Cast vs Extruded Acrylic vs PETG vs Polycarbonate Guide

The 30-second answer

The cast vs extruded acrylic vs PETG vs polycarbonate decision for retail display work is straightforward: cast PMMA is the right substrate for 95% of retail-facing display work because it wins on the four metrics that decide a 5-year program: optical clarity at the cut edge (laser flame-polishes cast itself; clouds extruded), edge polish quality under diamond polishing, UV yellowing resistance, and surface hardness for scratch resistance. PETG wins on shatter resistance for thin-wall packaging. Polycarbonate wins on ballistic-grade impact and high-temperature exposure. None of the alternates win on the metrics that decide retail display performance.

I founded Wetop in 2008 and we’ve stayed acrylic-only as a deliberate operational choice — not because we couldn’t run other substrates, but because the integration discipline that produces consistent quality is harder to maintain across multi-substrate production. The five sections below cover what each substrate actually does, with test data, and what the substitution risk costs over a typical 5-year program.

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Cast PMMA — why it’s the 95% answer for retail display work

Cast PMMA is the right substrate for retail display work because it wins on four specific metrics that decide whether the display reads premium at year five.

Optical clarity at the cut edge under CO2 laser. Cast PMMA flame-polishes itself under CO2 laser. The heat-affected zone produces a clean optical edge without secondary polishing. This is the single biggest production-line difference between cast and any other substrate — cast finishes cleanly off the laser, the others require secondary polishing.

Edge polish quality under diamond polishing. Cast PMMA holds optical-grade edge clarity at 1.1% haze (per ASTM D1003) for 5+ years.¹ Diamond polishing on cast produces a finished edge that’s stable across the substrate’s life.

UV yellowing resistance. Cast PMMA holds <3% haze increase at 5,000 hours of accelerated UV exposure (per ASTM G155 weatherometer protocol).² At typical retail or hospitality light exposure, that’s roughly 5-7 years of operating life before visible yellowing.

Surface hardness for scratch resistance. Cast PMMA Rockwell M85-M95 (per ASTM D785) — high enough that retail-floor handling produces minimal visible scratching across the program life.³

The cost premium for cast over the cheapest alternate (extruded PMMA) is 35-45% on raw substrate. On a typical retail display run, that’s $3-$5 per unit of material premium. Compared to the cost of replacing displays at 18 months under any of the alternate substrates, cast is the cheap decision.

Extruded PMMA — cheaper, looks identical day 1, fails at edge-lit + 12-month UV

Extruded PMMA is manufactured by forcing molten resin through a heated die — the same nominal material as cast PMMA but produced through a different process. The process orients polymer chains along the extrusion axis and locks residual stress into the sheet. That residual stress is what produces the failure modes.

Engraved channel haze under LED dwell. Extruded PMMA cut by CO2 laser releases residual stress at the cut surface over the following weeks. Under continuous LED dwell heat (typical edge-lit display, 35-45°C at the rim), the channel develops visible haze. Internal aging study at 18 months: extruded PMMA at 4.8% haze vs cast PMMA at 1.1% haze under identical operating conditions. The visible result: cloudy engraved content where it was crisp at install.

UV yellowing on bare extruded. Extruded PMMA shows visible yellowing at 1,500-2,500 hours of accelerated UV exposure — typically 12-18 months at retail spot lighting. Cast PMMA holds clarity at 5,000+ hours.

Edge polish thermal stress. Diamond polishing on extruded releases additional residual stress at the polished surface, which compounds the LED-dwell haze problem at any edge-lit application.

When is extruded fine? Internal jigs and fixtures (no buyer visibility, no UV exposure). Prototype iterations (when 12-month durability isn’t being tested). Hidden interior panels in multi-panel cases. Pure flat panels with no engraved or cut edges that show in the finished display. For everything else — the visible surfaces of any retail-facing display — cast is the right answer. For our deeper substrate comparison, see cast vs extruded acrylic.

PETG — buyer-favorite for “shatter-resistant” but loses edge-finish quality

PETG (polyethylene terephthalate glycol) is sometimes proposed as an acrylic alternative because it’s shatter-resistant — useful for packaging applications. For retail display, PETG loses on the metrics that decide premium read.

Edge polish chemistry. PETG doesn’t flame-polish under CO2 laser the way cast PMMA does. The cut edge is rough and requires secondary mechanical polishing. Diamond polishing works on PETG but produces a different finish quality than on cast PMMA — the edge has a slightly cloudy appearance even at optimal polish, because PETG’s surface isn’t as homogeneous as PMMA’s.

