Wool Sweater Testing

Wool sweater inspection mainly conducts scientific testing and analysis on fibre composition and content, colour fastness, pilling performance, dimensional stability, bursting strength and tearing strength, formaldehyde content and pH value, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Fibre composition and content: This is the basis for judging the authenticity and quality of the wool sweater. Through the chemical dissolution method or physical microscope method, the testing precisely determines the percentages of the components such as wool (usually including the sheep wool and cashmere), chemical fibres (such as the acrylic and polyamide), cotton and silk. The accurate composition marking is the key to safeguarding the rights and interests of the consumers and preventing the commercial fraud.

Colour fastness: Evaluates the stability degree of the colour of the wool sweater under the action of the various external factors. Mainly including the colour fastness to soaping, colour fastness to water, colour fastness to perspiration, colour fastness to rubbing (dry/wet rubbing) and colour fastness to light. The poor colour fastness will cause the contamination of the other clothes during washing, or the fading due to the perspiration and friction during wearing, affecting the appearance and use.

Pilling performance: Simulates and evaluates the degree of the surface fibres of the wool sweater being entangled to form the pills due to the friction during wearing and washing. This testing is usually carried out in a Martindale abrasion tester or pilling box, and the standard sample photos or instrumental rating are used as the judgement basis, directly related to the appearance retention and service life of the wool sweater.

Dimensional stability (shrinkage): Detects the change rate of the dimensions of the wool sweater in the length and width directions after the standard washing or relaxation treatment. Due to the scale structure of the wool fibres, the felting shrinkage is easy to occur under the damp-heat and mechanical action, and this testing is crucial for guiding the consumers to wash correctly and the production enterprises to formulate the reasonable processes.

Bursting strength and tearing strength: The bursting strength measures the anti-bursting ability of the garment when subjected to the expansion force in the vertical direction, simulating the force conditions of the parts such as the elbows and knees. The tearing strength evaluates the difficulty of the further expansion of the crack after the local part of the fabric is hooked. Both are the core physical indicators for evaluating the durability of the wool sweater.

Formaldehyde content and pH value: As the ecological safety indicators, the residual free formaldehyde content in the wool sweater is detected. The excessively high formaldehyde may cause the skin irritation and respiratory problems. The pH value reflects the residual acidity and alkalinity after the dyeing and printing processing of the textile. The human skin is weakly acidic, and the pH value exceeding the limit may also cause the skin discomfort or allergic reactions.

Odour and decomposable carcinogenic aromatic amine dyes: Through the sensory evaluation, it is checked whether the wool sweater has the abnormal odours such as the musty smell, high-boiling petroleum smell and fishy smell. At the same time, the prohibited azo dyes must be tested. This type of dyes can decompose to produce more than 20 kinds of carcinogenic aromatic amines under the specific conditions, and is the item strictly prohibited by the mandatory standards of the domestic and foreign textiles.

Testing Scope

Classification by product form: The testing covers all the types of the finished wool sweaters, including the pullovers, cardigans, vests and dresses. At the same time, it also includes the semi-finished raw materials such as the knitted yarns and wool tops used for producing the wool sweaters, controlling the quality of the final products from the source.

Classification by fibre type: Not limited to the pure wool sweaters, but also including the wool blended sweaters (such as the wool/acrylic, wool/cotton and wool/cashmere), cashmere sweaters and the products of the special animal fibres such as the merino wool sweaters. For the products of the different fibre compositions, the testing emphasis and standard requirements will be different.

Classification by applicable object: The testing scope covers the wool sweaters of the people of all ages, including the sweaters for the infants (36 months and below), children and adults. Among them, the infant and children textiles have stricter limit requirements on the indicators such as the formaldehyde, pH value, colour fastness and cord safety.

Classification by processing technology: Including the ordinary knitted wool sweaters, anti-shrinkage treated (machine washable) wool sweaters and specially finished (such as the antibacterial, anti-static and UV protection) wool sweaters. The products after the different process treatments need to add the corresponding functional item testing, to verify the claimed effects.

Classification by market circulation link: The testing serves the ex-factory inspection of the production enterprises, the incoming acceptance inspection of the brand merchants, the spot checks of the market supervision departments, the quality control of the e-commerce platforms and the commissioned appraisal of the consumers. It covers the whole-chain quality supervision from the production, circulation to consumption.

Classification by product grade: Applicable to the wool sweaters of all the quality grades. Whether it is the qualified product conforming to the national mandatory standards (GB 18401 and GB 31701), or the superior product and first-class product conforming to the higher industry standards (such as FZ/T 73018), all need to be graded through the corresponding testing.

Classification by export destination: For the wool sweaters exported to the different countries and regions, the testing needs to comply with the regulations and standards of the target markets, such as the OEKO-TEX® Standard 100 and REACH regulation of the EU, the CPSIA/ASTM standards of the US, and the JIS L standards of Japan. The testing scope is adjusted according to the regulatory requirements.

Testing Methods

Fibre composition analysis (ISO 17751 / GB/T 14593): For the wool/cashmere blended products, the optical microscope method (projection microscope or scanning electron microscope) is mainly adopted. The identification and counting are carried out by observing the morphological characteristics such as the scale structure and diameter, combined with the fibre diameter distribution for the quantitative analysis. This method is the internationally recognized arbitration method.

Colour fastness testing (ISO 105 / GB/T 3920 series): For the colour fastness to soaping, the specimen is sewn with the standard adjacent fabric, washed under the specified temperature, soap concentration and mechanical action, and the change in colour and staining grades are rated with the grey scales. For the colour fastness to rubbing, the dry and wet standard white cloths are used to carry out the reciprocating friction on the rubbing tester, rating the staining grade of the white cloth.

