Introduction:
Plastic materials are widely used in various fields, including industry, agriculture, construction, packaging, and machinery manufacturing. Due to their light weight, low cost, corrosion resistance, and easy processing, plastics have become indispensable in many industries. However, during use, plastics can undergo aging due to various factors, which can impact performance and even lead to product failure. This is especially crucial for plastic parts in outdoor applications, such as photovoltaic back sheets and enclosures for telecommunications equipment, which are exposed to harsh environments like sunlight, rain, and high temperatures. If these materials lack sufficient anti-aging properties, they will degrade prematurely. Thus, conducting aging tests to evaluate the durability of plastic materials is of great significance.

I. Main Purposes of Aging Testing for Plastic Materials

The purpose of aging testing is to assess the durability and stability of plastic materials under different environmental conditions, thereby predicting their lifespan and performance in real-world applications. By simulating various environmental factors, such as temperature, humidity, light, oxygen, and specific media, the aging process of plastic materials can be accelerated, enabling a comprehensive evaluation of their aging resistance. The significance of aging testing for plastic materials includes:

1. Evaluating Thermal Stability: Testing the stability of plastics under extreme temperatures to determine their long-term performance under continuous loads.
2. Assessing Physical Property Changes: Observing deformation, embrittlement, cracking, and other changes in plastic materials during high and low-temperature cycles.
3. Determining Service Life: Simulating real-world environments to predict the aging rate and lifespan of plastics in actual applications.
4. Supporting Product Optimization: Providing data for material improvement and manufacturing processes to help companies enhance product quality.

II. Aging Characteristics, Mechanisms, and Influencing Factors of Plastic Materials

1. Aging Characteristics of Plastics:
   Aging in plastics occurs when environmental factors over time, such as heat, light, high-energy radiation, mechanical stress, ultrasound, chemicals, and microorganisms, cause degradation in their chemical structure, leading to deteriorated physical, chemical, and mechanical properties. Plastic aging can be summarized into four types of changes: appearance changes, physical property changes, mechanical property changes, and electrical property changes.

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3. Mechanisms of Plastic Aging:

   • Chemical Aging: This is an irreversible chemical reaction resulting from changes in the molecular structure of polymers. It includes phenomena such as embrittlement of plastics and cracking of rubber.
   • Physical Aging: This occurs when external factors cause the glassy polymer to transition from a non-equilibrium state to an equilibrium state through the Brownian motion of small molecular chain segments. This process alters the material's physical and mechanical properties.

4. Factors Affecting Plastic Aging:
   The main external factors influencing plastic aging include:

   • (1) Radiation, (2) Oxygen, (3) Ozone, (4) Heat, (5) Moisture, (6) Mechanical Stress, and (7) Others.

III. Basic Principles and Evaluation Methods of Aging Testing for Plastic Materials

1. Natural Exposure Test Methods:
   Natural atmospheric aging tests study the aging of plastics under natural climatic conditions. This method involves exposing samples to outdoor environmental factors, where they undergo a combination of weather effects. By measuring the changes in properties before and after exposure, the aging resistance of the material can be evaluated.

   • Natural Storage Aging: Conducted in storage rooms or warehouses under natural climatic conditions or simulated real-world conditions, this test evaluates the aging resistance of materials based on property changes before and after exposure.
   • Marine Exposure Test: Samples are exposed to different marine environments, and their aging resistance is assessed by measuring the changes in properties before and after exposure.

   Natural aging tests closely simulate actual working conditions and use simple equipment. However, they require large facilities, extended test times, and are subject to weather changes, making it challenging to obtain quantifiable results. Results are applicable to specific exposure test sites.

2. Artificial Aging Tests:
   Artificial aging tests are conducted in laboratories and include the following methods:

   • Thermal Aging Test: This test evaluates the material's resistance to high temperatures. Samples are placed at temperatures above their usual operating conditions, and changes in properties before and after exposure are measured to assess heat resistance.
   • Hot-Humid Exposure Aging Test: This test exposes materials to hot, humid air to assess resistance to hot-humid environments based on property or appearance changes before and after exposure.
   • High-Pressure Oxygen and Air Thermal Aging Test: Conducted under high-temperature and high-pressure conditions, this test assesses weather resistance based on property or appearance changes before and after exposure.
   • Artificial Weathering Test: Samples are exposed to simulated environmental conditions, such as light, heat, oxygen, humidity, and rain, to assess weathering resistance based on changes in irradiance or radiation on the sample surface.

   The image shows Guangzhou Biaoji's high-pressure accelerated aging chamber (saturated) and flat-panel xenon lamp aging chamber, which are popular for their stability and high testing accuracy.

   

3. Melt Flow Rate (MFR) Method:
   The MFR method measures the melt flow rate of materials after aging under specified temperature and load conditions in a melt flow rate instrument. The melt flow rate decreases as aging time increases, and this rate is quantified to evaluate aging. Artificial aging tests are advantageous for their short test cycle, independence from field and climate, and high repeatability. However, they require sophisticated testing equipment and are commonly used for aging detection.