Aluminum-plastic Composite Flexible Tube Testing

Aluminium-plastic composite tube inspection mainly conducts scientific testing and analysis on the barrier performance testing, physical and mechanical property testing, sealing performance testing, hygiene and chemical safety performance testing, and printing quality and appearance 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

Barrier performance testing: Mainly evaluates the barrier ability of the aluminium-plastic composite tube against the oxygen and water vapour, which is the key to determining the shelf life of the contents. The oxygen transmission rate testing measures the compactness of the aluminium foil layer and the composite structure, preventing the oxidative deterioration of the contents. The water vapour transmission rate testing evaluates the moisture-proof performance of the material, ensuring that the cream and paste products will not dry out and harden or breed the microorganisms due to the water loss.

Physical and mechanical property testing: Covering the compression resistance, drop resistance, flexing resistance and peel strength of the tube. The compression testing simulates the transportation stacking and squeezing forces, ensuring that the tube body is not deformed or damaged. The peel strength testing evaluates the bonding fastness between the plastic inner layer and the aluminium foil layer, and between the aluminium foil layer and the outer printing layer, preventing the delamination that causes the barrier failure or poor appearance.

Sealing performance testing: Including the tube shoulder sealing, tube tail sealing strength and overall air tightness testing. Through the negative pressure or positive pressure testing, it is checked whether there are the leaks at the tube shoulder (the connection part of the tube body and the nozzle) and the tube tail heat-sealing part. This is the basis for preventing the contamination and deterioration of the contents and ensuring the normal extrusion.

Hygiene and chemical safety performance testing: In accordance with the relevant food, pharmaceutical or cosmetic packaging material standards, the migration amounts of the heavy metals (such as the lead, arsenic and cadmium), solvent residues and evaporation residues are detected. It is ensured that the tube will not release the hazardous substances when contacting the contents, guaranteeing the safety of the final products.

Printing quality and appearance testing: Checks the registration precision, colour consistency, adhesion and wear resistance of the printing patterns. Through the colorimeter, adhesion testing tapes and friction testing machines, it is evaluated that the brand marks are clear and durable, meeting the market appearance requirements, and preventing the printing ink migration from contaminating the contents.

Testing Scope and Application Fields

Cosmetic packaging tubes: Mainly used for the packaging of the products such as the creams, lotions, gels and toothpaste. The testing emphasis is on the oxygen and moisture barrier to maintain the efficacy of the active ingredients, ensuring the compatibility with the contents, and the tube tail sealing strength to ensure the sealing under the multiple squeezes.

Pharmaceutical packaging tubes: Used for the eye ointments, skin ointments and medical coupling gels. The testing requirements are extremely strict. In addition to the routine physical and mechanical properties, they must comply with the pharmaceutical packaging material standards (such as the YBB standards), and the detailed chemical safety, sterility and biocompatibility evaluations are carried out.

Food packaging tubes: Such as the packaging of the products like the jams, seasoning pastes and concentrated juices. The testing needs to follow the food contact material regulations (such as the GB 4806 series standards), emphatically focusing on the limits of the specific migration substances such as the heavy metals and plasticizers, as well as the sealing to prevent the microbial contamination.

Industrial product packaging tubes: Used for the adhesives, greases and sealants. The testing focuses on the tolerance of the tube to the chemicals (corrosion resistance and solvent resistance), the high-strength sealing performance and the physical stability at the different ambient temperatures.

Subdivision by the composite structure types: The testing emphasis is determined according to the specific structures (such as the PE/AL/PE, PET/AL/PE and NY/AL/PE). For example, the tubes containing the nylon (NY) layer need to additionally test their puncture resistance and high barrier properties; for the different plastic inner layer materials, the corresponding solvent residue and migration analyses need to be carried out.

Testing Methods and Standard Basis

Barrier performance testing method: The oxygen transmission rate usually adopts the coulometric method (isostatic method), referring to the standards such as GB/T 19789 and ASTM D3985. The water vapour transmission rate adopts the infrared sensor method or gravimetric method (dish method), referring to GB/T 26253, ASTM F1249 or GB/T 1037. The testing is carried out under the specified temperature and humidity conditions to obtain the precise transmission data.

