Color Fastness to Perspiration Testing for Polypropylene Weft Yarn

Color fastness to perspiration testing for polypropylene (PP) weft yarn evaluates how well the yarn's color resists change and transfer when exposed to artificial human sweat, in accordance with internationally recognized standards such as ISO 105-E04, GB/T 3922, and AATCC 15. This test is essential for manufacturers, brands, and buyers of woven fabrics, narrow fabrics, and technical textiles where PP weft yarn contacts human skin or adjacent moisture-sensitive fibers. A clear understanding of the sampling method, test procedure, and grading system helps ensure consistent product quality and compliance with buyer specifications.

Technical Overview

Color fastness to perspiration is the resistance of the color of a textile material to the action of human sweat. During actual wear, sweat—typically warm, slightly acidic or alkaline, and salt-rich—can cause dyestuff or pigment to bleed, change shade, or transfer onto adjacent fibers. The perspiration fastness test simulates this environment in a laboratory by exposing the specimen to artificial sweat solutions under controlled temperature, pressure, and time, then rating the degree of color change and staining against standard grey scales.

Polypropylene (PP) weft yarn is a 100% olefin yarn widely used as the filling yarn in woven structures such as webbing, tapes, labels, mattress ticking, carpet backing, and garment trims. Because polypropylene is highly hydrophobic, with a moisture regain of less than 0.1%, and is normally colored by mass pigmentation (spin dyeing with masterbatch) rather than conventional dyeing, its perspiration fastness is generally very high. However, laboratory verification remains necessary, because pigment migration, residual carriers, spinning finishes, or surface-printed effects can still cause staining or shade change under warm acidic or alkaline sweat conditions.

The most commonly applied test standards include:

• ISO 105-E04 (Textiles — Tests for colour fastness — Part E04: Colour fastness to perspiration)
• GB/T 3922 (Chinese national standard, technically equivalent to ISO 105-E04)
• AATCC 15 (Colorfastness to Perspiration, widely used for the North American market)
• DIN EN ISO 105-E04 and JIS L 0848 for European and Japanese market requirements

Testing Samples

Yarn Skein Specimens

For yarn delivered on cones or bobbins, the laboratory winds the polypropylene weft yarn closely onto a rigid frame or into a flattened skein to form a uniform test layer with the standard dimensions of 100 mm × 40 mm (ISO) or 60 mm × 60 mm (AATCC). The yarn layer must be dense and even so that the exposed surface is representative of the yarn bulk, avoiding gaps that would distort the assessment of color change.

Woven or Knitted Test Panels

When the client requires the result to reflect real fabric behavior, the weft yarn is first woven into a small plain panel or knitted into a sleeve, and the panel is then cut into standard test specimens. This approach is recommended for evaluating how the PP weft yarn will perform in the final woven construction, including any interaction with warp yarns and finishes.

Combined Specimen Assembly

Each test specimen is assembled in direct contact with adjacent fabric to measure staining. Options include a single piece of multifiber adjacent fabric (for example, ISO multifiber fabric No. 1 containing wool, acrylic, polyester, nylon, cotton, and acetate, or multifiber DW) or two single-fiber adjacent fabrics such as cotton and nylon. Specimens are conditioned in the standard atmosphere of 20 ± 2 °C and 65 ± 4% relative humidity before testing.

Testing Items

The perspiration fastness evaluation of polypropylene weft yarn typically covers the following items, each reported as a grey scale grade from 1 (poor) to 5 (excellent), with half-step grades permitted:

• Color fastness to acid perspiration — degree of color change of the yarn specimen (assessed with the grey scale for color change, ISO 105-A02)
• Color fastness to acid perspiration — degree of staining of the adjacent fabric(s) (assessed with the grey scale for staining, ISO 105-A03)
• Color fastness to alkaline perspiration — degree of color change of the yarn specimen
• Color fastness to alkaline perspiration — degree of staining of the adjacent fabric(s)
• Optional stain profiling on each component of the multifiber fabric to identify which fiber types are most affected
• Optional instrumental color measurement (spectrophotometer) to supplement or verify visual grading

Testing Methods

Apparatus and Reagents

The test requires a perspirometer (sweat tester) that applies a pressure of 12.5 kPa to the stacked specimens, a ventilated oven capable of maintaining 37 ± 2 °C (ISO) or 38 ± 1 °C (AATCC), standard grey scales, and artificial perspiration solutions freshly prepared with grade-3 water. The compositions are as follows:

