In-Depth Analysis of Thermoset Polyimide (Thermoset PI): High-Performance Solutions for Extreme Working Conditions

Thermoset polyimide is a class of polymer materials that, after heat curing, forms an infusible and insoluble structure with extremely high heat resistance, excellent mechanical strength, and electrical insulation properties. It is commonly used in aerospace, electronics, and high-temperature structural components.

Characteristics of Thermoset PI

Excellent high-temperature resistance
stable mechanical properties
outstanding electrical properties

resistant to chemical corrosion
good dimensional stability
wear-resistant

Allstar Material Thermoset Polyimide Processing Methods

Compression Molding
Lamination Molding
Casting Molding

Performance Advantage Analysis of Allstar Material's Thermoset Polyimide

The following performance advantages are mainly analyzed from the aspects of high temperature resistance, mechanical properties, electrical properties, chemical corrosion resistance, dimensional stability, and wear resistance of thermoset polyimide. According to different modified polyimides and processes, performance values vary greatly. We only analyze typical performance here.

High temperature resistance

The glass transition temperature (Tg) of thermosetting polypropylene (PI) is typically 250–400 °C.
Decomposition temperature (5% weight loss) is generally 500–600 °C (in air or nitrogen).
It can still be used continuously for extended periods at 250–300 °C, while most engineering plastics (such as PEEK and PEI) show a significant performance degradation above 250 °C.

Excellent mechanical properties (especially at high temperatures)

Tensile strength: 100–200 MPa (according to test standard ASTM D638).

Flexural strength: 120–250 MPa.

Modulus of elasticity: 2.5–5.0 GPa.It retains high strength at high temperatures, for example, at 200–250 °C, the strength retention rate can reach 70–80%.

Outstanding electrical performance

Dielectric constant (1 kHz, 25℃): Approximately 3.0–3.5.

Dielectric loss factor: Approximately 10⁻³–10⁻², very low.

Insulation breakdown strength: Approximately 100–300 kV/mm.”

Chemical corrosion resistance

Exhibits excellent resistance to most acids, alkalis, and solvents. It gradually degrades only in strong alkalis or some strong oxidizing agents. Even when immersed in 98% sulfuric acid, it exhibits high resistance (some data indicate that the strength retention rate can be above 80%, varying over time)

Good dimensional stability

Coefficient of thermal expansion (CTE): Approximately 20–50 × 10⁻⁶ /K, significantly lower than most plastics (e.g., PEEK ~ 47 × 10⁻⁶ /K). Low water absorption (<1%) ensures dimensional stability in humid and hot environments.

Wear-resistant

Coefficient of friction: approximately 0.3–0.4 (under dry friction conditions). Low wear rate, suitable for high-load friction components such as sliding bearings and seals.

Typical Application Fields of Thermoset PI

Thermoset polyimide (Thermoset PI), due to its excellent high-temperature performance, mechanical strength, electrical insulation, and chemical/radiation resistance, has become a key material in numerous cutting-edge and demanding application fields.

Aerospace Field

Thermoset PI is widely used to manufacture high-temperature structural components, insulation parts, bearings, seals for jet engines, as well as ablation-resistant components for missiles and spacecraft.

Electronics and Semiconductor Industry

with its excellent electrical properties and dimensional stability, it is used to manufacture test sockets for high-performance integrated circuits, wafer processing components, high-frequency connectors, flexible printed circuit (FPC) substrates, as well as high-temperature coil bobbins and wire insulation layers.

Automotive Electrical Systems

Thermoset PI can be used to manufacture valve plates for compressors and pumps, piston rings, wear-resistant bushings, high-temperature bearing cages, glass manufacturing equipment components, as well as seals and gaskets requiring chemical corrosion resistance.

Processing of Thermoset PI

The processing of thermoset polyimide (Thermoset PI) mainly employs two methods: compression molding and precision machining.

Compression Molding

Compression Molding (Direct Forming) is the primary method. PI powder or prepolymer is typically used, undergoing pressure holding and curing under high temperature (curing temperature usually needs to be raised in stages to 300°C - 400°C, or even higher) and high pressure (typical pressure 30 - 70 MPa or higher) conditions. This process involves imidization and crosslinking chemical reactions, taking considerable time (usually several hours) to form an irreversible crosslinked structure and obtain the final excellent properties.

Precision Machining

Precision Machining is also a critical process. Since Thermoset PI is usually supplied in semi-finished forms such as sheets and rods, final parts are often obtained through turning, milling, drilling, and other methods. Due to its high hardness and certain abrasiveness, carbide or diamond tools must be used during processing. At the same time, cutting speed and feed rate must be controlled (for example, recommended linear speed is usually below 60 m/min) to prevent overheating that could cause material cracking or performance degradation. Coolant is generally not recommended, or specific types must be selected.

Seeking PI Film Solutions with Both Exceptional Performance and Reliability?

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