Table of Contents
What is laminated glass?
Laminated glass is a type of composite glass product made by firmly bonding two or more pieces of glass together with a transparent adhesive material. Laminated glass is a type of safety glass that has high impact resistance and puncture resistance. When it is damaged by impact, foreign objects usually cannot penetrate it, and glass fragments will not detach from the bonding layer. Laminated glass also maintains a certain degree of visibility, thus providing a protective safety function. Laminated glass is also called laminated safety glass or laminated glass with interlayer.
What is PVB film? What are its characteristics?
PVB film is a polymer material made by plasticizing and extruding polyvinyl alcohol formaldehyde resin with a plasticizer, DHA.
The thickness of PVB film is generally 0.38mm and 0.76mm, and it comes in two types: clear film (used for building laminated glass) and colored film (with blue and green stripes as the main colors).
PVB film has good adhesion to inorganic glass and has characteristics such as transparency, heat resistance, cold resistance, moisture resistance, and high mechanical strength. It is flexible and tough, with a tensile elastic modulus of about 1/2000 of glass, but a fracture elongation rate of more than 3000 times that of glass. Its fracture energy is greater than that of stainless steel and high-strength fibers. Therefore, PVB film is an excellent intermediate adhesive material for car and airplane windshields. It is also widely used in the construction industry, such as in curtain walls, canopies, shop windows, bank counters, prison visit windows, steelmaking furnace screens, and various bulletproof laminated glass.
What is the process flow of laminated glass production?
The cleaned glass (which can be flat glass, tempered glass, or heat-bent glass) is laminated (excess film around the edges is removed), and a vacuum rubber sleeve is placed around the edge of the glass for vacuuming. The laminated glass is then sent to the pre-press and pre-heating room, where a vacuum tube is connected to remove the air between the glass and the film, while simultaneously heating to improve the vacuum effect. When the rubber sleeve is under vacuum, atmospheric pressure causes the glass and film to initially bond. The semi-finished product is then placed in a steam press and pushed into a high-pressure vessel to be heated and pressurized according to the process, fully bonding the glass and film.
What preparation work is required for PVB film?
Firstly, the PVB film must be cut according to the size of the glass and the amount of shrinkage after processing to compensate for the shrinkage during the hot pressing process. Secondly, when using PVB film stored at low temperature, the shrinkage depends on the shrinkage rate of the film itself and the stress generated when the film is laid out. If using a roll of PVB film with surface alkaline powder, the cut film needs to be washed in water with a pH of 10-25 to remove the surface alkaline powder.
What are the characteristics of laminated glass?
Laminated glass has the following characteristics:
High safety: In the event of accidental breakage, the glass fragments are firmly bonded to the middle (PVB film) layer, greatly reducing the harm to people and property. Especially when laminated glass is used in various new, special, and irregular buildings, it can prevent the harm caused by accidental glass breakage and falling.
Strong security protection: Laminated glass can resist external repeated impacts, and its multi-layer structure can even resist heavy objects or gun attacks. The protective function of laminated glass can even extend to blocking the shock wave generated by bomb explosions, minimizing harm to people.
Excellent sound insulation and noise reduction performance: The middle layer (PVB film) of laminated glass has good sound insulation and noise reduction effects. Its sound insulation performance is several times stronger than that of ordinary glass, and it can reduce noise from planes, cars, and machinery, creating a pleasant and comfortable internal environment. This is highly beneficial for high-tech work, life, and health in the 21st century.
Good UV shielding performance: Laminated glass can block more than 99% of harmful rays in sunlight, which greatly helps to protect people’s skin health and indoor buildings, furniture, exhibits, and commodities from UV radiation damage.
Currently, laminated glass has developed into a decorative material. The PVB film used in its manufacturing process is available in various colors and varieties in domestic and international markets. Laminated glass made with these numerous films not only offers safety, but also energy-saving benefits. Architectural laminated glass made with PVB functional films can effectively reduce the penetration of sunlight and lower cooling energy consumption. Similarly, laminated glass made with dark, low transmittance PVB films has stronger heat-blocking capabilities for the same thickness.
After years of production, use, and destructive testing, laminated glass is considered one of the best members of the glass family. It not only has the necessary performance of glass, but also maintains its integrity even after it is shattered. There are few glass fragments that can splash and harm people and objects. It is the preferred glass material for use in various fields such as construction, transportation, and aerospace in the 21st century.
What are the types of laminated glass?
As the main type of processed glass, laminated glass has a wide variety of types, which can be broadly categorized in the following ways:
According to the production method, laminated glass can be divided into two types: film laminated glass and cast-in-place laminated glass. Among them, film laminated glass can be further divided into high-pressure autoclave film laminated glass and one-step laminated glass.
According to the purpose of the product, laminated glass can be divided into automotive laminated glass, architectural laminated glass, railway vehicle laminated glass, ship laminated glass, aviation laminated glass, and other special laminated glass. Among them, automotive laminated glass can be further divided into windshield laminated glass and side window laminated glass according to usage position, and can also be divided into tempered laminated glass, sunshade laminated glass, electrically heated laminated glass, and laminated glass with a radio antenna according to application function. According to safety level, it can be divided into high-penetration-resistant laminated glass (HPR laminated glass) and ordinary laminated glass.
According to the shape of the product, laminated glass can be divided into flat laminated glass and curved laminated glass. Among them, curved laminated glass can be further divided into single-curved laminated glass, double-curved laminated glass, deep-curved laminated glass, and shallow-curved laminated glass.
According to the performance of laminated glass, it can be divided into the following types: bullet-resistant laminated glass, theft-resistant laminated glass, fire-resistant laminated glass, electrically heated laminated glass, decorative laminated glass, photochromic laminated glass, electromagnetic shielding glass, etc.
The factors affecting the impact resistance of laminated glass
① Adhesion between glass and PVB film: within a certain range, impact resistance is inversely proportional to adhesion.
② Influence of film thickness: impact resistance is directly proportional to film thickness.
③ Influence of glass thickness: generally, impact resistance is directly proportional to glass thickness.
④ Special glass treatment: glass can increase impact resistance through processes such as tempering.
Different types of films will also affect the impact resistance of glass.
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