Polycarbonate is a high-performance material that is often incorrectly referred to as a type of glass. This material is actually a type of plastic, specifically a thermoplastic polymer, which has physical properties far exceeding those of traditional glass in certain applications. Its unique combination of strength, clarity, and formability has made it a ubiquitous engineering material in modern manufacturing.
Defining Polycarbonate as a Material
Polycarbonate, or PC, is categorized as a thermoplastic polymer, meaning its long molecular chains allow it to be repeatedly melted and reformed without undergoing significant chemical degradation. The base structure of the material is characterized by carbonate functional groups linked to organic groups, most commonly derived from a chemical known as bisphenol A (BPA). This chemical structure gives the material its signature toughness and transparency.
The material is primarily manufactured through a chemical reaction called polymerization, where individual monomer units are linked together to form the long polymer chains. Modern production methods increasingly utilize a safer process called melt transesterification, which reacts bisphenol A with diphenyl carbonate. This manufacturing flexibility allows for the creation of various grades of polycarbonate, each tailored with specific additives for different commercial purposes.
Distinct Physical Properties
Polycarbonate is most renowned for its extraordinary impact resistance, a characteristic that sets it apart from almost all other transparent materials. It is consistently cited as being between 200 and 250 times more resistant to impact than standard plate glass of the same thickness. This strength is not due to rigidity but rather to the material’s ability to flex and absorb energy without fracturing.
The material’s density is also a major advantage, as it is only about 1.2 grams per cubic centimeter, making it roughly half the weight of traditional silicate glass. This significant reduction in mass simplifies installation and reduces structural load in large-scale applications. Polycarbonate offers excellent optical clarity, typically transmitting about 87% to 90% of visible light, which is comparable to many grades of glass. The material also maintains dimensional stability across a wide thermal range, with a sustained use temperature up to 120°C.
Common Uses and Applications
The combination of strength, light weight, and clarity makes polycarbonate a preferred material for high-demand safety and security applications. Its ability to stop projectiles without shattering makes it the material of choice for bullet-resistant security barriers and riot shields. The material is also extensively used in personal safety equipment, such as protective eyewear, face shields, and helmet visors.
In the automotive industry, polycarbonate is used to manufacture headlight and taillight lenses because of its impact resistance and ability to be molded into complex aerodynamic shapes. Consumer electronics rely on the material’s durability for use in smartphone cases, laptop housings, and the substrate layer for optical media like CDs and DVDs. Its light weight and resistance to breakage also make it suitable for construction applications like skylights and architectural glazing.
Polycarbonate Versus Traditional Glass
The choice between polycarbonate and traditional glass is a trade-off between impact resistance and surface durability. Polycarbonate’s molecular structure, which allows it to absorb impact energy, also makes it a relatively soft material that is highly susceptible to scratching. Standard glass, by contrast, possesses a much harder surface, giving it superior inherent scratch resistance.
While traditional glass is naturally stable under ultraviolet (UV) light, untreated polycarbonate tends to yellow and degrade over time when exposed to sunlight. To counteract this, commercial polycarbonate products are manufactured with specialized UV-stabilized coatings, which can also include anti-scratch properties. These specialized coatings and the higher raw material cost mean that polycarbonate is generally more expensive per unit thickness than standard glass.
In terms of cleaning, the softer surface of polycarbonate requires non-abrasive cleaners and specialized cloths to prevent hazing. Glass remains the preferred choice for architectural windows where scratch resistance and cost are primary concerns. Polycarbonate is selected in applications where safety, impact resistance, and light weight are the primary engineering requirements.