Polycarbonate (PC) covers a polymer family defined by carbonate ester linkages in the backbone, and only the aromatic subclass — predominantly bisphenol-A polycarbonate — has reached industrial scale as a structural engineering thermoplastic [S1][S3].
Aliphatic and aliphatic-aromatic polycarbonates exist but stay confined to low-mechanical, high-biocompatibility roles such as drug-release carriers, surgical sutures, and bone-support scaffolds, where their low melting points and glass-transition temperatures disqualify them from load-bearing service [S3]. This split — one commercial workhorse, two specialty branches — sets the classification logic used through the rest of this spec map.
Chemical-structure taxonomy: aromatic, aliphatic, aliphatic-aromatic
The first classification cut sits at the ester-group structure: aromatic PC (the bisphenol-A type), aliphatic PC, and aliphatic-aromatic PC each carry different backbone geometries that translate directly into mechanical performance [S1][S3].
Bisphenol-A PC is described as a linear polycarbonate polyester where carbonate groups alternate with other groups along the chain; the standard synthesis routes from bisphenol-A and phosgene (COCl₂) or via melt transesterification with diphenyl carbonate, producing an almost colourless glassy amorphous polymer with an Izod notched impact strength of 600–900 J/m for high-molecular-weight grades [S3]. Aliphatic grades such as polyethylene carbonate and polytrimethylene carbonate have low melting points, low glass-transition temperatures, and poor strength — explicitly ruled out as structural materials — but their biocompatibility and biodegradability earn them a place in controlled-drug-release carriers, surgical sutures, and bone-support implants [S3]. Aliphatic-aromatic PC sits between these two, with mechanical performance also too low for engineering plastics duty [S1]. Because the three sub-families target different duty cycles, spec sheets almost always pin the aromatic BPA grade as the default and call out aliphatic grades only when biodegradability is a procurement requirement.
Modified-PC functional grades: flame, UV, glass-filled, food-contact, antistatic
Beyond the base resin, the market segments modified PC into functional grades that bundle specific certifications or property packages: anti-static PC, conductive PC, glass-fibre-reinforced flame-retardant PC, UV/weather-resistant PC, food-grade PC, and chemically resistant PC [S3].
Flame behaviour: unfilled bisphenol-A PC achieves UL 94 V-2 rating without additives in some references and V-0 in others, with flame-retardant BI grade also cited — selection between V-0, V-2, and 5VA depends on the wall thickness tested (often 1.5 mm and 3.0 mm) and the end-equipment standard such as IEC 60695 or UL 746C [S3]. Glass-fibre reinforcement raises heat-deflection temperature by roughly 10°C over the base ~130°C figure, taking glass-filled grades into the 140°C band and pushing the UL temperature index up to 120–140°C for the reinforced compound [S3]. UV-resistant grades address PC's known yellowing under prolonged ultraviolet exposure, and food-contact grades respond to regulatory limits on bisphenol-A leachates in food and water-contact articles [S2][S3]. For procurement, the decision rule is: pick the base resin (BPA aromatic), then layer functional certification (UL yellow card, FDA/EU food contact, IEC 60695 flame, ISO 4892 UV) — not the other way around.
Key physical, thermal, and electrical spec bands
The published numeric envelope is narrow enough to be useful: density 1.18–1.22 g/cm³ (also listed as 1200 kg/m³), linear expansion coefficient 3.8×10⁻⁵ cm/°C, heat-deflection temperature 130–135°C, low-temperature limit around −45°C, dielectric constant 3.0–3.2, and arc resistance 120 s [S3].
Mechanical benchmarks separate PC from the acrylics it competes with: PC has a flexural modulus above 2400 MPa and creep rate below 100°C that stays low under load, versus polymethyl methacrylate (PMMA) which is cheaper and easier to cast into large parts but markedly worse on impact [S3]. For comparison, PC's high-molecular-weight grades hit Izod notched impact 600–900 J/m while standard ABS sits roughly an order of magnitude lower — a gap that explains why PC replaces ABS in laptop housings, router shells, and meter covers where the same mould needs higher heat and impact [S2][S3]. Three constraints engineers must respect: (1) PC hydrolyses at high temperature in humid environments and is unsuitable for repeated high-pressure steam service; (2) PC is notch-sensitive, so wall transitions need generous radii; (3) PC is attacked by strong alkalis and several organic solvents, which is why chemical-resistant grades get a separate designation rather than relying on the base resin [S2][S3].
PC alloys and blends: where the spec envelope actually moves
PC alloys are produced by physical blending or chemical grafting to push specific properties — high heat, chemical resistance, flow, or low-temperature ductility — beyond what neat PC delivers [S2].
