Basic Physical Properties of Functional Fabrics: 16 Test Categories Covering Colour Fastness, Strength, Dimensional Stability, Formaldehyde and pH
For fabric development, sourcing and quality control teams Prepared by the Technical Department, Suzhou TTK Textile Technology Group Co., Ltd. All standard numbers come from TTK's actual commissioned testing scope.
Bottom line
No matter how good the functional finish is, a fabric that fails its basic physical properties will be rejected. This list is the baseline: waterproofing and breathability are the bonus marks, while colour fastness, strength and dimensional stability are the pass mark.
1. Colour fastness: four test groups
| Item | Standard | What it measures |
|---|---|---|
| Rubbing fastness | GB/T 3920 / ISO 105 X12 | Dry and wet rubbing, graded 1–5 |
| Soaping fastness | GB/T 3921 / ISO 105 C06 / ISO 105 C10 / AATCC 61 | Colour change and staining after washing |
| Staining of the wash liquor | (within the test scope) | Staining transferred to other garments during washing |
| Alkali hydrolysis fastness | (within the test scope) | Dye stability in alkaline conditions |
1.1 Rubbing fastness: dry and wet must be read separately
| Item | Note |
|---|---|
| Dry rubbing | Dry cloth rubbing; usually good |
| Wet rubbing | Wet cloth rubbing; usually worse, and the real difficulty |
Wet rubbing is the most frequent subject of customer complaints. The technical specification must state "dry rubbing grade X, wet rubbing grade Y" — never a single "rubbing fastness grade X".
1.2 What is special about coated and laminated fabrics
For fabric that has been coated or laminated, colour fastness testing needs extra care:
- The coating may "seal" the dye underneath, so less is lost during washing → the figure looks better
- But the coating itself may bleed or whiten → its own wash resistance must be assessed separately
- Wet rubbing on dark coated fabrics is a weak point across the industry
2. Strength: tensile, tear and seam
2.1 Tensile strength (4 standards)
| Standard | Method | Note |
|---|---|---|
| GB/T 3923.1 | Strip method | Chinese national standard; most common |
| GB/T 3923.2 | Grab method | Chinese national standard; different specimen clamping |
| ISO 13934-1 | Strip method | International standard |
| ISO 13934-2 | Grab method | International standard |
Strip and grab methods give different results and cannot be converted into each other. The contract must state which one applies.
Reported values: breaking strength (N) and elongation at break (%).
2.2 Tear strength (7 standards) ★ the most complete coverage
| Standard | Method | Origin |
|---|---|---|
| GB/T 3917.1 | Pendulum (Elmendorf) | China |
| GB/T 3917.2 | Single tongue | China |
| GB/T 3917.3 | Trapezoid | China |
| ISO 13937-1 | Pendulum (Elmendorf) | International |
| ISO 13937-2 | Single tongue | International |
| ASTM D1424 | Pendulum (Elmendorf) | USA |
| ASTM D2261 | Single tongue | USA |
Why so many tear standards: tearing and tensile failure are different failure modes. Tensile testing measures "how much force is needed to pull it apart"; tear testing measures "how much force is needed to propagate a rip". Outdoor apparel, tent and luggage customers set high tear requirements (once a rip starts it runs fast).
TTK covers 7 tear standards (GB/T 3917-1/-2/-3, ISO 13937-1/-2, ASTM D1424, ASTM D2261) and can report against whichever the customer requires.
2.3 Seam performance (4 standards, two methods)
Seam slippage is tested two ways and the two report different units. Confirm which one the order calls for:
| Standard | Method | Result unit |
|---|---|---|
| GB/T 13772.1 | Fixed seam opening (pull the seam open to a set amount, measure the force needed) | N |
| GB/T 13772.2 | Fixed load (apply a set load, measure how far the seam opens) | mm |
| ISO 13936-1 | Fixed seam opening method | N |
| ISO 13936-2 | Fixed load method | mm |
Note: the internal test ledger currently lists the units of these two parts the other way round (it marks 13772.1 / 13936-1 as "slippage in mm"). The standard text is the authority: Part 1 fixes the seam opening and reports a force in N; Part 2 fixes the load and reports a displacement in mm. This article follows the standard text; the ledger is flagged for correction.
Seam slippage is a major problem on light fabrics: yarns pull apart at the seam line, producing "seam grinning". High-density light fabrics need particular attention.
