Other

70.07 - Safety glass, consisting of toughened (tempered) or laminated glass. - Toughened (tempered) safety glass : 7007.1 1 - - Of size and shape suitable for incorporation in vehicles, aircraft, spacecraft or vessels - - Other - Laminated safety glass : 7007.21 - - Of size and shape suitable for incorporation in vehicles, aircraft, spacecraft 7007.19 or vessels 7007.29 - - Other The term " safety glass " covers only the types of glass described below and does not refer to protective glass such as ordinary wired glass and selective absorption glasses (e.g., anti-glare glass, X-ray protective glass). (A) Toughened (tempered) glass. This is : (1) Glass obtained by reheating pieces of lass until they are soft but not soft enough to lose their shape. The glass is then coo ed rapidly by appropriate processes (thermaltoughened glass). f (2) Glass whose strength, durability and flexibility have been substantially increased by a corn lex physical-chemical treatment (e.g., ion-exchange) which ma include a mo!d fication of the surface structure (commonly known as " chemical y toughened glass "). Y This glass cannot be worked after manufacture because of the internal stresses set up by the processing and is therefore always produced in the shapes and sizes required before tempering. (B) Laminated glass. Safety glass of this type, commonly known as laminated glass, sandwich glass, etc., is made in sandwich form, with one or more interlayers of plastics between two or more sheets of glass. The plastics core usually consists of sheets of cellulose acetate, vinyl or acrylic products. Complete adhesion is obtained by a lyin considerable heat and pressure, sometimes after spraying the inside surfaces o?%e fiss sheets with a s ecial t e of adhesive. Another method IS to roduce a plastics film irectly on the glass s eets; t e glass sheets are then sealed together y applying heat and pressure. P ! P d R A characteristic of tou ened safety glass is that under the effect of shock it breaks into small ieces without sharp e ges or even disintegrates, thus reducing the danger of injury from flying gagrnents. Laminated s a f q glass normally cracks without shattering, but, should the impact be great enough to fiacture it, any flying pieces would not usually be sufficiently large to cause severe cuts. For special urposes, wire mesh may be incorporated in the laminated glass, or the plastics interlayers may e coloured. Because of these qualities these types of glass are used in motor car windscreens and windows, in doors, in ships' portholes, in protective gog les for industrial workers or dnvers, and for e epieces for gas masks or divers' helmets. Bu let proof glass is a special type of laminated g ass. f r This heading makes no distinction between unshaped and shaped (e.g., bent or curved) glass. However, curved safety glass havin the character of clock or watch glasses or of a kind used for sunglasses is classified in heading 70.1 . Safety glass incorporated in other articles and thus in the form of parts of machines, appliances or vehicles is classified with those machines, appliances or vehicles; similarly goggles containing lenses of safety glass fall In heading 90.04. % Multiple-walled insulatin lass, for exam le, that composed of a sandwich of two sheets of glass with an interlayer of glass fibre, a1 s in heading 79.08. Articles of toughened (tempered) lass and glass-ceramics, other than those of a kind used for the oses mentioned above, are c assified according to their individual character (e.g., toughened a l e r s , bornsilicate baking dishes and glass-ceramic plates in heading 70.13). B Plastics used as a substitute for safety glass are classified according to the constituent material (Chapter 39).