Flame-Retardant Textile Finishing: GB/T 5455 Judgement, Halogen-Free vs Brominated, and Coating vs Pad-Dry-Cure Durability
For fabric development, sourcing and compliance teams Prepared by the Technical Department, Suzhou TTK Textile Technology Group Co., Ltd. Standard numbers and test items come from TTK's actual commissioned testing scope.
Bottom line
Flame retardancy is not one figure — it is a combination of three (afterflame time, afterglow time and damaged length). Reporting only "passed flame retardancy" says nothing at all.
1. What GB/T 5455 actually judges
GB/T 5455 (Textiles — Burning behaviour — Determination of damaged length, afterglow time and afterflame time of vertically oriented specimens) is the flame-retardant test item in TTK's testing scope.
It measures three things:
| Indicator | Meaning | Unit |
|---|---|---|
| Afterflame time | How long the flame keeps burning after the ignition source is removed | seconds |
| Afterglow time | How long the specimen keeps glowing without flame after the flame goes out | seconds |
| Damaged length | The length of specimen destroyed by burning | mm |
All three must be reported. Some suppliers report only a passing damaged length while the afterflame time is out of limits — under many standards that is an outright failure.
1.1 Example of a specification (actual limits are governed by the standard text and the customer's requirement)
A form commonly used in company standards and customer requirements:
Tested to GB/T 5455:
Afterflame time <= 2 s
Afterglow time <= 2 s
Damaged length <= 150 mmNote: requirements differ widely between industries and customers. Protective, uniform, workwear and home-textile sectors set completely different thresholds. Write the customer's actual requirement — never assume a figure.
2. Four technical routes to flame retardancy
| Route | Principle | Durability | Hand feel | Cost |
|---|---|---|---|---|
| Inherently flame-retardant fibre | The fibre itself does not burn (aramid, FR polyester, modified acrylic) | Permanent | Depends on the fibre | High |
| Flame-retardant coating | Flame retardant added to the coating | Moderate (retained as long as the coating is) | Fairly stiff | Medium |
| Flame-retardant pad-dry-cure finishing | Flame retardant padded and cured into the fibre | Weaker (washes out) | Good | Low |
| Flame-retardant lamination | Laminated with a flame-retardant membrane or layer | Good | Moderate | Medium-high |
2.1 Coating vs pad-dry-cure: the key trade-off
| Item | FR coating | FR pad-dry-cure |
|---|---|---|
| Initial flame retardancy | Good | Good |
| Wash durability | Fairly good (as long as the coating survives, the retardancy survives) | Weaker (the retardant is hydrophilic and washes out easily) |
| Effect on hand feel | Fairly stiff, adds weight | Almost none |
| Suited to | Heavy fabrics, workwear, tents | Light fabrics, garments |
This is the pitfall buyers fall into most often: they accept "flame-retardant fabric" without asking whether it is coated or padded, then use it in a product that must be wash-durable and find it no longer flame retardant after 5 washes.
You must ask: after how many washes does it still have to be flame retardant?
3. Halogen-free vs brominated: a choice that is disappearing
3.1 The two routes compared
| Item | Halogen-free | Brominated |
|---|---|---|
| Retardant efficiency | Lower (higher loading needed) | High (effective at low loading) |
| Effect on performance | Higher loading, bigger effect on hand feel | Low loading, small effect on hand feel |
| Combustion smoke | Relatively low smoke and low toxicity | Heavy smoke, possibly corrosive gases |
| Regulatory direction | ✅ The mainstream direction | ⚠️ Restricted in some markets |
| Cost | Medium-high | Low |
3.2 Why halogen-free is now the norm
EU RoHS and REACH restrict certain brominated flame retardants. Export orders essentially have to go halogen-free.
But note: to reach the same performance, halogen-free retardants usually need a higher loading, so the loss of hand feel and strength is more pronounced. That trade-off has to be told to the customer up front.
3.3 One fact that must be stated precisely
"Halogen-free" does not mean "smoke-free and non-toxic". Halogen-free retardants still produce smoke and some toxic gases when burned — just more controllably than brominated systems.
