RpProto offers all materials meeting UL94V0 standards for rapid prototyping and production for CNC machining (ABS and PC), vacuum casting (Hei-cast 8260) and injection molding. UL94 materials allow machined or thermoplastic molded plastic parts to pass real-world testing as they can be used in environments containing flammable products.
UL 94 rating is the most commonly used standard for flammability of plastic materials. Used to evaluate the ability of a material to extinguish once ignited. The standard classifies plastics in six different classes, from least flame retardant to most flame retardant, according to their burning behavior in different directions and part thicknesses.
There are many evaluation methods depending on the burning speed, burning time, anti-drip ability and whether the dripping beads burn. Each measured material can have many values depending on its color and thickness. When choosing a material for a product, its UL rating must meet the wall thickness requirements of plastic parts. A UL rating must be specified along with a thickness value.
Introduction to UL 94 Flame Ratings
The UL 94 standard — formally titled Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances — is published by Underwriters Laboratories and covers six classifications, ordered from least to most flame-retardant:
HB (Horizontal Burn) — The lowest flammability rating. For specimens 3–13 mm thick, the burn rate must be below 40 mm/min; for specimens under 3 mm thick, below 76 mm/min, or the flame must extinguish before reaching the 100 mm mark.
V-2 (Vertical Burn) — After two 10-second flame applications, the flame must extinguish within 30 seconds. Flaming drips that ignite a cotton indicator below the specimen are permitted.
V-1 (Vertical Burn) — After two 10-second flame applications, the flame must extinguish within 30 seconds. No flaming drips; non-flaming drips are permitted.
V-0 (Vertical Burn) — After two 10-second flame applications, the flame must extinguish within 10 seconds. No flaming drips; non-flaming drips are permitted.
5VB (5-Flame Vertical/Plaque) — Five 5-second flame applications on vertical specimens; flame must extinguish within 60 seconds. No flaming or non-flaming drips. A separate plaque test is conducted but burn-through is permitted.
5VA (5-Flame Vertical/Plaque — Highest) — Same flame application procedure as 5VB. Flame must extinguish within 60 seconds. No drips of any kind. The plaque specimen must not burn through.
Full rating comparison table
| Rating | Test orientation | Max burn time (per flame app.) | Flaming drips allowed? | Non-flaming drips allowed? | Plaque burn-through? |
|---|---|---|---|---|---|
| HB | Horizontal | Burn rate <76 mm/min (≤3 mm) <40 mm/min (>3 mm) | N/A | N/A | N/A |
| V-2 | Vertical | 30 seconds | Yes | Yes | N/A |
| V-1 | Vertical | 30 seconds | No | Yes | N/A |
| V-0 | Vertical | 10 seconds | No | Yes | N/A |
| 5VB | Vertical + plaque | 60 seconds | No | No | Permitted |
| 5VA | Vertical + plaque | 60 seconds | No | No | Not permitted |
Important: Every UL 94 rating must be paired with a specific thickness value. A material datasheet listing “V-0 @ 3.0 mm” does not guarantee V-0 performance at 1.5 mm. Always confirm the certificate covers your part’s minimum wall thickness.
How to Choose a UL Rating for Different Wall Thicknesses
Wall thickness is arguably the most overlooked variable when specifying flame-retardant plastics. As thickness decreases, a material’s flame-retardant additives become less effective per unit cross-section — the same resin can drop from V-0 to V-2 simply by thinning the wall. The table below maps common part thickness ranges to the rating typically achievable, using materials available at RpProto.
| Wall thickness range | Achievable rating (typical) | Recommended process & material | Design note |
|---|---|---|---|
| < 0.8 mm (0.031″) | HB only in most resins | Vacuum casting — PT 8952 Urethane or specialized thin-wall FR grades | Avoid unless regulations permit HB. Increase wall or redesign to add ribs. |
| 0.8–1.5 mm (0.031–0.059″) | V-2 / V-1 | Vacuum casting — Hei-Cast 8263; Injection molding — Bayblend FR110 (ABS/PC) | Suitable for non-critical housings. Specify V-1 to prevent flaming drip risk. |
| 1.5–3.0 mm (0.059–0.118″) | V-0 | CNC machining — ABS (Polylac PA-765); Vacuum casting — AXSON PX330 or Hei-Cast 8263 | The most common range for electronic enclosures and appliance housings. |
| 3.0–6.0 mm (0.118–0.236″) | V-0 / 5VB | CNC machining — PC (Lexan 940); Injection molding — PPS Ryton R-4, PEEK Victrex 450G | High-performance resins can reach 5VB at this range. Verify with UL Yellow Card. |
| > 6.0 mm (0.236″) | 5VA | CNC machining or injection molding — PPSU Radel R-5000, PPS 40% GF (Ryton R-4) | Structural panels and thick-wall enclosures for high-voltage or industrial use. |
Higher-performance resins required. Standard FR grades may not certify. Always validate at the actual part thickness — not the nominal UDS thickness on the datasheet.
