Polymer Surfaces reflectance-transmittance

INTERACTIONS BETWEEN SEVERAL RADIATION SOURCES AND CERTAIN POLYMER SURFACES REFLECTANCE - TRANSMITTANCE CHARACTERISTICS... 

Reflectance spectroscopy is commonplace for samples that cannot be prepared for transmittance measurements. However, reflectance measurements must be carefully conducted as the reflected beam is not only indicative of the composition of the sample but is also affected by surface conditions at the sample plane. This makes the reflectance spectra, though indicative of material chemistry, difficult to interpret and generally less useful for quantitative analysis. Since the polarization of the beam is maintained for reflectance, especially specular reflectance methods, examination of orientation at polymer surfaces using reflection techniques is attractive [10]. Reflection-absorption modes involve the transmission of the infrared beam through the sample and subsequent reflection to pass through the sample again. Usually, sample preparation is difficult for such experiments and they... 

During ignition testing of several polymeric materials, it was found that the surface reflectance/absorptance characteristics had a definite Influence on the time of ignition. Since several of the polymers were either transparent or translucent, the monochromatic surface reflectance/absorptance had to be adjusted to account for energy transmittance. As a result, reflectance and transmittance measurements were made over the monochromatic wavelengths of 0.3 - 10.0 microns. Average values of reflectivity and transmissivity were calculated by... 

Reflectance of radiation from a polymer surface as well as the transmittance of radiation through a polymer material is a function of the wavelength of the radiation and the polymer material itself. 

A problem that may be encountered when analyzing a solid sample by transmittance spectroscopy is radiation scattering. Employing reflectance spectroscopy can sometimes reduce this problem. With this technique, the infrared spectra of most solid materials are easily obtained with little or no sample preparation. Spectra of a wide range of solid samples can be characterized with this technique, such as coatings on beverage containers and silicon wafers, polymer films, or other intractable samples. The reflectance technique, however, is less sensitive than the transmittance technique since about 80 /o of the infrared radiation is lost after being reflected off the sample surface. 

Applications of the fibre optics transmittance or ATR probe are in quality control, reaction monitoring, skin analysis, goods-in checking, analysis at high and low temperature, radioactive or sterile conditions, and hazardous environments. Applications of the reflectance probe are for turbid liquids, powders, surface coatings, textiles, etc. By using an on-line remote spectrophotometer, real-time information is gathered about a chemical process stream (liquids, films, polymer melts, etc.), as often as necessary and without the need to collect samples. This determines more reliable process control. Remote spectroscopy costs less to maintain and operate than traditional techniques. Fernando et al. [48] have compared different types of optical fibre sensors to monitor the cure of an epoxy resin system. 

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