Nonwoven Bag Inspection

Nonwoven bag inspection mainly conducts scientific testing and analysis on physical and mechanical property testing, grammage and thickness determination, colour fastness inspection, environmental protection and prohibited substance testing, drop test and appearance and dimensional deviation inspection, 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

Physical and mechanical property testing: Mainly evaluates the durability of the nonwoven bag under force. The key items include the tensile breaking strength, elongation at break and tearing strength. Through these tests, the load-bearing capacity, deformation resistance and tear resistance of the bag can be scientifically judged, ensuring that it meets the daily use or specific load-bearing requirements, and preventing the damage caused by insufficient physical properties.

Grammage and thickness determination: The grammage (mass per unit area) and thickness are the core physical parameters for measuring the basic specifications of the nonwoven material. Accurately determining these two indicators is the basis for evaluating the material uniformity, cost control and subsequent properties (such as strength and stiffness). A precision electronic balance is usually used to determine the grammage, and a thickness gauge is used for multi-point measurement to ensure the representativeness of the data.

Colour fastness inspection: This inspection evaluates the colour stability of the printed or dyed parts of the nonwoven bag under the conditions such as friction, washing and light exposure. It mainly includes the colour fastness to dry/wet rubbing, colour fastness to washing and colour fastness to light. Poor colour fastness will cause colour migration, contaminating the contents or affecting the appearance, and is an important basis for evaluating the quality of the printing and dyeing processes.

Environmental protection and prohibited substance testing: In response to the increasingly strict environmental protection requirements, this testing is crucial. The main screening items include migratable fluorescent whitening agents, formaldehyde content, specific azo dyes (decomposable carcinogenic aromatic amines) and the content of heavy metals (lead, cadmium, mercury and chromium), ensuring that the product meets the relevant domestic and foreign ecological textile and consumer product safety regulations.

Drop test: Simulates the situation of the nonwoven bag falling from a certain height in actual use, testing the bonding strength between the handle and the bag body and the impact resistance of the bag body. Usually, a load of the specified mass is placed into the bag for multiple free-fall drops, and after the test, it is checked whether the bag body and the handle are damaged, unstitched or broken.

Appearance and dimensional deviation inspection: The overall quality of the nonwoven bag is checked by visual inspection and measuring instruments. This includes checking whether the printed pattern is clear, and whether there are defects such as misregistration, stains, damage and broken needles; at the same time, the dimensions such as the length, width, side thickness and the length and width of the handle are precisely measured, judging whether they meet the design tolerance requirements.

Testing Scope

Raw nonwoven fabric: The inspection report covers the testing of the nonwoven fabric, the basic material constituting the bag body. This includes the performance evaluation of the base materials produced by different processes such as spunbonded nonwoven, spunlaced nonwoven and thermal bonded nonwoven, ensuring that they meet the quality prerequisites of the subsequent bag-making processing and final use.

Printing and decorative parts: The testing scope extends to all the decorative elements on the bag body. This includes the ink layers printed by flexographic printing, gravure printing or screen printing, as well as the patterns or logos added through the processes such as lamination, heat transfer printing and embroidery. The main evaluations are their adhesion firmness, colour fastness and safety.

Handles and connection parts: The handle is the key force-bearing part of the nonwoven bag and is the key scope of the inspection. Regardless of whether the handle material is the self-contained nonwoven, webbing, rope or plastic, its own strength and the firmness of the connection parts with the bag body, such as sewing, heat sealing or riveting, need to be tested.

Finished bags (different specifications and styles): The inspection covers all the finished bags of all specifications and styles in the final shipment state. This includes the common vest bags, tote bags and drawstring bags, as well as the bags of different sizes (such as large, medium and small) and different structures (such as with inner pockets, lamination and hard lining), ensuring the quality consistency of the batch products.

Products with specific functions: For nonwoven bags with special functions, the testing scope needs to be correspondingly extended. For example, antistatic bags need to test their surface resistivity; laminated bags need to test the peeling strength of the film; and bags claimed to be "degradable" need to be verified for the biodegradability in accordance with the relevant standards.

Key control points of the production process: The scope of a comprehensive inspection report can also trace back to the monitoring of the key links of the production process, such as the incoming material inspection, the monitoring of the printing process parameters, and the records of the temperature and pressure control in the bag-making process, for systematic quality tracing.

Testing Methods

Standard method basis: The testing of nonwoven bags strictly follows the test methods recognized at home and abroad. Domestically, the national standard series such as GB/T (for example, GB/T 3923.1 Textiles — Tensile properties of fabrics and GB/T 4802.1 Pilling testing) and the industry standards are mainly adopted. For international trade, the international or regional standards such as ISO, ASTM and EN are often adopted, ensuring the reliability and comparability of the test results.

