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Polycarbonate / Lexan

Polycarbonate for Tough Sign Faces and Lighted Signs

Polycarbonate is a tough transparent thermoplastic used for sign faces, lighting diffusers, protective panels, and applications where impact resistance matters. LEXAN is one of the best-known polycarbonate brands and includes sheet grades made specifically for signs and LED lighting.

Material

Solid Polycarbonate Sheet

Common Sign Range

About 3 to 6 mm

Environment

Indoor & Outdoor by Grade

Graphics

Second-Surface · Print · Vinyl

Overview

What Is Polycarbonate?

Polycarbonate is a clear or translucent engineering plastic known for high impact resistance and good light transmission.

Sign-grade polycarbonate is used where a plastic face needs to tolerate handling, weather, or impact better than a more brittle sheet. Manufacturers also produce white, diffusing, textured, and UV-resistant grades for illuminated signs and lighting applications.

Illuminated Sign Faces White or diffusing sheet for cabinets, light boxes, and LED-backed sign faces.
Protective Sign Covers Clear tough panels where impact or vandal resistance matters.
Second-Surface Graphics Graphics applied or printed behind clear sheet for added face protection.
Lighting Components Diffusers and covers used to hide light sources and spread illumination.

Sign Grades

Polycarbonate Thickness and Sign-Specific Sheet

Polycarbonate sheet is available across a wide gauge range. Sign-grade LEXAN products are commonly offered around 0.093 to 0.236 inch, or roughly 2.4 to 6 mm, with specialty lighting and exterior grades available outside that range.

2.4 to 3 mm
Thin Sign Face
Useful for supported sign faces, protective covers, and compact lighting applications.
Support, cabinet dimensions, and forming method still matter.
4 to 4.5 mm
Heavier Sign Sheet
Adds stiffness for larger faces and more demanding assemblies.
Often used where impact resistance and panel stability are both important.
6 mm
Thicker Polycarbonate
More material depth for protective panels and larger fabricated components.
Weight, mounting, and thermal movement become more important as thickness increases.

Material Comparison

Polycarbonate vs Acrylic for Signs

Polycarbonate
Acrylic
Impact
Very high impact resistance; useful for protective and demanding sign applications.
Impact
More brittle than polycarbonate but widely used for polished sign faces and letters.
Surface
Tough substrate, though standard sheet can scratch and may need the right coating or care.
Surface
Harder surface feel and excellent optical appearance.
Sign Fit
Strong choice for cabinets, diffusers, protective covers, and exposed faces.
Sign Fit
Strong choice for dimensional letters, polished panels, office signs, and clear decorative work.

Graphics & Fabrication

How Polycarbonate Is Used in Sign Production

Polycarbonate can be cut, drilled, routed, formed, decorated, and printed when the sheet grade and process are compatible. Sign-face grades may also be made for second-surface decoration so the graphics sit behind the clear face.

Second-Surface Decoration Printing or applied graphics placed behind clear sheet for a protected finished face.
Direct Graphics Compatible sheets can receive print, paint, or applied vinyl.
Thermoforming Polycarbonate can be heat formed for shaped faces and fabricated sign parts.
LED Diffusion Specialty white and diffusing grades help hide individual light sources.

Light Box Faces

Rigid Polycarbonate Faces vs Flex Faces

Light box signs use one of two kinds of face. Small and medium cabinets usually take a rigid polycarbonate panel. Large cabinets, the kind on a shopping center pylon or a wide storefront, often use a flexible vinyl face stretched across the frame instead.

Rigid Polycarbonate
Flex Face
Size
Best for faces up to a few feet across.
Size
Spans large cabinets without seams or bracing.
Look
Crisp and flat, with graphics behind or on the face.
Look
Stretched tight on the frame. Very even lighting across big areas.
Changes
Swap the whole panel when the brand changes.
Changes
Replace the printed face without rebuilding the cabinet.

See our light box signs page for cabinet options.

Sun & Heat

Yellowing, UV and Expansion

Uncoated polycarbonate yellows and hazes in years of direct sun. Sign faces are made from UV protected grades for that reason, and choosing the right grade is the difference between a face that stays white and one that turns cream on the south side of the building.

Polycarbonate also expands about three times as much as aluminum with heat. A face fitted tight in a metal cabinet in winter can bow in summer, so faces are cut with room to move inside the retainers.

Refacing

Replacing a Cracked or Faded Sign Face

A cracked or yellowed face rarely means a new sign. If the cabinet, wiring and lighting are sound, a new polycarbonate face with fresh graphics brings it back for a fraction of the cost. This is also the usual way a new tenant takes over the previous tenant’s light box.

Refacing is often the best value.

Send a photo of the cabinet and its measurements. See our sign repair and refacing page for how we handle it.

Choosing the Material

When Polycarbonate Is the Right Choice

  • The sign face needs high impact resistance.
  • The project uses a cabinet, LED system, or protective cover.
  • You need clear or translucent plastic with exterior-rated options.
  • The panel may be handled or exposed more aggressively than a standard acrylic face.

Consider another material when

  • Acrylic: polished edge quality, engraving, or decorative dimensional lettering is the priority.
  • ACM: the job needs an opaque rigid panel rather than a clear or translucent plastic.
  • Expanded PVC: the sign is an opaque printed panel or routed display piece.

FAQs

Polycarbonate Sign Questions

Is polycarbonate better than acrylic for a sign face?

For faces within reach of the street or exposed to impact, yes, because polycarbonate is far tougher. Acrylic is chosen for polished letters and panels mounted out of reach.

Why do sign faces turn yellow?

Years of sun break down plastics that are not UV protected. Sign grade polycarbonate is made with UV protection to slow that down.

Is LEXAN the same as polycarbonate?

LEXAN is a well known brand of polycarbonate sheet. Other manufacturers make polycarbonate for sign faces too.

Can you replace just the face of my light box?

Yes. If the cabinet and lighting are sound, we can cut a new face, apply the new graphics and fit it into the existing frame.

How thick should a polycarbonate sign face be?

Many sign faces fall between about 3 and 6 mm. Larger faces need thicker sheet or support so they do not bow.

On This Guide

Quick Facts

Material

Polycarbonate

Common Gauges

About 3 to 6 mm

Environment

Indoor & Outdoor by Grade

Common Uses

Sign Faces · Diffusers · Covers

Related Materials

Not Sure Which Material Fits?

Send the sign size, location, mounting method, artwork, and a site photo if you have one.

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Need Help Choosing a Sign Material?

Tell Us What the Sign Needs to Do

We can compare materials based on the sign size, location, graphics, mounting method, project term, and site conditions.

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