The common commercial families in the alloy space, each with a clear engineering target: PC/ABS (best flow and low-temperature impact for laptop and printer housings, also documented as the material behind early iBook and iPod shells), PC/PBT (chemical and fuel resistance for under-bonnet connectors and pump housings), PC/PMMA (higher surface hardness and UV stability for automotive interior trim), and PC/PET (glass-fibre reinforced, balanced stiffness and heat for structural brackets) [S2]. PC is also blended with polyester pellets extruded from petroleum-derived PET; in finished mouldings the difference shows up as heat dissipation — PC spreads heat more evenly than ABS, the trade-off being a more brittle failure mode on impact [S2]. For an engineer choosing between an alloy and a modified-PC grade, the rule of thumb is: pick an alloy when the property gap (flow, chemical resistance, surface hardness) is too wide to close with fillers, and pick a modified grade (glass-filled, flame, UV) when the gap can be closed inside a single-phase PC system. The broader polymer comparison in PA 6,6 vs PC selection logic is a useful cross-reference for the same heat-impact-stiffness decision.
Industrial applications and the capacity baseline
The three largest application sectors are glazing, automotive, and electrical/electronics, followed by industrial machinery parts, optical media, packaging, and medical devices [S3].
By sector volume: in developed-market consumption patterns, electrical/electronics and automotive together account for roughly 40%–50% of PC use, while in China at the time of the cited baseline the same two sectors sat near 10% — a gap that framed the projected demand uplift [S3]. China-specific capacity notes list 20-plus hollow-sheet extrusion lines consuming about 70 kt of PC per year for construction, projected to roughly double to 140 kt by 2005 [S3]. Global production capacity tracked in the same source moved from 1.85 Mt in 2000 to 2.20 Mt in 2001, 2.65 Mt in 2002, 2.75 Mt in 2003, with forecasts of 2.90 Mt in 2004 and 3.25 Mt in 2005 — a roughly 12% CAGR over the period [S2]. Representative downstream uses cited: CDs/DVDs (the dominant optical-media format), eyeglass lenses, reusable water bottles, bullet-resistant and riot-control glazing (banks, embassies, detention centres), aircraft canopies, headlamp lenses, instrument panels, helmet face shields, medical device housings sterilised by gamma irradiation, and kidney-dialyser components [S2][S3]. For sensor and instrumentation housings where PC and industrial PC enclosures overlap as material/process terms, the spec is usually an FR grade with a documented UL yellow card.
Comparison matrix: aromatic PC vs aliphatic PC vs PC/ABS vs PMMA
The selection trade-off lines up cleanly on four engineering criteria — use it as a quick reference when a spec sheet only lists two of the four properties.
Decision criteria: (1) notched impact strength; (2) heat-deflection temperature; (3) chemical/UV resistance; (4) processability and cost. Aromatic BPA PC: impact 600–900 J/m, HDT ~130–135°C (≈140°C glass-filled), moderate UV resistance (yellowing without stabiliser), good injection mouldability, mid-to-high cost [S3]. Aliphatic PC: impact too low for structural use, HDT well below the aromatic grade, biodegradability is the differentiator, cost high for biomedical grades [S3]. PC/ABS alloy: impact below neat PC but well above ABS alone, HDT typically 100–110°C, better flow and surface finish, lower cost than neat PC [S2]. PMMA: impact a fraction of PC (the comparison repeated across sources), HDT similar, better UV and scratch behaviour than PC, lowest cost of the four, castable into large parts [S2][S3]. The verdict in plain terms: structural transparent part with impact priority → aromatic PC; biocompatible scaffold with degradation priority → aliphatic PC; opaque housing needing flow and surface finish → PC/ABS; large clear panel with cost priority and low impact risk → PMMA.
Limitations, failure modes, and what the base resin will not do
PC's spec sheet hides a short list of disqualifying weaknesses that drive most of the alloy and modification work in the industry.
Documented failure modes: hydrolytic degradation at elevated temperature in humid environments (rules out repeated autoclave and high-pressure steam service), notch sensitivity that demands generous fillet radii at wall transitions, organic-solvent stress cracking (ketones, esters, aromatic hydrocarbons), strong-alkali attack, and progressive yellowing plus loss of impact under prolonged UV exposure without stabiliser [S2][S3]. The bisphenol-A leachate issue is the other constraint that keeps food-contact and drinking-water grades under separate regulatory regimes — over 100 published studies are cited in [S2] examining BPA migration, and the recommended practice is to avoid sodium-based and other alkaline cleaners on PC food-contact articles to prevent accelerated BPA release [S2]. For procurement, this means a resin qualified to the same UL yellow card and FDA/EU food-contact listing can still be disqualified at the equipment level by a cleaning-agent spec — surface chemistry has to be checked against the maintenance procedure, not just the datasheet.
Trackable signals to watch on the next spec revision: UL yellow-card updates for 5VA flame ratings at 1.5 mm wall, EU food-contact listing changes for BPA-derived PC in contact with hot liquids, and any published revision to ISO 7823 (PC sheet performance classes) that would re-tier the glazing grades cited above.
The underlying component specifications are covered under polycarbonate, and pressure transmitter.