FDM Part VII Polycarbonates

FDM Polymers — A Technical Reference ›

Part VII — Polycarbonates

Polycarbonate (PC) is the highest-T_g amorphous polymer routinely accessible at the consumer FDM tier — and the polymer most likely to be sold under a name that doesn't describe what's in the spool. Almost every "PC" filament is an alloy or composite, not pure polycarbonate; the engineering envelope and the processing window both depend on which.

15. PC and PC blends — deep dive

Polycarbonate (PC) occupies a specific niche in the FDM polymer hierarchy: amorphous, transparent in its pure form, with T_g ~145–150 °C, HDT around 135–145 °C at 0.45 MPa, tensile yield 60–70 MPa, and high notched-impact resistance on the correct test basis. Neat PC resin can reach roughly 60–85 kJ/m² notched Izod in ductile failure, but many PCTG grades also publish no-break or very high resin-basis impact results; compare impact only when method, specimen type, print orientation, and dry/conditioned state match. PC blends sit lower than neat PC but remain high-toughness FDM engineering materials. It is the engineering workhorse for parts that load at 100–130 °C in service — automotive under-hood brackets, electronics enclosures, optical mounts, structural components. The catch is that pure unmodified PC is rare in commercial FDM filament. The market divides into PC alloys (blended with another polymer at the resin level to reduce warp and shift mechanical balance) and PC composites (compounded with fibers, conductive additives, flame-retardant packages, or PTFE). Choosing between them is the entry-level skill for using "PC" in FDM; printing them well is the next-level skill.

15.1 Polycarbonate chemistry

BPA-polycarbonate (bisphenol-A polycarbonate) is the dominant chemistry — a thermoplastic polyester of carbonic acid condensed with the bisphenol-A diol. The bulky aromatic groups and the carbonate linkage produce a polymer that is amorphous (no crystallinity, full transparency in clear grades, no Schlieren texture), glass-like in mechanical character (high stiffness combined with substantial impact toughness), high-T_g, and processable from 280–320 °C in injection molding. Major Western branded resins underlie much of the commercial PC filament market: Covestro Makrolon, SABIC Lexan, Mitsubishi Iupilon, and Trinseo Calibre — with Teijin, LG Chem, Lotte, and Wanhua now also among the largest global PC producers. Filament TDS rarely identify the base resin; differences in molecular weight, additive packages, and (for alloys) the partner polymer account for most brand-to-brand variance in printed performance.

BPA itself is a regulated monomer with documented endocrine-disruption concerns at consumer-exposure levels. In finished polymer form only trace unreacted monomer remains, which is the relevant context for printed-part safety — effectively negligible for printed surfaces, but worth flagging for risk-communication purposes when end users ask. For applications where BPA is a regulatory or perceptual concern, Eastman Tritan (a TMCD-rich terpolymer marketed as a polycarbonate substitute, covered in Chapter 8) offers hydrolytic stability superior to PC (which hydrolyzes in hot water) at the cost of a substantially lower HDT (~95–110 vs ~135–145 °C), without using BPA. Tritan-class resin carries food-contact certification at the resin level — but, as §8.9 stresses, that certification does not transfer to a printed part: FDM layer lines harbor contamination and hotend residue, so any food- or medical-contact use requires sealing and its own qualification regardless of the resin's pedigree.

15.2 The PC labeling problem (deepening §2.4)

Part I §2.4 introduced the principle: "PC" on a filament label is almost always an alloy or composite. The detail matters for procurement and process planning.

PC alloys blend PC with another polymer at the resin level. The partner polymer raises one property at the expense of another. PC/ABS is the dominant alloy: ABS lowers T_g and HDT, lowers room-temperature notched impact relative to neat PC while improving low-temperature impact and reducing notch sensitivity (the butadiene phase absorbs energy), reduces warp during cooling, improves processability, and lowers cost. The trade is well-balanced for general-purpose engineering work. PC/PBT is the second-most-common alloy: PBT is a semi-crystalline polyester; the alloy retains PC's stiffness and high T_g while adding chemical resistance and crystallinity-driven impact retention. The alloy carries a T_m value on its TDS (typically 220–230 °C from the PBT phase) where pure PC does not. PC/ASA combines PC's heat resistance with ASA's UV stability; relevant for outdoor parts but rare in commercial filament. PC/PCTG retains PC transparency and stiffness while adding PCTG's toughness; rare, and rarely announced.

