Composite Wood Flooring Inspection

Composite wood flooring inspection mainly conducts scientific testing and analysis on formaldehyde emission inspection, surface abrasion resistance inspection, dimensional stability inspection, surface stain resistance inspection, internal bond strength inspection and modulus of rupture and modulus of elasticity 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

Formaldehyde emission inspection: This is the most critical environmental safety indicator of composite wood flooring, directly related to indoor air quality and human health. It is mainly determined in accordance with the national standard GB/T 39600-2021 "Classification of formaldehyde emission of wood-based panels and their products". The test method is usually the 1 m³ chamber method, which precisely measures the formaldehyde concentration released into the air per unit time of the flooring by simulating the actual service environment, and carries out the grade determination of E1 grade, E0 grade or ENF grade according to the limit values.

Surface abrasion resistance inspection: This inspection is used to evaluate the ability of the floor surface decorative layer to resist wear, directly affecting the service life of the product. It is carried out in accordance with the national standard GB/T 18102-2020 "Laminated floor covering". A Taber abrasion tester or equipment of the same principle is used to perform rotary friction on the floor surface with abrasives at a specific rotational speed and pressure, recording the number of revolutions when the decorative pattern is worn through. Usually, household class I is ≥6000 revolutions and household class II is ≥4000 revolutions.

Dimensional stability inspection: Mainly tests the expansion, shrinkage and warping deformation of composite wood flooring under different temperature and humidity environments. The test items include the expansion rate of length, width and thickness. Usually, the specimen is soaked in water at a certain temperature or placed in a constant temperature and humidity chamber at a specific humidity for a period of time, and then its dimensional change is measured, to evaluate its ability to resist environmental humidity changes and prevent gaps or warping after installation.

Surface stain resistance inspection: Evaluates the ability of the floor surface to resist erosion and contamination by common pollutants (such as vinegar, coffee, lipstick and shoe polish). According to the standard provisions, a specific pollutant is applied to the floor surface and covered for a specified time, and then cleaned with a specified cleaning agent or clean water. It is observed whether there are stain marks or gloss changes on the surface, to judge its ease of cleaning and durability in daily use.

Internal bond strength inspection: A key indicator for testing the bonding strength between the fibers or particles inside the substrate of composite wood flooring (usually high density fiberboard or particleboard). A universal testing machine is used to apply a tensile force to the specimen perpendicular to the board surface until it is pulled apart, recording the maximum failure tensile force and calculating the strength value per unit area. Too low an indicator tends to cause problems such as delamination and blistering of the floor in use.

Modulus of rupture and modulus of elasticity inspection: These two are important mechanical property indicators for measuring the load-bearing capacity and bending deformation resistance of composite wood flooring. The modulus of rupture reflects the maximum stress that the floor can withstand when loaded to fracture, while the modulus of elasticity reflects its ability to resist elastic deformation. The three-point bending method is used for the inspection, applying a load to the middle of a strip specimen on a universal testing machine, and the load and deformation curve is recorded through sensors and the results are calculated.

Testing Scope

Laminated floor (high-pressure laminate composite flooring): This is the most common type of composite wood flooring, composed of a wear layer, a decorative layer, a high density fiberboard substrate and a balance moisture-proof layer. Its inspection scope comprehensively covers all the above test items, especially focusing on surface abrasion resistance, internal bond strength and formaldehyde emission. It is a product category of key concern in market supervision spot checks and consumer attention.

Engineered wood flooring (solid wood composite flooring): Usually uses plywood or multi-layer plywood as the substrate, with thin wood veneer of precious tree species applied on the surface. In addition to general performance, its inspection scope especially pays attention to the surface board thickness, interlayer bonding strength, surface board material identification, and heat and moisture dimensional changes, to ensure that it combines the solid wood appearance with the stability of the composite structure.

Stone plastic composite (SPC) and wood plastic composite (WPC) flooring: These new types of composite flooring mainly use limestone powder, polyvinyl chloride or wood powder and plastic as raw materials. In addition to general items such as dimensional stability and abrasion resistance, the inspection scope also especially includes special inspections for their material characteristics, such as the dimensional change rate under heating, residual indentation, cigarette burn resistance and the emission of volatile organic compounds (TVOC).

Locking system and installation flatness: The inspection scope extends to the connection components of the flooring. The dimensional accuracy, fit clearance, integrity after repeated assembly and disassembly, and the tensile strength of the lock of the tongue and groove of the flooring need to be inspected. At the same time, the overall flatness after simulated installation of multiple floor boards is measured to evaluate the installation effect and convenience.

Flame retardancy inspection: For composite wood flooring used in public places with special fire protection requirements (such as hospitals, schools and hotels), the inspection scope needs to add flame retardancy items. The inspection is carried out in accordance with GB 8624 "Classification for burning behaviour of building materials and products", determining indicators such as the combustion heat value, smoke density and burning droplets to determine its combustion performance grade (such as B1 grade difficult-to-ignite material).

Antibacterial and anti-mold performance inspection: For floor products used in humid environments such as kitchens and bathrooms or places with special hygiene requirements, the inspection scope can be extended to antibacterial and anti-mold performance. In accordance with relevant standards, after inoculating specific bacteria or mold spores and culturing under suitable conditions, the antibacterial rate is calculated or the mold growth condition is observed to evaluate the additional functions of the product.

