AATCC standards to determine the colorfastness of Lyocell fibers

The American Association of Textile Chemists and Colorists (AATCC) provides several standardized test methods to determine the colorfastness of Lyocell fibers, which is a regenerated cellulose fiber like Tencel. Since lyocell is a cellulosic fiber, it shares many testing requirements with cotton and rayon, though its high wet strength and tendency to fibrillate (form micro-hairs) can influence specific results.

The following are the primary AATCC standards used to evaluate Lyocell.

1. Colorfastness to laundering (accelerated)

Standard: AATCC TM61: This is the most common test for Lyocell apparel. It simulates the effects of five home or commercial launderings in a single 45-minute lab test.

• The process: A fabric specimen is placed in a stainless steel canister with a detergent solution and a specified number of stainless steel balls to provide mechanical abrasion.
• Lyocell note: Because Lyocell can fibrillate when wet, this test is critical for observing frosting or surface color changes caused by fiber abrasion rather than just dye loss.

2. Colorfastness to crocking (rubbing)

Standard: AATCC TM8 (Crockmeter Method): This test determines how much color transfers from the Lyocell surface to a white test cloth through rubbing.

• Dry vs wet: Both dry and wet crocking are tested. Lyocell typically performs well in dry crocking but may show more color transfer in wet crocking due to the fiber's high moisture absorption.
• Evaluation: Results are rated using the AATCC Chromatic Transference Scale or Gray Scale for Staining.

3. Colorfastness to Light (Xenon-Arc)

Standard: AATCC TM16.3: This method measures how well the dyed Lyocell resists fading when exposed to a continuous light source that mimics natural sunlight.

• The process: Samples are exposed to a Xenon-arc lamp in a controlled chamber.
• Significance: This is vital for Lyocell used in summer wear or home textiles (curtains), as cellulosic fibers can be sensitive to UV degradation depending on the dye type used (e.g., reactive dyes).

4. Colorfastness to perspiration

Standard: AATCC TM15: This evaluates the resistance of dyed Lyocell to acid perspiration, which is crucial for close-to-skin apparel like activewear or undergarments.

• The process: The specimen is wetted with simulated acid perspiration, backed with a multi-fiber strip (to check for staining), and placed under pressure in a "perspiration tester" at an elevated temperature for 6 hours.

5. Colorfastness to water

Standard: AATCC TM107: While similar to the perspiration test, this uses distilled water to ensure that color doesn't bleed or migrate when the garment gets wet (e.g., from rain or accidental spills).

Evaluation and rating

All the above tests are evaluated using standardized scales:

• Gray scale for color change: Measures the difference in color between the tested sample and the original.
• Gray scale for staining: Measures how much color was transferred to the adjacent ‘multi-fiber’ test strip (usually containing acetate, cotton, nylon, silk, viscose, and wool).
• Ratings: Both scales use a 1-5 system:
• 5: Negligible or no change/staining (Best).

1: Severe change/staining (Worst).