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FR-4 is a composite material composed of woven fiberglass cloth with an epoxy resin binder that is flame resistant (self-extinguishing). "FR" stands for "flame retardant", and does not denote that the material complies with the standard UL94V-0 unless testing is performed to UL 94, Vertical Flame testing in Section 8 at a compliant lab.
Most glass fibers have limited solubility in water but are very dependent on pH. Chloride ions will also attack and dissolve E-glass surfaces. E-glass does not actually melt, but softens instead, the softening point being "the temperature at which a 0.55–0.77 mm diameter fiber 235 mm long, elongates under its own weight at 1 mm/min when ...
Glass fibers have been produced for centuries, but the earliest patent was awarded to the Prussian inventor Hermann Hammesfahr (1845–1914) in the U.S. in 1880. [3] [4]Mass production of glass strands was accidentally discovered in 1932 when Games Slayter, a researcher at Owens-Illinois, directed a jet of compressed air at a stream of molten glass and produced fibers.
The density of water is about 1000 kg/m 3 or 1 g/cm 3, because the size of the gram was originally based on the mass of a cubic centimetre of water. In chemistry , g/cm 3 is more commonly used. See also
Unless stated otherwise, the properties of fused silica (quartz glass) and germania glass are derived from the SciGlass glass database by forming the arithmetic mean of all the experimental values from different authors (in general more than 10 independent sources for quartz glass and T g of germanium oxide glass).
Densities using the following metric units all have exactly the same numerical value, one thousandth of the value in (kg/m 3). Liquid water has a density of about 1 kg/dm 3, making any of these SI units numerically convenient to use as most solids and liquids have densities between 0.1 and 20 kg/dm 3. kilogram per cubic decimetre (kg/dm 3)
The density is determined by weighing the sample in air and then in a liquid of known density. Application of Archimedes’ principle leads to the following expression for the measured density of the sample in terms of measured weight, where subscripts “a” and “L” refer to water and liquid, respectively: [ 5 ]
The C-values are the glass component concentrations like Na 2 O or CaO in percent or other fractions, the b-values are coefficients, and n is the total number of glass components. The glass main component silica (SiO 2 ) is excluded in the equation below because of over-parametrization due to the constraint that all components sum up to 100%.