Scanning Electron Microscopy
Scanning Electron Microscopy (SEM) is an excellent tool for examination of surfaces at high magnifications. It produces a pseudo three-dimensional image and has the added benefit of being free from many of the aberrations which are troublesome in light microscopy. Magnification typically ranges from as low as x20 to as high as x50,000 or more. Because of the low signal yield, insulating properties, and composition, most polymer materials have a practical magnification limit of x10,000 to x20,000. Specialized field emission SEM's may have higher magnifications. A straining stage accessory is available to study behavior of materials under tensile strain.
- To study polymer blends, it is important to know the morphology of the components if the blend contains incompatible materials. Amounts of additives used in the processing as well as the processing conditions themselves affect the phase domain type and size. To obtain images of the separated phases, the specimens are frozen and fractured in a reproducible manner. Preparation of the sample for examination in the microscope usually involves carbon coating by evaporation and/or sputter coating with a heavy atom (gold or gold/palladium are most common). When the mixtures are not too complex, the component phases are readily identified. Micrographs are recorded for measurement and reference.
- Coatings on synthetic and natural fibers can enhance the fibers' properties and performance. Many coatings are patented and competitors often seek ways to beat the rules. When magnified, the surface characteristics of coated and uncoated fibers can be apparent. SEM imaging of fabrics with proprietary coatings has been used in defense of patent rights claims.