The core of material selection for plastic gears is matching the load, temperature, and wear resistance requirements of the intended use scenario. They are mainly divided into three categories: general-purpose plastics, engineering plastics, and high-temperature specialty plastics. Different categories vary significantly in strength, temperature resistance, and cost, requiring selection based on specific needs.
General-Purpose Plastics
General-purpose plastics offer high cost-effectiveness and are easy to injection mold, but their strength and wear resistance are generally average, making them suitable only for low-load, short-life applications. Nylon (PA, polyamide) has certain toughness and self-lubricating properties, and is impact-resistant, but its tendency to absorb water leads to dimensional instability. Unreinforced versions have lower strength and are often modified by adding glass fiber (PA+GF 10%-30%) to improve strength and wear resistance. It is a commonly used gear material among general-purpose plastics, suitable for toy gears, auxiliary transmission gears in simple household appliances, and gears for light-load office supplies. Polypropylene (PP) has lower cost and is resistant to acid and alkali corrosion, but it has poor rigidity, is easily deformed at high temperatures (temperature resistance ≤90℃), and has weak wear resistance. It is suitable for disposable equipment gears and decorative gears with low speed and no load requirements.
Engineering Plastics
Engineering plastics offer superior strength, wear resistance, and temperature resistance compared to general-purpose plastics, making them suitable for most conventional transmission applications and a common material for plastic gears. Polyoxymethylene (POM, commonly known as "acetal") exhibits outstanding overall performance, with good self-lubrication, high rigidity, high dimensional stability, temperature resistance ≤120℃, better wear resistance than nylon, and no water absorption issues. It also offers high transmission precision and is the most widely used material for plastic gears, covering almost all conventional applications with low to medium loads, such as printer transmission gears, automotive interior gears, core transmission gears in home appliances, and gears in office equipment. Furthermore, by adding specific sliding grade additives to POM resin, the noise performance of gears can be improved, making it suitable for applications such as office automation equipment where quiet operation is crucial. Polycarbonate (PC) offers high transparency and strong impact resistance, but poor wear resistance and susceptibility to stress cracking. Its temperature resistance is ≤130℃, making it suitable for gears requiring visible transmission and low-load, impact-resistant applications. ABS resin has a balance of rigidity and impact resistance, and is easy to dye, but it has low temperature resistance (≤80℃) and poor wear resistance. It is prone to wear and deformation after long-term use. It is suitable for low-speed, light-load appearance gears and auxiliary gears for non-core transmissions.
High-Temperature Specialty Plastics
High-temperature specialty plastics offer high strength and high temperature resistance, capable of withstanding medium to high loads and harsh environments, but they are costly and difficult to process. Polyetheretherketone (PEEK) exhibits excellent performance, with a temperature resistance up to 250℃, high strength, high wear resistance, resistance to oil and chemical corrosion, and good dimensional stability. However, it is costly, requires high temperature and pressure for processing, and is difficult to mold. It is suitable for auxiliary gears around automotive engines, high-load gears in industrial equipment, and gears in medical equipment. PEEK material has a low density (approximately 1.32 g/cm³), good self-lubricating properties, and outstanding wear resistance. Under specific testing conditions, its wear rate is lower than that of steel gears. Furthermore, its damping characteristics can absorb vibration energy, achieving silent transmission. Polyphenylene sulfide (PPS) has a temperature resistance of ≤220℃, strength and wear resistance close to PEEK, and is resistant to acids, alkalis, and high-temperature oil stains. Its cost is lower than PEEK. It is often modified by adding glass fiber or mineral fillers to improve rigidity and temperature resistance, making it suitable for applications such as auxiliary gears in automotive transmissions, industrial water pump gears, and gears in high-temperature zones inside electronic devices. Polyimide (PI) has high temperature resistance, but is brittle, difficult to process, and expensive. It is suitable for special gears in extreme high-temperature environments, and its application in the civilian sector is limited.
