extends the
hypothesis that close ratio matching of polarity components between adhesive and substrates predicts stronger adhesion.