On a polycarbonate order, the words sheet, panel, board, and glazing operate as separate specification classes. They are not interchangeable labels for the same extruded or molded product. ISO 11963:2019 classifies polycarbonate sheet by type, dimensions, and characteristics, but it does not assign a commercial meaning to panel or board. A specification that conflates these terms can lead to a multiwall panel being supplied where a machined solid board was required, or an unclassified extruded sheet being installed in a safety-glazing location. The practical distinction depends on thickness range, manufacturing history, edge detail, surface finish, impact certification, and weathering behavior. For example, a clear solid sheet of 3 mm thickness may have luminous transmittance above 89 % and haze below 1.5 % under ASTM D1003-13, but it does not become glazing until it meets CPSC 16 CFR 1201 or ANSI Z97.1. The following sections separate the four terms according to the data an order must carry.

Sheet, Panel, Board, Glazing: What Each Word Means on a Polycarbonate Order

Within a procurement specification, the first sorting criterion is whether the polycarbonate product is flat solid sheet, structured multiwall panel, thick solid board, or certified glazing. These classes are not mutually exclusive; a panel can also be a glazing product if it is tested to the applicable safety-glazing method. The table below separates the common industrial meanings according to geometry, manufacturing route, and dimensional control.

The thickness boundaries in the table are not fixed by a single ISO clause; they are industry-dependent and must be confirmed against the manufacturer’s extrusion or molding capacity. What changes with class is not chemistry—general-purpose unfilled polycarbonate remains similar—but the tolerances, failure modes, and compliance path.

For solid extruded sheet, the order term sheet usually implies continuous flat product produced through a flat die and polished or embossed roll stack. General-purpose unfilled polycarbonate has a melt flow rate of 6 g/10 min to 18 g/10 min under ISO 1133-1:2022 at 300 °C/1.2 kg; extrusion grades are commonly selected in the 6 g/10 min to 10 g/10 min range to maintain melt strength. Pre-drying is mandatory. The granulate or sheet stock must reach 0.02 % moisture or less before processing, typically after 4 h at 120 °C for thicknesses up to 6 mm. Residual moisture above this threshold produces splay, bubbles, and a measurable loss in impact strength. Tensile yield stress of extruded sheet is 60 MPa to 70 MPa under ISO 527-2, and notched Izod impact at 3.2 mm is generally 600 J/m to 850 J/m under ASTM D256. These values are grade-dependent and should not be entered into a structural calculation without lot-specific test data. Thickness tolerance for solid sheet is not a single number; it scales with nominal thickness and width. A 3 mm sheet may carry a tolerance of ±0.15 mm, while a 10 mm sheet may carry ±0.5 mm, depending on the manufacturer’s process capability. The purchaser must specify whether the tolerance band applies to the sheet as extruded or to the finished cut panel after shrinkage.

When a Multiwall Panel Substitutes for Solid Sheet, Which Load Path Changes?

Multiwall polycarbonate panels are structural profiles with a repeated cored cross-section. The term panel on an order often refers to this product class even though it is still polycarbonate sheet under ISO 11963:2019. Solid sheet carries flexural load through a continuous rectangular cross-section; a multiwall panel carries the same load through a thinner face shell and ribs, producing a different bending stiffness per unit mass. The order therefore cannot specify only an equivalent solid-sheet thickness. It must specify the number of walls, the cavity height, the rib spacing, the face wall thickness, and the orientation of any coextruded UV-protection layer. A 16 mm triple-wall panel has a published thermal transmittance around 2.4 W/m²K to 2.7 W/m²K in manufacturer data sheets; a low-emissivity or IR-reflective coextrusion can shift the value below 2.0 W/m²K, but the exact value depends on cavity geometry and must be called out as a system, not as a bare panel.

Thermal movement is also class-specific. Polycarbonate expands at approximately 0.065 mm/m/°C. A 2000 mm panel subjected to a 40 °C temperature rise requires approximately 5.2 mm of expansion allowance. Failure to provide edge clearances of this magnitude leads to buckling, edge abrasion, or fastener pull-out. The panel edge closure must use breathable anti-dust tape and neutral-cure silicone; acetic-acid-cure silicone is incompatible with polycarbonate and can initiate stress cracking around fastener holes.