Testing Methods

1 m³ chamber method (formaldehyde emission): This is currently the internationally recognized most scientific formaldehyde testing method, closest to the actual use conditions. A sample of specified surface area is placed in a climate chamber with strictly controlled temperature, humidity and air exchange rate, allowing the formaldehyde to freely release into the air in the chamber. The air in the chamber is regularly collected with an absorption solution, and the formaldehyde concentration is analyzed by the acetylacetone spectrophotometric method or high-performance liquid chromatography (HPLC) until a stable state is reached, finally calculating the formaldehyde emission.

Taber abrasion test method: A standard method for determining surface abrasion resistance. The floor specimen is fixed on a rotating platform, with two abrasion wheels equipped with specific models of grinding wheels installed above and a specified pressure applied. The equipment is started to rotate the platform, and the grinding wheels rub the specimen surface accordingly. After each certain number of revolutions, it is paused and observed until the decorative layer is worn through to expose the substrate, recording the total number of revolutions as the abrasion resistance revolutions.

Three-point bending test method: A classic mechanical method for determining the modulus of rupture and modulus of elasticity. A strip floor specimen is placed horizontally on two support rollers with a fixed distance between the two support points. At the center of the span, a load is applied downward at a constant speed through a loading indenter until the specimen fractures. The testing machine automatically records the load-deflection curve, and the modulus of rupture and modulus of elasticity are calculated through formulas.

Boiling test and drying test: Enhanced inspection methods for evaluating the water and heat resistance of engineered wood flooring. The specimen is placed in boiling water and boiled for a specified time, then placed in an oven at a specific temperature for drying, and this cycle is repeated several times. By observing whether the specimen develops defects such as delamination, blistering and cracking, and measuring its dimensional change, the glue line durability and dimensional stability under extreme conditions are evaluated.

Surface scratch resistance test (cross-cut method): A method for evaluating the adhesion between the surface decorative layer and the substrate of the floor. A dedicated cross-cut tester with 6 or 11 cutting blades is used to make grid-shaped cuts on the floor surface with uniform pressure. Then a dedicated adhesive tape is tightly adhered to the cross-cut area and quickly torn off. According to the degree of coating detachment at the grid edges, a rating of 0-5 is carried out against the standard atlas.

Dimensional stability test method (water immersion method / humidity method): There are mainly two methods. The water immersion method is to completely soak the specimen in water at a specified temperature (such as 20±2 ℃) for a certain time (such as 24 hours), and measure the water absorption expansion rate of its length and width. The humidity method is to place the specimen in a constant temperature and humidity chamber at a specific temperature and humidity (such as temperature 20 ℃ and humidity changing from 65% to 85%) for treatment, and measure its dimensional change rate after equilibrium.

Testing Standards

Domestic Standards:

1. GB/T 39600-2021, Classification of formaldehyde emission of wood-based panels and their products

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

3. GB 8624-2012, Classification for burning behaviour of building materials and products

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

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

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

1 m³ formaldehyde climate chamber: The core equipment for formaldehyde emission testing. The chamber body is made of inert material with an internal volume of 1 m³, equipped with precise temperature control (usually 23±0.5 ℃), relative humidity control (usually 45±3%), air exchange rate control (usually 1.0±0.05 times/h) and an air circulation system, ensuring a highly stable and repeatable test environment and providing the basis for accurate measurement.

Spectrophotometer or high-performance liquid chromatograph (HPLC): Analytical instruments for quantitative analysis of formaldehyde concentration. The spectrophotometer is based on the reaction of acetylacetone with formaldehyde to generate a yellow compound, measuring the absorbance at a wavelength of 412 nm and calculating the concentration through a standard curve. The HPLC method has higher sensitivity and anti-interference ability, separating through a chromatographic column and detecting with a UV detector, giving more precise results.

Computer servo-controlled universal material testing machine: Key equipment for mechanical property testing. It can be used for various tests such as internal bond strength, modulus of rupture, modulus of elasticity and lock tensile strength. Through the computer servo system, the loading speed and force are precisely controlled, and it is equipped with high-precision sensors, collecting and processing load and displacement data in real time, automatically generating test reports and curve charts.

Taber abrasion testing machine: A standard instrument dedicated to surface abrasion resistance testing. It is composed of a rotating platform, loading arms, abrasion wheels, a counter and a vacuum suction system. Its key components are standard abrasion wheels such as CS-10 or H-18, and precisely adjustable weights, to provide standardized pressure and friction conditions, ensuring the comparability of test results between different laboratories.

Constant temperature and humidity test chamber: An environmental simulation device for simulating different temperature and humidity environments, used for tests such as dimensional stability and equilibrium moisture content. It can precisely control the temperature and humidity in the chamber within a certain range (such as temperature 10-80 ℃ and humidity 20%-98% RH), and can be programmed for high and low temperature cycling or long-time constant temperature and humidity tests, testing the performance of the product under complex environments.

Precision measuring instrument set: Including vernier calipers (accuracy 0.02 mm), micrometers, flatness measuring instruments (or feeler gauges) and angle gauges. They are used to precisely measure the length, width, thickness, tongue height, groove depth, diagonal difference, edge straightness of the floor specimen, as well as the joint height difference and gap width after installation, ensuring that the product dimensional accuracy meets the standard requirements.