The sweet spot for most V-0 materials. The widest material selection is available here, including economical ABS and ABS/PC blends.
5VB and 5VA become achievable. High-glass-fiber-filled engineering resins (PPS, LCP, PEEK) perform best at structural thicknesses.
Effect of colorants and additives on UL rating
A UL 94 certification applies to a specific formulation at a specific color and thickness. Adding a colorant, UV stabilizer, or processing lubricant — even in small amounts — can alter the base resin’s flame-retardant performance and void the listing. Key rules to follow:
- Always use a pre-compounded FR blend that carries its own UL Yellow Card for the actual color you need.
- If custom color-matching is required, work with a certified compounder to reformulate and test the blend at part thickness.
- Glass-fiber fillers generally maintain or improve FR ratings; rubber-impact modifiers and plasticizers tend to lower them.
- Black colorants (carbon black) can improve V-0 performance; lighter pigments vary significantly by chemistry.
UL 94 V-0 Rated Materials Available at RpProto
RpProto stocks certified flame-retardant materials across all three major prototyping and low-volume production processes. All materials listed below have certified UL 94 V-0 performance and are available for immediate quoting.
Vacuum casting (urethane casting) — V-0 materials
| Material | UL 94 Rating | Key properties | Typical applications |
|---|---|---|---|
| AXSON PX330 | V-0 | ABS-like, paintable, good impact resistance | Consumer electronics housings, control panels |
| Hei-Cast 8263 | V-0 | Rigid polyurethane, good surface finish, low shrinkage | Electrical enclosures, industrial equipment covers |
| BJB TC-891 FR | V-0 | High stiffness, low halogen content | Medical device housings, aerospace interior brackets |
| PT 8952 Urethane | V-0 | Flexible-to-semi-rigid, good tear strength | Cable management, gaskets, flexible covers |
Injection molding — V-0 materials
| Resin family | Grade / Trade name | UL 94 Rating | Notable properties |
|---|---|---|---|
| ABS | Polylac PA-765 | V-0 | Cost-effective, good surface quality |
| ABS/PC blend | Bayblend FR110, FR 3010; Cycoloy C2950, C6600 | V-0 | Improved impact vs. ABS alone; broad thickness window |
| LCP | Vectra E130i (30% GF) | V-0 | Excellent dimensional stability, high-temperature rated |
| PA (Nylon) | RTP 203 FR (20% GF) | V-0 | Good chemical resistance, moderate cost |
| PBT | Valox 420SEO (30% GF) | V-0 | Good electrical insulation, low moisture absorption |
| PC | Lexan 940; Lexan 3412R (20% GF) | V-0 | High optical clarity available; very high impact |
| PEEK | Victrex 450G | V-0 | Continuous use to 250 °C; biocompatible grades available |
| PP | Maxxam FR PP 301 | V-0 | Lightweight, excellent chemical resistance |
| PPS | Ryton R-4 (40% GF) | V-0 | Inherently FR without halogen additives; high stiffness |
| PPSU | Radel R-5000 NT | V-0 | Steam-autoclavable; transparent grades available |
| TPE | Santoprene 251 | V-0 | Overmolding-compatible rubber-like feel |
Industry Applications: Where UL 94 Ratings Matter Most
Flame-retardant plastics are not universal requirements — the appropriate rating depends heavily on the end-use environment, proximity to ignition sources, regulatory framework, and consequences of failure. Below are the three industries where RpProto most commonly produces UL 94-compliant parts, along with the typical rating requirements and preferred materials for each.
Electronics & Electrical Equipment
- Switchgear housings and busbars
- Circuit breaker and fuse box enclosures
- Power supply and inverter covers
- PCB connector and terminal block bodies
- EV battery module separators
- Cable jacketing and conduit
Typical requirement: V-0 at ≤1.6 mm. Key standards also include IEC 62368-1 (AV/IT equipment) and IEC 60335 (household appliances), both of which mandate V-0 for parts near live conductors. Preferred materials: ABS/PC blends (Bayblend FR), PC (Lexan 940), PBT (Valox 420SEO).
