PC Basic FAQ

Polycarbonate has a wide range of applications because of its desirable properties. Some of its applications across different industries are as follows:

• Construction: Used for safety shields and roofing sheets because it is 250 times stronger than glass.
• Automotive: Ideal for headlamp lenses and instrument panels because of its high impact resistance and lightweight.
• Electronics: Used for electrical housings, LED light covers, and more because of its high electrical insulating properties.
• Medical equipment: Its transparency and temperature resistance make it suitable for sterilization.

Consumer goods: Useful for making food storage containers and water bottles.

An untreated PC will turn yellow and become brittle when exposed to prolonged UV rays from the sun. Although transparent, PC has lower light transmission (≈88%) compared to acrylic glass (≈92%).

Polycarbonates are composed of long, amorphous molecular chains with carbonate group and bisphenol A (BPA) residues. PC is highly susceptible to hydrolysis and environmental stress cracking by aprotic solvents, many alcohols, and strong bases.

The glass transition temperature is the temperature at which the material loses its rigidity and becomes rubbery. Blending PC with ABS lowers its T₈ to around 130°C.

However, it is sensitive to UV light in its natural state, although most commercial-grade polycarbonate used outdoors is treated with UV-stabilized coating or co-extrusion layer, which prevents yellowing and degradation.

Due to its high viscosity, it requires higher molding temperatures, which can add to the injection molding costs. Other key injection molding requirements include:

• Drying: It must be dried before molding to prevent defects like silver streaks, which lower product strength.
• Uniform thickness: Make sure the design has consistent wall thickness to prevent warpage.

• Environmental degradation: long-term exposure of untreated PC to UV radiation can cause yellowing.
• Surface damage: Polycarbonate surfaces can scratch easily during cleaning or handling.
• Manufacturing defects: Inadequate drying before molding can lead to silver streaks, bubbles, or weakened parts.

This category is used for all plastic resins that don’t fit into categories 1 – 6, including polycarbonate, nylon, and bioplastics. The purpose of the code is to identify the polymer type for sorting and recycling.

Food-grade polycarbonate complies with FDA regulations for direct food contact. However, since polycarbonate is made using bisphenol A (BPA), there are health concerns regarding hormone disruption. Consequently, many consumers are always seeking BPA-free alternatives like polypropylene.

The different techniques that can be used to improve polycarbonate’s wear resistance are as follows:

• Hard coatings: Apply UV-curable coatings or siloxane-based coatings to create a glass-like, abrasion-resistant surface.
• Silicone-based additives: Add 1-3% silicone additives (like PDMS) to increase internal lubrication and lower the coefficient of friction.
• Polymer blending: Blend PC with 10-20% PMMA to increase surface hardness or with PBT to improve wear resistance.
• Nanocomposite reinforcement: This is the addition of nanofillers (0.5-2% by weight), including alumina, nanosilica, or graphene oxide, to the PC matrix.
• Annealing: Slow heating and cooling can relax the molecular structure to improve impact strength.
• Surface modification: Deposit thin hard coatings on the surface using plasma treatment.

The table below shows how the properties of the standard PC compare to the modified version.

Some of the key methods used to identify polycarbonate are:

1. The edge test: Polycarbonates have a slight blue or dark tint to their edge. On the other hand, acrylic will remain crystal clear.
2. The physical strength test: It is nearly impossible to break polycarbonate by hand.
3. The burn test: PC produces a yellow flame when burning and emits a significant amount of black smoke. When removed from the flame, it can self-extinguish.
4. The acetone test: This is not a definitive test, but applying acetone can sometimes make PC brittle or slightly hazy.
5. Density: Pure polycarbonate has a density of 1.20 g/cm³, which is denser than water. Therefore, it will sink when placed in a bowl of water.

Other techniques you can use to prevent PC from yellowing include:

• Proper installation: Ensure the side with the UV protection is facing outward.
• Controlled maintenance: Clean with mild soap and water only. Solvents like alcohol and acetone will strip the UV coating.
• Environmental control: Install or store in cooler environments (below 35°C).
• Sacrificial coatings: Use acrylic or silicone-based sprays. Reapply every 1-2 years.

PC is either recycled through mechanical methods, where it is shredded, cleaned, and remelted, or via chemical recycling (chemolysis), where it is broken down into raw monomers.

For low-volume prototypes of complex parts, CNC machining may be the preferred method. Other techniques that can be used for shaping polycarbonate include hot forming for sheets and CNC turning or milling for solid shapes. Ensure proper heat control to avoid warping.

The high demand for PC in the electrical and electronics industry is driven by the need for durable, heat-resistant, and flame-retardant materials. PC is used in the electronics industry for smartphone and laptop casings, LED light covers, and 5G infrastructure equipment.

Below is a brief explanation of how polycarbonate costs compare to other materials.

• Acrylic (plexiglass): It is generally 40-50% cheaper, making it the better choice for budget-sensitive projects.
• Glass: A 4 mm polycarbonate sheet is 30-50% cheaper than tempered glass, if you include installation.
• ABS plastic: Cheaper than polycarbonate, but manufacturers will sacrifice heat resistance and tensile strength.
• Polypropylene: Significantly cheaper than polycarbonate, especially for high-volume manufacturing.

China’s installed capacity is expected to increase significantly, growing from roughly 2,320 kilotons in 2021 to around 5,000 kilotons by 2034. Major global manufacturers in Asia with significant production include Covestro, SABIC, Lotte Chemical, LG Chem, and Chimei.

The price of higher-quality solid or multi-wall sheets for specialized applications can range from $15 to over $50 per square meter.

Other factors that will influence the cost of polycarbonate include:

• Raw material: Since polycarbonate is derived from bisphenol A and phosgene, its price will be affected by fluctuations in crude oil and natural gas prices.
• Manufacturing: The manufacturing process for PC is complex. The need for optical-grade, high-quality, or food-grade certifications increases costs.
• Specialized coatings: Features like UV protection coatings, scratch-resistant treatments, or anti-glare finishes add significantly to the costs.
• Order volume: Bulk orders (e.g., >100 sq. meters) significantly lower the per-unit price compared to retail.
• Geopolitics and logistics: Disruptions in the global supply chain, such as trade tariffs and transportation bottlenecks, can lead to price spikes.

Opal white and standard bronze or grey hues are common and generally less expensive. On the other hand, custom colors, special tints, or specific metallic finishes (for example, gold or silver mirror) attract higher production costs. Also, only minimum quantities are often needed. The combination of these factors pushes up the price.