PC composites compound PC with a filler or additive. PC-CF and PC-GF add stiffness and HDT at the cost of brittleness and abrasion. ESD-PC with conductive additives (carbon nanotubes or specialty carbon black) drops surface resistivity into the electrostatic-dissipation range. FR-PC with flame-retardant packages targets UL94 V-0 compliance. PC/PTFE with PTFE compounded in provides low-friction surfaces for wear applications.

Filament TDSs typically disclose "PC blend" (alloy with partner unnamed) or "PC + N% [filler]" (composite with the loading specified). The mechanical envelope, processing window, and printability all depend on which approach was used. Prusament PC Blend, Bambu PC, and PolyMax PC — the three most well-documented general-purpose PC products on the consumer market — are all alloys with undisclosed partner polymers; Polymaker's PC-ABS and PC-PBT, by contrast, name their alloy partners explicitly.

15.3 General-purpose PC blends

This is the consumer default for "I need PC behavior on prosumer hardware." Mechanical envelope: tensile yield ~40–65 MPa across the category — PC-dominant blends at the top, PC/ABS and PC/PBT alloys lower (Table 15.1) — below pure PC's 60–70, T_g 109–145 °C depending on the alloy partner, HDT @ 0.45 MPa 95–145 °C. Print at 260–290 °C nozzle, 100–115 °C bed, enclosed chamber strongly recommended (passive 40–50 °C adequate for most parts up to ~150 mm; active chamber preferred above that). Brass nozzles wear acceptably on unfilled PC blends. The category includes:

Product	Class	Tg(°C)	HDT @ 0.45 MPa (°C)	Tensile yield (MPa)	Notes
Prusament PC Blend	PC alloy (partner not disclosed)	—	113	63	Most widely-documented consumer PC; published printed-specimen data
Bambu PC	PC (alloy-tuned for lower shrinkage)	145	112	55	Active chamber 45–60 °C specified; glue plate; dry before printing
PolyMax PC	Engineered PC alloy (partner not disclosed)	113	—	53.4	Anneal recommended at 90 °C for 2 h for stress relief
Polymaker PC-ABS	PC/ABS alloy (explicit)	109	—	40	Vicat 135 °C; entry-level toughness; lowest cost in family
Polymaker PC-PBT	PC/PBT alloy (explicit)	140	—	42	Crystallizing alloy; Tm 223 °C on TDS; chemical resistance step-up
AzureFilm PC-ABS	PC/ABS alloy	—	120	—	Automotive-positioning; budget tier

_{Table 15.1 — General-purpose consumer PC blends. The Tg spread from 109 °C (Polymaker PC-ABS) to 145 °C (Bambu PC) reflects the alloy-partner choice directly: more ABS lowers Tg, more PC raises it. Procurement note: tensile values from Polymaker products and Prusament (63 MPa, published as tensile yield per ISO 527-1) are XY printed-coupon yield figures, while Bambu values are XY tensile strength — not directly comparable as written. Always cross-check the TDS test method before ranking products on tensile.}

15.4 PC-CF and PC-GF composites

Fiber-reinforced PC raises stiffness, HDT, and dimensional stability — and lowers warp tendency on long flat parts where unfilled PC's thermal-contraction stress dominates — at the cost of brittleness, abrasion, and substantially compromised Z-strength. Loading is typically 10–30 wt%.

Product	Filler	HDT @ 0.45 MPa (°C)	Tensile yield (MPa)	Notes
Prusament PC Blend CF	~10–15% CF (loading not disclosed)	114	64	Hardened nozzle advised; matches Prusament PC Blend on Tg with stiffness gain
Spectrum PC CF	10% CF	140	76	Vicat 150 °C; dry box yes; hardened nozzle
Ultrafuse PC GF30	30% glass fiber	134	36	Tg 142 °C; very stiff; lower elongation; abrasive; drying 100 °C / 4–16 h; vendor nozzle window 280–330 °C exceeds the Table 15.6 family range
3DXTech CarbonX PC-CF	~15% CF	~140	—	US industrial line; ISO 9001; hardened nozzle mandatory

