Scanning electron microscopy interfacial adhesion

L. H. Lee (Xerox Corporation We are really fortunate to have Dr. Buchanan here giving us a latest account about recent developments in scanning electron microscopy. SEM has been one of the useful tools for us to examine adhesive interfaces. New techniques described in this paper should enable us to observe the interfacial area with greater precision. 

ABSTRACT. The paper details the use of scanning electron microscopy, surface reflectance infrared spectroscopy, Auger electron spectroscopy, ion scattering spectroscopy, secondary ion mass spectroscopy, and x-ray photoelectron spectroscopy in the analysis of polymeric adhesives and composites. A brief review of the principle of each surface analytical technique will be followed by application of the technique to interfacial adhesion with an emphasis on polymer/metal, fiber/matrix, and composite/composite adhesion. 

The choice of techniques and their application is complicated by the aims of the analysis and whether or not this is quantitative. Scanning electron microscopy (SEM), for example, is widely applied to assess the extent of interfacial adhesion in filled polymer composites, usually through examination of fracture surfaces. However, the information obtained is generally non-quantitative, although estimates of interfacial shear strength are possible from fibre pull-out measurements in short-fibre reinforced polymer composites [55]. 

The poly(methyl methacrylate) molecules were dispersed in the natural rubber matrix, or vice versa, to form spherical droplets, as observed by optical photographs or scanning electron microscopy. The compatible natural rubber/poly(methyl methacrylate) blends had been made by the addition of the graft copolymer of natural rubber-gr t-poly(methyl methacrylate) as the compatibilizing agent due to its ability to enhance the interfacial adhesion between the two homopolymers. Moreover, Nakasorn and coworkers reported that natural rubber-gr i -poly(methyl methacrylate) could be blended with poly(methyl methacrylate) via a dynamic vulcanization technique with a conventional sulfur vulcanization system. The natural rubber-gra/t-poly(methyl methacrylate) was synthesized by a semi-batch emulsion polymerization technique via different bipolar redox initiation systems, i.e. cumene hydroperoxide and tetraethylene pentamine. ... 

The role of silica-only systems on adhesion has been studied using model compounds with squalene [59]. It was shown that the mechanism for increased adhesion to brass-coated wire-to-rubber was not just a simple improvement of the physical properties of the rubber, but that silica moderated the thickness and composition of the interfacial layer by a chemical interaction. SEM-EDX (scanning electron microscopy with energy dispersive analysis of X-rays), XPS, AES and PIXE (proton induced X-ray emission spectroscopy) revealed that silica affected the relative concentrations of compounds present in the interfacial layer, promoting zinc oxide formation in particular. 

The microscopy method is a method in which the interfacial condition between the fillers and polymer matrix can be directly observed. The most commonly used is scanning electron microscopy (SEM). By SEM observation of the morphological structure of impact or tensile cross-sections of polymer matrix composites, the filler dispersion in the overall situation and overall interfacial adhesion of the fillers and polymer can... 

Mechanical properties of natural fiber reinforced composites are mainly influenced by the level of dispersion and interfacial adhesion between the matrix and fibers and microscopy is one of the most effective methods for morphological observations. In this study, scanning electron microscope (SEM) was used to investigate the dispersion of natural fiber and interfacial morphologies and the images are shown in Figures 3.2 (film surface) and 3.3 (cryo fractured surface). The SEM pictures show the differently shaped particles and the more or less spherical lignin-based particles. 

---