• ISO acid solution: L-histidine monohydrochloride monohydrate 0.5 g/L, sodium chloride 5 g/L, and disodium hydrogen orthophosphate 2.2 g/L, adjusted to pH 5.5
• ISO alkaline solution: L-histidine monohydrochloride monohydrate 0.5 g/L, sodium chloride 5 g/L, and disodium hydrogen orthophosphate 5 g/L, adjusted to pH 8.0 with 0.1 mol/L sodium hydroxide
• AATCC 15 solution: L-histidine monohydrochloride monohydrate 0.25 g/L, sodium chloride 10 g/L, lactic acid 1 g/L, and disodium hydrogen phosphate 1 g/L, adjusted to pH 4.3 (acidic only)

Procedure per ISO 105-E04 / GB/T 3922

• Immerse the combined specimen completely in the perspiration solution at a liquor ratio of 50:1 for 30 minutes at room temperature, pressing and agitating gently to ensure full penetration.
• Remove the specimen and squeeze out excess liquid so that the specimen retains approximately its own mass of solution (about 100% wet pickup).
• Place the combined specimen flat between the plates of the perspirometer, applying a pressure of 12.5 kPa.
• Keep the loaded perspirometer in the oven at 37 ± 2 °C for 4 hours.
• Remove the specimen, open it out, and dry it in air at a temperature not exceeding 60 °C, keeping the specimen and adjacent fabric in contact only along one line.
• Evaluate the color change of the specimen and the staining of each adjacent fabric under standard illuminant D65 using the grey scales, and report the grades for both acid and alkaline conditions.

Procedure per AATCC 15

For shipments to North American buyers, the AATCC 15 method may be specified. The specimen, in contact with a multifiber or cotton adjacent fabric, is soaked in the pH 4.3 acid perspiration solution for 30 minutes, wrung to 100% wet pickup, clamped in the perspirometer, and held at 38 ± 1 °C for 6 hours. After air drying, color change is rated with the AATCC grey scale for color change and staining with the AATCC grey scale for staining or the chromatic transference scale.

Evaluation and Acceptance Criteria

Mass-pigmented polypropylene weft yarn normally achieves grade 4–5 for color change and grade 4 or higher for staining, because the pigment is locked inside the polymer matrix during spin dyeing. Most buyer specifications and product standards require a minimum of grade 4 for color change and grade 3–4 for staining; results below grade 3 in either category are generally considered a failure and indicate possible pigment instability, excessive finish, or contamination. Test reports should clearly state the standard used, the adjacent fabric type, the solution pH, and the individual grades for acid and alkaline exposure.

Applications

Perspiration fastness testing of PP weft yarn is directly relevant wherever the woven end product contacts skin or is exposed to humid, sweat-laden environments. Typical applications include:

• Sports and activewear trims, linings, and woven tapes where sweat exposure is constant and prolonged
• Woven elastic waistbands, headbands, and watch straps with skin contact zones
• Garment labels, ribbons, and narrow fabrics sewn into underwear and swimwear
• Shoe uppers, linings, and insole fabrics subject to foot perspiration
• Mattress ticking, furniture webbing, and upholstery bindings in humid service conditions
• Carpet and rug constructions, including edge bindings and backing layers
• Export quality control and buyer compliance programs for major apparel and home-textile brands

FAQ

What grade is required to pass the perspiration fastness test for PP weft yarn?

Although acceptance criteria are set by the buyer or product standard, the common requirement is grade 4 minimum for color change and grade 3–4 minimum for staining. Spin-dyed polypropylene weft yarn typically passes with grade 4 to 4–5 in both categories.

Why must both acidic and alkaline sweat solutions be tested?

Fresh human sweat is mildly acidic (around pH 4.5 to 6.5), while bacterial decomposition on the skin can shift perspiration toward alkaline conditions (around pH 8). Testing both solutions ensures the yarn color remains stable across the full range of real-world wear conditions; ISO 105-E04 requires both, while AATCC 15 uses only the acidic solution.

Why does polypropylene weft yarn usually show excellent perspiration fastness?

Polypropylene is dyed by melt pigmentation, meaning the color pigment is dispersed throughout the polymer before extrusion and becomes physically encapsulated inside the fiber. Since there are no surface dye layers and the fiber itself absorbs almost no water, sweat has very little medium through which color can migrate.

How much yarn sample is needed for a full test?

A practical submission is approximately 10 to 20 grams of yarn per condition, or at least one meter of woven mini-panel, to allow duplicate specimens for acid and alkaline tests plus retained portions in case of retesting.

What is the difference between ISO 105-E04 and AATCC 15?

The two methods differ in sweat solution composition and pH, test temperature (37 °C versus 38 °C), exposure time (4 hours versus 6 hours), specimen size, and the grey scale system used for grading. Results from the two methods are not directly interchangeable, so the correct standard should be confirmed with the buyer before testing.

How long does a typical perspiration fastness test take?

The laboratory exposure itself is only 4 to 6 hours plus drying and conditioning time. Including specimen preparation, testing, evaluation, and reporting, the normal turnaround is 3 to 5 working days.