Select the UL 94 class required for the particular polymeric part by the equipment standard or project specification. Then match the compound, color and minimum finished section to the material’s classification. I make that comparison for the gland body, cap, locknut and other polymer pieces separately, because they can use different materials and serve different functions.
The result should be a material and part design that meet the application. V-0, V-1 and V-2 describe different burning behavior in a vertical specimen test. Glow-wire, needle-flame, oxygen-index and thermal-aging results help answer other design questions. Use each where the equipment requires that property.
Key takeaways
- Establish the required test and class for the part’s location and function.
- Compare the exact grade, production color and minimum section together.
- Include manufacturing tolerance when checking wall thickness.
- Choose the relevant thermal-aging property for the part’s duty.
- Carry the selected material into the gland’s sealing, mechanical and environmental checks.
Which UL 94 class does the equipment require?
UL 94 covers small-scale flammability tests for plastics used in devices and appliances. Start with the equipment’s applicable construction requirement: identify the polymer component, its location and the accepted test method. I put that requirement beside the component on the assembly drawing before comparing material grades.
A cap next to internal wiring, an external body and a sealing insert can have different roles. The cap transmits tightening force; the body carries the mounting thread; the insert grips and seals the cable. Their material choices need to satisfy the relevant fire requirement alongside those physical duties.
If a specification says only “flame-retardant nylon,” resolve the method and acceptance class with the responsible engineer or certification body. The useful purchasing description names the part, material grade, required class, relevant thickness and production color. A building or industry label alone leaves those choices open.
| Selection input | Practical decision |
|---|---|
| Equipment and destination market | Identify the applicable product requirement and accepted evaluation route |
| Part position and nearby ignition sources | Apply the requirement for that location and construction |
| Named method and class | Select a material record or component evaluation that answers it |
| Wall, ribs and other relevant sections | Compare the minimum finished dimensions with the applicable material conditions |
| Service temperature and mechanical duty | Select the relevant thermal and strength properties alongside flammability |
For a project requiring a V-0 material at the relevant section, shortlist grades with that coverage. Where another class or component method is accepted, use that route. This keeps the choice tied to the equipment design and gives purchasing a clear specification.
What changes between V-0, V-1 and V-2?
The vertical test observes how a prepared specimen burns after a flame is removed, including continued flaming, glowing and drops. Afterflame is continued flaming after removal of the ignition source. Afterglow is continued glowing without flame.
UL Solutions’ combustion-test explanation distinguishes these selected criteria:
| Vertical-test observation | V-0 | V-1 | V-2 |
|---|---|---|---|
| Afterflame after each application | At most 10 s | At most 30 s | At most 30 s |
| Total afterflame for ten applications | At most 50 s | At most 250 s | At most 250 s |
| Flaming drops ignite the cotton indicator | Not permitted | Not permitted | Permitted |
The complete method also covers specimen preparation, afterglow and burning to the holding clamp. Use those full criteria for testing and classification. The table highlights why V-0 has tighter time criteria and why dripping separates V-1 from V-2.
I consider the surrounding construction when applying the requirement: a burning drop can carry heat toward another component below the part. The V-2 guide explains that behavior in more detail.
HB uses horizontal burning; 5V uses a different exposure; VTM addresses thin materials. Compare alternatives within the method required by the equipment. Similar letters in their class names do not establish an interchangeable construction.
Read the material grade, color and thickness together
A UL Yellow Card is a digital record of recognized safety and performance properties for a named polymer material. UL’s reading guide explains the program and its material databases. Start with the manufacturer and full grade designation, including any suffix, then read the applicable classification row.
The UL abbreviation guide identifies Min Thk. mm, flame class and color codes. ALL means any color, AO means all opaque colors, BK means black, and NC means natural material without pigmentation. I read those fields together and match them with the proposed part’s specification.
Separated dark gland components sit beside rectangular and round material samples, with a flame-test setup in the background.
For example, a black cap needs a material/color combination covered for black production. A natural-color entry requires a corresponding check if the supplier later proposes pigmentation. Masterbatch is a concentrated additive mixture used to introduce color or other ingredients; it belongs in the formulation review.
The part drawing supplies the other half of the comparison. Locate the relevant minimum section and its measurement position. Include molding tolerance and any local thinning at the assessed feature. Agree on how production inspection will measure that section so the design and incoming checks use the same dimension.
How do wall thickness and thermal duty change the UL 94 choice?
Assume a hypothetical project requires a V-0 black cap, with an assessed minimum section of 1.80 ±0.15 mm. The relevant part temperature is assumed to be 110°C, and impact endurance is part of the material-selection requirement. These inputs and material rows are invented for the comparison; they are not product ratings.
