Polycarbonate Sheets — Complete Guide
Polycarbonate (PC) is a high-performance thermoplastic polymer with exceptional impact strength — up to 250 times stronger than glass at the same thickness — while being lightweight, virtually transparent and UV-stabilised. Polycarbonate sheets are the material of choice for skylights, canopies, atriums, greenhouses, swimming pool roofs, sound barriers, building facades and security glazing.
Originally developed by GE / Bayer (Lexan™ / Makrolon™) in 1953, polycarbonate is now made by SABIC, Bayer, Covestro, Palram, Brett Martin, Tuflite and Indian brands like Tuflite, Plasto-Logic and Sintex. Indian polycarbonate sheets typically conform to ASTM D6849, ISO 11963 and IS 14443 (related plastics).
What is Polycarbonate?
Polycarbonate is a high-molecular-weight thermoplastic produced by polymerisation of bisphenol-A and phosgene. The resulting clear granules are extruded into solid sheets or co-extruded into hollow multi-wall panels. UV-stabilised polycarbonate sheets carry a co-extruded UV-protective layer (10 microns thick) on the sun-facing side to prevent yellowing.
A 4 mm twin-wall polycarbonate sheet weighs only 0.8 kg/m² (less than 1/10th the weight of glass) but is impact-resistant enough to survive a hammer blow. UV-stabilised sheets carry a 10-year warranty against yellowing or hailstone damage.
Types of Polycarbonate Sheets
| Type | Description | Use |
|---|
| Solid Polycarbonate | Single solid layer, transparent | Skylight, security glazing |
| Twin-wall Hollow | 2-wall with vertical ribs | Canopy, greenhouse roofing |
| Multi-wall (3/4/5/7-wall) | Multiple layers + cross ribs | Premium skylights, thermal insulation |
| Honeycomb | Hexagonal cell structure | Premium insulation, large spans |
| Corrugated | Trapezoidal / sinusoidal profile | Industrial roof, daylight panels |
| Embossed / Diamond / Prismatic | Textured for light diffusion | Glare-free skylight |
| Standing Seam | Click-lock profile | Premium roof, no exposed screws |
| Cellular U-Lock | Interlocking sheets | Vertical walls, partitions |
| Sandwich (PC + Aluminium) | Composite ACP-style | Facade cladding |
| Mirror / Solid Coloured | Tinted / coloured | Decorative panels |
Standard Sizes & Thicknesses
| Type | Common Thickness | Sheet Size |
|---|
| Solid Polycarbonate | 1.5 / 2 / 3 / 4 / 5 / 6 / 8 / 10 / 12 mm | 1220 / 1500 / 1830 / 2050 mm width x 3000 / 6000 mm length |
| Twin-wall (Multi-wall) | 4 / 6 / 8 / 10 / 16 mm | 2100 mm x up to 11.8 m |
| Multi-wall 16/20/25/32 mm | 16 / 20 / 25 / 32 mm | 2100 mm x up to 11.8 m |
| Corrugated | 0.8 / 1.0 / 1.2 / 1.5 / 2.0 mm | 900 / 1080 mm cover width x 3000–6000 mm |
| Embossed / Diamond | 0.8 / 1.0 / 1.5 / 2 / 3 mm | 1220 mm x 3000–6000 mm |
| Standing Seam | 0.8 / 1.0 / 1.2 mm | 500–600 mm cover width x project length |
Physical Properties
| Property | Value |
|---|
| Density | 1,200 kg/m³ |
| Tensile Strength | 62–72 MPa |
| Flexural Strength | 90–100 MPa |
| Impact Strength (Izod) | 650–1000 J/m (200× glass) |
| Modulus of Elasticity | 2.3 GPa |
| Light Transmission (Clear, 4 mm) | 80–90% |
| Thermal Conductivity | 0.20 W/m.K (better than glass) |
| Coefficient of Thermal Expansion | 65–70 x 10⁻⁶ /°C |
| Operating Temperature | −40 to +120 °C |
| Heat Deflection Temperature | 130–140 °C |
| Fire Rating | UL 94 V-2 / Class B-s1, d0 |
| UV Resistance | 10-year warranty (UV-stabilised) |
| Sound Reduction (4 mm) | ~25 dB |
Multi-wall Polycarbonate — U-value Comparison
| Thickness | Structure | U-value (W/m².K) | Light Transmission |
|---|
| 4 mm | Twin-wall | 3.9 | 82% |
| 6 mm | Twin-wall | 3.6 | 80% |
| 8 mm | Twin-wall | 3.3 | 80% |
| 10 mm | Twin-wall | 3.0 | 78% |
| 16 mm | Triple-wall | 2.4 | 70% |
| 20 mm | 5-wall | 1.8 | 62% |
| 25 mm | 5-wall X structure | 1.5 | 55% |
| 32 mm | 7-wall X structure | 1.2 | 45% |
Installation — Step by Step
- Framework: MS / aluminium framework with rafters and purlins. Slope minimum 5° (preferred 10°–15°).