Medical Devices & Diagnostics
- Imaging equipment outer housings
- Surgical robot covers and arm guards
- Infusion pump and ventilator enclosures
- Laboratory instrument chassis
- Patient monitoring device bodies
- Dental and ophthalmology equipment
Typical requirement: V-0 or 5VB; IEC 60601-1 (medical electrical equipment) requires V-0 or better for plastic enclosures in contact with or near mains power. Halogen-free and biocompatible grades are often specified simultaneously. Preferred materials: PPSU (Radel R-5000), PEEK (Victrex 450G), PC (Lexan 940), BJB TC-891 FR for cast prototypes.
Aerospace & Defense
- Cabin interior brackets and trim panels
- Avionics bay covers and rackmount blanks
- UAV airframe structural brackets
- Ground support equipment enclosures
- Radar and antenna housings
- Satellite sub-assembly structural parts
Typical requirement: 5VA (strictest); FAR 25.853 (commercial aircraft interior) requires self-extinguishing behavior exceeding standard V-0. Many aerospace programs require halogen-free FR formulations and LOI (Limiting Oxygen Index) >28% in addition to UL 94. Preferred materials: PPS (Ryton R-4), PEEK (Victrex 450G), LCP (Vectra E130i), BJB TC-891 FR for cast prototypes.
Choosing the right rating for your industry
| Industry / Application | Minimum typical rating | Governing standard | Notes |
|---|---|---|---|
| Consumer electronics (Class II, no earth ground) | V-0 | IEC 62368-1 | Parts enclosing live conductors or within 13 mm of them |
| Household appliances | V-0 | IEC 60335-1 | All enclosures adjacent to heating elements |
| Industrial control panels | V-0 | UL 508A / IEC 61439 | V-2 permitted for parts >50 mm from live parts |
| Medical electrical equipment | V-0 | IEC 60601-1 | Halogen-free often required for patient-contact zones |
| EV battery systems | 5VA | IEC 62619 / UL 2580 | Cell separators and module housings require strictest rating |
| Commercial aircraft interiors | 5VA | FAR 25.853 | Heat release rate tested separately (OSU 65/65) |
| Lighting fixtures (Class P) | V-2 | UL 844 / IEC 60598 | V-2 sufficient for outer globe; V-0 for parts near lamp |
| 3D-printed functional prototypes | HB | Internal / form-fit-function | For non-production testing only; upgrade for final parts |
Vertical vs. Horizontal Burn Test Methods (V-0, V-1, V-2)
The test procedure for V-0, V-1, and V-2 is identical in method — only the pass/fail criteria differ. Five bar specimens, each 127 mm × 12.7 mm, are clamped vertically. A gas burner flame is applied to the lower end for 10 seconds, removed, and the afterflame time is recorded. After the afterflame extinguishes, the flame is re-applied for a second 10-second application. A cotton indicator is placed 305 mm (12 inches) below to catch any flaming drips.
Results are rated across all five specimens. For a batch to pass V-0: no individual specimen may afterflame more than 10 seconds; total afterflame time for the group of 5 specimens may not exceed 50 seconds; no flaming drips may ignite the cotton; and no specimen may burn up to the clamp.
Get quote for UL 94 V-0 plastic parts now.
Frequently Asked Questions
Yes. RpProto offers UL 94 V-0 compliant vacuum casting using four certified polyurethane resins: AXSON PX330 (ABS-like, excellent surface finish), Hei-Cast 8263 (rigid, low shrinkage), BJB Enterprises TC-891 FR (low halogen, suitable for medical/aerospace), and PT 8952 Urethane (flexible-to-semi-rigid, good for cable management components). These materials allow you to produce functional prototypes or low-volume production runs of 5–50 units per mold set that meet real-world flammability testing requirements without the cost of hard tooling.
A UL 94 certificate applies to a specific formulation at a specific color and thickness. Adding a colorant, UV stabilizer, or lubricant — even in small amounts — can alter the base resin's flame-retardant behavior and potentially void the UL listing. Carbon black pigments (used in black parts) often help maintain or improve FR performance; lighter pigments vary unpredictably by chemistry. For UL-critical production parts, always specify a pre-compounded flame-retardant blend that carries its own UL Yellow Card for the actual intended color. If custom colors are required, work with a certified compounder to reformulate and re-test the blend at part thickness before committing to production tooling.
