When selecting a transparent, glass-like material, Polycarbonate (PC) and Acrylic (Polymethyl methacrylate or PMMA) are frequently considered. Both are lightweight, thermoplastic polymers that offer greater strength and flexibility than traditional glass. Choosing between them requires comparing their properties to determine which material offers greater overall strength for a specific application.
Impact Resistance and Durability
Polycarbonate is the choice when the primary concern is absorbing sudden, forceful blows without fracturing. It is tough, boasting an impact resistance 20 to 30 times greater than acrylic, and up to 250 times more resistant to impact than a comparable thickness of glass.
This superior performance results from polycarbonate’s molecular structure, which allows it to flex and stretch significantly upon impact. The material absorbs energy and deforms locally instead of resisting the force rigidly, making it virtually shatterproof. This non-brittle behavior makes it the standard for high-security and safety applications, such as machine guards and riot shields.
Acrylic plastic has a much more rigid structure. While it is about 17 times stronger than glass, a high-velocity impact typically results in brittle failure, causing the material to crack or shatter. This rigidity translates into a higher tensile strength (resistance to being pulled apart), with acrylic measuring around 80 megapascals (MPa) compared to polycarbonate’s 60 to 70 MPa. Acrylic’s higher tensile strength allows it to sustain a greater static load before failure, despite its lower impact tolerance.
Optical Properties and Surface Hardness
When visual quality is a priority, acrylic generally outperforms polycarbonate in light transmission. Acrylic transmits up to 92% of visible light, giving it a superior, crystal-clear appearance that is clearer than many forms of glass. Polycarbonate transmits slightly less light, typically falling in the 86% to 88% range.
This difference in light transmission is often a deciding factor for applications like museum display cases or high-end picture framing. The performance contrast reverses when considering surface hardness, as acrylic is a much harder material. This hardness gives acrylic a natural advantage in scratch resistance.
The softer surface of polycarbonate is susceptible to scratching and abrasion from everyday use and cleaning. To combat this weakness, polycarbonate often requires a specialized hard-coating to achieve durability comparable to standard acrylic. For applications where appearance must be maintained long-term, such as signage or outdoor windows, acrylic’s natural resistance to minor surface wear is a benefit.
Fabrication, Cost, and Appropriate Use
The methods required to shape and manipulate each material differ, impacting the ease and cost of fabrication. Polycarbonate’s flexibility allows it to be cold-formed or bent without applying heat, making it simpler to work with in certain manufacturing processes. It can also be easily drilled close to edges without the risk of cracking.
Acrylic, due to its rigidity, requires specific tools and thermoforming, where heat must be applied to bend or shape the material to prevent cracking. While acrylic is easier to cut and offers superior bonding with solvent cements, polycarbonate is more forgiving for simple modifications like drilling and routing.
Polycarbonate is typically the more expensive option, costing 30% to 35% more than a comparable sheet of acrylic. This cost difference, combined with material properties, guides their appropriate uses. Polycarbonate is the material of choice for safety-focused applications like hockey rink barriers, security glazing, and machine guards where impact is expected. Acrylic is best suited for retail displays, large aquariums, and architectural elements where optical clarity and surface finish are valued over maximum impact resistance.