- UV Side: Identify UV-stabilised side (marked with tape or printed). This must face the sun!
- Allow Expansion: Allow 4 mm gap per metre of sheet length for thermal expansion
- Drill Holes: Holes 8–10 mm oversize for screws (allows expansion). Never directly screw — use slotted holes.
- Cutting: Cut solid sheets with fine-tooth saw; cut multi-wall with circular saw + masking tape (prevents chip-out)
- Seal Cells: Multi-wall cells must be sealed at top (with breather tape) and bottom (with vent tape) to prevent moisture entry
- Profile / Cap System: Use H-profile / U-profile / aluminium snap-on caps for joints. Apply silicone sealant.
- Screws: Use stainless steel screws with neoprene / EPDM washer (never directly on sheet)
- Spacing: 500–750 mm c/c, never closer to edge than 50 mm
- Slope Direction: Multi-wall sheets must be installed with ribs running down the slope (water drainage)
- Final Sealing: Silicone sealant at all perimeter joints & cap junctions
Tests on Polycarbonate Sheets
- Light Transmission Test — ISO 13837
- Impact Resistance — ASTM D256 (Izod), D5420 (falling dart)
- Tensile Strength — ASTM D638
- Flexural Strength — ASTM D790
- UV Weathering — ASTM G155 (Xenon arc, 2000 hr)
- Yellowing Index (delta YI)
- Fire Performance — UL 94 / ASTM D1929 / ASTM E84
- Thermal Expansion Test
- Heat Deflection Temperature — ASTM D648
- Hail Impact Test (steel ball / ice ball)
- Cell Geometry & Wall Thickness
- Solar Heat Gain Coefficient (SHGC)
Polycarbonate vs Glass vs FRP — Comparison
| Parameter | Polycarbonate | Glass | FRP |
|---|
| Density | 1200 kg/m³ | 2500 kg/m³ | 1500 kg/m³ |
| Impact Strength | 250× glass | Baseline | 40× glass |
| Light Transmission | 80–90% | 85–92% | 70–85% |
| UV Resistance | 10 yr (UV protected) | Excellent | 5–10 yr |
| Yellowing | Possible without UV layer | None | Yes (over time) |
| Scratch Resistance | Poor (use coating) | Excellent | Poor |
| Sound Reduction | 20–30 dB | 28–35 dB | 15–25 dB |
| Operating Temp | −40 to +120 °C | −100 to +400 °C | −40 to +90 °C |
| Cost (Rs/sqft) | 80 – 400 | 50 – 300 | 60 – 200 |
| Best for | Skylights, canopies | Premium glazing | Industrial roof |
Uses of Polycarbonate Sheets
- Skylights (residential, commercial, industrial)
- Canopies for car porches, balconies, entrances
- Atrium and dome roofs in shopping malls, hotels
- Greenhouses and agricultural sheds
- Swimming pool covers and enclosures
- Patio covers and pergolas
- Bus stops, metro stations, railway shelters
- Industrial roof daylight panels (in steel sheet roofs)
- Sound barriers (motorways, railways)
- Walkway covers (between buildings)
- Bank teller / security glazing (multi-layer)
- Riot shields and machine guards
- Greenhouse walls and partitions
- Sports stadium roofs (long spans)
- Helicopter cockpit canopies
- Sign boards and back-lit displays
- Toll plaza canopies
- Cycle / scooter parking sheds
Advantages
- Virtually unbreakable — 250× impact strength of glass
- Lightweight (1/2 weight of glass) — lighter structures
- 80–90% light transmission (better than FRP)
- Excellent UV resistance with UV-coated layer (10 year warranty)
- Self-extinguishing — UL 94 V-2 fire rating
- Operates from −40 to +120 °C (extreme weather)
- Excellent thermal insulation (multi-wall U-value 1.2–3.9)
- Easy to cut, drill and shape on site (no expert needed)
- Cold-bendable to large radii (no heat forming required)
- Many tints and finishes available
- Anti-condensation coatings available (greenhouse)
- Sound dampening for highway / railway barriers
- Can withstand hailstones up to 50 mm dia
- Recyclable (Resin Code 7 / OTHER)
- Available in standing-seam, click-lock for clean facades
Disadvantages