_{Table 15.2 — Reinforced PC composites. The Ultrafuse PC GF30 tensile-yield value of 36 MPa is notable: it appears lower than the unfilled PC Blend (~60 MPa) because FDM-specific voids and weak inter-bead interfaces initiate failure before the material can yield — molded PC-GF30 is far stronger than unfilled PC — so the reported "yield" is effectively a printed break-strength value. Modulus and HDT are the relevant engineering numbers for these grades, not yield strength. Picking GF30 for tensile applications misreads the data.}

15.5 ESD-safe PC

PC in its native form is electrically insulating, with surface resistivity commonly on the order of 10¹⁵ Ohm/sq (use the current TDS for engineering decisions). For electronics housings, IC handling fixtures, ESD-sensitive workspace tooling, and certain aerospace applications, ESD-grade PC is compounded with conductive additives (multi-wall carbon nanotubes or specialty carbon black) to drop the surface resistivity into the electrostatic-dissipative target range, commonly about 10⁴–10⁹ Ohm/sq or a vendor-specific dissipative band.

Product	Conductive additive	Surface resistivity	HDT @ 0.45 MPa (°C)	Notes
3DXTech 3DXSTAT ESD-Safe PC	Conductive carbon (CNT-class)	>106–109 Ohm/sq (IEC 60093)	135	Tg 143 °C; hardened nozzle mandatory; the consumer-tier ESD-PC default
Prusament PC Space Grade Black	Carbon-based additives (CNT-class)	ESD-dissipative range (TDS-published)	137.6	Specialty tier; published low-outgassing metrics; hardened nozzle required; price premium reflects qualification testing rather than performance step-up

_{Table 15.3 — ESD-safe PC filaments accessible to consumer users. CNT-loaded filaments are mildly abrasive — less so than chopped-fiber grades — but hardened nozzles are still recommended for production volumes; PCD or ruby nozzle tips extend service life on these materials. The Prusament Space Grade price premium (~$269/kg vs ~$50/kg for the standard PC Blend) is a procurement decision rather than a performance one — buy it for the documented outgassing data, not the HDT.}

15.6 Flame-retardant PC and PC/ABS-FR

For enclosures near ignition sources, electronics housings subject to UL approval, transit and rail-vehicle applications, and other safety-critical work. FR additives — typically halogen-free phosphorus-based or sulfonate packages — lower flammability ratings to UL94 V-0 (self-extinguishing within 10 seconds of flame removal, no flaming drips). The trade-off matters: in PC/ABS-FR systems the phosphorus-based FR package plasticizes the alloy, lowering T_g and HDT by 30–50 °C compared to pure PC, while straight-PC FR grades can hold T_g essentially unchanged (Bambu PC FR, 145 °C — Table 15.4).

Product	Class	FR rating	Tg(°C)	HDT @ 0.45 MPa (°C)	Notes
Forward AM Ultrafuse PC/ABS FR Black	PC/ABS + halogen-free FR	UL94 V-0; EN 45545-2:2016 R26 (EL10), HL1–HL3 at 1.5/3.0 mm	94	86	Rail-vehicle certifications make this the procurement default for transit work; verify the R-set against the application's requirement
Spectrum PC/ABS FR V0	PC/ABS + halogen-free FR	UL94 V-0	—	— (HDT @ 1.8 MPa: 90)	Vicat 104 °C; print 240–265 °C; enclosure recommended for larger parts
Bambu PC FR	PC + FR (halogen content not disclosed)	UL94 V-0 (claim)	145	113	Highest Tg in the FR-PC category; FR additive package not detailed in TDS

_{Table 15.4 — Flame-retardant PC and PC/ABS filaments. The Tg spread (94 °C for Ultrafuse vs 145 °C for Bambu PC FR) is the key engineering signal: the spread is driven first by the base polymer — Ultrafuse is a PC/ABS alloy while the Bambu product is a straight PC — and only secondarily by the FR chemistry; FR compliance and maximum operating temperature remain competing goals within a given base polymer. Pick by certification first (which standard does your application require?), then by thermal envelope.}

15.7 PC/PTFE (low-friction wear surfaces)

PC matrix compounded with PTFE for low-friction sliding surfaces — bushings, guides, wear plates, mechanical interfaces where COF matters. The PTFE phase lowers the coefficient of friction and the wear rate against itself and against metal counterfaces; the PC matrix carries the structural load.

