Plastics are versatile materials used in countless applications, from everyday objects to specialized industrial components. Polycarbonate and acrylic are frequently employed as transparent alternatives to glass. While they might appear similar at first glance, these two materials possess distinct properties that make them suitable for different purposes. Understanding their differences is important for selecting the appropriate material for a given application.
Understanding Polycarbonate and Acrylic
Polycarbonate is a thermoplastic polymer known for its unique combination of strength and optical clarity. It belongs to a group of polymers containing carbonate groups in their chemical structures. This material can be heated, molded, and cooled repeatedly without significant degradation, allowing for various fabrication processes.
Acrylic, often referred to by brand names like Plexiglas, is also a thermoplastic, specifically a polymer of methyl methacrylate (PMMA). Like polycarbonate, acrylic can be softened by heat and shaped, making it highly adaptable for manufacturing. Its chemical composition contributes to its glass-like appearance and ease of processing.
Key Distinguishing Properties
Polycarbonate exhibits significantly higher impact resistance compared to acrylic. It is virtually unbreakable, offering up to 250 times the impact resistance of glass and approximately 30 times that of acrylic. Acrylic, while still 10 to 17 times more impact resistant than glass, is more rigid and can crack under extreme impact.
Acrylic generally offers superior light transmission, allowing up to 92% of light to pass through, which is slightly more than glass. Polycarbonate transmits about 88% of light, sometimes appearing with a slight tint. This difference can be noticeable in certain visual applications.
Acrylic typically outperforms polycarbonate in scratch resistance. Acrylic surfaces are more resistant to scratching and denting, though they can be polished to remove minor abrasions. Standard polycarbonate is more susceptible to scratching, but specialized abrasion-resistant coatings can significantly improve its surface hardness.
Polycarbonate can withstand higher temperatures, with a continuous service temperature up to approximately 115°C (240°F) and a melting point around 288°C (550°F), making it suitable for applications exposed to heat. Acrylic has a lower heat resistance, with a maximum continuous service temperature generally around 71-88°C (160-190°F) and begins to soften around 99-104°C (210-220°F).
Acrylic inherently possesses strong UV resilience and can block a high percentage of UV rays, often without additional coatings. Standard polycarbonate can yellow over time with prolonged UV exposure unless specifically treated with UV-stabilizing coatings during manufacturing.
In terms of weight, both materials are considerably lighter than glass. Polycarbonate has a density of about 1.2 g/cm³, while acrylic is slightly denser at approximately 1.18 g/cm³. Chemical resistance also differs; polycarbonate generally shows resistance to many acids, oils, and alcohols, but it can be affected by ketones, ethers, and aromatic hydrocarbons. Acrylic is resistant to certain chemicals but can be damaged by strong solvents like ammonia or acetone.
Where Each Material Excels
Polycarbonate’s exceptional impact resistance makes it the preferred material for applications requiring high levels of security and durability. It is widely used in safety equipment such as safety goggles, face shields, and riot shields. Its strength also makes it suitable for bullet-resistant glazing, machine guards, and protective barriers in industrial settings. Furthermore, polycarbonate is a common material for automotive headlight lenses and aerospace components.
Acrylic, with its superior optical clarity and scratch resistance, excels in applications where visual aesthetics and transparency are paramount. It is frequently chosen for display cases, retail fixtures, and aquariums, where its glass-like appearance enhances product presentation. Acrylic is also used for optical lenses, picture frames, and secondary glazing in windows. Its ability to be easily polished to restore clarity makes it suitable for signs and artistic sculptures.
Practical Considerations for Use
The cost of these materials often influences selection. Polycarbonate is typically more expensive than acrylic, sometimes costing about 35% more. Acrylic generally offers a more economical solution when extreme impact resistance is not a primary requirement.
Both materials can be cut, drilled, and molded, but their workability differs. Polycarbonate is more flexible and can be cold-formed or bent without heating, and it is less likely to crack when drilled. Acrylic is more rigid and usually requires heat for bending or forming, though it is generally easier to cut and bond with adhesives.
Polycarbonate’s higher chemical resistance allows it to be cleaned with a wider range of chemical agents, although certain strong solvents should still be avoided. Acrylic should be cleaned with mild soapy water and a soft cloth, as harsh chemicals like ammonia or acetone can cause damage or hazing. Dust and debris should always be removed before wiping either material to prevent scratching.