External wording must be accurate: write "halogen-free flame retardant", and do not use vague expressions such as "non-toxic flame retardant" or "eco-friendly flame retardant".
4. Combining flame retardancy with other functions
Flame-retardant fabric is rarely a single-function product, and combinations interfere:
| Combination | Risk |
|---|---|
| Flame retardant + water resistance (coating) | The retardant and the water repellent may interfere with each other; the two finishes must be verified separately |
| Flame retardant + UV protection | Some UV auxiliaries affect the flame-retardant system |
| Flame retardant + other functional auxiliaries | Silver-ion auxiliaries may react with the retardant; a small-sample trial is required before combining |
| Flame retardant + moisture permeability | A thicker FR coating reduces moisture vapour transmission |
The rule: any combination must be retested for flame retardancy — never assume that separate tests prove the combination.
5. Writing it correctly: a technical specification template
Flame-retardant requirement (GB/T 5455):
Afterflame time <= 2 s
Afterglow time <= 2 s
Damaged length <= 150 mm
Wash requirement: the above values still met after 10 washes per GB/T 8629
Retardant system: halogen-free
Process: flame-retardant coating (or pad-dry-cure finishing — state which)Five things must be stated: the three indicators, the wash count, the retardant system, and the process.
6. Suzhou TTK Textile Technology Group's concrete capability
Testing coverage
| Item | Standard |
|---|---|
| Flame-retardant performance | GB/T 5455 |
Process capability
| Item | Detail |
|---|---|
| Flame-retardant coating | ✅ Achievable on the company's own coating lines |
| Flame-retardant lamination | ✅ FR lamination process (listed among the lamination items) |
| Flame-retardant pad-dry-cure finishing | ✅ One of the functional finishing items |
| Flame-retardant camouflage fabric | ✅ Related process combination (note: military-supply business is not claimed externally, per the red line) |
| Supporting processes | Dry / wet / transfer coating, TPU/PU/PTFE/PE membrane lamination |
Note: "flame retardant" is among TTK's functional finishing items and is one of the externally available processes. The specific retardant system (halogen-free or brominated) is configured to the customer's requirement.
Test report inventory
Suzhou TTK Textile Technology Group holds 591 unique test reports on outdoor functional fabrics (issued by FCL), after de-duplication.
7. Six common pitfalls
| Pitfall | What it looks like | Correct approach |
|---|---|---|
| Reporting only "pass" | No figures for the three indicators | Report afterflame, afterglow and damaged length |
| No wash count stated | Not flame retardant after washing | State after how many washes it still passes |
| Coating and padding not distinguished | Customer needs wash durability but padding was used | Establish the wash requirement before choosing the process |
| Testing to a lower standard | Tested to a weak standard, reported as a high grade | Test to the customer's industry standard |
| No retest after combining | FR and water resistance tested separately, never retested together | Combinations must be retested |
| Vague claims | "Eco-friendly flame retardant", "non-toxic flame retardant" | Write "halogen-free flame retardant" |
8. Recommended working order for development teams
- Confirm the customer's industry standard (workwear, outdoor and home textiles have different thresholds)
- Confirm the specific values for the three indicators
- Confirm the wash requirement (this decides coating vs padding)
- Confirm the retardant system (halogen-free / brominated, according to the target market)
- Confirm whether other functions are combined (combinations must be retested)
- Test post-wash performance at the sample stage
Appendix: complete list of related standards
Flame retardancy: GB/T 5455 (damaged length, afterglow time and afterflame time, vertical direction)
Washing (for post-wash testing): GB/T 8629, ISO 6330, AATCC 135
Related physical properties: GB/T 3923.1 (breaking strength), GB/T 3917 series (tear strength), GB/T 5453 (air permeability)
Compliance: RoHS, REACH
*The standard numbers and test items in this article come from TTK's actual commissioned testing scope. For standard texts, consult the official published versions from the issuing bodies; this article cites standard numbers and test method essentials only. Specific flame-retardant grade requirements are governed by the customer's industry standard.*
The processes and testing capability described in this article come from Suzhou TTK Textile Technology Group Co., Ltd. The company's core business is textile finishing and functional fabric development, located in Shengze, Wujiang, Suzhou, Jiangsu.