If a break could injure someone — or you are drilling holes in it — use polycarbonate. If it is a display, a sign face, or a cover nobody is going to hit, use acrylic and spend the difference elsewhere. Both are what people mean when they say plexiglass. Everything below is why, with the numbers and the thickness to order.
Here is the thing almost everyone gets wrong. Acrylic and polycarbonate land in the same neighborhood on tensile strength — 10,000 to 11,000 psi for cell cast acrylic against 9,500 to 10,500 psi for polycarbonate sheet depending on grade. And acrylic is the stiffer of the two, with a flexural modulus around 480,000 psi against polycarbonate's 350,000, so under a static load an acrylic panel deflects less.
The difference is not strength. It is ductility. Acrylic stretches 4 to 5% before it fails. Polycarbonate stretches 150%. That single number is the whole story: acrylic reaches its strength and then snaps, while polycarbonate reaches its strength and then keeps deforming, absorbing energy the entire way. It is why one takes 24 inch·lbs of impact and the other takes 800.
Specify by failure mode, not by strength. Ask what happens when the part gets hit, and the answer picks the material for you.
When someone calls and asks which one they need, this is the order we work through it in. It settles the question in about a minute, and you can run it yourself right now.
Nothing hits it, no holes, and it has to still look good in five years — that is acrylic. It costs less, and it stays clearer. If you land somewhere in the middle there are two materials that split the difference: impact modified acrylic, and polycarbonate with a hard coat on it. Ask about them, because neither one shows up on a comparison chart.
Five charts that between them answer most of the question. Every value below is a published property from Calsak's data sheets or a typical published value for cell cast acrylic, and every chart is drawn to a linear scale — no truncated axes, no rescaling to make a bar look better.
This is Calsak’s published comparison chart for PolyGuard, drawn to a linear scale. Polycarbonate absorbs roughly 33× acrylic and 133× glass, and the two small bars really are that small. One honest caveat: ASTM D 3763 is written for rigid plastics, so the glass figure is the manufacturer’s reference point rather than a formal ASTM result for glass. Treat glass as the benchmark it is meant to be, and treat the acrylic-to-polycarbonate ratio as the number you can actually design against.
This one chart explains the one above it. Acrylic reaches its strength and snaps. Polycarbonate reaches its strength and keeps deforming, absorbing energy the whole way. The difference between the two materials is not strength — it is ductility.
Acrylic is the clearest material here, and the only one that holds its number as it gets thicker — float glass carries iron that costs it light with every extra millimeter (90% at 1/8″, 89% at 1/4″, 85% at 1/2″), while acrylic stays at 92%. Do not over-read the gap at thin gauges though: three points is not why you would choose acrylic over glass. Weight and breakage are. The AR polycarbonate hard coat costs about two points of transmission and earns them back on any panel that gets handled.
This is the trade you make when you buy impact resistance. The hard-coated PolyGuard AR grade closes most of the gap — only 2.4% delta haze after 100 Taber cycles — and it is worth the money on anything that gets wiped, handled, or scrubbed. On a bare sheet in a high-traffic spot, acrylic will still look better in five years.
Polycarbonate runs 20 to 80°F hotter than acrylic depending on grade. Both are well above anything a display or a sign will see, so this only decides the specification when the part lives near process heat, a light source, or an enclosure that traps it. Plan to stay comfortably below these numbers in continuous service.
| Property | Acrylic (cell cast) | Polycarbonate |
|---|---|---|
| Impact & toughness | ||
| Instrumented impact, D 3763 | 24 in·lbs | 800 in·lbs |
| Izod impact, notched | 0.3–0.4 ft·lbs/in | 17 ft·lbs/in |
| Izod impact, unnotched | Breaks | No break |
| Elongation at break | 4–5% | 150% |
| Failure mode | Cracks and shatters into blunt pieces | Deforms, dents, stays in the frame |
| Strength & stiffness | ||
| Tensile strength | 10,000–11,000 psi (brittle — no yield) | 9,500–10,500 ultimate / 8,700–9,000 yield (yields, then draws) |
| Flexural strength | 16,000 psi | 14,000 psi |
| Flexural modulus (stiffness) | 480,000 psi | 350,000 psi |
| Rockwell hardness | M 93–100 | M 74 / R 118 |
| Optical & surface | ||
| Light transmission | 92% | 88% clear, 86% abrasion-resistant grade |
| Scratch resistance | Good | Poor unless you buy the hard-coated AR grade |
| Yellowing outdoors | Inherently UV stable — will not yellow | Needs a UV grade; sign grade carries a 10 year warranty |
| Edge quality when polished | Glass clear, flame polishes | Acceptable, does not flame polish the same way |
| Heat & environment | ||
| Heat deflection @ 264 psi | 205–215°F | 228°F sign grade / 288°F AR grade |
| Thermal expansion | 0.000041 in/in/°F | 0.000038 in/in/°F |
| Water absorption, 24 hr | 0.3–0.4% | 0.15% |
| Chemical resistance | Crazes with alcohol, ammonia, acetone | Better, but attacked by alkalis and some solvents |
| Fabrication | ||
| Solvent cementing | Yes — strong, near-invisible joints | Poor. Mechanically fastened or specialty adhesive |
| Laser cutting | Excellent, flame-polished edge | Not recommended — discolored, gassy edge |
| Drilling | Notch sensitive. Plastic-point bit and clearance required | Forgiving. Drills close to like metal |
| Cold bending | No — it cracks | Yes |
| Thermoforming | Forms at 340–380°F cell cast, holds detail | Must be dried first or it bubbles |
| Commercial | ||
| Relative cost | Lower | Higher |
| What we stock | Acrycast cell cast by Calsak | PolyGuard by Calsak |
Polycarbonate values are Calsak's published PolyGuard figures. Acrylic values are Calsak's published Acrycast figures where available, otherwise typical published values for cell cast acrylic sheet. Typical properties, not specifications. For structural glazing, guarding, or anything code-driven, work from the data sheet and tell us what you are building.
