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Material Selection

• Nylon PA66: Offers high mechanical strength and good wear resistance. Suitable for connecting general mechanical structures, such as fastening non-critical components around automobile engines.
• PP (Polypropylene): Features excellent chemical resistance and flexibility. Commonly used for connecting low-pressure parts in chemical equipment and pipeline systems.
• PVC: Cost-effective with moderate corrosion resistance. Ideal for cost-sensitive applications with low environmental requirements, such as assembling simple plastic furniture.
• PVDF: Exhibits exceptional acid, alkali, and corrosion resistance. Performs well in harsh chemical environments like electroplating and chemical industries, making it suitable for equipment connections in such conditions.

Size Considerations

• Diameter: Determined by the thickness of the connected components and the load they bear. For thicker parts or high-load applications (e.g., connecting plastic components in automobile chassis), larger-diameter screws are required to ensure connection strength.
• Length: Must fully penetrate the connected components with sufficient thread engagement length. Typically, the thread engagement length should be at least 1.5 times the screw diameter to ensure a reliable connection.

Head Type Selection

• Pan Head: Has a large contact area, distributing force over a wider surface to reduce pressure on the component surface. Suitable for connecting soft plastics or thin materials, such as securing plastic partitions inside computer cases.
• Countersunk Head: Sits flush with the component surface for a smooth, aesthetic appearance. However, it creates high hoop stress during tightening, which may cause stress cracking in plastic parts. Not recommended for plastic connections unless appearance is critical and strict testing is conducted.
• Hex Head (External): Can be tightened with a wrench, providing high torque. Suitable for applications requiring strong fastening force, such as assembling large plastic equipment.
• Hex Socket Head (Internal): Compact design allows use in confined spaces while delivering high tightening torque. Commonly used for securing small plastic structural parts in electronic devices with limited space.

Drive Type Selection

• Phillips Drive: Easy to align with screwdrivers, facilitating quick tightening and removal. The most common drive type, widely used in various plastic screws.
• Slotted Drive: Requires precise alignment of the screwdriver but is convenient for simple tools, such as plastic screws in children’s toys.
• Hex Drive: Compatible with hex wrenches, delivering higher torque. Suitable for high-tightening-force applications, such as connecting plastic components in industrial equipment.
• Pozidriv Drive: Engages tightly with screwdrivers to transmit greater torque. Used in applications requiring high fastening force and anti-loosening performance, such as securing plastic screws in precision electronic devices.
• Torx Drive: Offers excellent torque transmission and anti-loosening properties. Ideal for applications demanding high fastening reliability, such as critical plastic components in aerospace and automotive industries.

Thread Specification

• Metric Threads: Such as M2, M2.5, M3, etc. Widely used domestically, with high when paired with matching nuts or threaded holes. Suitable for most domestically produced equipment and products.
• Unified Threads (Imperial): Such as 2-56, 4-40, 6-32, etc. Commonly used in imported equipment or products manufactured to American standards, particularly in electronics and telecommunications industries.

Application Environment Factors

• Temperature Conditions: For high-temperature environments, select heat-resistant plastic screws (e.g., PTFE screws maintain stability at elevated temperatures). In low-temperature environments, consider plastic brittleness and choose cold-resistant materials.
• Chemical Environments: In corrosive environments (e.g., acids, alkalis), use corrosion-resistant plastics like PVDF or PP. In organic solvent environments, ensure material compatibility to avoid corrosion or dissolution.
• Electrical Environments: Plastic screws are preferred for insulation and anti-interference in electrical/electronic equipment. Materials like nylon or PC meet insulation requirements.
• Vibration Environments: For vibrating applications, choose plastic screws with anti-loosening structures (e.g., thread-forming screws) or use threadlockers to prevent loosening.