Acrylic and polycarbonate look almost identical at first glance. Both are clear thermoplastics, both come in cast and extruded sheet, both are used as the lit face of channel letters and lightboxes. The day-one quote from two vendors using the two different materials might land within five percent of each other. The five-year story is completely different.
Acrylic — PMMA, polymethyl methacrylate — is the default for illuminated signage in India. Cast acrylic, the higher grade, is supplied in sheets typically 3 mm, 4.5 mm, 6 mm, 8 mm, and up. Optical clarity is excellent at around 92 percent light transmission for clear sheet. Translucent white acrylic for lit signage runs 30 percent to 60 percent light transmission depending on the opacity grade. UV stability is good — proper cast acrylic from a known mill (Plexiglas, Acrylite, Donchamp, Asia Poly) holds colour and clarity for ten to fifteen years outdoor in Indian conditions.
Polycarbonate — PC — is the impact specialist. Tensile and impact strength is roughly thirty times that of acrylic. The same brick that cracks a 3 mm acrylic face will bounce off 3 mm polycarbonate with a scuff. This matters in three situations: ground-level signage in high-traffic public areas, lightboxes within easy throwing range of a footpath, and any signage where breakage liability for a falling fragment is a real concern. Schools, transit hubs, public hospitals — polycarbonate.
Where polycarbonate fails — and this is what cheaper vendors do not tell you — is UV. Standard polycarbonate yellows. The yellowing is visible in eighteen to twenty four months on a south-facing facade in central Karnataka. The fix is UV-stabilised polycarbonate with a co-extruded UV layer on the weather-side face. Sabic Lexan, Covestro Makrolon, and Palram Palsun are the names to look for. The UV-stabilised grade costs roughly 35 to 45 percent more than acrylic at equivalent thickness. Procurement teams who specify generic polycarbonate and accept the lowest bid get a yellow sign in two years. Specify the grade, the brand, and ask for the UV warranty in writing.
Light transmission and diffusion behaviour also differ. Acrylic diffuses light beautifully when you back it with white LED modules — the face glows evenly, hot spots are easier to control. Polycarbonate is more transparent and tends to show LED module pattern through if the face is too thin or the module spacing too wide. For polycarbonate faces over LED arrays you need a diffusion film or a deeper return depth on the channel letter to allow the light to spread before it hits the face. Standard rule: for letter return depth less than 80 mm with polycarbonate face, add a 50 micron polyester diffusion film behind the face.
Cost benchmarks May 2026. Cast acrylic 3 mm white translucent: rupees 95 to 130 per square foot at trade quantities. Co-extruded UV-grade polycarbonate 3 mm white translucent: rupees 175 to 240 per square foot. Same dimensions in 4.5 mm acrylic: 140 to 180. Polycarbonate 4.5 mm UV: 260 to 320. These are sheet costs only — fabrication, routing, edge treatment, mounting, and LEDs are separate.
The failure modes worth quoting in your tender. Acrylic crazes — fine surface cracking — when exposed to incompatible solvents or when stressed at the fastener holes. Drill before bonding, not after. Use chemical anchors with rubber grommets, never direct screw-through with a counter-sink head, the stress riser will craze the sheet within a year. Polycarbonate, when the wrong grade is used, will yellow as discussed and also chemically attacked by certain cleaning agents — IPA and ammonia-based glass cleaners can cause cloudiness. Specify cleaning protocol in the handover, mild soap and water only.
Thermoforming. If your design has curved letters or a domed face, polycarbonate forms easier with less surface change but requires drying the sheet before forming because absorbed moisture will cause bubbles. Acrylic forms cleanly but is more prone to stress lines if the form temperature is wrong. For deep-formed faces — Pepsi-style domed letters, drive-thru menu boards — most quality vendors run polycarbonate.
Fire behaviour. Acrylic is rated B2 in DIN 4102 — normal flammability — and burns cleanly with a sweet smell, dripping. Polycarbonate is rated B1 — flame retardant, self-extinguishing. For interior signage in malls, airports, hospitals, and public buildings where the local fire code or the property management requires B1 minimum, polycarbonate is mandatory. Bring the spec sheet to the architect early, not at install.
The procurement framing question is this: what is the failure cost? If a sign goes down in your retail outlet for two weeks while a replacement face is fabricated and shipped, what does that cost you in lost brand visibility and replacement spend? If it is more than fifteen thousand rupees, the polycarbonate premium is justified for any face below 4 metres above ground line. Above that, acrylic with a properly specified UV grade and a serious return depth will give you a ten-year run.
We build both routinely. The breakdown of what we used and why is logged on every project handover document — see the AMC schedule format on /amc and the typical project specification on /services for corporate signage.
A further consideration worth surfacing during procurement evaluation is matched-batch acrylic. For multi-store retail rollouts where brand colour consistency matters across sites, specify same-batch translucent acrylic for the entire rollout. Different production batches of the same nominal colour and opacity grade can vary by 3 to 5 percent in transmission, which is invisible at a single site but glaringly obvious when two outlets are visible from the same parking lot. Quality vendors will hold inventory of a single mill batch for a multi-site rollout — ask for the mill batch number on the supply note, not just the brand name.
Edge finishing is another spot where cheaper builds skip the work. Cast acrylic should be flame polished or diamond polished on visible edges if the construction is acrylic-only. Polycarbonate edges are matt by default and benefit from edge sealing with clear silicone to prevent dust ingress between the layers of a multi-laminated face. Both materials should never be bonded with cyanoacrylate (super glue) — the adhesive crazes both surfaces. Use methacrylate adhesive for acrylic and polyurethane adhesive for polycarbonate, both with the correct cure time before handling.
Cleaning protocol matters for both. Acrylic faces should be cleaned only with a soft microfibre cloth and dilute mild soap solution, never with paper towels which leave micro-scratches that show up as cloudiness over time. Polycarbonate is more tolerant of cleaning method but reacts badly to ammonia-based cleaners, so the standard glass cleaner that the housekeeping team brings to the site will damage a polycarbonate sign within months. Document the cleaning protocol on the AMC handover sheet and brief the facilities team during commissioning — this is the single cheapest thing procurement can do to extend the visible life of a lit face.
Thermal expansion needs design accommodation. Both materials expand and contract with temperature: acrylic about 7 mm per metre across the typical Indian temperature range from a 12 degree winter morning to a 48 degree summer afternoon, polycarbonate similar at about 6.5 mm per metre. The signage construction must allow for this movement: oversize the fastener holes, use silicone sealant rather than rigid mechanical bonding at the perimeter, and avoid edge-clamping that locks the sheet in place. Signs that ignore this constraint develop stress cracks at the fastener holes within two years. The fix at design stage is trivial; the fix in the field is full face replacement.
For large lit faces (over 2 metres in any dimension), specify a single sheet rather than multiple bonded panels wherever possible — bonded seams in a lit face are visually intrusive at night because the bond line shows as a bright streak. If the design requires a face larger than the maximum sheet size (typically 2 metres x 3 metres for cast acrylic), plan the seam at a horizontal break in the graphic and use a butt-joint with adhesive rather than overlap.
Send your design intent, install location, and required life to /contact and we will return a material recommendation per face along with the cleaning and maintenance protocol that goes on the handover sheet.