Optical clarity at depth. PETG at thicknesses above 6 mm shows visible green-tint shift, similar to glass. Cast PMMA holds neutral clarity through 50+ mm thickness without color shift.

UV resistance. PETG holds clarity for ~1,500 hours of UV exposure before visible haze increase — about a third of cast PMMA’s resistance window. For sustained-UV applications (retail spot lighting, sunlight exposure), PETG fails the lifetime test.

Surface hardness. PETG Rockwell M65-M75 — about 75% of cast PMMA’s hardness. Visible scratching from retail-floor handling is meaningfully more frequent on PETG.

PETG is the right substrate for thin-wall packaging (food clamshells, healthcare specimen containers, child-product lids) where shatter resistance matters more than optical and surface characteristics. We don’t use PETG for retail display work because the retail context doesn’t reward shatter resistance as much as it punishes the optical and edge-finish degradation. For the broader plastic comparison context, see our acrylic plastic box vs polycarbonate vs PETG guide.

Polycarbonate — wins on impact, loses on UV yellowing + scratch

Polycarbonate (PC) is sometimes proposed for retail display work because it’s the most impact-resistant common transparent polymer. For retail display where impact rarely happens and visual quality decides everything, PC is the wrong call on three axes.

UV yellowing. PC visibly yellows at 800-1,200 hours of UV exposure — about 25% of cast PMMA’s resistance. Under retail spot lighting (5,000-7,000 K LED at 800+ lux), PC starts showing visible yellow tint within 6-12 months. The yellowing is dramatic enough that PC retail display panels are usually replaced before the impact-resistance benefit ever matters.

Surface scratch sensitivity. PC Rockwell M70-M75 — softer than cast PMMA. Surface scratching from retail-floor handling is more frequent and more visible.

Edge polish quality. PC’s polish chemistry is less responsive to diamond polishing than cast PMMA. Optical-grade edges on PC require additional polishing steps and produce slightly cloudy finished edges.

Per-clarity material cost. PC’s raw substrate is slightly more expensive than cast PMMA. After accounting for the additional polishing labor and the shorter operating life under UV, PC’s lifetime cost on retail display work is meaningfully higher than cast PMMA.

Polycarbonate wins on three specific scenarios: ballistic-grade impact resistance (security panels, riot shields, blast-shielded display), high-temperature exposure above 125°C (industrial machinery enclosures, near-furnace work), and applications requiring deep flexibility without fracture. For retail display work — which is essentially never any of those — cast PMMA wins on every other axis.

The 4-substrate test matrix at a glance

The decision matrix below summarizes the four substrates against the metrics that decide retail display performance. The semantic palette: green = recommended, gray = baseline, orange = alternate, red = fail-mode-illustrative.

The matrix is supplier-agnostic — the substrate properties are documented in the ASTM standards cited above, not Wetop-specific.⁴ The implication for buyers: when a supplier proposes “or equivalent” substrate substitution, the substitution almost always trades 4 of 5 retail-relevant metrics for marginal cost savings. That trade only makes sense in the narrow PETG and PC scenarios named below.

When the spec sheet says “or equivalent” — what to push back on

The “cast acrylic or equivalent” clause on a spec sheet is where substrate substitution risk lives. The clause opens the door to extruded PMMA, PETG, or polycarbonate substitution by suppliers optimizing on material cost. The substitution is invisible at delivery — none of the alternates show meaningful difference on a freshly-shipped panel.

Where the difference shows up: 12-24 months later, when the engraved channel develops haze on extruded substitution, or the edges cloud on PETG substitution, or the panel yellows on polycarbonate substitution. By then the program has typically completed its rollout phase and the failure mode shows up across the full deployed inventory simultaneously.

What to push back on:

• Strike “or equivalent” from any spec sheet where substrate choice matters. Replace with explicit “cast PMMA only, mill cert required for every batch.”
• Ask for mill certs at quote stage, not delivery stage. The cert names the actual production process for the batch your panels were cut from.
• Request a sample with mill cert before committing to bulk production. The cert establishes the substrate is what was specified and creates an audit trail.
• Add a substrate-substitution clause to the PO: any mid-run substitution requires written approval from the buyer.

Suppliers who push back on these clauses are signaling they were planning to use the substitution flexibility. Suppliers who include all four as defaults are operating at audit-ready substrate discipline. The framework is supplier-agnostic — apply it to Wetop, to any other acrylic supplier on your shortlist. Suppliers who answer cleanly are usually suppliers who can deliver against the spec. Our own answers — cast-PMMA-only floor since 2008, the ISO 9001 surveillance history, the certifications and facility scope — are documented on our about page for the same supplier-qualification check.

