Polycarbonate (Lexan) FAQ: 13 Common Questions Answered

Polycarbonate (PC) is the go-to transparent thermoplastic when impact resistance is non-negotiable. Sold under brand names including Lexan (SABIC) and Makrolon (Covestro), it is 250 times more impact-resistant than glass and 30 times stronger than acrylic. This FAQ covers the most common questions buyers and engineers ask when evaluating polycarbonate sheet, rod, and tube for industrial, safety, and glazing applications.

How does polycarbonate compare to acrylic?

Polycarbonate and acrylic (PMMA) are the two dominant transparent plastics, but they serve different design priorities. Polycarbonate has dramatically higher impact resistance — typically 250× glass and 30× acrylic — making it the standard for machine guards, safety shields, and bullet-resistant panels. Acrylic has better UV resistance out of the box (no yellowing without UV coating), superior scratch resistance, higher optical clarity (~92% light transmission vs. ~88% for PC), and is easier to polish and cement. For outdoor architectural glazing where aesthetics matter, acrylic often wins. For impact-critical applications, polycarbonate wins. See the full polycarbonate vs. acrylic comparison for a side-by-side spec table.

Are there UV-stabilized polycarbonate grades?

Standard polycarbonate yellows and becomes brittle with prolonged UV exposure — it is essentially not suitable for outdoor use without UV protection. UV-stabilized grades are available in two forms:

UV-coated: A UV-absorbing hard coat is co-extruded or applied to one or both surfaces. Most Lexan and Makrolon multi-wall and flat sheet is UV-coated on the weathering face and marked with a "UV" or "SL" designation.
UV-stabilized resin: Some solid sheet grades incorporate UV absorbers throughout the resin. These outperform surface-coated grades in service conditions where the surface may be abraded.

For outdoor glazing applications expected to last 10+ years, specify UV-coated or UV-stabilized solid sheet and confirm the manufacturer's weathering warranty (typically 5–10 years against more than 50% transmission loss).

Can polycarbonate be machined without cracking?

Yes, with appropriate technique. Polycarbonate is an amorphous thermoplastic with high ductility — it does not shatter during machining, but it is prone to stress cracking if solvents contact machined surfaces afterward. Best machining practices:

Use sharp, neutral-to-positive rake carbide tooling; dull tools generate heat and stress.
Keep cutting speeds moderate (400–600 SFM) and feeds light.
Use a mist coolant or compressed air; avoid flood coolant with aromatic content.
Do not use coolants containing chlorinated solvents, ketones, or esters — these cause stress crazing.
Drill with brad-point bits or zero-rake flute drills for clean entry holes.
Anneal parts at 250°F (121°C) for 1–4 hours after machining to relieve residual stress before any solvent contact.

For more detail on tooling and fixturing, see the polycarbonate machining guide.

How is polycarbonate bonded or cemented?

Polycarbonate can be bonded using:

Methylene chloride (MC): A fast-acting solvent cement that works by dissolving the mating surfaces. Provides strong bonds but is highly regulated due to health hazards. Use with ventilation and proper PPE.
Weld-On 40 and similar PC-specific cements: Slower-setting, acrylic-and-solvent blends formulated specifically for polycarbonate.
Two-part urethane adhesives: Flexible, high-impact bond without solvent stress-cracking risk. Preferred for bonded assemblies that will be used outdoors or where solvent contact is a concern.
UV-curable adhesives: Good for optical assemblies; require UV-transmissive substrates.

Avoid standard cyanoacrylates (stress-crack risk) and any solvent-based adhesive containing ketones, esters, or aromatic solvents. For transparent structural bonds, acrylic cement and methylene chloride techniques overlap — the PC vs. acrylic page covers bonding tradeoffs.

Can polycarbonate be heat-bent or formed?

Yes. Polycarbonate can be line-bent with a strip heater and oven-formed or thermoformed at 340–375°F (171–190°C). Key points:

Line bending: Requires a strip heater and slow, even heating across the bend line. Heat until the material is pliable but not bubbly (surface bubbling indicates moisture-related degradation — pre-dry sheets at 250°F for 2–4 hours before forming).
Oven thermoforming: Polycarbonate thermoforms at higher temperatures than acrylic and is more prone to moisture-related surface degradation if not pre-dried. Sheets must be dried before thermoforming.
Cold bending: PC can be cold-bent to gentle radii (bend radius ≥ 100× thickness) without heating, useful for curved glazing panels.

Polycarbonate's high impact strength is retained through thermoforming if processing temperatures and cooling rates are controlled properly.

How long does polycarbonate last outdoors (5–10 years)?

