What are the aging characteristics of PBT

As an important engineering plastic, polybutylene terephthalate (PBT) is widely used in many fields such as automobiles, electronics and home appliances. Its excellent mechanical properties, thermal stability and chemical resistance make it the material of choice for many industrial applications. However, during long-term use, the aging characteristics of PBT gradually emerge, becoming a key factor affecting its service life and reliability. Therefore, it is particularly important to deeply study the aging mechanism and manifestations of PBT.

Definition and mechanism of aging
Aging refers to the process in which the physical and chemical properties of a material change due to environmental factors (such as light, temperature, humidity and oxygen, etc.) and mechanical loads during use. For PBT, its aging can be mainly divided into four types: thermal aging, photoaging, oxidative aging and hydrolysis.
Thermal aging: Under high temperature conditions, the molecular chains of PBT may break or cross-link, resulting in a significant decrease in mechanical properties. The results of thermal aging are usually manifested as increased brittleness and reduced toughness of the material, which poses a threat to its reliability in high-temperature applications.
Photoaging: Ultraviolet (UV) radiation can cause the breakage of PBT molecular chains and generate free radicals, leading to material degradation. The manifestations of light aging usually include the appearance of cracks on the surface of the material, changes in color and reduced strength, which may affect its application in outdoor environments.
Oxidative aging: In the presence of oxygen, PBT may undergo oxidation reactions, resulting in changes in its molecular structure. This process accelerates the degradation of the material and has an adverse effect on its physical properties, especially in high-oxygen environments.
Hydrolysis: In a humid environment, water molecules penetrate into the interior of PBT and react with the molecular chains, resulting in a decrease in material performance. Hydrolysis usually increases the water absorption rate of PBT and reduces its mechanical strength, which is particularly evident under wet conditions.

Aging characteristics performance
The aging characteristics of PBT can be evaluated in the following aspects:
Mechanical properties changes: As aging progresses, the mechanical properties of PBT, such as tensile strength, impact strength and ductility, usually decrease significantly. This is due to the degradation of physical properties caused by the breakage and cross-linking of molecular chains.
Thermal properties changes: The aging process may affect the heat deformation temperature (HDT) and melting temperature of PBT, resulting in a decrease in its stability in high temperature environments, thereby limiting its application areas.
Changes in optical properties: Light aging can cause color changes in PBT materials, and the surface may turn yellow or fog, which directly affects the appearance and transparency of the material and reduces its market competitiveness.
Changes in dimensional stability: During the aging process, PBT may warp, crack, or change in size, which will affect its performance in precision applications and reduce the overall quality of the product.

Aging test method
In order to accurately evaluate the aging characteristics of PBT, the following test methods are usually used:
Heat aging test: Place the PBT sample in a high temperature environment and regularly measure the changes in its mechanical and thermal properties to evaluate its thermal stability and durability.
Light aging test: By using a xenon lamp or UV lamp to simulate solar radiation, observe the performance changes of PBT under different radiation intensities and times, so as to evaluate its anti-light aging ability.
Oxidative aging test: Aging experiments are carried out in an environment with controlled oxygen concentration to evaluate the performance changes of PBT under oxidative conditions and help predict its performance in actual applications.
Hydrolysis test: PBT samples are immersed in water and their mechanical properties and water absorption are regularly measured to evaluate their hydrolysis characteristics to ensure that the material can still maintain excellent performance in a humid environment.