For the broader substrate decision context including extruded-only, see our cast vs extruded acrylic guide. Our acrylic displays and acrylic cases are all produced in cast PMMA as standard. For a real-world example of cast PMMA across a multi-store program, see the 50-store retail display rollout case study. For buyers wanting substrate samples in cast vs the alternates for their specific application, send the brief over to our team — we’ll send a substrate sample set with mill certs alongside the relevant ASTM-spec references for your retail conditions.

Cost: raw material, fabrication, and total delivered

Across the 4-substrate matrix, cost ranking from lowest to highest delivered is roughly: extruded PMMA < cast PMMA < PETG < polycarbonate. The biggest gap sits between PMMA (cast or extruded) and polycarbonate. Indicative distributor pricing for a 6mm × 1m² sheet runs roughly $30–$55 in cast PMMA versus $50–$85 in polycarbonate in the US market — a 35–50% raw-material premium for PC. Always cross-check current quotes with distributors like ePlastics, Piedmont Plastics, or your regional sheet supplier; brand and order volume move these numbers materially.

Four variables actually determine the total cost gap on any specific project. First, the raw-material cost gap widens further when specifying UV-stabilized polycarbonate, which carries an additional premium over standard PC grades. Second, fabrication speed — cast PMMA laser-cuts in minutes what polycarbonate takes hours to CNC-route and polish. PETG can be laser cut but tends to char without nitrogen assist. Extruded PMMA cuts comparably to cast but requires care on the polish pass. Third, edge finishing labor — polycarbonate needs mechanical edge finishing after every cut; PMMA’s flame or diamond polish is a single finishing pass after laser cutting (see our diamond vs flame polishing guide for the edge-finish trade-offs). PETG occupies a middle ground where flame polishing produces inconsistent clarity. Fourth, scrap rate — polycarbonate’s scratch-on-handling sensitivity and PETG’s moisture absorption during thermoforming both produce more rejected parts per run than cast PMMA, adding indirect cost.

In our floor experience pricing all four substrates against equivalent retail-display specs, cast PMMA typically lands at 40–60% lower total delivered cost than polycarbonate on equivalent panels. The exception is when the application genuinely requires polycarbonate’s impact resistance or PETG’s deep-draw thermoforming — there, the higher cost is the cost of the correct material, and we will tell a buyer directly when their use-case actually calls for the substitution.

”Acrylic vs plexiglass vs polycarbonate” — clearing up the terminology

In RFQ conversations, brand names and generic terms get used interchangeably and create unnecessary spec ambiguity. Short decoder:

• Acrylic = PMMA = Plexiglas® = Perspex® = Lucite® — all the same material (poly(methyl methacrylate)), different brand or regional trade names. “Cast PMMA” and “cast acrylic sheet” are the same thing.
• Polycarbonate = PC = Lexan® (SABIC) = Makrolon® (Covestro) = Tuffak® (Plaskolite) — same material, different brand families with broadly similar specs but different impact-modifier and UV-package recipes.
• PETG has no widely-used trade-name shorthand — it shows up on RFQs as “PETG”, “copolyester”, or sometimes “Vivak” (a Plaskolite trade name).

When an RFQ says “Lexan display case,” the buyer means polycarbonate, and we’ll clarify on the call whether that’s the right material for the application. When an RFQ says “plexiglass case,” they mean acrylic, and it almost always is the right call. When an RFQ poses “acrylic vs plexiglass vs polycarbonate” as a comparison question, they’re really asking “acrylic vs polycarbonate” — plexiglass and acrylic are the same material under different names.

For the related transparent-glazing comparison versus glass, see our guide on acrylic vs glass for displays — the three-way framing of acrylic, glass, and polycarbonate covers most of the transparent-panel decision space.

Footnotes

1. ASTM International. ASTM D1003-21 — Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics. https://www.astm.org/d1003-21.html ↩

2. ASTM International. ASTM G155-21 — Standard Practice for Operating Xenon Arc Light Apparatus for Exposure of Materials. https://www.astm.org/g0155-21.html ↩

3. ASTM International. ASTM D785-23 — Standard Test Method for Rockwell Hardness of Plastics and Electrical Insulating Materials. https://www.astm.org/d0785-23.html ↩

4. International Association of Plastics Distribution — Plastics Material Resources — trade-association comparison of transparent plastics (PMMA, PETG, polycarbonate) covering material properties, procurement grades, and application guidance for B2B buyers. ↩