Chemical stability testing to Chinese national standards (GB standards) evaluates how plastics, rubber, coatings, glass, and other materials resist degradation when exposed to acids, alkalis, salts, solvents, and other aggressive media. This technical guide summarizes the applicable GB test methods, typical sample types, measured parameters, laboratory procedures, and industrial applications, helping manufacturers and exporters plan compliant evaluation programs with accredited third-party laboratories.
Technical Overview
Chemical stability, often referred to as chemical resistance, describes the ability of a material to preserve its chemical composition, physical structure, and mechanical performance after contact with liquid, gaseous, or solid chemical media. Under the Chinese national standard system, commonly abbreviated as GB (Guobiao), this property is evaluated through standardized exposure and measurement procedures published as national test method standards.
The majority of chemical stability test methods in China are published as GB/T recommended national standards, many of which are technically harmonized with international counterparts such as ISO 175 for plastics, ISO 1817 for rubber, ISO 2812 for paints and varnishes, and ISO 719 for glass. Product-specific GB standards cite these method standards and define acceptance criteria, such as maximum permissible mass change or minimum mechanical property retention.
Core principles of chemical stability testing under the GB system include:
- Controlled exposure of standardized specimens to defined chemical media at specified temperatures and durations
- Measurement of changes in mass, dimensions, appearance, and mechanical properties before and after exposure
- Comparison of results against classification grades or acceptance limits defined in the governing product standard
- Use of conditioned specimens and calibrated equipment to ensure reproducible and comparable results between laboratories
Testing is typically performed by accredited third-party laboratories or in-house quality departments to support material qualification, supplier approval, quality control, regulatory compliance, and failure analysis.
Testing Samples
Sample selection and preparation follow the requirements of the applicable method standard. Specimens are generally conditioned in a standard atmosphere before testing to ensure that measured changes reflect chemical exposure rather than environmental history.
Plastics and Polymer Materials
Sheets, films, rods, tubes, injection-molded plates, and machined test pieces are evaluated for resistance to chemical liquids under GB/T 11547, the national adoption aligned with ISO 175. Specimen geometry, thickness, and edge finish are controlled because these factors influence liquid uptake and measured property changes.
Rubber and Elastomer Products
Seals, O-rings, hoses, diaphragms, gaskets, and vulcanized sheets are tested for resistance to liquids under GB/T 1690, aligned with ISO 1817. Standard test pieces may be cut directly from finished products when molded specimens are unavailable, with the sampling location documented.
Coatings and Paint Films
Coated test panels applied to glass, metal, or other defined substrates are prepared and cured according to the coating specification, then evaluated for resistance to liquids under GB/T 9274, aligned with ISO 2812.
Glass and Ceramic Materials
Glass grains of specified particle size, container sections, and laboratory glassware are assessed for hydrolytic resistance under GB/T 6582, aligned with ISO 719, and for resistance to boiling mixed alkali solution under GB/T 6580, aligned with ISO 695.
Metals, Alloys, and Surface Treatments
Metal components, plated parts, and treated surfaces are evaluated for chemical and corrosion resistance against cleaning agents, process chemicals, and environmental media, supporting material selection and protective system design.
Packaging and Functional Components
Food-contact materials and articles, medical consumables, battery components, and electronic parts are assessed for chemical compatibility, stability, and migration behavior using the applicable national food safety test standards and GB/T 14233.1 chemical analysis methods where relevant.
Testing Items
Depending on the material and the referenced standard, chemical stability testing commonly reports the following parameters:
- Percentage change in mass after exposure, measured immediately after removal and after drying or reconditioning
- Changes in dimensions, thickness, and volume, including swelling behavior
- Visual appearance assessment: discoloration, blistering, crazing, cracking, softening, tackiness, dissolution, and loss of adhesion
- Retention of mechanical properties: tensile strength, elongation at break, flexural strength, impact strength, and Shore hardness
- Changes in functional properties such as electrical characteristics, sealing force, or barrier performance
- Hydrolytic and alkali resistance classification of glass, including grading equivalent to the HGA/HGB hydrolytic resistance classes of ISO 719
- Extractables and migration quantities for food-contact and medical applications
Typical test media include distilled water, standard acids such as sulfuric, hydrochloric, nitric, and acetic acid, alkalis such as sodium hydroxide and sodium carbonate, salt solutions, organic solvents such as ethanol, acetone, toluene, and heptane, mineral oils, fuels, and detergents. Media are selected to simulate actual service conditions or as mandated by the product standard.
