Cork Flooring Testing

Cork flooring testing mainly conducts scientific testing and analysis on dimensional stability, abrasion resistance, surface stain resistance, impact resistance, formaldehyde emission and light fastness, 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

Dimensional stability (swelling rate): This is the core test item of cork flooring, used to evaluate its expansion and shrinkage performance under different humidity conditions. Usually, the specimen is immersed in water at a specified temperature or placed in a high-humidity environment for a period of time, and the percentage change in its length, width and thickness is measured. Excellent dimensional stability means that the flooring is not prone to warping or gaps due to environmental humidity changes after installation.

Abrasion resistance: This test simulates the wear on the floor surface caused by daily walking and furniture movement. A Taber abrasion testing machine is usually used to grind the floor surface at a specific rotational speed and load, measuring the number of revolutions required to wear a certain thickness or the mass loss per unit revolution. This indicator is directly related to the durable years and appearance retention ability of the cork flooring.

Surface stain resistance: Evaluates the ability of the surface coating of cork flooring to resist the penetration and erosion of common pollutants (such as coffee, red wine, vinegar and shoe polish). During the test, the pollutant is dropped on the specimen surface and covered for a specified time. After removal, it is observed whether there is discoloration, corrosion or residue on the surface, to judge the convenience of its cleaning and maintenance.

Impact resistance: Determined by the falling ball impact test. A steel ball of a specified diameter and mass is dropped freely from a specific height onto the floor surface, and it is observed whether cracks, indentations or other permanent damage occur on the surface. This item reflects the cushioning and recovery performance of cork flooring under accidental impacts such as heavy objects falling.

Formaldehyde emission: In view of indoor environmental protection requirements, this is a mandatory safety test item. In accordance with the chamber method or the desiccator method, the formaldehyde content released into the air per unit area of the cork flooring under specified temperature and humidity conditions is determined. The results must comply with the E1 grade or stricter limit requirements of national mandatory standards (such as GB 18580).

Light fastness: Evaluates the ability of the surface color of cork flooring to resist fading under light. The specimen is exposed together with blue wool standards in a xenon arc aging test chamber for a specified time. By comparing the degree of color change of the specimen before and after exposure (usually rated with a gray scale card), the color stability after long-term use is judged.

Lock strength: For click-lock cork flooring, this test is crucial. Vertical or horizontal tensile or compressive forces are applied to the tongue and groove of the flooring through dedicated fixtures until the lock separates or fails, recording the maximum load. This data is directly related to the overall flatness and connection firmness of the floor after installation.

Testing Scope

Pure cork flooring: Refers to products made by pressing natural cork particles for both the surface layer and the base layer. Testing needs to comprehensively cover its physical and mechanical properties, especially compression resilience, density and dimensional stability, which are the key indicators reflecting its "soft" characteristics and comfortable foot feel.

Cork composite flooring: Usually composed of a cork surface layer and substrates such as high density fiberboard (HDF) and multi-layer plywood. Testing needs to focus on the bonding strength between the surface layer and the substrate, the physicochemical properties of the substrate itself (such as water absorption thickness swelling) and the formaldehyde emission of the overall product.

Cork acoustic flooring: This type of product adds a dedicated cork cushion layer or soundproofing material in the structure. In addition to conventional items, the testing scope needs to especially add acoustic performance tests such as impact sound improvement and airborne sound insulation to verify its claimed noise reduction effect.

Coated cork flooring: Refers to products with a protective layer of UV paint, water-based paint or oil wax on the surface. Testing needs to focus on evaluating the performance of the coating, including surface abrasion resistance, scratch resistance, stain resistance, cigarette burn resistance, as well as the adhesion and hardness of the coating.

Commercial and household grade cork flooring: According to the different traffic density of the place of use, the strictness and emphasis of testing differ. Commercial grade products need to pass higher-level abrasion resistance, impact resistance and stain resistance tests, and their technical indicators (such as abrasion resistance revolutions) are usually significantly higher than household grade products.

Products of different specifications and batches: Testing needs to cover all conventional specifications of the product (length, width and thickness). At the same time, for products of the same model from different production batches, sampling testing needs to be carried out to ensure the continuous stability and consistency of product quality.

Testing Methods

Dimensional stability test (GB/T 18102): In accordance with the national standard, the specimen is conditioned at (20±2) ℃ and (65±5)% RH until the mass is constant, and the initial dimensions are measured. It is then immersed in distilled water at (20±1) ℃ (such as for testing thickness swelling) or placed in an environment of (30±2) ℃ and (90±5)% RH (such as for testing length and width expansion) for a specified time, taken out, dried and measured again, and the dimensional change rate is calculated.

