Aluminum Foil Filter Screen Testing

Aluminium foil filter screen inspection mainly conducts scientific testing and analysis on the physical and mechanical property testing, mesh count and aperture size testing, thickness and grammage testing, air permeability, surface aluminium foil adhesion uniformity testing and flame retardant property testing, 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 evaluating the tensile strength, elongation and puncture resistance of the aluminium foil filter screens. These indicators directly affect the structural integrity and durability of the filter screens during the installation and use processes, preventing the tearing or damage caused by the improper forces.

Mesh count and aperture size testing: The number of the meshes per unit length (mesh count) and the actual aperture sizes of the single meshes are precisely measured through the optical microscopes or image analysers. This is the core parameter of evaluating the filtration precision of the filter screens, ensuring that they can meet the interception requirements for the specific dust particle sizes.

Thickness and grammage testing: The micrometer callipers or thickness gauges are used to measure the thicknesses of the aluminium foil materials, and the precision balances are used to measure the masses per unit area (grammage). These two parameters are related to the physical strengths, air permeability and raw material consumption of the filter screens, and are the basic items of the quality control.

Air permeability (air resistance) testing: Under the standard pressure difference conditions, the air flow rates passing through the filter screens per unit area per unit time are measured. The air permeability is the key indicator of measuring the ventilation performance of the filter screens, affecting the equipment energy consumption and filtration efficiency.

Surface aluminium foil adhesion uniformity testing: The uniformity of the coating or lamination of the aluminium foil on the substrate (such as the glass fiber mesh) is evaluated. Through the visual inspection or image comparison method, ensuring that the aluminium foil layers have no missing coating, blistering or peeling phenomena, to guarantee their good electrical conductivity and flow guiding properties.

Flame retardant property testing: According to the relevant standards (such as GB 8624), the vertical burning or limiting oxygen index testing is carried out on the filter screen samples. The aluminium foil itself is non-combustible, but the flame retardant characteristics of its overall structures under the high temperatures or open flames need to be verified, ensuring the use safety.

Corrosion resistance testing: Through the salt spray test chambers simulating the corrosive environments, the corrosion resistance of the aluminium foil layers in the salt-containing and humid air is evaluated. This is particularly important for the filter screens used in the coastal or industrial acid atmosphere, and is related to their service lives.

Testing Scope

Aluminium foil filter screens for HVAC systems: Applied to the primary and medium efficiency filtration sections of the central air conditioners and fresh air systems. The testing emphases are their dust holding capacities, air resistance change rates and structural stability under the long-term use, ensuring the balance between the ventilation efficiency and energy consumption.

Aluminium foil filter screens for cleanroom high-efficiency filters: As the support layers or diversion layers of the high-efficiency filters (HEPA/ULPA). The testing focuses on the extremely high mesh count precision, extremely low self-generation dust amounts and excellent chemical compatibility, preventing the pollution of the clean environments.

Aluminium foil filter screens for automotive air filters: Used in the automobile engine intake systems. In addition to the routine properties, the durability under the high temperatures (engine compartment environments), high humidity and oil mist environments, as well as the vibration fatigue resistance need to be emphatically tested.

Aluminium foil filter screens for industrial dust collection: Applied to the industrial smoke and dust treatment equipment such as the bag filters. The testing scope includes the wear resistance, anti-static properties (preventing the dust adsorption), as well as the anti-aging ability under the specific chemical gas environments.

Aluminium foil filter screens for kitchen fume purification: Used in the mechanical filtration sections of the commercial kitchen fume purification equipment. The core testing items are the oil stain adhesion resistance, easy cleaning, as well as the anti-deformation and anti-oil oxidation abilities under the high-temperature oil fume environments.

Special function aluminium foil filter screens: Such as the antibacterial coating aluminium foil filter screens and anti-static aluminium foil filter screens. In addition to the basic items, the testing scope needs to specially verify the effectiveness, durability and safety of their claimed special functions.

Testing Methods

Tensile testing method (GB/T 3923.1): The universal material testing machines are used to stretch the standard-size filter screen specimens at the constant rates until the fracture, recording the maximum forces and elongations, calculating the tensile strengths and elongation at break, and evaluating their mechanical strengths.