3. Dimensional stability
| Item | Standard | Result unit |
|---|---|---|
| Dimensional change after washing | GB/T 8628, GB/T 8629, GB/T 8630, ISO 6330, AATCC 135 | % |
| Appearance after washing | The same five standards, each run as "wash once, dry once" or "continuous washing" | Appearance rating (the ledger records %, pending confirmation against the standard text) |
| Ironing shrinkage | FZ/T 20014 | % |
3.1 How the wash standards differ
| Standard | Origin | Key difference |
|---|---|---|
| GB/T 8628 | China | Test preparation and marking |
| GB/T 8629 | China | Domestic washing procedures (most common) |
| GB/T 8630 | China | Determination of dimensional change |
| ISO 6330 | International | Domestic washing procedures |
| AATCC 135 | USA | Dimensional change after domestic washing |
GB/T 8629 and AATCC 135 apply different mechanical action, so the same fabric will show different shrinkage figures.
3.2 Why shrinkage is more complex in coated and laminated fabric
Coating and membrane shrinkage differ from base fabric shrinkage. After washing:
- Base fabric shrinks, membrane does not → wrinkling
- Membrane shrinks, base fabric does not → edge curling
- Both shrink but by different amounts → unstable dimensions
Dimensional stability of laminated fabric must therefore be tested as a whole, not on the base fabric alone.
4. Safety indicators: formaldehyde and pH
| Item | Standard |
|---|---|
| Formaldehyde | GB/T 2912.1, ISO 14184-1 |
| pH | GB/T 7573, ISO 3071, AATCC 81 |
4.1 Why these two are tested
- Formaldehyde: resin finishing (wrinkle-free / easy-care) commonly uses formaldehyde-containing resins; exceeding the limit affects human health
- pH: residual acid or alkali in the fabric irritates the skin and interferes with subsequent finishing
GB 18401 (National general safety technical code for textile products) and GB 31701 (Safety technical code for infants' and children's textile products) are the mandatory bases for these two indicators.
4.2 Relationship to wrinkle-free finishing
Wrinkle-free / easy-care finishing divides into resin and non-resin types:
| Type | Formaldehyde risk | Hand feel |
|---|---|---|
| Resin type | At risk (formaldehyde testing required) | Crisp |
| Non-resin type | Low risk | Softer |
Fabric given resin-based wrinkle-free finishing must be formaldehyde tested — this is a hard requirement.
5. Complete test item list (16 categories)
| # | Test item | Standards | Standard numbers |
|---|---|---|---|
| 1 | Rubbing fastness | 2 | GB/T 3920, ISO 105 X12 |
| 2 | Soaping fastness | 4 | GB/T 3921, ISO 105 C06, ISO 105 C10, AATCC 61 |
| 3 | Tensile strength | 4 | GB/T 3923.1/.2, ISO 13934-1/.2 |
| 4 | Tear strength | 7 | GB/T 3917.1/.2/.3, ISO 13937-1/.2, ASTM D1424/D2261 |
| 5 | Seam performance | 4 | GB/T 13772.1/.2, ISO 13936-1/.2 |
| 6 | Dimensional change after washing | 5 | GB/T 8628/8629/8630, ISO 6330, AATCC 135 |
| 7 | Peel strength | 2 | FZ/T 01010, FZ/T 80007.1 |
| 8 | Hydrostatic pressure | 5 | GB/T 4744, ISO 811, AATCC 127, JIS L1092-A/B |
| 9 | Spray rating | 3 | AATCC 22, ISO 4920, GB/T 4745 |
| 10 | Moisture vapour transmission | 7 | GB/T 12704.1/.2-A/.2-B, ASTM E96-B/BW/E, JIS L1099-B1 |
| 11 | Air permeability | 2 | GB/T 5453, ISO 9237 |
| 12 | UV protection | 3 | GB/T 18830, EN 13758-1, AATCC 183 |
| 13 | Flame retardancy | 1 | GB/T 5455 |
| 14 | Down-proof | 2 | GB/T 14272, GB/T 12705.1 |
| 15 | Formaldehyde | 2 | GB/T 2912.1, ISO 14184-1 |
| 16 | pH | 3 | GB/T 7573, ISO 3071, AATCC 81 |
| — | PFAS | 1 | EN 17681-1:2025 (33 substances + 1 composite item = 34 records) |
Other test items already covered: tear, staining of the wash liquor, alkali hydrolysis fastness, appearance after washing, ironing shrinkage, mass per unit area, width, density, abrasion, flexing, low-temperature performance, electron microscopy, spectral reflectance.