Without UV protection, standard polycarbonate yellows noticeably in 1–3 years of outdoor exposure and becomes brittle within 5 years. UV-stabilized or UV-coated grades significantly extend service life. Quality UV-coated sheet (e.g., Lexan Margard, Makrolon GP UV) typically carries manufacturer weathering warranties of 10 years for retention of 50% of original impact strength and no more than a defined change in yellowness index. For the most demanding outdoor applications (>10 years, coastal or high-UV environments), UV-stabilized solid PC sheet with a hard coat is the specification. Acrylic is the more economical alternative for outdoor applications where impact resistance is not critical.

What color options are available for polycarbonate sheet?

Polycarbonate sheet is available in:

Clear: The most common; ~88% visible light transmission
Translucent whites and grays: For diffuse lighting applications
Bronze and gray tints: For solar control in architectural glazing
Opaque colors: A wide range for machine guards, enclosures, and industrial panels
Mirrored and specialty finishes: Available from select fabricators

Multi-wall (twin-wall, triple-wall) PC is most commonly available in clear and opal/white. Custom colors typically require minimum order quantities and longer lead times than standard clear or bronze sheet.

Is there a mar-resistant or hard-coated polycarbonate?

Yes. Standard polycarbonate scratches readily and is not suitable for applications where surface clarity must be maintained long-term without protection. Mar-resistant grades include:

Lexan Margard (SABIC): A hard-coated Lexan product with a silicone hard coat on both surfaces; significantly better scratch resistance and UV stability than uncoated PC.
Makrolon GP UV: UV-stabilized with improved weathering; available with optional hard coat.
Acrylite Resist (acrylic-coated PC): A co-extruded product with an acrylic cap layer for scratch resistance — combines PC impact strength with acrylic surface hardness.

For applications where optical clarity and scratch resistance are critical (sight gauges, display covers, instrument panels), compare hard-coated PC against acrylic — acrylic pencil hardness (2H–3H) exceeds standard PC (B) even without a hard coat.

What is the difference between Lexan and Makrolon?

Lexan (SABIC) and Makrolon (Covestro) are both trade names for polycarbonate resin produced by major manufacturers; neither is inherently superior. Both companies produce a broad range of grades: standard, UV-stabilized, flame-rated, glass-filled, and optical. The resin properties are very similar within equivalent grades. Brand choice is typically driven by supply availability, distributor relationships, and whether a specific grade from one manufacturer meets a particular processing or certification requirement. For commodity sheet and rod applications, the two are interchangeable within comparable grades.

Is polycarbonate bullet-resistant?

Solid polycarbonate is the primary material in ballistic-resistant glazing, but "bullet-resistant" is a function of thickness and panel construction, not an intrinsic property at thin gauges. A single 1/4″ (6.35 mm) PC sheet is not bullet-resistant. Rated ballistic panels for UL 752 Level 1 (9mm) typically require 1.25″ (31.75 mm) or more of solid PC or laminated PC/glass. Multi-layer laminated panels (PC + glass or PC + acrylic) are used for higher threat levels. Specify the UL 752 or NIJ level required for your application and work with a certified fabricator — do not rely on unrated sheet thickness alone. See the polycarbonate grades and specifications guide for thickness and rating data.

Can polycarbonate be thermoformed into complex shapes?

Yes. Polycarbonate thermoforms into complex shapes including compound curves, deep draws, and multi-axis geometries. It is widely used for machine guards with complex profiles, medical device enclosures, and vehicle interior components. The thermoforming window is narrower than acrylic (PC is more sensitive to moisture and processing temperature), and parts must be designed with appropriate draft angles and radii to avoid thinning at corners. Sheet must be pre-dried before forming. Post-forming annealing at 250–275°F (121–135°C) relieves residual stress and reduces susceptibility to stress cracking in service.

Is polycarbonate FDA-approved for food contact?

Select polycarbonate grades are FDA 21 CFR 177.1580 compliant for use in food-contact applications. However, due to concerns about bisphenol A (BPA) migration — PC is made from BPA — many food and beverage applications have shifted to BPA-free alternatives such as Tritan copolyester, acrylic, or PETG for direct-contact applications. For food-processing machine parts that do not have prolonged direct contact with food (guards, enclosures, sight windows), FDA-compliant PC remains widely used. Confirm FDA compliance status with the specific sheet lot, and consult current FDA guidance if BPA migration is a regulatory concern in your application.

What is polycarbonate's maximum service temperature?

Polycarbonate has a continuous service temperature of approximately 240–265°F (115–130°C) and a heat deflection temperature (HDT) of 270°F (132°C) under 264 psi load. This is substantially higher than acrylic (HDT ~185°F / 85°C) but well below PEEK or nylon in high-temperature applications. PC retains useful impact resistance down to at least -40°F (-40°C). For applications requiring transparency above 265°F continuous, consider Ultem PEI — though optical clarity in Ultem is amber rather than water-clear.

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Frequently asked questions — Polycarbonate FAQ

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