Testing Methods
Full Immersion Method
Specimens are completely immersed in the test liquid at a controlled temperature, commonly 23 °C ± 2 °C or elevated temperatures such as 40 °C, 50 °C, 70 °C, or the boiling point of the medium, for a defined period such as 24 hours, 72 hours, 7 days, or longer. After exposure, specimens are wiped, weighed, measured, and tested immediately or after drying and reconditioning, following GB/T 11547 for plastics and GB/T 1690 for rubber.
Spot, Patch, and Immersion Methods for Coatings
Under GB/T 9274, a drop of the test liquid may be placed on the coating surface, an absorbent medium saturated with the liquid may be held against the film under a cover, or the entire coated panel may be immersed. Damage is assessed visually and quantitatively through indicators such as gloss loss, softening, blistering, or loss of adhesion.
Glass Grain Hydrolytic Resistance Method
Under GB/T 6582, glass grains of specified size are boiled in water for a defined period, and the extracted alkali is quantified by acid titration, allowing classification into hydrolytic resistance grades. Resistance to boiling aqueous mixed alkali solution is separately evaluated under GB/T 6580.
Post-Exposure Mechanical and Physical Evaluation
Exposed and unexposed control specimens are tested under the corresponding property standards, for example tensile testing of plastics per GB/T 1040, tensile properties of rubber per GB/T 528, and indentation hardness per GB/T 531. Property retention is calculated and compared with specification limits, giving a quantitative measure of chemical stability.
Evaluation and Reporting
Laboratories report exposure conditions, measured changes, calculated retention values, and a conclusion on the resistance level. Where the governing product standard defines grades or pass/fail criteria, results are reported against those limits; otherwise, comparative data are provided to support material selection and design decisions.
Applications
Chemical stability testing to GB standards is applied across a wide range of industries:
- Automotive and transportation: validation of hoses, seals, fuel system components, and interior trim against fuels, oils, coolants, and cleaning agents
- Chemical processing and industrial equipment: qualification of linings, pipes, valves, gaskets, and protective coatings for contact with process chemicals
- Medical devices and pharmaceutical packaging: compatibility, stability, and extractables assessment of consumables and container-closure materials
- Food contact materials: migration and resistance testing supporting compliance with national food safety standards for repeated use and cleaning
- Construction and infrastructure: durability evaluation of pipes, waterproofing membranes, sealants, and architectural coatings
- Electronics and batteries: chemical resistance of insulating materials, printed circuit boards, and cell components against electrolytes and solvents
- Research, development, and quality control: material screening, supplier qualification, incoming inspection, and failure analysis
FAQ
What is the difference between GB and GB/T standards?
GB standards issued without the "/T" suffix are mandatory national standards enforceable by regulation, while GB/T standards are recommended technical standards adopted voluntarily. Most chemical stability test methods are GB/T method standards that product standards cite together with specific requirements and acceptance limits.
Which GB standards are used for chemical stability testing?
Commonly applied methods include GB/T 11547 for the resistance of plastics to chemical liquids, GB/T 1690 for the resistance of rubber to liquids, GB/T 9274 for the resistance of paints and varnishes to liquids, and GB/T 6582 and GB/T 6580 for the hydrolytic and alkali resistance of glass. These methods are largely harmonized with ISO 175, ISO 1817, ISO 2812, ISO 719, and ISO 695 respectively.
How are test liquids and exposure conditions selected?
Media, temperature, and duration are selected to reproduce actual service conditions or to follow the requirements of the governing product standard. Each method standard specifies standard reagent solutions, exposure temperatures, and exposure times so that results remain comparable between laboratories.
How long does chemical stability testing take?
Exposure periods typically range from 24 hours to several weeks depending on the standard and material. Including specimen preparation, conditioning, exposure, and post-exposure testing, complete programs commonly take one to six weeks.
Are GB test results accepted internationally?
Because many GB/T methods are aligned with their ISO counterparts, results generated by accredited third-party laboratories are widely accepted in international supply chains. Buyers should nevertheless confirm which specific standard edition and acceptance criteria a target market or customer requires before testing begins.