Pilling testing (ISO 12945-2 / GB/T 4802.1): In the Martindale method, the circular specimen is rubbed with the same fabric or standard abrasive in a Lissajous trajectory under the specified pressure, and after the specified number of times, the rating is carried out by comparison with the sample photos or using the instruments under the standard lighting conditions, divided into grades 1-5. The higher the grade, the better the anti-pilling property.

Dimensional stability testing (ISO 5077 / GB/T 8629 and 8630): The standard washing procedure (such as the 5A procedure in the national standard) and drying procedure (such as the line drying, flat drying or oven drying) are used to treat the specimen. Before and after the treatment, the specimen is conditioned under the standard atmosphere, and the distances between the marked points are precisely measured, calculating the dimensional change rates in the various directions.

Formaldehyde content determination (ISO 14184-1 / GB/T 2912.1): The water extraction method is adopted. The specimen is oscillating-extracted in a 40 ℃ water bath for a certain time, the extract reacts with the acetylacetone reagent, the absorbance is measured with a spectrophotometer at the wavelength of 412 nm, and the formaldehyde content is calculated through the standard working curve, with the result expressed in mg/kg.

Bursting strength testing (ISO 13938-2 / GB/T 19976): A constant-rate-of-extension (CRE) type bursting strength testing machine is used. The specimen is clamped on the ring clamps of the fixed base, the spherical ball burst probe vertically pushes against the specimen at a constant speed until it bursts, and the maximum force value is recorded, which is the bursting strength, with the unit of Newton (N).

pH value determination (ISO 3071 / GB/T 7573): The specimen is cut into pieces, and oscillating-extracted in the carbon dioxide-free distilled water or potassium chloride solution. A calibrated pH meter is used to directly measure the pH value of the extract. To ensure the accurate results, the measurement needs to be completed as soon as possible after the extraction, and the liquid temperature during the testing is recorded.

Testing Standards

Domestic Standards:

1. GB 18401-2010, National general safety technical code for textile products

2. GB 31701, Safety technical code for infants and children textile products

3. FZ/T 73018, Wool knitted goods

4. GB/T 2912.1, Textiles — Determination of formaldehyde — Part 1: Free and hydrolysed formaldehyde (water extraction method)

5. GB/T 3920-2024, Textiles — Tests for colour fastness — Colour fastness to rubbing

6. GB/T 4802.1, Textiles — Determination of fabric propensity to surface pilling — Part 1: Circular locus pilling tester method

7. GB/T 8629, Textiles — Domestic washing and drying procedures for textile testing

8. GB/T 7573-2009, Textiles — Determination of pH of the aqueous extract

International Standards:

1. ISO 105, Textiles — Tests for colour fastness

2. ISO 13934-1, Textiles — Tensile properties of fabrics — Part 1: Determination of maximum force and elongation at maximum force using the strip method

3. ISO 12945-2, Textiles — Determination of fabric propensity to surface pilling, fuzzing or matting — Part 2: Modified Martindale method

4. ISO 5077, Textiles — Determination of dimensional change in washing and drying

5. ISO 14184-1, Textiles — Determination of formaldehyde — Part 1: Free and hydrolysed formaldehyde (water extraction method)

6. ISO 17751, Textiles — Quantitative analysis of cashmere, wool, other special animal fibres and their blends

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Optical microscope and scanning electron microscope (SEM): The optical microscope (especially the projection microscope) is the essential equipment for identifying the animal fibres such as the wool and cashmere, used to observe the scale density, morphology and medulla layer. The scanning electron microscope can provide the fibre surface morphology images with higher magnification and stereoscopic observation, used for the precise identification and scientific research analysis.

Martindale abrasion/pilling tester: This instrument is the core equipment for evaluating the abrasion and pilling performance of the fabric. By driving the relative motion between the specimen and the abrasive, it simulates the friction in the actual wearing. The instrument can set the pressure, friction trajectory and number of times, and automatically count. The test results have good repeatability, and it is widely used in the textile laboratories.

Automatic shrinkage testing machine: An automated equipment integrating the washing, spinning and drying, which can precisely execute the standard washing procedures (temperature, water level, mechanical action and time) and drying procedures. Compared with the manual operation, its temperature control is precise and the actions are consistent, greatly improving the reproducibility and comparability of the test results.

Universal material testing machine: Used for the mechanical property tests such as the bursting strength, tearing strength and tensile strength. Through the high-precision sensors and control system, it can precisely control the test speed, collect the force-displacement curve, and automatically calculate the parameters such as the maximum force value and elongation at break, with the objective and accurate data.

Spectrophotometer and colour fastness rating light source cabinet: The spectrophotometer is used for the quantitative analysis of the chemical items such as the formaldehyde content. The standard light source cabinet provides the standard illuminants such as D65 and TL84, ensuring that the colour fastness rating (change in colour and staining) and colour difference evaluation are not affected by the ambient light, guaranteeing the objectivity and consistency of the rating results.

pH meter and oscillating water bath: A high-precision laboratory pH meter, equipped with a combined electrode, used to measure the pH value of the extract, with the resolution of at least 0.01 required. The constant temperature oscillating water bath can provide the constant temperature and uniform oscillation conditions for the specimen extraction process of the items such as the formaldehyde and pH value, ensuring the sufficient extraction.

Gas chromatography-mass spectrometer (GC-MS): This is the cutting-edge equipment for detecting the trace hazardous substances such as the decomposable carcinogenic aromatic amine dyes, pesticide residues and some hazardous volatile organic compounds (VOCs). It has the characteristics of good separation effect, accurate qualitative and quantitative analysis and extremely high sensitivity, and is the key instrument in the ecological safety testing field.