- Scratches easily — use hard-coated variety for high-use areas
- Yellows over time if UV protection compromised
- Higher cost than FRP or ordinary plastic
- Thermal expansion is high (65–70 ppm/°C) — must allow expansion gaps
- Chemical incompatibility with some cleaners (ammonia, solvents)
- Cannot use cleaning chemicals like acetone, benzene
- Joints / cell ends must be sealed to prevent dust / moisture / algae inside
- Solid PC is heavy (12 mm = 14.4 kg/m²)
- Lower scratch resistance than glass
- Birds may collide (use bird-strike pattern)
- Static electricity attracts dust (use anti-static coating)
- Cannot withstand high temperatures (> 140°C)
- UV protection only on one side — must face sun correctly
Quantity Estimation
| Item | Per m² |
|---|
| Polycarbonate Sheet | 1.05 m² (with 5% overlap / wastage) |
| Aluminium H / U Profiles | 1.0 m per joint |
| Self-drilling Screws + Washers | ~5 nos |
| Breather + Solid Sealing Tape | 2 m perimeter / sheet |
| Silicone Sealant | ~30 g |
| Wastage (cutting / handling) | 5 – 10% |
Cost (Approximate, Indian Market)
| Sheet Type | Rate (Rs / sqft) |
|---|
| Solid PC 3 mm (clear) | 180 – 280 |
| Solid PC 6 mm (clear) | 350 – 550 |
| Twin-wall 6 mm | 80 – 130 |
| Twin-wall 8 mm | 100 – 160 |
| Multi-wall 10 mm | 140 – 220 |
| Multi-wall 16 mm | 200 – 320 |
| Multi-wall 25 mm (X structure) | 350 – 550 |
| Corrugated PC 0.8 mm | 70 – 120 |
| Embossed / Diamond / Prismatic | 120 – 200 |
| Aluminium Profiles (H / U) per metre | Rs 80 – 200 |
| Complete canopy / shed (incl. structure + sheet + labour) | Rs 250 – 600 / sqft |
Best Practices
- Always install with UV-protected side facing the sun
- Never drill or screw directly on sheet — use oversize holes with washers
- Provide 4 mm expansion gap per metre of sheet length
- Seal multi-wall cell ends with breather tape (top) and vent tape (bottom)
- Use aluminium / polycarbonate H / U profile joints (not silicone-only)
- Run multi-wall ribs / cells parallel to slope (for drainage)
- Maintain minimum 5° slope (10–15° preferred)
- Clean with soft cloth and mild soap water only
- Never use abrasive cleaners, scrubbers, ammonia or solvents
- Use neoprene / EPDM washers, never metal washers
- Buy from branded manufacturer (Tuflite, Sintex, SABIC) for UV warranty
- Use Diamond / Prismatic for glare-free skylights over computer halls
- Cover sheets with brown / black film during transport to avoid scratches
- Allow 24 hr acclimatisation before installation in sunlight
Applicable Standards
| Standard | Description |
|---|
| ASTM D6849 | Standard practice for polycarbonate sheet products |
| ASTM D635 | Rate of burning of self-supporting plastics |
| ASTM D638 | Tensile properties of plastics |
| ASTM D790 | Flexural properties of plastics |
| ASTM D256 | Izod impact strength of plastics |
| ASTM D1929 | Self-ignition of plastics |
| ASTM E84 | Surface burning characteristics |
| ASTM G155 | Xenon-arc weathering |
| UL 94 | Plastic flammability classification |
| EN 13501 | Fire classification of construction products |
| IS 14443 | Plastic-coated sheets & films — Specification |
Conclusion
Polycarbonate sheets are the modern engineer’s choice for any application that needs transparency + impact strength + light weight + UV durability. From entrance canopies and patio covers to industrial skylights, atrium roofs and security glazing, no other material delivers this combination of properties at this price.
For solid weatherproof roofing, use GI / colour-coated steel sheets; for traditional flat roofs, use RCC slabs; for premium aesthetic residential sloped roofing, look at Mangalore tiles or bitumen shingles; for daylight-only or hybrid daylight installations, combine polycarbonate with these other systems.