Polycarbonate (PC) and Polyvinyl Chloride (PVC) are two of the most widely used thermoplastic materials in modern manufacturing. Each possesses a unique set of properties that determine its suitability for a given application. Both materials are polymers valued for their durability and versatility, yet they differ significantly in their fundamental mechanical and environmental performance. The question of which material is “stronger” depends entirely on the specific definition of strength being used.
Defining Mechanical Strength: Impact and Tensile Properties
The most common understanding of material strength is its ability to resist shattering upon sudden impact, and in this metric, polycarbonate is the clear winner. PC is renowned for its exceptional toughness. Its impact resistance is significantly higher than that of most common plastics, including PVC, sometimes being up to 250 times stronger than glass at the same thickness.
Polyvinyl Chloride, particularly in its rigid form, offers good mechanical strength but is much more brittle than PC. Under a sharp, sudden blow, rigid PVC is prone to cracking or shattering, a weakness amplified in cold temperatures. While PVC can be compounded with additives to improve its impact resistance, it still falls substantially short of PC’s inherent impact properties.
The comparison shifts when focusing on tensile strength, which measures a material’s resistance to being pulled apart. Rigid PVC can exhibit tensile strength values ranging from 31 to 60 megapascals (MPa), demonstrating its capacity to handle sustained pulling forces. Polycarbonate shows a comparable tensile strength, often falling between 28 and 75 MPa depending on the specific grade. Therefore, a rigid PVC formulation may perform similarly or slightly better under a slow, continuous pulling load.
Long-Term Durability: Temperature and Chemical Resistance
Polycarbonate maintains its structural integrity across a much broader temperature range than PVC. PC can operate continuously in temperatures up to 120°C, and some high-heat grades can withstand up to 140°C, making it suitable for environments with significant thermal fluctuations. In contrast, PVC begins to soften and deform at much lower temperatures, typically losing shape when exposed to heat exceeding 60 to 70°C.
Polyvinyl Chloride possesses superior resistance to a wider array of chemical agents than polycarbonate. PVC is highly resistant to many acids, alkalis, and salts, which is why it is used extensively in chemical processing. Polycarbonate, however, is vulnerable to damage from certain common chemicals, particularly strong solvents, aromatic hydrocarbons, and oils. Exposure to these substances can cause PC to weaken, crack, or dissolve over time.
Ultraviolet (UV) light exposure also affects the long-term strength of both materials. Standard PVC is inherently more resistant to UV degradation than raw PC, which will yellow and weaken over time without protection. Manufacturers typically apply a co-extruded UV-protective layer to polycarbonate sheets to maintain its clarity and durability in outdoor use. With this specialized coating, PC’s lifespan under harsh sunlight is significantly extended.
Application Contexts and Material Trade-offs
The ultimate choice between polycarbonate and PVC is based on a performance-to-cost trade-off dictated by the application’s most demanding requirement. Polycarbonate’s superior impact resistance and high thermal stability justify its higher cost for critical uses. It is the preferred material for safety glazing, machine guards, protective eyewear, and automotive headlamp lenses where impact protection is paramount.
Polyvinyl Chloride is a significantly more cost-effective material, making it ideal for large-volume, non-structural applications. Its excellent chemical resistance and ease of fabrication make it perfect for plumbing pipes, weather-resistant siding, and electrical insulation. In these applications, the material’s lower impact strength is an acceptable compromise for the substantial cost savings.
For situations requiring absolute resistance to sudden, forceful impact and exposure to high temperatures, polycarbonate is the stronger and more appropriate material. Conversely, when cost-effectiveness, chemical resistance, and ease of manufacturing are the primary concerns, PVC provides a functionally robust and economical alternative.