Coatings continued thickness

Coated fibers are generally characterized in terms of coating uniformity, continuity, thickness and composition. Scanning electron microscopy can be used for the first three types of characterization, while X-ray powder diffraction and/or transmission electron microscopy (+ EDS/EELS) can provide compositional information [194]. The residual porosity within the coating is also considered, particularly if a hermetic coating is needed for environmental protection of the fiber. 

Although they are expensive, deposition chambers of virtually any size can be constructed. The versatility of the process enables the simultaneous coating of many small parts of varying configurations. However, this is mainly a batch process and difficult to apply in a continuous fashion. Parylenes can also be deposited onto a cold condenser and then stripped off as a free film, or they can be deposited onto the sm-face of objects as a continuous, adherent coating in thickness ranging from about 0.004 mil to 3 mil or more. The deposition rate is normally about 0.02 mil/min. On cooled substrates, the deposition rate can be as high as 1.0 mil/min. 

In the pre-coat mode, filter aids allow filtration of very fine or compressible solids from suspensions of 5% or higher solids concentration on a rotary drum pre-coat filter . This modification of the rotary drum vacuum filter uses an advancing knife to skim off the separated solids and the uppermost layer of the thick pre-coat continuously, until the whole of the pre-coat is removed and a new layer has to be applied. This makes it possible to discharge very thin cakes as well as that part of the pre-coat which has been penetrated into by the sohds and partially blinded. 

The war itself also drove the development of improved and miniaturised electronic components for creating oscillators and amplifiers and, ultimately, semiconductors, which made practical the electronic systems needed in portable eddy current test instruments. The refinement of those systems continues to the present day and advances continue to be triggered by performance improvements of components and systems. In the same way that today s pocket calculator outperforms the large, hot room full of intercormected thermionic valves that I first saw in the 50 s, so it is with eddy current instrumentation. Today s handheld eddy current inspection instrument is a powerful tool which has the capability needed in a crack detector, corrosion detector, metal sorter, conductivity meter, coating thickness meter and so on. 

The range of ultrasonic, eddy-current and magnetic defectoscopes, structuroscopes and thickness gauges for metals and coatings are continuously modernized. 

Polyesters are also used in continuous filament spunbonded nonwovens (see Nonwoven fabrics). Reemay spunbonded fabric is composed of continuous filament PET with a polyester copolymer binder. These spunbonded fabrics are available in a wide range of thicknesses and basis weights and can be used for electrical insulation, coated fabric substrates, disposable apparel for clean rooms, hospitals, and geotextiles (qv). 

---