Spectrum PC/PTFE is the most widely available commercial product in this niche, with HDT 140 °C (annealed) and tribological metrics published on the TDS. Print at 265–295 °C nozzle, 90–120 °C bed, with chamber recommended and Magigoo PC adhesive specified by the manufacturer.

Hotend material constraint. PTFE decomposition is a graded process, not a single threshold: fluoropolymer SDS data and NIOSH/PlasticsEurope guidance describe particulate fume release and polymer-fume-fever risk becoming relevant around 300–350 °C, active pyrolysis near 400 °C, and the more hazardous gases — hydrogen fluoride and carbonyl fluoride — appearing at higher temperatures still, roughly 400 °C and above (see §5.3). PC/PTFE filaments process at 265–295 °C nozzle — stay at the low end, since the margin to fume onset is minimal at the top of the range — which is still well above the safe temperature for PTFE-lined hotends (PTFE liners soften and outgas above ~240–250 °C even before decomposition becomes a concern). PC/PTFE printing requires an all-metal hotend without exception; this is the single most common process-incompatibility error on this filament.

15.8 Consolidated property envelope

Across the four product categories above, the property envelope spans a range wide enough that "PC" as a generic spec is operationally meaningless. The table below collects the headline numbers from each category for direct comparison. Every figure inherits the datasheet-reading caveats consolidated in §22.4 — printed-part stiffness lands below TDS values, heat figures depend on the test behind them, and the brand variance documented in Table 15.8's caption dominates the category labels.

Category	Tg range (°C)	HDT @ 0.45 MPa (°C)	Tensile (MPa)	Nozzle (°C)	Best for
General-purpose PC blend	109–145	95–145	40–65	260–290	Default engineering work, electronics enclosures, brackets to 100 °C service
PC-CF / PC-GF composite	~113–142+	114–140	36–76	275–300	Stiff brackets, fixtures, jigs to 130 °C service; structural parts
ESD-PC	143	135–138	55–70	270–300	Electronics housings, IC handling, ESD-sensitive workspaces, space hardware
FR-PC / PC/ABS-FR	94–145	86–113	n/p (Table 15.4)	240–280	Safety-critical enclosures, transit/rail-certified parts, UL-rated electronics
PC/PTFE	—	140 (annealed)	55	265–295	Low-friction bushings, guides, wear surfaces; all-metal hotend required

_{Table 15.5 — PC family consolidated envelope. The Tg range column captures the single most consequential procurement variable across the category: a 50 °C swing on Tg reshapes the service-temperature envelope completely. Specifying "PC" without specifying which sub-category is the most common procurement error in this polymer family — easy to make on a parts BOM, hard to recover from in a production setting.}

15.9 Print process and calibration

PC family parameters vary more by sub-category than within any single one. The starting points below assume a 0.4 mm hardened-steel nozzle (PC Blend tolerates brass; everything fiber- or CNT-loaded does not) and an enclosed build space.

Parameter	PC Blend	PC-CF / PC-GF	ESD-PC	FR-PC	PC/PTFE
Nozzle (°C)	260–290	275–300	270–300	240–280	265–295
Bed (°C)	100–115	100–115	110–120	90–110	90–120
Chamber	passive 40–50 °C	passive 40–50 °C	passive 45–60 °C	passive 40–50 °C	active 45–55 °C
Part cooling (%)	0–10	0	0	0–10	0
Max volumetric (mm3/s)	8–12	6–10	7–10	8–11	6–9
Pressure advance	0.025–0.05	0.035–0.06	0.030–0.05	0.030–0.05	0.030–0.05
Nozzle hardness	brass OK	hardened mandatory; PCD/ruby preferred	hardened mandatory; PCD/ruby preferred	brass OK; hardened on FR-CF variants	hardened recommended
Drying	80–100 °C, 6–8 h	90–110 °C, 8–10 h	80–100 °C, 6–8 h	60–80 °C, 4–16 h	80–100 °C, 6–8 h
Hotend type	all-metal	all-metal	all-metal	all-metal	all-metal only

