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Quick answer: choose by how the sign will fail, not by the spec sheet

The comparison between acrylic and polycarbonate comes down to one trade. Acrylic (PMMA) sends more light and holds its colour for decades without any coating. Polycarbonate (PC) survives impacts that would turn acrylic into sharp fragments. On the quotes we write, the mapping is short:

• Spec polycarbonate when the panel sits below roughly 2.5 m (8 ft) and people can touch it, throw at it, or lean on it. Drive-through menu boards, transit shelter panels, school corridors, kiosk covers.
• Spec acrylic when the panel is high up, backlit, or sits where nothing can reach it. Illuminated channel letters, facade signage above eye level, shopfront fascias.
• Spec polycarbonate on coastal and typhoon sites where wind carries debris, even if the sign is high. The impact margin is worth more than the clarity.
• Spec acrylic when the sheet is printed or lit — solvent bonding, flame polishing and laser cutting all work on PMMA and none of them work the same way on PC.

Price follows the choice: for the same thickness, acrylic typically runs about 20–40% cheaper than polycarbonate. That gap closes quickly once you count replacement visits.

What each material actually is

Acrylic is polymethyl methacrylate, sold under names like plexiglass and Plexiglas. It is a rigid thermoplastic with a hard surface. Its optical clarity is the reason most illuminated signage uses it, and its natural UV stability means it does not need a protective layer to survive sunlight.

Polycarbonate is a different polymer with a different job. It is noticeably tougher and softer at the surface, and it holds up under heat better than acrylic. Its famous property is impact strength: polycarbonate is commonly cited at roughly 250 times the impact resistance of glass, or 20 to 30 times that of acrylic. It flexes instead of shattering.

Both materials are transparent and both weigh far less than glass. Neither is a general upgrade of the other. Picking wrong rarely causes an immediate failure. It causes a failure two or three years later, which is the expensive kind.

Acrylic vs polycarbonate at a glance

Property	Acrylic (PMMA)	Polycarbonate (PC)	What it means for an outdoor sign
Light transmission, clear grade	About 92%	About 86–89%	Acrylic reads brighter on day one, but plain glass is already ~90%, so the headroom is small
Impact strength	Roughly 10–17× glass; brittle under sharp hits	Roughly 250× glass, about 20–30× acrylic	This is the property that decides almost every signage argument
Surface hardness	Rockwell M93–M102; polishable	Soft; needs a hard coat to survive contact	Acrylic takes a scratch out with polishing, PC scratches are close to permanent
Continuous temperature limit	About 77–85 °C (170–180 °F)	About 116 °C (240 °F)	Matters for panels sitting near LED drivers and lighting cavities
UV behaviour outdoors	Naturally UV resistant; cast grade holds clarity 10–20 years	Standard grade hazes in 2–3 years; UV co-extruded grade reaches 10+ years	PC must be bought as a UV-stabilised grade, or it is a short-term product
Laser cutting	Works, with a clean polished edge	Not practical; it melts and gives off gas	Saw, router or CNC for PC; laser plus flame polish for acrylic
Thermal expansion	Higher than PC; needs mountings that move	Lower; still needs movement room	Fixed bolts are the single most common avoidable failure on acrylic
Chemical resistance	Resists dilute acids and alkalis well	Attacked by acetone, toluene, gasoline and ketones	Cleaning agent choice can craze a PC panel in one wipe
Relative cost	About 20–40% lower than PC	Higher per sheet	Cheapest sheet plus two call-outs is rarely the cheapest sign

Figures are ranges taken from the published data sheets of five suppliers and distributors, plus our own fabrication notes. Individual brands differ, and the transmission column in particular varies by grade and thickness.

The four rules we use on the quote desk

Rule 1: if the public can reach it, spec polycarbonate

Anything at or below roughly 2.5 m in a public space should be polycarbonate unless the client has a reason to insist on glass-like clarity. Acrylic does not crack under a knock, it breaks, and the fragments are sharp. Safety glazing standards, machine guarding and school corridor panels all land on polycarbonate for this reason.

We have not seen a client regret paying for PC on a ground-level face. We have seen several regret the acrylic one.

Rule 2: backlit or printed signage stays acrylic

An illuminated face, an edge-lit letter, a Second-surface printed graphic: acrylic wins on looks and on how it can be joined. It accepts solvent welding and flame polishing. Polycarbonate can be solvent bonded with care but cannot be laser cut, and its slight warm tint shows in white and neutral designs.

LED light boxes belong to acrylic for the same reason. See our guide on thickness for LED light boxes.

Rule 3: typhoon and coastal sites pull toward polycarbonate

In the Philippines, southern Vietnam and the rest of the tropical belt, the panel does not fail because of the sun first. It fails because wind carries debris into it. A 5 mm acrylic face at eye level in a typhoon corridor is a risk decision, not a cost decision.

