 
Elaboration
The manufacture of glass is carried out in a special furnace at about 1550°C/2822°F (E-glass) using finely ground raw materials from carefully selected quarries. The glass leaves the furnace at a very high temperature and is used to feed bushings (blocks pierced with hundreds of holes) of platinum alloy.
The majority of Vetrotex products are based on E-glass. Other glasses are also used, for example, R-glass (high mechanical performance), D-glass (high dielectric performance) and AR-glass (alkali and corrosion resistant glass).
Forming
The basic glass strand is made by forming. Forming is achieved by drawing the molten glass flowing from the holes of the bushing at high speed. This forms between fifty and several hundred filaments. These filaments are defined by their diameters: from 5 to 13 microns (1µm = 1/1000 mm).
Sizing
The individual filaments of Vetrotex reinforcements receive a coating of size at the forming stage, immediately after they leave the bushing. This size, made up of organic products dispersed in water, is designed to give the glass strand certain characteristics necessary for the end application. For textile applications, sizes are generally starch/oil based. For some applications, special sizes may contain film formers other than starch, as well as a silane-type chemical “coupling agent,” which enhances the mechanical and ageing properties of the end product.
Vetrotex products are either manufactured immediately after they leave the bushing (direct roving) or made up of basic strands subjected to finishing operations (twisting for yarns, plying, texturizing, assembly of rovings, chopping of strands and warping).
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