Overview
Polyamide-imide (PAI) is an advanced engineering plastic combining the properties of polyamides and polyimides. Developed in the 1960s, it bridges the gap between conventional plastics and high-cost polyimides, offering superior performance at a moderate price. PAI is synthesized through polycondensation of trimellitic anhydride and aromatic diamines, resulting in a semi-crystalline or amorphous structure. PAI is commercially available under trade names like Torlon (Solvay). Its unique molecular structure provides exceptional thermal stability (continuous use up to 250°C) and mechanical properties, making it a preferred material for demanding industrial applications where metals or ceramics are impractical.
Physical and Chemical Properties
PAI exhibits a glass transition temperature (Tg) of 275–290°C, with a thermal decomposition onset above 280°C. It retains 70% of its tensile strength at 200°C, outperforming most thermoplastics. The material has a low coefficient of thermal expansion (3–6 × 10⁻⁵/°C), matching metals in dimensional stability. Chemically, PAI resists hydrocarbons, weak acids, and bases but may degrade in strong alkalis or oxidizing agents. Its dielectric strength (20–25 kV/mm) and volume resistivity (10¹⁶ Ω·cm) make it ideal for electrical applications. The polymer is inherently flame-retardant (UL94 V-0 rating) without additives.
Main Applications
In aerospace, PAI is used for bushings, thrust washers, and turbine components due to its weight-saving potential and high strength-to-weight ratio. The automotive industry employs it in transmission seals and electrical connectors where thermal cycling resistance is critical. Electrical applications include circuit breakers, insulating washers, and chip carriers. Industrial uses encompass non-lubricated bearings, pump components, and semiconductor processing equipment. PAI films serve as flexible circuit substrates in electronics. Recent developments explore 3D-printed PAI parts for customized high-temperature fixtures.
Safety and Storage
PAI is stable under normal conditions but requires precautions during processing. Machining generates fine dust—use local exhaust ventilation and PPE (respirators, goggles). Thermal degradation above 300°C releases carbon monoxide, hydrogen cyanide, and nitrogen oxides. Store PAI raw materials in sealed containers away from moisture to prevent hydrolysis. Processed parts have excellent long-term stability if protected from UV exposure and chemical contamination. Disposal should follow local regulations for thermoset plastics, with incineration only in approved facilities with scrubbers.
B2B Procurement Guide
When sourcing PAI, specify required certifications (e.g., ISO 9001, AS9100 for aerospace). Key parameters include tensile strength (100–200 MPa), impact resistance (50–120 J/m), and thermal index (UL rating). Verify supplier testing data for batch consistency. Consider form factors: pellets for injection molding, rods/tubes for machining, or pre-impregnated fibers for composites. Lead times for specialty grades may extend to 8–12 weeks. For cost-sensitive projects, recycled PAI (regrind) offers 20–30% savings but with reduced mechanical properties. Establish long-term contracts to mitigate price volatility linked to raw material (TMA/MDI) markets.
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