PC - Polycarbonate

Polycarbonate (PC) is a high-performance amorphous engineering thermoplastic distinguished by its extraordinary combination of impact resistance, optical transparency, and thermal stability. Discovered independently by Bayer and General Electric in 1953, polycarbonate has become one of the most widely used engineering plastics for applications demanding clarity, toughness, and dimensional precision.

The global polycarbonate market was valued at approximately $20 billion in 2024 and is projected to grow at a compound annual growth rate (CAGR) of 5.5% through 2030, driven by expanding demand in automotive lighting, LED diffusion, electronic displays, and sustainable building materials. Global production exceeds 6 million tonnes annually, with bisphenol A (BPA) polycarbonate accounting for over 95% of commercial production according to industry data from IHS Markit.

Polycarbonate resins comply with ASTM D3935 specifications for polycarbonate molding and extrusion materials. Select grades meet FDA 21 CFR 177.1580 for food-contact applications, USP Class VI for medical devices, and UL 94 V-0 classification at thicknesses as low as 0.5 mm for electrical and electronic applications. Optical grades conform to ASTM D1003 for light transmission and haze measurements.

Key properties of polycarbonate include:

• Outstanding impact strength — virtually unbreakable under normal conditions, with notched Izod impact values exceeding 600 J/m. PC maintains impact resistance across a wide temperature range from -40°C to 130°C.
• Exceptional optical clarity with light transmission of 88–90% and low haze, rivaling glass for transparency while being 250 times more impact-resistant.
• High heat deflection temperature of 130–145°C, allowing continuous service at temperatures well above most other transparent thermoplastics.
• Excellent dimensional stability with low mold shrinkage (0.5–0.7%) and minimal creep under sustained load, producing precise and consistent parts.
• Inherent flame resistance — polycarbonate is self-extinguishing and achieves UL 94 V-2 without additives. Flame-retardant grades achieve V-0 at thin wall sections.
• Good electrical insulating properties with stable dielectric characteristics across a wide frequency and temperature range.
• Broad design freedom with the ability to produce complex thin-walled geometries, living hinges, and integrated optical features through injection molding.

Chemistry and Structure

Polycarbonate is produced by the reaction of bisphenol A (BPA) with phosgene (interfacial process) or diphenyl carbonate (melt process). The carbonate linkage (–O–CO–O–) in the polymer backbone, combined with the rigid bisphenol A aromatic rings, provides the unique combination of toughness, transparency, and heat resistance that distinguishes polycarbonate from other amorphous thermoplastics.

The amorphous structure of polycarbonate is responsible for its optical clarity — the absence of crystalline regions eliminates light scattering. Molecular weight is carefully controlled during polymerization to balance melt flow (processability) against mechanical performance, with higher molecular weight grades offering greater toughness at the expense of higher melt viscosity.

Available Grades

General-Purpose PC provides the standard balance of impact strength, optical clarity, heat resistance, and processability for injection molding and extrusion. These grades are used in a wide range of applications from electronics housings to automotive components and consumer products.

Optical and Light-Diffusion PC grades are engineered for precision lighting applications with controlled light transmission, haze, and diffusion characteristics. These grades are essential for LED lenses, light guides, automotive headlamp lenses, and architectural lighting panels where uniform light distribution is critical.

Flame-Retardant PC grades achieve UL 94 V-0 at wall thicknesses as low as 0.5 mm using non-halogenated flame retardant systems. These grades maintain high transparency and impact strength while meeting stringent fire safety requirements for electrical enclosures, battery housings, and telecommunications equipment.

Glass-Fiber-Reinforced PC grades containing 10% to 40% glass fiber deliver enhanced stiffness, tensile strength, and heat deflection temperature while reducing thermal expansion and creep. These grades are used in structural components, housings requiring tight dimensional tolerances, and parts subjected to sustained mechanical loads.

FDA Food-Contact PC grades comply with FDA 21 CFR 177.1580 and are produced with tightly controlled residual monomer levels. These grades serve food processing equipment, reusable water bottles, food storage containers, and baby bottles where regulatory compliance and safety are paramount.

Processing

Polycarbonate is processed primarily by injection molding and extrusion. Recommended melt temperatures are 280–320°C with mold temperatures of 80–120°C. Higher mold temperatures improve surface finish, reduce internal stress, and enhance impact performance. PC requires thorough drying to moisture content below 0.02% before processing — desiccant dryers at 120°C for 3–4 hours are standard practice.

Polycarbonate is also processed by sheet extrusion (for thermoforming, glazing, and signage), film extrusion, blow molding, and multi-component (2K) injection molding. Post-processing options include hard coating for abrasion resistance, anti-fog and anti-reflective coatings, UV protection layers, printing, and metallization. PC is compatible with insert molding and overmolding techniques for complex multi-material assemblies.