High-Grade Engineering PET for Industrial Parts
As a high-performance engineering plastic, engineering PET holds a significant position in the industrial sector due to its exceptional mechanical strength, chemical resistance, and processing stability. Typical applications include relay housings, slide rails, and machined parts.
The specialized operating environments and performance requirements of these components necessitate the use of lower-grade materials, necessitating the reliance on high-specification engineering PET. Creep, warping, and water absorption are key issues driving material upgrades.
Relay Housings: Creep Resistance is a Core Requirement for Electrical Safety
Relay housings place extremely stringent demands on material stability and safety. As core circuit control components, relays are widely used in home appliances, automotive electronics, and industrial automation equipment. Their housings must not only protect the delicate contacts and coils within from dust and moisture, but also withstand long-term temperature fluctuations and mechanical stress.
Low-grade PET materials, due to their low molecular chain regularity and poorly controlled crystallinity, are prone to creep—the slow plastic deformation of the material under constant stress—over extended use. For example, relays in automotive engine compartments are exposed to high temperatures of 80-120°C for extended periods.
Low-grade PET housings can experience creep, widening seal gaps and allowing external oil, dirt, and moisture to penetrate, leading to contact oxidation or short circuits. In severe cases, this can even cause equipment downtime.
High-grade engineering PET, however, undergoes modification processes such as glass fiber reinforcement and mineral fillers to significantly enhance the molecular chain's resistance to deformation, keeping the long-term creep rate below 0.5%. It also offers excellent temperature resistance, maintaining structural stability within a temperature range of -40°C to 150°C, ensuring the protective performance and service life of the relay housing.
Slide Components: Warpage Resistance is Key to Maintaining Motion Precision
Slides, as key components for linear motion in mechanical systems, place extremely high demands on material dimensional accuracy and warpage resistance. Whether used in furniture drawer slides, conveyor rails for industrial automation equipment, or automotive seat adjustment rails, they all require smooth operation and precise positioning accuracy during long-term reciprocating motion.
Low-grade PET material is prone to warping and deformation due to uneven crystallization rates and insufficient internal stress release during the molding process. This occurs when components cool due to internal stress imbalances, resulting in dimensional deviations such as bending and twisting.
For example, if low-grade PET is used for conveyor rails in industrial assembly lines, warpage can exceed 0.2mm/m. This can lead to uneven clearances between the rail and the slider, causing jerking and noise during movement, and even accelerated component wear, shortening equipment maintenance cycles.
High-grade engineering PET, through optimized molding processes (such as precise control of injection temperature, pressure, and cooling rate) and the introduction of anti-warpage modifiers, effectively reduces internal stress in the material, keeping warpage to within 0.05mm/m.
Furthermore, its enhanced surface hardness (Rockwell hardness exceeding R110) and wear resistance reduce the friction coefficient between the rail and slider, ensuring stable movement during long-term use.
Machined Components: Water Absorption Resistance is Critical for Maintaining Structural Stability
As core components of industrial equipment, machined components often must maintain structural strength and dimensional stability under complex operating conditions (such as humid environments and exposure to chemical media). This places stringent demands on the material's water absorption resistance.
Low-grade PET materials, due to the polar ester groups in their molecular chains, are susceptible to water molecules, leading to water absorption—volume expansion and a decrease in mechanical strength after absorbing water in a humid environment.
For example, if machined joints used in water treatment equipment are made of low-grade PET, long-term immersion in water can cause the material to absorb more than 3% of water, leading to dimensional expansion and leakage at the joint's connection to the pipe. Simultaneously, their tensile strength may drop from 60 MPa to below 45 MPa, making them unable to withstand the water pressure within the pipe and ultimately causing rupture.
High-grade engineering PET improves its water absorption resistance in two ways: first, by adding hydrophobic modifiers (such as silane coupling agents) to the material to reduce the number of binding sites between the molecular chain and water molecules; second, by using a blending modification process, blending it with low-water-absorbent resins such as polycarbonate (PC) and polyphenylene sulfide (PPS) to reduce the overall hydrophilicity of the material. The modified engineering PET can control its water absorption rate to below 0.5%.
Even in long-term humid environments, it can still maintain over 90% of its initial mechanical strength, ensuring the structural stability and service life of machined parts.
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