_{Table 15.6 — PC family starting print parameters. The hotend-type row is the most overlooked spec: PTFE-lined Bowden-style hotends rated to 240 °C are ubiquitous on Tier 1 hardware and will outgas or degrade at PC processing temperatures regardless of nozzle wear, before any process tuning has a chance to matter. Per-spool calibration on the actual machine remains mandatory; the values above are polymer-chemistry starting points.}

Moisture is the second-most-impactful variable. PC absorbs 0.3–0.5% water at saturation; PC-CF and PC-GF slightly less at saturation — carbon and glass fibers are non-hygroscopic, so equilibrium uptake scales with the matrix fraction — though uptake can be faster along fiber–matrix interfaces. Moisture symptoms: stringing despite tuned retraction, surface roughness, audible "sizzle" or popping in the melt zone, and compromised interlayer bonding. Active drying before every serious print is the standard for engineering work; the Part I §3.5 drying table specifies PC at 80–100 °C for 6–8 h and the reinforced grades at 90–110 °C for 8–10 h. Dry-box storage during printing extends the printable window for opened spools.

15.10 Bed adhesion strategy

PC presents the opposite problem from polypropylene: PC adheres too strongly to smooth PEI when properly hot. The grip is sufficient to tear the spring steel sheet or pull PEI fragments away from the magnetic substrate during part removal. Strategy depends on print volume and how often the surface switches between PC and other materials.

Surface	PC compatibility	Adhesion strategy	Notes
Smooth PEI	Over-grips; sheet damage on removal	Glue stick, PVP coating, or Magigoo PC as release layer	Standard prosumer plate; release layer is non-negotiable for engineering parts
Textured PEI	Acceptable; reduced grip	Bare for small parts; Magigoo PC for larger	Less likely to damage on removal; cosmetic surface texture transfers to first layer
G10 garolite	Best long-term solution	Bare; bed 100–115 °C; cool fully before removal	Engineering default for repeated PC printing; zero adhesive residue; durable across many prints
CryoGrip Glacier	Unverified for PC — BIQU does not list PC compatibility	Community-reported bare at bed 90–100 °C, near the plate's rated limit	Frost-effect engineered sheet; cold-release on cool-down; treat as experimental for PC
Glass / borosilicate	Marginal	Magigoo PC mandatory	Works but releases unpredictably; not the engineering choice
Polycarbonate sheet	Over-grips catastrophically	Do not use	PC-on-PC bonding is mechanically inseparable on cool-down

_{Table 15.7 — Bed adhesion strategies for PC family materials. G10 garolite is the engineering default for production PC work because its surface chemistry grips PC during printing and releases cleanly on cool-down without consumable adhesives — a workflow advantage that compounds over many prints.}

The cost case for garolite is concrete. Standard spring-steel PEI plates damaged by over-grip during PC removal cannot be repaired; replacement runs $30–60 per sheet and is the dominant ongoing cost of running PC on PEI without a release layer.

15.11 Annealing

PC is amorphous; annealing does not change crystallinity (there is none). What annealing does for PC is relieve residual stress from rapid layer cooling — useful for parts with thick walls, sharp corners, or geometric stress concentrators where as-printed residual stress would otherwise cause delayed cracking. The dimensional cost is modest: typical PC parts shrink 0.3–0.5% during a stress-relief anneal.

Common vendor schedules: PolyMax PC 90 °C for 2 h (stress relief); Bambu PC and PC FR 85–100 °C for 6–12 h. The temperature must stay below T_g by ~10–15 °C to avoid distortion in thin walls — 100 °C is the practical upper bound for most consumer PC blends despite the T_g being 109–145 °C. Cool slowly (switch oven off, leave the part inside until ambient) to avoid trapping new stress. The PC/PBT alloy (Polymaker PC-PBT) is the exception: the PBT phase is semi-crystalline and responds to annealing similarly to other semi-crystalline polymers, with HDT and stiffness gains beyond simple stress relief. Schedule per the vendor TDS for that product specifically.

15.12 Brand landscape (consumer-accessible)

The consumer-accessible PC market clusters around eight vendors with well-documented engineering-grade SKUs. Sealed-cartridge industrial PC materials (Stratasys PC-ABS and PC-ESD, locked to Fortus/F-series printers) are out of scope per the Part I §1.2 prosumer-tier framing.

