Polyetherimide
[CAS# 61128-46-9]

Identification

• Classification: Catalysts and additives >> Polymer
• Name: Polyetherimide
• Synonyms: PEI
• Molecular Formula: (C₃₉H₃₀N₂O₆)_n
• CAS Registry Number: 61128-46-9
• SMILES: Nc7cc(ccc7)N.O1C(=O)c2c(ccc(c2)Oc3ccc(cc3)C(C)(C)c4ccc(cc4)Oc5cc6c(cc5)C(=O)OC6=O)C1=O

Properties

• Density: 1.27 g/mL (25 ºC) (Expl.)

Safety Data

• Hazard Symbols: GHS07 Warning
• Hazard Statements: H302-H315-H319
• Precautionary Statements: P501-P270-P264-P280-P302+P352-P337+P313-P305+P351+P338-P362+P364-P332+P313-P301+P312+P330

Discovory and Applicatios

Polyetherimide, commonly abbreviated as PEI, is a high-performance thermoplastic polymer belonging to the class of polyimides. It is characterized by an aromatic backbone with alternating ether and imide linkages, which confer excellent thermal stability, mechanical strength, and chemical resistance. PEI is an amorphous polymer, which differentiates it from semicrystalline engineering plastics, and this amorphous nature contributes to its transparency and dimensional stability under load. Its glass transition temperature typically exceeds 215 °C, making it suitable for applications that require resistance to high temperatures.

The discovery of polyetherimides is linked to the development of high-performance polymers in the 1970s and 1980s, aimed at producing materials with improved thermal and chemical stability for aerospace, automotive, and electronics industries. PEI was designed to combine the desirable properties of polyimides, such as thermal and oxidative resistance, with processability similar to conventional thermoplastics. This balance of properties allows PEI to be fabricated by standard thermoplastic processing techniques, including extrusion, injection molding, and thermoforming, unlike classical polyimides that typically require high-temperature curing.

Chemically, PEI is composed of repeating units in which an aromatic imide group is connected via an ether linkage to another aromatic unit. The imide group provides rigidity and high thermal stability, while the ether linkage imparts flexibility and toughness to the polymer chain. This combination results in a polymer that maintains structural integrity under mechanical stress and elevated temperatures. The molecular weight and distribution of the polymer chains are carefully controlled during synthesis to achieve the desired balance of processability and mechanical performance.

The synthesis of polyetherimide typically involves the polycondensation of aromatic diamines with dianhydrides. One common route uses bisphenol A-based diamines and phthalic anhydride derivatives to form the imide linkages. The reaction conditions are designed to minimize defects in the polymer backbone and achieve high molecular weights necessary for mechanical strength. Post-synthesis, the polymer is often stabilized to remove residual monomers or oligomers that could affect thermal or mechanical properties.

PEI exhibits excellent mechanical properties, including high tensile strength, modulus, and impact resistance, even at elevated temperatures. It is resistant to creep and maintains dimensional stability under load, making it suitable for precision components. Chemically, PEI is resistant to a wide range of organic solvents, acids, and bases, although strong oxidizing agents and concentrated mineral acids can degrade the polymer. Its combination of thermal and chemical resistance, along with flame retardancy, makes PEI suitable for demanding industrial applications.

In industry, polyetherimide is widely used in aerospace components, automotive parts, electrical connectors, and medical devices. Its electrical insulating properties and stability under heat make it ideal for printed circuit boards, high-performance connectors, and components in electronic assemblies. In the medical field, PEI’s biocompatibility and sterilization resistance allow it to be used in surgical instruments and implantable devices. Additionally, its transparency and resistance to deformation enable applications such as lens substrates, display panels, and lighting components.

Polyetherimide can be blended with other thermoplastics, reinforced with fibers, or filled with additives to tailor its properties. Fiber reinforcement, such as glass or carbon fibers, significantly increases stiffness and dimensional stability, while flame-retardant additives enhance safety in electrical and transportation applications. PEI’s versatility in processing and formulation allows manufacturers to design components that meet stringent mechanical, thermal, and regulatory requirements.

Overall, polyetherimide is a versatile, high-performance thermoplastic that combines thermal stability, mechanical strength, chemical resistance, and processability. Its aromatic imide backbone with ether linkages provides the unique balance of rigidity and toughness, making it suitable for a wide range of demanding applications in aerospace, electronics, automotive, and medical fields. PEI remains a key material in modern engineering due to its ability to perform reliably under extreme conditions while being processable using conventional thermoplastic fabrication methods.