From Microscopy to NIR: Modern Methods for Fiber Analysis

The fiber composition of textiles is directly related to product quality, comfort, and consumer health. Through fiber content testing, we can identify the raw material composition of a product to determine whether it meets expected quality standards. At the same time, it provides consumers with essential information regarding comfort, durability, and potential allergic reactions, helping them make more informed purchasing decisions.

Importance of Fiber Identification

Fiber identification is a fundamental and crucial task in textile testing. As the variety of textile products continues to expand, fiber materials have evolved from natural and chemical fibers to functional composite fibers. The increasing similarity in appearance and texture makes it difficult to determine fiber types accurately through sensory judgment alone. Correct fiber identification not only serves as the basis for quality inspection, labeling, and trade settlement but also plays a vital role in raw material control, process design, product development, and environmental testing within textile enterprises.

The importance of fiber identification can be summarized as follows:

1. Protecting Consumer Rights: Accurate fiber labeling prevents false claims and safeguards consumers’ right to know and choose.
2. Guiding Production and Processing: Since fibers differ significantly in their physical and chemical properties, identification results help optimize dyeing, blending, and weaving parameters.
3. Ensuring Fair Trade: In import and export inspections, precise fiber identification is essential for enforcing trade contracts.
4. Supporting Research and Development: Accurate identification assists in evaluating the properties of new fibers and optimizing formulations and processes in material innovation.

Common fiber identification methods include microscopic analysis, chemical solubility testing, and near-infrared spectroscopy (NIR). The first two, based on national and industry standards, are highly accurate and reliable, while NIR, a rapid and non-destructive method, has seen growing use in recent years.

Overview of Relevant Standards

Fiber identification and quantitative analysis in China are mainly governed by two standards:

1. FZ/T 01057 — Test Method for Identification of Textile Fibers
   This industry standard focuses on qualitative analysis, determining the types of fibers present. It includes methods such as microscopic observation, burning, solubility, and dye reaction. Among these, the microscopic method is the most fundamental and widely applied. FZ/T 01057 emphasizes identifying fibers based on external morphology and cross-sectional characteristics, suitable for both single fibers and blended samples.
2. GB/T 2910 — Textiles — Quantitative Chemical Analysis of Fiber Mixtures
   This national standard focuses on quantitative analysis, determining the percentage composition of fiber mixtures. The principle relies on the different solubility behaviors of various fibers in specific chemical reagents. By dissolving and weighing, the proportion of each fiber type can be calculated. GB/T 2910 includes multiple sub-standards (GB/T 2910.1–2910.24), each designed for different fiber blend systems using appropriate solvent combinations and procedures.

In summary:
FZ/T 01057 focuses on qualitative identification, while GB/T 2910 emphasizes quantitative analysis.
In practice, fiber testing usually begins with FZ/T 01057 to identify fiber types, followed by GB/T 2910 for quantitative determination.

Microscopic Method (Based on FZ/T 01057)

1. Principle

• Cotton: ribbon-like twists in the longitudinal view, kidney-shaped cross-section.
• Wool: scaly surface structure.
• Polyester: smooth, featureless circular cross-section.
• Nylon: smooth and transparent surface.
• Viscose: irregular cross-section with radial grooves.

By comparing the microscopic characteristics of an unknown sample with those of standard reference fibers, the fiber type can be determined. The following is a detailed article on our website about the microscopic method for identifying fiber components：https://fyitester.com/microscopic-computerized-fiber-analysis/

2. Procedure

1. Sampling: Cut an appropriate amount of fiber and remove impurities.
2. Slide preparation: Place a drop of glycerin or aqueous solution on a glass slide, disperse the fibers, and cover with a cover slip. For cross-sectional observation, prepare a fiber cross-section slice.
3. Microscopic observation: Use a biological or polarizing microscope to observe the longitudinal and cross-sectional morphology and record the features.
4. Comparative analysis: Compare the observed features with standard fiber atlases to identify the fiber type.

3. Scope of Application

The microscopic method is suitable for most natural fibers (such as cotton, flax, silk, and wool) and some synthetic fibers, especially for single-component samples. It is most effective for fibers with distinct surface structures but less accurate for synthetic fibers with similar morphologies (e.g., regular and modified polyester).

4. Applicable Instruments

Model	Observation Type	Main Test Items	Measurement Range	Objectives
YG002C	Longitudinal observation	Diameter	2–200 μm ± 0.5 μm (adjustable)	4×, 10×, 20×
YG002C1	Longitudinal observation	Diameter, content	2–200 μm ± 0.5 μm (adjustable)	4×, 10×, 20×
YG002C2	Longitudinal and cross-sectional observation	Diameter, content, cross-sectional area	2–200 μm ± 0.5 μm (adjustable)	4×, 10×, 20×

5. Advantages and Limitations

• Intuitive and fast: Enables quick differentiation between natural fibers (e.g., cotton, hemp, wool) and certain synthetic fibers through direct observation of surface and cross-sectional features.
• Wide applicability: Suitable for both natural fibers and synthetic fibers with distinct morphological features (e.g., bamboo-like nodes of flax, bark-like striations of ramie).
• Limitations: Difficult to accurately identify smooth, circular synthetic fibers (e.g., polyester, nylon); auxiliary methods such as burning or solubility tests may be required.
• Subjectivity: Results depend on the operator’s experience and equipment precision, which may lead to interpretation bias.

