What Is Laminated Glass?
Laminated glass is a type of safety glass that holds together when shattered. Laminated glass is the only glass to provide durability, high-performance and multi-functional benefits while at the same time preserving the aesthetic appearance of the glass. Laminated glass is produced by bonding layers of two or more glasses together under pressure and heat, with a resin called PVB (polyvinyl butyral). The PVB sticks with the glass, forms chemical as well as mechanical bonds. When laminated with annealed glass, the layer maintains the geometric integrity of the pane in case of breakage. The PVB is the main element that keeps the glass from breaking apart easily and provides high sound insulation. It is mandatory these days for car manufacturers to use laminated glass in windscreens. The property of a laminated glass is a total culmination of the PVB thickness, PVB color, refractive index, visible light transmittance clarity, shading coefficient clarity, UV clearance, tensile elongation and strength, specific gravity and heat, thermal conductivity, coefficient of thermal expansion, and emissivity.
Advantages of laminated glass
Laminated glass is safe as it is not easy to break with the inter-layer of glass resisting against the force of the impact. Even if the glass breaks, it will not shatter into pieces of sharp fragments as they stick to the inter-layer between the glasses. The inter-layer keeps the layers of the glass bonded even when broken, and its high strength prevents the glass from breaking up into large sharp pieces. This produces a characteristic ‘spider web’ creating pattern when the impact is not enough to completely pierce the glass. It can maintain its strength for a long time and there is only a little wear and tear effect. As it is strong, it also provides benefits for security purpose. In most cases, with two layers of glass and an inter-layer in between, it is a very good barrier to sound as the sound is absorbed by the inter-layer when it passes through the glass. Also laminated glass has a higher aesthetic value due to the green tint in the laminated glass which gives it a unique yet aesthetical appearance when used.
Steps to create laminated glass for windscreen
The process of laminating glass for windscreen starts by making raw glass ready for shaping and cutting. It is mostly done by machines (robots). A cutting wheel scores the windscreen shape onto the glass sheet. To cut out the shape, the glass is snapped at the cutting line. After the glass has been cut, the edges are smoothed using a sanding belt machine. This is called seaming. Thereafter the glass is washed in de-ionized water to remove dirt and particles. The glass is also sprayed with talcum powder, which prevents the two sheets from sticking together in the bending furnace.
A black outer border is silk-screened onto the outer perimeter of one of the pieces. The glass pieces are then inspected visually against a wall of lights for marks, hairline cracks and other imperfections. Then the glass is placed onto the bending mould. Bending moulds come in all shapes and sizes, depending on the vehicle the glass is intended for. The glass is carried on the bending mold into the bending furnace, where it is heated to over 6000c and sag bends into the desired shape. It is then slowly cooled to anneal the now shaped glass.
Two sheets of bent glass are bonded together with a layer of Poly Vinyl Butyral (PVB). The final lamination takes place in an autoclave, a special pressure vessel that uses both heat and pressure to form a single, strong bonded windscreen. In order to ensure high quality standards, each windscreen undergoes a detailed visual inspection at the end of the manufacturing process. After final inspections, the windscreens are fitted with additional bits such as rear-view mirror brackets and other trim, mouldings, etc.
A percentage of the windscreens manufactured undergo an impact test where a steel ball as heavy as 2.2 kg is dropped from a 4 meters height. If it doesn’t go through the windscreen, it means the windscreen passed the safety test.
For the highest quality windscreens, fitted anywhere in the South West by our skilled Technicians based in Gloucester, Cheltenham, Bristol and Swindon, call UK Autoglaze on 0800 953 0047 (for free)