Mechanical property testing method: The peel strength testing refers to GB/T 8808, using a tensile testing machine to separate the composite layers at a constant speed. The sealing testing commonly uses the negative pressure method (GB/T 15171) or coloured water method, in which the tube is immersed in water and vacuumized to observe the bubbles. The compression testing simulates the stacking pressure, carried out according to GB/T 4857.3 or the customer-designated conditions.

Chemical safety performance testing method: The migration testing of the heavy metals and other substances is usually based on the GB 31604.1 series and GB 4806 series standards, using the inductively coupled plasma mass spectrometry (ICP-MS) or atomic absorption spectrometry (AAS). The solvent residues adopt the headspace gas chromatography-mass spectrometry method (HS-GC/MS), precisely determining the residual solvent contents such as the benzene series and ketones.

Printing and appearance testing method: The printing adhesion adopts the cross-cut method or tape method (referring to GB/T 13217.7). The wear resistance is tested with a friction testing machine (such as the Sutherland friction tester). The colour difference is measured with a spectrophotometer, and the ΔE value is compared with the standard colour plates, evaluated according to the CIELAB colour space.

Comprehensive standard system: The testing of the aluminium-plastic composite tube needs to integrate the multiple standards, including the national standards (GB/T and GB), industry standards (such as the QB/T and YBB), international standards (ISO and ASTM) and the customer's enterprise standards. The testing laboratory needs to select the appropriate standard system for the compliance judgement according to the final use of the product.

Testing Standards

Domestic Standards:

1. GB/T 19789, Packaging materials — Test method for oxygen gas permeability of plastic film and sheeting — Coulometric sensor

2. GB/T 26253, Packaging materials — Test method for water vapour transmission rate of plastic film and sheeting — Infrared detection sensor

3. GB/T 1037, Test method for water vapour transmission of plastic film and sheet — Cup method

4. GB/T 8808, Test method for peel strength of flexible laminated plastic materials

5. GB/T 15171, Test methods for seals of flexible packages

6. GB 4806, National food safety standards — Food contact materials and articles (series)

International Standards:

1. ASTM D3985, Standard test method for oxygen gas transmission rate through plastic film and sheeting using a coulometric sensor

2. ASTM F1249, Standard test method for water vapor transmission rate through plastic film and sheeting using a modulated infrared sensor

3. ISO 2528, Sheet materials — Determination of water vapour transmission rate — Gravimetric (dish) 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

Gas transmission rate tester: The core equipment for precisely measuring the transmission rates of the gases such as the oxygen and water vapour. The modern instruments mostly adopt the computer control, with the high-precision sensors (such as the coulometric sensors and infrared sensors), and can carry out the multi-chamber testing at the same time, providing the environmental chambers with the precise temperature and humidity control.

Universal material testing machine: Used for the mechanical property tests such as the peel strength, tensile strength, tube tail heat-sealing strength and compression resistance. The equipment is equipped with the fixtures and sensors of the various specifications, controls the test speed and modes through the software, and automatically records the force-displacement curves, calculating the various strength indicators.

Sealing tester: The negative pressure sealing tester and positive pressure sealing tester are commonly used. The negative pressure instrument vacuumizes through a vacuum chamber and observes the sample leakage; the positive pressure instrument fills the compressed air into the tube and immerses it in the water, or detects the micro-leakage through the pressure decay method, with the high sensitivity.

Analytical chemistry instruments: Including the gas chromatography-mass spectrometry (GC-MS) for the solvent residue and volatile substance analysis; the inductively coupled plasma mass spectrometer (ICP-MS) for the trace heavy metal element analysis; and the UV-visible spectrophotometer for the determination of the specific migration substances. These equipment are the cornerstones of the chemical safety evaluation.

Printing quality testing equipment: The colorimeter (spectrophotometer) is used for the quantitative colour management; the friction testing machine evaluates the printing wear resistance; and the cross-cut knives and pressure-sensitive tapes are used for the adhesion testing. In addition, the high-resolution image measuring instruments or microscopes can be used to detect the printing registration precision and micro-defects.