The smallest permitted wall is 1.65 mm. Suppose candidate A has the required V-0/color coverage from 1.50 mm, while candidate B has it from 1.70 mm. Assume A has an impact RTI of 105°C and B has 120°C at their applicable listed conditions.
| Hypothetical check | Candidate A | Candidate B |
|---|---|---|
| Required V-0 and black color | Covered | Covered |
| Listed minimum thickness | 1.50 mm | 1.70 mm |
| Margin at the 1.65 mm finished minimum | +0.15 mm | −0.05 mm |
| Assumed applicable impact RTI | 105°C | 120°C |
| RTI minus the assumed 110°C comparison temperature | −5°C | +10°C |
In this worked comparison, I found that neither candidate clears both assumed screening conditions. A fits the section but needs a material with suitable impact endurance for the thermal duty. B clears that thermal comparison but needs a geometry or tolerance change to meet its thickness condition.
For B, retaining ±0.15 mm would require a nominal section of at least 1.85 mm to reach 1.70 mm at the lower limit. Alternatively, the 1.80 mm nominal section would need a negative tolerance of no more than 0.10 mm. These are equality boundaries for the example, with no added dimensional allowance. Set the practical allowance and inspection decision using the actual process capability and measurement uncertainty. The useful design variable is the finished minimum, not nominal wall alone. My calculation also shows that increasing B’s nominal section by 0.05 mm clears only the assumed thickness boundary; it adds no dimensional reserve. Before choosing that change, check tool access, cap clearance, mold filling and the force transferred to the insert. A tighter tolerance is useful only if production can maintain it and inspection can distinguish a conforming part. Choose another compound if the geometry or process cannot support the required minimum. Then evaluate the revised part in the finished equipment.
The cable-gland material guide connects those choices with temperature, fluids, sunlight and mechanical loading. A material change should improve the complete duty of the part, rather than solving one condition while creating a fit or sealing problem.
When does the design need a glow-wire or needle-flame test?
Glow-wire testing uses an electrically heated wire to represent brief heating from sources such as glowing elements or overloaded resistors. IEC 60695-2-10:2026 specifies the apparatus and common procedure. Choose the particular material or end-product method from the equipment requirement.
| Result | Test object | How I use it in selection |
|---|---|---|
| GWEPT, IEC 60695-2-11 | End product under the specified heated-source exposure | Check the required component or finished construction and its observed response |
| GWFI, IEC 60695-2-12 | Standard material specimens | Use the flammability index within the permitted material-preselection route |
| GWIT, IEC 60695-2-13 | Standard material specimens | Use the ignition-temperature index with its defined test basis and preselection conditions |
GWFI concerns the qualifying extinguishing and dripping response. GWIT is an index derived from the qualifying test temperature using the method’s prescribed increment. The material methods can support the defined preselection process for end-product glow-wire requirements. Read the required route, specimen thickness and material identity together. For example, first identify whether the equipment requirement calls for a test on its actual component or accepts a material preselection route. For a component test, preserve the specified part geometry and mounting in the sample. For a material route, compare the exact compound and thickness under the named process. That choice determines which sample to prepare and which result to request from the laboratory, avoiding a test that answers a different question from the one the design needs to resolve.
Needle-flame testing uses a small flame as the exposure. IEC 60695-11-5:2016 applies to equipment, subassemblies, components and combustible materials. Its observations contribute to the end-use fire-hazard assessment. For a specified component test, identify the actual part and mounting, flame exposure, subsequent burning and effects on surrounding material.
I select the test object before preparing samples. A material bar helps choose a resin; a component test examines the specified component construction. Keeping that distinction clear avoids repeating a material test when the design decision concerns the finished shape or its surroundings.
How should oxygen index influence a material comparison?
Oxygen index, or OI, is the minimum oxygen concentration by volume in an oxygen/nitrogen mixture that supports combustion under the specified laboratory conditions. ASTM D2863-23e1 describes that measurement and its specimen procedures.
Use OI to compare the stated combustion response on a consistent test basis. Check material identity, specimen form, procedure and test temperature before comparing values. A hypothetical OI of 32% describes the gas mixture associated with the result; it is not a percentage probability of fire.
If the equipment asks for a UL 94 class, select that class directly. If it asks for an oxygen-index value, apply the specified OI method and threshold. This gives each result a useful place in the material specification without creating a conversion between unrelated test outputs.
Match RTI to the property the gland part needs
Relative thermal index (RTI) describes long-term thermal endurance for a particular material property under the listed conditions. UL’s thermal-aging explanation describes aging specimens at several temperatures and measuring the changes in their properties. The specimens in that process are aged without mechanical load.
Read the property heading as well as the temperature. Electrical, impact and strength behavior can age differently, so a material record can have separate values:
| RTI field | Selection question |
|---|---|
| Elec | Is the material’s electrical-property endurance suitable for its insulating duty? |
| Imp | Is impact-property endurance suitable for the part’s relevant mechanical duty? |
| Str | Is strength-property endurance suitable for the function being assessed? |
In the worked example, I used the assumed impact field because impact endurance was part of that requirement. An electrical RTI of 125°C would not resolve candidate A’s assumed 105°C impact condition. Read the relevant listed thickness and color conditions too.