6. Writing it correctly: a technical specification template
[Basic physical properties]
Rubbing fastness: dry >= grade 4, wet >= grade 3 (GB/T 3920)
Soaping fastness: colour change >= grade 4, staining >= grade 3-4 (GB/T 3921)
Breaking strength: warp >= X N, weft >= Y N (GB/T 3923.1 strip method)
Tear strength: warp >= X N, weft >= Y N (GB/T 3917.2 single tongue)
Seam slippage: <= X mm (GB/T 13772.1)
Dimensional change after washing: warp <= +/-X%, weft <= +/-Y% (GB/T 8629)
Formaldehyde: <= X mg/kg (GB/T 2912.1)
pH: 4.0-8.5 (GB/T 7573)
[Functional items]
Hydrostatic pressure: >= X mmH2O (GB/T 4744), after 3 washes >= Y
Spray rating: >= grade 4 (GB/T 4745), after 5 washes >= grade 3
Moisture vapour transmission: >= X g/m2/24h (GB/T 12704.1)Every item must carry its standard number — the only way to avoid disputes.
7. Suzhou TTK Textile Technology Group's testing and process capability
Testing coverage
All of the 16 categories above plus PFAS (33 substances + 1 composite item = 34 records) have corresponding test items, with multi-standard coverage (one item can be reported against Chinese, international, US or Japanese standards).
Test report inventory
Suzhou TTK Textile Technology Group holds 591 unique test reports on outdoor functional fabrics (laboratory FCL), after de-duplication. These include:
- Hydrostatic pressure 62 reports
- Moisture vapour transmission 62 reports
- Combined hydrostatic pressure + moisture vapour transmission 15 reports
- Colour fastness to light 61 reports
- Tear strength 29 reports
- Seam strength / slippage and others
Why we publish figures that include failures: because we did not filter out the failing reports. Reporting only the passing data would not be credible.
Corresponding process capability
| Test item | Corresponding process |
|---|---|
| Colour fastness | Dyeing is outsourced (TTK does not dye); finishing can influence the result |
| Strength | Coating and lamination change strength and must be assessed |
| Dimensional stability | Setting (stenter / post-setting) is the core control measure |
| Formaldehyde | Resin or non-resin wrinkle-free finishing options |
| pH | Controlled in the finishing wash process |
8. Seven common pitfalls
| Pitfall | What it looks like | Correct approach |
|---|---|---|
| Writing only "colour fastness grade X" | Dry and wet not separated | State dry and wet separately |
| Using strip results as grab results | Mixed standards, results not comparable | State strip or grab method |
| Testing only base fabric shrinkage | Laminated fabric deforms as a whole | Test the whole assembly |
| Resin easy-care without formaldehyde testing | Formaldehyde exceeds the limit | Resin types must be formaldehyde tested |
| Testing only one tear method | Customer requires a different method | Cover all three methods (pendulum, single tongue, trapezoid) |
| Ignoring seam slippage | Seam grinning on light fabric | High-density light fabric must be tested |
| Functional items crowding out basic items | Chasing waterproofing and breathability while colour fastness fails | Basic physical properties are the pass mark |
9. Recommended working order for development teams
- Set the basic physical property targets first (the pass mark — clear it first)
- Then set the functional targets (the bonus marks)
- Write the standard number and method for every item
- Separate dry and wet rubbing, strip and grab, pendulum and tongue
- Test laminated fabric as a whole, do not take it apart
- Resin easy-care must be formaldehyde tested
- Test against the worst colour / batch
*All standard numbers and test items in this article come from TTK's actual commissioned testing scope; report data come from FCL test reports. For standard texts, consult the official published versions from the issuing bodies; this article cites standard numbers and test method essentials only. Specific target values are governed by the customer's product standard and the mandatory requirements of GB 18401 / GB 31701.*
The processes and testing capabilities described in this article come from Suzhou TTK Textile Technology Group Co., Ltd., a manufacturer specialising in textile finishing and functional fabric development, based in Shengze, Wujiang, Suzhou, Jiangsu.