Physical property test methods: Strength tests such as tensile and tearing are usually carried out on a universal material testing machine. The specimens are prepared according to the standard provisions (strip method or grab method), the gauge length and tensile speed are set, and the test continues until the specimen breaks, with the system recording the maximum force and elongation. The drop test is carried out according to the height, load and number of drops specified by the standard.

Colour fastness test methods: For the colour fastness to rubbing, a rubbing fastness tester is used, and the sample is rubbed back and forth with standard dry/wet white cloths under a certain pressure, and then the staining grade of the white cloth is rated with the grey scales. For the colour fastness to washing, the specimen is sewn with a standard adjacent fabric, washed in a soaping solution at a specific temperature and time, and after drying, the change in colour and staining are rated.

Chemical substance test methods: The detection of hazardous chemical substances mostly adopts the instrumental analysis method. For the formaldehyde content, the water extraction method is commonly used, and after colour development with acetylacetone, the determination is carried out with a spectrophotometer. For the azo dyes and heavy metals, high-precision equipment such as high-performance liquid chromatography-mass spectrometry (HPLC-MS) and inductively coupled plasma mass spectrometry (ICP-MS) are usually used for qualitative and quantitative analysis.

Appearance and dimension inspection methods: Under a standard light source cabinet (such as the D65 light source), the visual inspection is carried out by trained inspectors at the specified viewing distance and angle. For the dimension measurement, a steel ruler or tape measure with an accuracy of not less than 0.1 cm is used, and the key part dimensions are measured in the flat state of the sample and compared with the design specifications.

Environmental test methods: For the degradation performance test, it needs to be carried out under controlled composting conditions. The specimen is mixed with the inoculum, cultivated under the specified temperature, humidity and ventilation conditions, and the amount of carbon dioxide produced is regularly measured or the mass loss and fragmentation are observed, to evaluate its ultimate aerobic biodegradation ability.

Testing Standards

Domestic Standards:

1. GB/T 3923.1-2013, Textiles — Tensile properties of fabrics — Part 1: Determination of breaking force and elongation at breaking force using the strip method

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

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

4. GB/T 3921-2008, Textiles — Tests for colour fastness — Colour fastness to washing with soap or soap and soda

International Standards:

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

2. ISO 105, Textiles — Tests for colour fastness

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

Universal material testing machine: It is the core equipment for testing the physical and mechanical properties of nonwoven bags. It can carry out various mechanical tests such as tensile, compression, bending, peeling and tearing. Through high-precision sensors and control systems, the parameters such as the force, displacement and elongation can be accurately measured, and the stress-strain curve is automatically generated, providing precise data for evaluating the load-bearing and durability of the bag.

Standard light source colour matching cabinet: Provides a stable and uniform standard light source environment (such as D65 daylight and TL84 shop light), used to judge the colour consistency, colour difference and the change in colour and staining grades after the colour fastness tests of the nonwoven bags. It can eliminate the interference of the ambient light, ensure the objectivity and accuracy of the colour evaluation, and is the essential equipment for the appearance inspection.

Colour fastness tester series: Including the rubbing fastness tester, washing fastness tester, perspiration fastness tester and light fastness tester. These equipment can simulate and standardize various external action conditions (friction, washing, perspiration and light exposure), scientifically evaluating the fixation stability of the dyes or pigments on the nonwoven fabric.

Analytical chemistry instruments: Precision instruments for detecting hazardous substances. An atomic absorption spectrometer (AAS) or an inductively coupled plasma optical emission spectrometer/mass spectrometer (ICP-OES/MS) is used to precisely determine the heavy metal contents. A high-performance liquid chromatograph (HPLC) and a gas chromatography-mass spectrometer (GC-MS) are used to analyse organic compounds such as formaldehyde, azo dyes and plasticizers.

Thickness gauge and electronic balance: The thickness gauge (commonly the dial gauge type or electronic type) is used to measure the thickness of the nonwoven fabric and its products under a standard pressure, evaluating the bulkiness or uniformity of the material. The high-precision electronic balance (with an accuracy of up to 0.001 g) is used to determine the grammage (mass per unit area) of the nonwoven fabric, and is the basic tool for controlling the raw material cost and quality.

Environmental simulation test equipment: Including the constant temperature and humidity chamber, the perspiration fastness oven, the UV aging test chamber and the biodegradation test system. These equipment can simulate the conditions that the product may encounter in actual use, storage or specific environments (such as composting), evaluating its performance changes or degradation behaviour, and providing verification for the product service life and environmental claims.