What is Heat Treated Glass?
Heat treated glass is a type of glass that undergoes thermal or heat treatment during manufacturing. This treatment involves heating the glass to its softening point and then rapidly cooling or annealing it to increase its strength and alter other important properties.
Types
There are different types that are commonly used:
Tempered Glass
Tempered or toughened Heat Treated Glass is heat treated to significantly increase its strength and durability. During manufacturing, standard float glass is heat soaked to create internal stresses and then cooled rapidly, which creates a compression stress layer on the surface while leaving the inner portion in a tensile stressed condition. This makes tempered glass 4-5 times stronger than standard annealed glass and able to resist breakage into small safe pieces upon impact. It is commonly used as safety glass for windows and doors due to its enhanced mechanical strength and safety properties.
Heat Strengthened Glass
Like tempered glass, heat strengthened glass also goes through a thermal treatment process of heating and controlled cooling. However, the cooling rate is slower than tempered glass, resulting in higher internal stresses. Heat strengthened glass gains 2-3 times more mechanical strength than regular float glass but doesn't completely shattered into small pieces like tempered glass upon breakage. It finds applications where safety from shattering is important but is not concerning for security purposes.
Laminated Glass
Laminated glass consists of two or more pieces of glass held together by an interlayer, usually polyvinyl butyral (PVB). The glass layers are toughened or heat strengthened before lamination. Laminated glass offers high impact resistance because the interlayer binds the glass tightly and holds broken glass fragments. It is used extensively as safety glazing for doors and windows in buildings requiring security against break-ins.
Specialty Heat Treated Glass
Some other types created for specific purposes include wired glass, patterned wired glass and wire reinforced glass. Wired glass has a wire mesh embedded between two layers of glass to prevent shattering and project flying glass shards if broken. It provides basic security and has fire resistance applications. Patterned wired glass comes in decorative designs and is used in partitions and vision panels of doors and walls. Wire reinforced glass uses a single layer of glass reinforced with wire webbing for medium security applications.
Properties
The heat treatment process significantly alters the physical and safety properties of glass. Here are some key attributes of heat treated glass:
Enhanced Strength
As discussed earlier, tempered, heat strengthened and laminated glass exhibit 2-5 times higher mechanical strength compared to regular annealed float glass. The compressive stress layer formed during heat strengthening or tempering makes the glass resistant to impact and breakage.
Improved Durability
The high strength and resistance to breaking into sharp shards makes heat treated glass withstand impacts, pressure changes, and temperature fluctuations better than regular float glass over long usage.
Enhanced Safety
One of the primary purposes of heat treatment is to make glass safer. Tempered and laminated glass shatter into small cubical or oblong-shaped pieces instead of jagged shards upon breakage, significantly reducing injury risks from sharp edges and flying glass fragments.
Sound Insulation
The high strength allows for multiple glass layers to be laminated without compromising thickness. The air pockets in the laminate provide sound insulation properties. Laminated glass reduces noise transmission by upto 50%.
Fire Resistance
Wired glass and wire reinforced glass are heat strengthened to hold their structural integrity longer when exposed to high temperatures during fires. They provide an extra barrier against the spread of flames. The multilayered structure of laminated glass also makes it naturally fire resistant.
UV Protection
Some types of heat strengthened or coated glass help filter or block out UV rays to protect contents from sun damage. This property finds use in solar control and low-emissivity glass applications.
Increased Security
While enhancing safety against accidental breakage, laminated glass and wired glass constructions additionally provide burglar resistance by preventing easy smashing or access once broken. This makes them suitable for security glazing purposes.
Applications
Based on their distinct properties, various types of heat treated glass find widespread applications in:
- Doors and windows in residential and commercial buildings that require compliance with safety standards and insulation benefits.
- Automotive and transportation glazing like windshields, side and rear windows, rooftop glazing and partitions.
- Furniture, appliances, cooktops, microwave ovens that utilize glass as a functional material requiring impact and thermal resistance.
- Solar panels, greenhouses, atriums, skylights and other architectural applications where durability against weathering is important besides aesthetics.
- Artwork, framed displays, hazardous area glazing, crime-resistant glazing, bulletproof glazing using specially heat treated glass compositions.
- Photovoltaic modules, solar thermal collectors where specialized glass coatings enhance light transmission and filtration.
I hope this article provided useful information on the various types, their unique material properties and applications. Proper heat treatment during manufacture allows standard soda-lime glass sheets to gain enhanced structural integrity, safety and functional performance for diverse industrial uses.
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About Author:
Ravina Pandya, Content Writer, has a strong foothold in the market research industry. She specializes in writing well-researched articles from different industries, including food and beverages, information and technology, healthcare, chemical and materials, etc. (https://www.linkedin.com/in/ravina-pandya-1a3984191)
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