Brand	Catalog	Distinguishing notes
Prusament (Prusa Polymers)	PC Blend; PC Blend Carbon Fiber; PC Space Grade Black	Three-tier line from consumer engineering through space-qualified specialty; published printed-specimen data; the most-documented consumer PC brand
Bambu Lab	PC; PC FR	Tuned for reduced shrinkage; specifies chamber 45–60 °C; FR variant carries UL94 V-0 claim; mainstream consumer pricing
Polymaker	PolyMax PC; PolyLite PC; PC-ABS; PC-PBT	Engineered alloys with partner polymers named on the TDS for PC-ABS and PC-PBT; PolyMax PC is the unnamed alloy in the consumer tier
Forward AM (BASF)	Ultrafuse PC/ABS FR Black; Ultrafuse PC GF30	Rail-vehicle FR certification (EN45545-2) on the FR product; GF30 is the stiffest commonly-available PC composite at the consumer tier
3DXTech	3DXSTAT ESD-Safe PC; CarbonX PC-CF	US industrial line; ISO 9001 manufacturing; ESD product is the consumer-tier ESD-PC default; price 1.5–2× consumer equivalents
Spectrum Filaments	PC CF; PC/PTFE; PC/ABS FR V0	European industrial line; the only consumer-accessible PC/PTFE product; halogen-free FR formulation
AzureFilm	PC-ABS	Budget tier; automotive positioning; published HDT 120 °C
Nanovia	PC family (PC-CF and PC-ABS variants)	French specialty manufacturer; product documentation requires distributor access; mechanical envelope places products in the engineering tier

_{Table 15.8 — Consumer-accessible PC brand landscape (early 2026). Prusament, Bambu, and Polymaker dominate consumer-tier shelves and account for the majority of community-shared print profiles. Forward AM Ultrafuse and 3DXTech are the engineering-qualification defaults. Spectrum's PC/PTFE is the only consumer access point for that specific composite chemistry. Brand cross-substitution within a sub-category (e.g., Prusament PC Blend vs Bambu PC) is not free — the alloy partner differs even when neither brand names it, and the printed envelope can shift 10–20% on tensile and substantially more on Tg.}

15.13 Application fit

Choose general-purpose PC blend when: the part loads mechanically at service temperatures 80–120 °C (engine-bay components away from direct heat, electronics housings in warm environments, machine guards near motors); the selected PC blend's printed notched-impact performance is required and has been compared against PETG/PCTG on the same test basis; the part will be solvent-bonded or vapor-finished (PC responds well to dichloromethane bonding for engineering joints, with the handling caveats of §5.3); cost and printability outweigh the maximum thermal envelope.

Choose PC-CF or PC-GF when: the part needs the stiffness of a metal-replacement filament without crossing into PPA territory on cost or process discipline; HDT to 140 °C is required; dimensional stability under load matters more than impact toughness; the design uses fiber-aligned geometry where Z-strength is not the binding constraint. PA6-CF (Chapter 13) is the alternative if moisture is well-controlled and higher impact toughness is needed; PPA-CF (Chapter 14) is the alternative if moisture is uncontrolled or service temperature exceeds PC's ceiling.

Choose ESD-PC when: the application requires surface resistivity in the 10⁴–10⁹ Ohm/sq range, or the dissipative band specified by the applicable standard, with PC-class structural performance — electronics handling fixtures, IC-test jigs, semiconductor tooling. The Prusament Space Grade product additionally addresses vacuum-service outgassing for space-hardware work.

Choose FR-PC when: certification (UL94 V-0, EN45545 for rail, equivalent for aerospace) is in scope. Pick by certification standard first; the thermal envelope follows.

Avoid the PC family when: the part loads outdoors for long durations (BPA-PC yellows under UV; ASA is the right answer); food contact is in scope (BPA migration concerns; a copolyester — PCTG, or Tritan-based filament — is the alternative, subject to the §8.9 caveat that resin-level food-contact status does not transfer to printed parts); service temperature stays below 80 °C and impact toughness is not the binding constraint (PCTG saves 30–40% on filament cost and prints more reliably); the part requires fatigue resistance under cyclic load (PC notch-cracks; PA612 and PA11 from Chapter 13 retain ductility better).

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