These are the calls that come in week after week, and what we tell people when they do. Thickness is where most of the money is, so it is here rather than buried on a spec sheet. Sizes are the finished panel, not the sheet.
| The job | Use | Thickness | Why |
|---|---|---|---|
| It takes a hit, or it gets drilled | |||
| Window covers for snow and ice | Polycarbonate | 3/8″ 1/4″ on small windows |
Ice coming off a metal roof arrives with real energy, and every one of these gets drilled for mounting. Cut the panel 1½ to 2″ oversize on each side so it covers the trim. Above 1/2″ you are into bullet resistant material: heavier, far more expensive, and no better at this. |
| RV, UTV and ATV windshields and windows | Polycarbonate | 1/4″ | Gravel, branches, and mounting holes in every one. We cut flat panels from your old one or from a drawing. We do not form curves — if the original is bent, we are not the shop for it. |
| Machine guards and equipment windows | Polycarbonate | 1/4″ 3/8″ on wide spans |
A break here injures somebody, which overrides every other line on this page. Gray tint is available if there is glare on the operator. |
| Parts that get bolted into a machine | Polycarbonate | 1/4″ | Bolt flanges mean holes, and holes mean acrylic will find the hole eventually. If the part also runs warm, say so — polycarbonate holds up 20 to 80°F higher. |
| Nothing hits it — buy the cheaper one | |||
| Table top protector | Acrylic | 3/16″ 1/4–3/8″ over 4 ft |
1/8″ ripples and reads cheap at any real size. Acrylic is also the stiffer of the two, so it sags less across an unsupported span, and it stays clear. Rippled and frosted finishes hide scratches on a patio table. |
| Cabinet door, shower panel, framed glazing | Acrylic | 3/16″ minimum | 1/8″ is too flimsy once it is framed and people push on it. 3/16″ also matches the thickness of the glass it is usually replacing, so it drops into the existing channel. |
| Sign faces, displays, light boxes | Acrylic | 1/8–3/16″ | Appearance is the specification. Acrylic is the only one of the two that lasers with a clean flame polished edge and solvent cements into an assembly. |
| Backing panels, wall protection, shop templates | Acrylic | 1/8–1/4″ | The cheapest thing that does the job when nothing is going to hit it. If you need to see faint layout lines through it, stay with clear sheet rather than anything textured. |
| Neither one — there is a better answer | |||
| Greenhouse, patio and gazebo roofs | Twin wall | 6mm or 8mm | For a roof, twin wall polycarbonate costs less than flat sheet in either material, carries the span, and insulates. We stock it in 4×8 and 4×10 with the H and U channel to join and cap it. Twin wall → |
| Bullet resistant and security glazing | Polycarbonate | 1/2″ and up | Price climbs steeply above 1/2″ and again at 1″, so this is worth scoping properly before anyone commits a budget. Tell us the threat level you are being asked to meet and we will quote against it. |
Thickness recommendations are what we tell customers on the phone for these jobs, not a code reference. Anything structural, code driven or life safety comes off the data sheet with your loads in it — tell us what you are building. One more thing before you order either one: each material has a way of failing that catches people out, and knowing which one you can live with is the actual decision.
Neither material is better. They fail differently, and you pick the failure you can accept.
Acrylic fails by cracking. Put a sharp internal corner in a loaded acrylic part and it will find that corner eventually. Solvent-cement a machined part without annealing it first and it will craze at the joint months later. Both of those are avoidable if you know about them, and both catch people out constantly.
Polycarbonate fails by looking bad. It scratches, it hazes when you clean it with the wrong thing, and if you specify the wrong grade for an exposed location it will not be clear in five years. The hard-coated AR grade solves this and it costs more. Budget for it up front rather than discovering the problem after installation.
