What are the most critical factors in accelerated aging testing?

Key indicators in accelerated aging testing mainly include mechanical property retention, appearance changes, chemical composition changes, electrical performance parameters, and sealing performance. These indicators collectively constitute the core evaluation criteria for whether a product or material can maintain its function and safety after simulated long-term use. Different industries and product types emphasize different indicators, but all revolve around a systematic evaluation of the "performance degradation trend" rather than simply "failure."

1. Mechanical Performance Indicators: Assessing the Structural Integrity of Materials

Mechanical properties are the direct basis for determining whether a material has become embrittled, softened, or experienced a decrease in strength.

Tensile strength retention rate: The ratio of tensile strength after aging to the initial value. A retention rate ≥80% is often used as a pass/fail standard.

Elongation at break retention rate: Reflects the material's toughness. A retention rate ≥50% is a common industry criterion.

Impact strength and flexural strength: Applicable to the evaluation of structural components made of plastics and composite materials.

Typical applications: Plastic products, rubber seals, automotive interior parts, etc.

2. Appearance change indicators: Reflect the degree of surface aging. Appearance changes are the most intuitive aging phenomenon perceived by users and are also early warning signals of failure.

Color difference (ΔE): Measured using a colorimeter; ΔE ≤ 2.0 is considered no significant color change.

Gloss change: Assessing the ability of coatings and plastics to maintain surface gloss.

Chinting, blistering, and cracking levels: Rated according to ISO 4628 standards; level 0 indicates no damage.

Typical applications: Coatings, building materials, outdoor advertising, automotive exterior parts.

3. Changes in chemical composition and molecular structure: Detecting microscopic changes such as the breaking of internal chemical bonds and the formation of oxidation products through instrumental analysis.

Active Ingredient Content Determination: Determination of active ingredients and antioxidant consumption rates.

Degradation Product Analysis: Detection of polymer oxidation and hydrolysis products using HPLC or GC-MS.

FTIR Infrared Spectroscopy: Identification of new functional groups such as C=O and OH to determine the degree of oxidation.

DSC/TGA Thermal Analysis: Detection of glass transition temperature (Tg) and thermal decomposition temperature changes.

Typical Applications: Pharmaceuticals, cosmetics, and polymer material research and development.

4. Electrical Performance Indicators: Core evaluation items for electronic products. Used to assess the reliability of insulating materials, PCBs, and semiconductor devices under humid heat or bias conditions.

Volume Resistivity, Surface Resistivity: Reflects whether insulation performance has decreased.

Dielectric Strength, Leakage Current: Detects the risk of breakdown under high voltage conditions.

Electrochemical Migration (ECM) Tendency: Observation of dendrite growth in HAST tests.

Typical Applications: Electronic components, automotive modules, and medical device circuits.

5. Sealing and Microbial Barrier Performance (Medical Device Specific): Key indicators to ensure aseptic packaging maintains a sterile state throughout its shelf life.

Sealing Strength Test: Detects whether the heat-sealed edge cracks.

Microbial Challenge Test: Simulates bacterial penetration ability to verify barrier effectiveness.

Sterility Test: Performs sterility checks after accelerated aging to confirm no contamination.

Typical Standards: ASTM F1980, ISO 11607

6. Functional Indicators: Verification of performance for specific products. Different products have unique functional requirements, necessitating specific testing and verification.

Basis: Changes in functional indicators directly affect user experience and safety.