Microscopic image analysis method: The optical microscopes or electron microscopes equipped with the measurement software are used to take photos of the filter screen samples. The software automatically identifies and counts the mesh numbers, measures the aperture sizes and their distributions. The results are objective and accurate.

Air permeability testing method (GB/T 5453 / ISO 9237): The fabric air permeability testers are adopted. The specimens are clamped on the test heads of the fixed areas (such as 20 cm²), and under the specified pressure differences (such as 100 Pa or 200 Pa), the air permeability values displayed by the instruments are directly read.

Grammage determination method (GB/T 24218.1): The analytical balances with the precision of 0.001g are used to weigh the masses of the circular or square filter screen specimens of the known areas (usually 100 cm² or larger), and the masses per unit area (g/m²) are obtained through the calculation.

Salt spray testing method (GB/T 10125): The filter screen specimens are placed in the salt spray test chambers, continuously sprayed with the sodium chloride solution of the specific concentration, forming the corrosive environments. After the specified times (such as 24h, 48h and 96h), the specimens are taken out to observe the surface corrosion, blistering or coating peeling conditions.

Vertical burning testing method (GB/T 5455): The filter screen specimens of the specified sizes are vertically suspended, ignited from their lower edges with the standard flames for a certain time. After removing the flame sources, the afterflame times, afterglow times and damaged lengths of the specimens are recorded, evaluating their flame retardant grades.

Air resistance-dust holding capacity combined testing method: On the dedicated filter media testing benches, the air flows containing the standard test dust (such as the ASHRAE dust) continuously pass through the filter screens, and the rising curves of the filter screen air resistances during the testing processes are monitored in real time until the final resistances are reached, calculating their dust holding capacities.

Testing Standards

Domestic Standards:

1. GB 8624, Classification for burning behaviour of building materials and products

2. GB/T 10125-2021, Corrosion tests in artificial atmospheres — Salt spray tests

3. GB/T 3923.1, Textiles — Tensile properties of fabrics — Part 1: Determination of breaking force and elongation at breaking force (strip method)

4. GB/T 5453, Textiles — Determination of the permeability of fabrics to air

5. GB/T 24218.1, Textiles — Test methods for nonwovens — Part 1: Determination of mass per unit area

6. GB/T 5455, Textiles — Burning behaviour — Determination of damaged length, afterglow time and afterflame time of vertically oriented specimens

International Standards:

1. ISO 9237, Textiles — Determination of the permeability of fabrics to air

2. ISO 9227, Corrosion tests in artificial atmospheres — Salt spray tests

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: Used to carry out the mechanical property testing such as the tensile, tearing and bursting. The equipment is equipped with the high-precision transducers and control systems, and can output the force-displacement curves. It is the core equipment of evaluating the mechanical properties of the filter screens.

Digital fabric air permeability tester: The core components include the specimen clamping devices, pressure difference adjustment systems, flow measurement units and microprocessors. It can automatically adjust and stabilize the test pressure differences, precisely measure the air flows, and directly display the air permeability rates.

Precision thickness gauge/micrometer calliper: Adopting the contact or non-contact (laser) measurement principles, with the high resolutions (usually reaching the micrometre level) and stable measurement pressures, used to accurately obtain the thickness data of the filter screens and their coatings.

Laboratory-grade analytical balance: The sensitivity needs to reach 0.001g or higher, equipped with the wind shields, ensuring that the light filter screen samples are free from the air flow interference during the weighing. It is the basic equipment of measuring the grammage and calculating the other parameters.

Salt spray corrosion test chamber: Composed of the spraying systems, chamber heating devices, saturated air barrels and control systems, which can precisely control the chamber temperatures, spraying amounts and sedimentation rates, simulating the harsh salt spray corrosion environments.

Optical/electron microscope and image analysis system: The microscopes provide the high-magnification and large-depth-of-field testing images. The image analysis software automatically completes the statistics and measurement of the apertures and mesh counts through the algorithms such as the grey level recognition and edge detection, improving the efficiency and accuracy.

Comprehensive filter media property testing bench: The integrated equipment that can simulate the actual working conditions and carry out the dynamic testing of the items such as the air resistance, filtration efficiency and dust holding capacity. Usually including the aerosol generators, particle counters, pressure transducers and automatic dust generation devices.