Tell us three things — what the part does, what could hit it, and whether anyone is going to be looking through it — and we will tell you which one to use, including the times the answer is neither. We stock both in Sparks and cut them to size the same day, so this is a conversation with material on the floor behind it rather than a catalog lookup. Call (775) 358-8211 or send us the details. Free delivery in Reno, Sparks, Carson City, Fernley and USA Parkway.
Trick question, and it is why so many specs get written wrong. Their tensile numbers are close — both sit around 10,000 psi — and acrylic is actually the stiffer material. Worth knowing that those two numbers do not mean the same thing: acrylic's is a brittle fracture stress with no yield, polycarbonate's is a yield point it draws past. Size a part to “equal tensile strength” and you can end up with one that shatters instead of denting. What separates them is toughness: acrylic elongates 4 to 5% before it fails, polycarbonate elongates 150%. Polycarbonate absorbs roughly 33 times the impact energy. If your question is really “which one survives being hit,” the answer is polycarbonate, decisively.
Polycarbonate, in the abrasion-resistant grade. The impact case is not close, and the AR hard coat handles the daily wiping and handling that would haze a bare sheet within a year. If the guard is purely a dust shield with no impact and no contact, acrylic will save you money — but be honest with yourself about whether a tool can ever reach it.
Acrylic, almost always. It is inherently UV stable, it will not yellow, it holds a polished edge, it laser cuts cleanly for dimensional letters, and it costs less. Polycarbonate outdoors relies on a UV cap layer, and if that layer faces the wrong way the sign yellows. The exception is a sign in a high-vandalism location, where impact beats appearance.
Polycarbonate, or a laminated polycarbonate-acrylic composite for rated glazing. Do not specify plain acrylic for anything security-rated. If you need a UL-rated assembly rather than a sheet, tell us the level you are working to — that is a specific product, not a thickness of stock material.
Cell cast acrylic. It solvent cements into a strong, near-invisible joint, and polycarbonate does not bond that way at all. Both creep under sustained load, so thickness is worked from water depth and panel span rather than guessed. Give us the internal dimensions and water height. Extruded acrylic is not the right grade for this — it crazes at the joints.
Acrylic, yes, and beautifully — cell cast lasers to a flame-polished edge, which is why it is the standard for laser-cut letters and displays. Polycarbonate, no. It leaves a discolored, gassy edge and the fumes are not something you want in the machine. Polycarbonate gets sawn, routed, or sheared.
Acrylic, by a wide margin — Rockwell M 93 to 100 against polycarbonate's M 74. This is the trade you are making when you buy impact resistance. The hard-coated polycarbonate grade closes most of the gap (2.4% delta haze at 100 Taber cycles) and it is worth the money on anything that gets touched.
Both are stocked in Sparks and cut to size the same day, one piece or a full sheet. We carry Acrycast cell cast acrylic and PolyGuard polycarbonate, both from Calsak. Specialty grades, tints, and thicker plate come in on short lead times.
Polycarbonate, yes. It cuts and drills close to how wood does — a fine tooth blade, a jigsaw, an ordinary twist bit — and it forgives a wandering cut. Acrylic is the one that bites. It chips on the exit side, it melts and welds itself back together behind a dull blade, and it cracks out from a hole if the bit grabs. We get calls most weeks from somebody who bought a sheet, tried to cut it at home and split it. If you want to do the work yourself, buy polycarbonate. If the job needs acrylic, send us the sizes and it comes off the saw square and to size, which is usually cheaper than buying the sheet twice.
For most jobs, no. It matters in three places. Laser cutting: cast cuts with a clean flame polished edge, extruded does not do it as well. Solvent bonding: cast makes stronger, clearer joints. Thickness tolerance: cast varies more sheet to sheet while extruded is more consistent, which matters when the part has to slide into a channel. The masking is the giveaway on a sheet you already own — paper mask is usually cast, film mask is usually extruded. Tell us whether the part gets lasered or bonded and we will make sure you get the right one in your size.
Acrylic is the less expensive of the two at the same thickness, which is why it wins for backing panels, sign faces and covers that nobody touches. Polycarbonate costs more, the hard coated grade costs more again, and above 1/2″ the price climbs into a different category entirely. Worth knowing that thickness moves the number more than the material does — going from 1/8″ to 1/4″ doubles the material in the part. Send us the finished size and the thickness and you get a real number back the same day rather than a range.
No. We cut, drill and fabricate the panel to your sizes and you or your installer put it in. That is deliberate — the fit is only right when whoever mounts it has measured the opening. For window covers around Truckee, Donner and Incline we work with installers who do this every winter, so ask and we will point you at somebody.
Full acrylic specs, grades and stock → · Full polycarbonate specs, grades and data sheets → · Twin wall polycarbonate →
Whatever you need — one piece or one hundred, a quick cut or a full fabrication run — we're here. Serving Northern Nevada since 1979.