Then assess the finished entry’s temperature limits. The seal, cable jacket, molded geometry, tightening loads and mounting can constrain service. Long-term material aging and a short temperature excursion are different design cases. Use the part and equipment requirements for both, including the relevant mechanical loads and thermal cycle.
Carry the resin choice into the finished cable entry
The selected polymer must still work as a gland component. IEC 62444:2010 addresses complete cable-gland construction and performance as supplied. I check the changed part in the intended body, cap, insert and mounting combination.
| Design duty | Check alongside the selected flame class |
|---|---|
| Cable fit and retention | Cable profile, diameter range, grip and support |
| Enclosure sealing | Cable-facing seal, wall seal, mounting and required ingress protection |
| Tightening and impact | Part geometry, assembly method and relevant complete-gland performance |
| Outdoor or chemical exposure | Actual formulation, UV conditions, liquids and temperature |
| Low-smoke or halogen requirements | The separately specified material or component method |
| Fire-resisting penetration or emergency circuit | The required tested assembly or system construction |
I include the seal and accessories in that comparison. A rigid polymer body and a flexible sealing insert often have different functions and material needs. Choose each against its own applicable requirements while preserving the assembled entry’s performance.
For specific projects, use the railway fire-safety guide and halogen-free material guide. For a wall or floor penetration requiring a fire duration, use the specified fire-rated entry system. Those requirements address properties beyond the small-specimen flame class.
Keep production changes connected to the selection
Record the selected grade, color, relevant material row, part revision and minimum section in the production specification. Identify the approved additives and molding conditions where they form part of the evaluated material or component construction.
When a supplier proposes a different grade, pigment, filler, recycled content or molding source, compare the change with the recognized conditions and equipment requirements. A smaller wall or altered gripping feature also needs a review of the affected functions. I start with what physically changed, then identify the material, dimensional or finished-product checks needed for that change.
For incoming parts, verify identity and the designated critical dimensions through the agreed inspection method. Keep the review connected to the part number so an unchanged catalogue name does not obscure a revised compound or geometry.
Conclusion
Choose the UL 94 class from the equipment requirement, then select the exact compound, color and minimum section that meet it. I compare the relevant thermal-aging property and service conditions at the same time, so the preferred material suits both the flame requirement and the part’s job.
The worked comparison shows why the class alone is only one selection input. Thickness tolerance can change the shortlist, and thermal duty can change it again. Carry the final material and geometry into the complete gland’s sealing, retention and environmental assessment.
FAQs about UL 94 ratings for non-metallic cable glands
Which UL 94 class should I specify for a nylon cable gland?
Use the class or component method accepted by the equipment standard or project specification for the particular part and location. Identify the body, cap, insert and accessories separately, then match the selected grade, color and minimum section to that requirement.
What is the practical difference between V-1 and V-2?
Both use the vertical test with the same selected afterflame limits, while the cotton-indicator criterion distinguishes flaming-drop behavior. V-2 permits flaming drops to ignite the indicator; V-1 does not. Use the complete method and the equipment’s accepted class for selection.
How do I check a material classification against wall thickness?
Locate the relevant minimum finished section on the drawing and include its negative tolerance. Compare that lower limit with the applicable material row, including color and class. If it is too small, choose a covered grade, revise the geometry or establish an achievable tighter tolerance.
When should I use glow-wire instead of a UL 94 material result?
Follow the method required by the equipment. Glow-wire uses a heated source and can involve end-product testing or a defined material-preselection route. Establish the required test object and conditions before choosing between a material record and a component evaluation.
Which RTI value matters for a polymeric gland part?
Choose the electrical, impact or strength property relevant to the part’s duty, at the applicable listed conditions. Then assess the finished gland’s temperature limits together with its seal, cable, geometry, mechanical load and mounting. A material RTI is one input to that complete selection.
Sources and technical references
- UL Solutions — Combustion (Fire) Tests for Plastics, accessed 2026-10-28.
- UL Solutions — How to Read the Yellow Card, accessed 2026-10-28.
- UL Solutions — Color Codes and Abbreviations for Plastics Recognition, accessed 2026-10-28.
- UL Solutions — Thermal Aging Tests for Plastics, accessed 2026-10-28.
- IEC 60695-2-10:2026 — Glow-wire apparatus and common procedure, accessed 2026-10-28.
- IEC 60695-2-11:2021 — Glow-wire end-product test, accessed 2026-10-28.
- IEC 60695-2-12:2021 — Glow-wire flammability index, accessed 2026-10-28.
- IEC 60695-2-13:2021 — Glow-wire ignition-temperature index, accessed 2026-10-28.
- IEC 60695-11-5:2016 — Needle-flame method, accessed 2026-10-28.
- ASTM D2863-23e1 — Oxygen index, accessed 2026-10-28.
- IEC 62444:2010 — Cable glands for electrical installations, accessed 2026-10-28.