Extruded Particleboard Testing

Extruded particleboard testing mainly conducts scientific testing and analysis on modulus of rupture and modulus of elasticity, internal bond strength, water absorption thickness swelling, surface bonding strength, formaldehyde emission and screw holding power, 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

Modulus of rupture and modulus of elasticity: These are key mechanical indicators for measuring the bending deformation resistance and load-bearing capacity of particleboard. The modulus of rupture reflects the failure stress of the specimen under the maximum load, while the modulus of elasticity characterizes the stiffness of the material in the elastic deformation stage. Testing usually simulates the performance of the board under transverse loading, and is the core basis for evaluating its applicability as load-bearing members (such as shelves and tabletops).

Internal bond strength: This indicator is used to evaluate the firmness of the bond between the particle particles inside the particleboard, as well as between the particles and the adhesive. By applying a tensile force perpendicular to the board surface, the force required for failure is determined. Insufficient internal bond strength tends to cause problems such as delamination and blistering of the board in use, directly affecting its service life and structural stability.

Water absorption thickness swelling: This test item is used to evaluate the dimensional stability of particleboard in humid environments. After the specimen is soaked in water for a specified time, the change rate in the thickness direction is measured. A lower water absorption thickness swelling means that the board has better moisture resistance, making it suitable for places with high humidity such as kitchens and bathrooms.

Surface bonding strength: Mainly aimed at extruded particleboard that has been surfaced with impregnated paper film, veneer or coated treatment. It tests whether the bonding force between the surfacing material and the substrate (particleboard) is firm, preventing defects such as peeling and blistering of the surfacing layer in use, and is an important basis for evaluating the quality of secondary processing.

Formaldehyde emission: This is a core environmental indicator concerning indoor environmental safety and human health. It tests the formaldehyde gas that is residual in and slowly released from adhesives such as urea-formaldehyde resin used in the particleboard. The current national standard (such as GB/T 39600-2021) divides the emission into E1 grade, E0 grade and ENF grade according to the level of release, and it is a mandatory test item.

Screw holding power: Evaluates the ability of the board to hold screws, directly related to the connection strength and durability after furniture assembly. The test is divided into face screw holding power and edge screw holding power, and the edge performance is usually the weak link. This indicator is crucial for judging whether the board is suitable for connection parts that require frequent assembly and disassembly or load bearing.

Testing Scope

Classification by density: Testing covers extruded particleboard of different densities, usually divided into low density (<0.65 g/cm³), medium density (0.65-0.80 g/cm³) and high density (>0.80 g/cm³) boards. Different density grades correspond to different mechanical properties and uses, and the performance index requirements in the testing standards also differ accordingly. Targeted testing needs to be carried out according to the nominal density of the product.

Classification by surface condition: The testing objects include bare boards without surfacing, sanded boards, and boards after various surfacing treatments, such as melamine-impregnated paper surfaced boards, decorative veneer surfaced boards, PVC film surfaced boards and coated boards. After surfacing, additional attention needs to be paid to surface performance, such as abrasion resistance, stain resistance, scratch resistance and surface bonding strength.

Classification by service environment: Testing is divided according to the humidity conditions of the intended service environment of the board, mainly including ordinary boards used in the dry state, moisture-resistant boards used in the humid state and exterior boards used outdoors. Different environment categories have completely different requirements for the physical and mechanical properties of the board, especially the water absorption thickness swelling and internal bond strength.

Classification by function and use: The testing scope is determined according to the final use, such as general-purpose particleboard for ordinary furniture manufacturing, structural particleboard for load-bearing structures and particleboard for flooring substrates. For boards of different uses, the focus of test items and the index limits differ significantly.

Classification by formaldehyde emission grade: Testing and grading are carried out according to the formaldehyde emission limit values specified in the national standards, mainly divided into E1 grade (≤0.124 mg/m³), E0 grade (≤0.050 mg/m³) and ENF grade (≤0.025 mg/m³). The specified chamber method or gas analysis method needs to be adopted for testing, and conformity determination is carried out for products of different grades.