Abrasion resistance test (GB/T 18103): Mainly adopts the Taber abrasion test method. The specimen is fixed on a rotating platform, and grinding wheels of a specified model (such as H-22) and load (such as 500 g or 1000 g) are used. After each certain number of revolutions (such as 100 revolutions), the mass loss is weighed, or the total number of revolutions required to wear through the surface decorative layer is recorded. The results are expressed in "revolutions" or "mg/100r".

Formaldehyde emission testing (GB 18580): Currently, the 1 m³ chamber method is mainly adopted. A specimen with a surface area of 1 ㎡ is placed in a climate chamber with temperature (23±0.5) ℃, relative humidity (45±3)% and air exchange rate (1.0±0.05) times/h. The air in the chamber is regularly extracted and the formaldehyde concentration is determined by the acetylacetone spectrophotometric method until a stable state is reached, and the formaldehyde emission per unit area and unit time (mg/m³) is calculated.

Impact resistance test (GB/T 24508): Adopts the falling ball impact test. The specimen is placed face up on a rigid horizontal base, and a steel ball with a diameter of (42.8±0.2) mm and a mass of (324±5) g is dropped freely from different heights (such as 500 mm and 1000 mm) onto the specimen surface. After impact, the steel ball is removed and the impact point is observed for cracks under the specified lighting conditions.

Surface stain resistance test (GB/T 17657): A variety of contaminants specified in the standard (such as acetone, coffee and blue-black ink) are selected. The contaminants are respectively dropped or coated on the specimen surface and covered with a watch glass to prevent evaporation. After being placed for a specified time (such as 16-24 hours), it is cleaned with clean water or a specified solvent, dried, and the surface change is observed and compared with the uncontaminated area, and rated according to the obviousness of the stain marks.

Lock strength test (GB/T 24508 Appendix C): A universal material testing machine with dedicated fixtures is used. After the lock parts of two floor boards are correctly assembled, their two ends are clamped respectively. A vertical tensile force (for testing tensile strength) or a horizontal shear force (for testing shear strength) is applied to the lock connection at a constant speed until the lock separates or fails, recording the maximum load value during the process (in N/m or N).

Testing Standards

Domestic Standards:

1. GB 18580-2025, Indoor decorating and refurbishing materials — Limit of formaldehyde emission of wood-based panels and finishing products

2. GB/T 18102-2020, Laminated floor covering

3. GB/T 17657-2022, Test methods of evaluating the properties of wood-based panels and surface decorated wood-based panels

4. GB/T 1931-2009, Method for determination of moisture content of wood

5. GB/T 1936.1-2009, Method of testing in bending strength of wood

International Standards:

1. ISO 12460-1, Determination of formaldehyde emission of wood-based panels — Part 1: 1 m³ chamber method

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

Constant temperature and humidity climate chamber: Used for the conditioning of specimens before testing, as well as tests significantly affected by temperature and humidity such as dimensional stability and formaldehyde emission. It is required that the temperature and humidity control in the chamber is precise and stable, with good spatial uniformity, and it is the basic equipment for ensuring the comparability and accuracy of test results.

Taber abrasion testing machine: Dedicated equipment for evaluating the surface abrasion resistance of flooring. Its core components include a rotating platform, loading arms and abrasion grinding wheels. By precisely controlling the rotational speed, load and number of abrasion revolutions, the wear condition of the material surface can be quantitatively simulated and measured, and it is a key instrument for flooring durability evaluation.

Universal material testing machine: Equipped with various fixtures, it can be used for various mechanical property tests of cork flooring such as lock strength, modulus of rupture, modulus of elasticity and surface bonding strength. Its high-precision load sensors and displacement sensors can accurately record the force-displacement curve during the test, thereby calculating various strength indicators.

1 m³ formaldehyde emission climate chamber: Specially used for the arbitration test method of formaldehyde emission of wood-based panels and their products. The chamber body is made of inert, low-adsorption materials, and the internal environmental parameters (temperature, humidity, air exchange rate and air flow velocity) are automatically and precisely controlled, and combined with the sampling system and analytical instruments, continuous or intermittent monitoring of the formaldehyde concentration is realized.

Falling ball impact test device: Composed of a vertical guide rod, a release mechanism, a steel ball of a specified mass and diameter, and a rigid base. The impact energy is controlled by adjusting the release height. The structure is relatively simple, but the guide rod is required to have good verticality and the release mechanism to be flexible without obstruction, to ensure the accuracy and repeatability of the impact.

Spectrophotometer: Used to determine the absorbance of the formaldehyde solution in formaldehyde emission testing (acetylacetone method), thereby calculating its concentration. The instrument needs to be regularly calibrated with standard solutions, ensuring that its measurement accuracy and linear range at a specific wavelength (usually 412 nm) meet the testing requirements.

Precision measuring tools: Including micrometers (for measuring thickness), vernier calipers (for measuring length and width) and electronic balances (for weighing). The precision of these tools is directly related to the reliability of the test results of basic physical properties such as dimensional stability and density, and they must be regularly calibrated to ensure that they are in a valid state.