Wind-load resistance for overhead and vertical glazing is evaluated under EN 16153:2013, but the allowable deflection limit is usually set by the building code, not by the panel alone. A deflection limit of span/20 is common for multiwall glazing in some national annexes; however, the supporting profile and sealant system must be included in the test. Condensation risk in multiwall cavities is a separate design input. Drainage openings must be specified on the order if the panel is to be used in a humid environment; closed cells without drainage can retain moisture and reduce light transmission through algae and mineral deposition.

In machining and machine-guarding orders, the word board typically specifies a solid polycarbonate product with thickness above 12.7 mm and often up to 100 mm. The order should state whether the part is to be supplied as raw stock or as a machined component. Because polycarbonate is notch-sensitive under sustained load, sawed or routed edges in board can become crack initiation sites if the stock was not annealed after thickness reduction. Annealing at 120 °C for a soak time proportional to thickness reduces molded-in stress; some processor schedules use 1 h per 10 mm of thickness, but the required cycle must be validated by crossed-polarizer or solvent-dip inspection. Water absorption at equilibrium under 23 °C and 50 % RH is approximately 0.35 %, which is low but sufficient to alter dimensional stability in precision machined parts. Coolant selection is limited because ketone, chlorinated, and aromatic solvents produce environmental stress cracking in polycarbonate. Machining is typically performed with carbide-tipped tools and positive rake angles; excessive feed force raises local temperature above the glass transition and can create micro-crazes at the cut edge. Mechanical properties for board are similar to sheet: tensile yield stress 60 MPa to 70 MPa, Vicat softening temperature around 145 °C under ISO 306/B50, and continuous service temperature below 120 °C for load-bearing components. The difference lies in the acceptance criterion: board is often ordered for a machined part, so the inspection plan should include flatness after sawing, edge stress, and hole diameter tolerance rather than only optical haze.

Polycarbonate Glazing Test Regimes and Safety-Identification Requirements

Glazing is not a material but a tested and labeled application class. A polycarbonate sheet or multiwall panel becomes glazing only after it has passed the required impact test and carries the appropriate safety markings. In the United States, architectural safety glazing is regulated by CPSC 16 CFR 1201, and safety glazing for building applications is also tested to ANSI Z97.1. In Europe, solid and multiwall polycarbonate sheets for roof and wall applications are covered by EN 16240:2013 and EN 16153:2013, respectively. These standards address dimensional tolerances, weathering, and mechanical properties, but the final structure must also satisfy local building-code reaction-to-fire classification under EN 13501-1.

Accelerated weathering under ISO 4892-2 does not guarantee field service life; it is a comparative test. UV-stabilized polycarbonate grades rely on a coextruded or coated UV-absorbing layer, and installation that orients the unprotected side toward the sun produces premature yellowing and impact loss. Clear uncoated polycarbonate sheet exposed at high UV irradiation can retain only a fraction of its initial notched impact strength after several thousand hours. Published data for this specific configuration is limited because exposure conditions and additive packages vary. For clear 3 mm solid polycarbonate glazing, luminous transmittance is commonly 86 % to 90 % and haze is below 1.5 % under ASTM D1003-13. Multiwall panels are lower in transmittance because of multiple internal reflections; the order should specify total solar transmittance and light transmittance separately if solar control is required.

When an order combines sheet, panel, board, and glazing language in a single line item, the required tolerances become incompatible unless the purchaser separates the terms. A single line item reading “polycarbonate board, clear glazing, 10 mm” does not define whether the product is to be supplied as a certified drop-tested glazing lite or as a machinable stock shape. This ambiguity affects cost and liability. A 10 mm solid sheet may meet the impact resistance of CPSC 16 CFR 1201 in a framed configuration, but the same sheet, when sawed into a board and drilled with untested edge distances, may not retain the original impact rating. The order must specify whether the material is to be supplied with a certificate of compliance, a test report under a named standard, or only as a material property data sheet. If a fabricator performs secondary machining after safety-glazing certification, the certification may be void unless the finished assembly is retested. Procurement documents should therefore separate the material designation from the fabricated part designation and from the safety-glazing designation. Tolerance stack across sawing, machining, and installation can exceed the original sheet thickness tolerance by a factor of three if the flatness and hole-position tolerances are not specified independently.