Chemical Dissolution Method (Based on GB/T 2910)

1. Principle

2. Procedure

1. Sample pretreatment: Remove impurities such as oils, sizing agents, and finishing residues.
2. Weighing: Accurately weigh a specified mass of the dried sample.
3. Dissolution: Select appropriate reagents and conditions (temperature, time) according to the standard to dissolve one type of fiber.
4. Filtration and cleaning: Filter out the solution, retain the undissolved fibers, rinse thoroughly, and dry.
5. Weighing and calculation: Weigh the remaining fiber and calculate the percentage composition of each component based on mass differences.

3. Characteristics

Feature Type	Description
Analytical nature	A quantitative analysis method that accurately measures the proportion of each component in a blend.
High accuracy	Measurement error is typically within ±1%, making it one of the most authoritative quantitative methods.
Wide applicability	Suitable for natural fibers, synthetic fibers, and multi-component blends.
Good repeatability	Results are stable and reproducible under standard test conditions.
Complex operation	Requires multiple steps of dissolution, filtration, and drying; relatively time-consuming.
Use of chemical reagents	Requires attention to safety and environmental protection.

4. Scope of Application

The chemical dissolution method is applicable to quantitative analysis of blends containing two or more fibers.
Due to significant differences in chemical stability among fibers, the GB/T 2910 standard specifies different testing methods and solvent systems for various blend types (e.g., cotton/polyester, wool/acrylic, viscose/polyester, etc.).

Near-Infrared Spectroscopy Method (Based on FZ/T 01144—2018)

1. Principle

The Near-Infrared Spectroscopy (NIR) method is a spectroscopic technique based on the vibrational absorption of molecular bonds such as C–H, O–H, and N–H.
Different fibers have distinct chemical compositions, resulting in unique “fingerprint” absorption spectra in the near-infrared region.
By analyzing these spectral characteristics, NIR enables rapid identification and quantification of fiber types and compositions.
This method is established according to FZ/T 01144—2018 Textiles — Quantitative Analysis of Fibers — Near-Infrared Spectroscopy Method.

2. Characteristics

• Fast and non-destructive: Enables on-site or online detection without the need for solvents or complex sample preparation.
• Multi-component capability: When properly calibrated, NIR can simultaneously analyze multiple fiber types—ideal for large-scale screening and production monitoring.
• Environmentally friendly and safe: Minimizes or eliminates the use of chemical reagents.
• Model-dependent: Requires a high-quality calibration dataset (based on reference chemical methods) and periodic model updates to account for new fiber types, dyes, or finishing processes.
• Sensitive to fabric properties: Fabric structure, color, and surface treatments can affect spectral accuracy; dark or highly absorptive dyes may require correction or sample exclusion.
• Higher technical and cost requirements: Equipment and modeling expertise are crucial, and model transfer between instruments requires standardization or recalibration.

3. Scope of Application

NIR spectroscopy is suitable for rapid analysis of natural fibers, synthetic fibers, and their blends.
It is widely used for on-site screening and laboratory-assisted testing, though it demands careful sample preparation, model development, and calibration to ensure accuracy.

Comparison of Three Fiber Identification Methods

Method	Principle	Type	Advantages	Disadvantages	Application Scope
Microscopic Method	Observation of fiber morphology	Qualitative	Intuitive, simple, low cost	Limited distinction for similar synthetics; operator-dependent	Single or simple blended fibers
Chemical Dissolution Method	Differential solubility in reagents	Quantitative	High accuracy, wide applicability	Time-consuming, involves chemicals	Quantitative analysis of blended fibers
Near-Infrared Spectroscopy	Spectral absorption feature analysis	Qualitative + Quantitative	Rapid, non-destructive, eco-friendly	High cost, requires model calibration	Rapid testing and auxiliary analysis

In summary, the microscopic method serves as the most fundamental qualitative approach, the chemical dissolution method remains the most authoritative quantitative technique, while the NIR spectroscopy method represents the future direction of intelligent and efficient fiber identification in modern textile analysis.

Conclusion

Fiber identification plays a vital role in textile quality control. By applying FZ/T 01057 and GB/T 2910, fibers can be analyzed both qualitatively and quantitatively.
The microscopic method helps identify fiber types, the chemical dissolution method provides accurate composition data, and the near-infrared method offers a fast, non-destructive, and eco-friendly alternative.

In practice, combining these methods ensures reliable results, while near-infrared spectroscopy represents the future trend toward efficient and sustainable textile testing.