If the site is exposed, polycarbonate is the safer call even when the panel is high and clarity would normally rule. Our thickness chart already assumes one extra step for hot humid climates. When the exposure is that aggressive, the step is not enough on its own.

Rule 4: budget for the second sheet

Acrylic is cheaper per sheet and more expensive per year in high-contact locations. Polycarbonate costs more upfront and survives contact. Write down where the panel is, how often people touch it, and how many years the sign is meant to run. The arithmetic usually settles the question.

Two installation rules that decide whether the sheet survives

Material choice gets the attention. Installation decides the warranty claim.

Acrylic: slotted holes, never fixed bolts

Acrylic expands and contracts more than polycarbonate with temperature. A hole drilled to the finished bolt diameter and then tightened against the sheet puts the panel under cyclic stress at that point, and the panel cracks at the fastener. The standard fix is a slotted or elongated mounting hole, sometimes with a gasket behind the head.

Distributors describe fixed fasteners as the most common avoidable failure mode in acrylic signage. It is also the easiest one to get right at the fabricating stage, and the hardest to justify afterwards to a client who cannot see the reason.

Polycarbonate: order the UV layer at the mill

Standard polycarbonate loses meaningful clarity within two to three years of direct sun. The repair, where one exists, is a co-extruded UV protective cap layer. That layer is a manufacturing specification applied at the extruder. It cannot be brushed on later or added by the sign shop.

So when you order polycarbonate for outdoor use, UV-stabilised grade on both faces is not an upgrade option. It is the default, and it has to be in the order. The same discipline applies on the acrylic side: cast grade, not extruded grade, for anything that sees sun. Extruded acrylic yellows and hazes within two to three years in direct exposure.

Six things the spec sheets leave out

The transmission advantage is smaller than the marketing suggests

Acrylic at about 92% against ordinary glass at about 90% is a two-point gap. Polycarbonate at 86–89% actually sits below plain glass. If a buyer switches to acrylic purely to "get more light than glass", the numbers will not justify the spend. Where acrylic genuinely earns its place is year ten, not day one, when a PC panel has hazed and the acrylic has not.

Published transmission numbers disagree

Interstate Plastics lists polycarbonate at 86–88%. Aochuang Sign lists 85–89% for UV grades. Ready Plastics uses 88%. Treat the range as real and ask the mill for its own figure at your thickness rather than quoting a round number.

Polycarbonate scratches are close to permanent

Acrylic's surface is harder and can be brought back to clarity by polishing. Polycarbonate scratches from keys, rings and ordinary cleaning cloths, and without a hard coat those marks stay. In a retail setting where someone wipes the panel daily, that is a visible maintenance cost.

Heat limits matter inside illuminated boxes

Acrylic's continuous use temperature sits around 77–85 °C. Inside a sealed light box near a driver, in a dark coloured panel in summer, that margin can get thin. Polycarbonate's roughly 116 °C limit gives design room. Some of this is handled by picking the right thickness for the light box, but material matters too.

The cleaner can ruin it

Polycarbonate is attacked by acetone, methylene chloride, toluene and gasoline. One wipe with a solvent-based cleaner will craze the surface. Acrylic resists dilute acids and alkalis much better. Give site teams a one-line cleaning rule: mild detergent and water, soft cloth, no solvents.

Cheap sheet plus two call-outs is not cheap

A lower sheet price on acrylic is real, typically 20–40%. It is also where the comparison usually stops. Add the breakage risk in public areas and the labour of a re-hang, and the total usually moves back toward polycarbonate on exactly the projects where polycarbonate was recommended.

Where these two materials sit in our range

To be direct about who is writing this: Jin Yu supplies acrylic sheet, cast acrylic mainly, in the thicknesses covered in our thickness guide, in colours and clear grades, and we do not stock polycarbonate. That is a supply decision, not a claim that acrylic is the better material.

What we can say with evidence:

• Acrylic holds its colour outdoors without a coating when it is cast grade, installed with movement room, and mounted at a sane span.
• Acrylic is the material to choose when the design depends on light, edge glow, printed graphics or polished edges.
• Polycarbonate is the material to choose when the design depends on not breaking. We will tell you that clearly when the panel is at eye level in a public space.

If you are still choosing between rigid substrates rather than between these two, our comparison of PVC foam board against acrylic covers the third common option.

How these figures were sourced

The impact, transmission, hardness, temperature and UV-life ranges come from the published comparison pages and data sheets of five suppliers and distributors, including Laird Plastics, Interstate Plastics, Ready Plastics, Aochuang Sign and Acrylic Sheets. Where those sources disagree we have given the range rather than picking one. Weathering behaviour for polycarbonate is tied to ASTM D4329, the standard practice for UV exposure testing of plastics.

Where we have added judgement rather than a published figure, it is written as our own note on the quotes we write, and it is not presented as a test result. If a figure is a range from one manufacturer's catalogue, this article says so.