Testing Methods

Physical and mechanical property testing: Mainly carried out in accordance with GB/T 17657-2022 "Test methods of evaluating the properties of wood-based panels and surface decorated wood-based panels". The modulus of rupture and modulus of elasticity adopt the three-point bending method; the internal bond strength uses a tensile fixture to pull the specimen perpendicular to the board surface; the water absorption thickness swelling requires soaking the specimen in water at (20±1) ℃ for a specified time and then measuring; the screw holding power is tested by screwing the screw into the board to a specific depth and then performing a pull-out test.

Formaldehyde emission testing: The current national standard (GB/T 39600-2021) specifies the 1 m³ chamber method as the arbitration method. A sample of specified surface area is placed in a climate chamber with strictly controlled temperature, humidity and air exchange rate. After the formaldehyde concentration in the chamber air reaches equilibrium, sampling and analysis are carried out and the emission is calculated. In addition, the gas analysis method or the desiccator method can also be used as the method for internal quality control of the factory.

Dimensional stability testing: In addition to the water absorption thickness swelling, it also includes the determination of moisture content, density and density difference within the board. The moisture content adopts the gravimetric method, drying at (103±2) ℃ to constant weight; the density is calculated by measuring the mass and volume of the specimen; the density difference within the board is evaluated by measuring the density at different positions of the same board in sections to assess the uniformity of board production.

Surface performance testing: In the surface bonding strength test, a surface layer of a specified area is cut out and a peeling tensile test is carried out with a dedicated fixture. For surfaced boards, multiple performance tests such as surface scratch resistance, abrasion resistance, stain resistance, dry heat resistance and cigarette burn resistance also need to be carried out in accordance with the standard, to simulate various situations that may be encountered in actual use and evaluate their durability.

Sampling and conditioning: The prerequisite for all testing is scientific sampling and standardized conditioning. Samples need to be randomly selected from batch products and kept away from edges and defective parts. Before testing, the samples must be placed under standard climate conditions of temperature (20±2) ℃ and relative humidity (65±5)% until the mass is constant, to ensure the comparability and accuracy of test results.

Testing Standards

Domestic Standards:

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

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

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

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

Universal mechanical testing machine: The core equipment for almost all mechanical property tests such as modulus of rupture, modulus of elasticity, internal bond strength, surface bonding strength and screw holding power. It needs to be equipped with corresponding three-point bending fixtures, tensile fixtures and dedicated screw pull-out fixtures. The equipment should have high-precision load sensors and displacement measuring systems, and be regularly calibrated by metrological departments.

Climate chamber and formaldehyde analysis system: Used for formaldehyde emission testing. The 1 m³ climate chamber needs to precisely control the internal temperature, relative humidity, air exchange rate and air flow velocity. The supporting analysis system usually includes formaldehyde sampling devices (such as absorption bottles), a high-performance liquid chromatograph (HPLC) or the ultraviolet-visible spectrophotometer required by the acetylacetone spectrophotometric method, for quantitative analysis of the collected air samples.

Constant temperature and humidity conditioning chamber: Used for standard conditioning of test samples so that their moisture content reaches equilibrium with the standard atmospheric conditions. The equipment must be able to stably maintain the internal environment within the range of temperature (20±2) ℃ and relative humidity (65±5)% for a long time, which is the basis for ensuring the accuracy and reliability of all subsequent physical and mechanical property test data.

Thickness gauge and length measuring tools: Used to precisely measure the dimensions of the specimen, including thickness, length and width. For thickness measurement, micrometers or electronic thickness gauges with spherical probes and measuring pressure complying with the standard need to be used. Vernier calipers or steel rulers are used for length and width. The precision of dimensional measurement directly affects the calculation results such as density and swelling rate.

Constant temperature water bath and drying oven: The constant temperature water bath is used for the water absorption thickness swelling test, and needs to maintain the water temperature at a constant (20±1) ℃. The drying oven is used to determine the moisture content of the board, requires good temperature uniformity and can be maintained at (103±2) ℃. Both are key equipment for evaluating the water resistance and moisture state of particleboard.

Dedicated surface performance testing instruments: Including surface abrasion testing machines (such as the Taber abrasion tester), scratch testers, stain resistance test devices, dry heat resistance test benches and cigarette burn test racks. These devices are used to systematically evaluate the surface durability of surfaced particleboard, simulating wear, scratching, high temperature and contamination in daily use.