Epoxy Resin Curing: It serves as a curing agent and extinction agent for epoxy resins. When used in epoxy systems, PMDA helps to enhance the mechanical properties, heat resistance, and chemical resistance of the cured products. The cured epoxy resins can be applied in various fields, such as coatings for industrial equipment, adhesives for high - strength bonding, and electrical insulation materials in transformers and motors.
Polyester Resin Cross - Linking: PMDA acts as a cross - linking agent for polyester resins. By introducing cross - links into the polyester structure, it improves the resin's dimensional stability, hardness, and solvent resistance. The cross - linked polyester resins find applications in the production of high - quality paints, coatings, and fiberglass - reinforced plastics.
Electrical Insulation: Due to the high - performance polymers produced using PMDA, it plays a vital role in the manufacturing of advanced electrical insulation materials. These materials are essential for ensuring the safe and efficient operation of electrical and electronic devices, especially in high - temperature and high - voltage environments.
Dye and Pigment Industry: PMDA is involved in the synthesis of certain dyes, such as phthalocyanine blue dyes. These dyes are widely used in the textile, printing ink, and paint industries for their excellent color fastness and vividness.
Plastic and Coating Additives: In the plastics and coatings industries, PMDA - based derivatives can be used as additives to improve the performance of the final products. For instance, they can enhance the adhesion, gloss, and durability of coatings, and improve the heat resistance and mechanical properties of plastics.
Preparation Methods
Gas - Phase Oxidation of Durene: This method is characterized by its simplicity. The dehydration - to - anhydride process can be omitted. It uses air as the only oxidant (eliminating the need for oxidants like nitric acid, permanganic acid, or chromic acid) and does not require the catalyst separation process necessary in liquid - phase methods. It is suitable for continuous production and easy to automate. The raw material can also start from 1,2,4 - trimethylbenzene. In the presence of a catalyst, it reacts with propylene through alkylation to form 1,2,4 - trimethyl - 5 - propylbenzene, which is then catalytically oxidized with air in the gas phase to obtain pyromellitic dianhydride.
Chloromethylation, Oxidation, and Cyclization of Xylene: Starting from p - xylene or m - xylene, through a series of reactions including chloromethylation, oxidation, and cyclization, pyromellitic dianhydride can be obtained.
Safety Information
Health Hazards: PMDA is toxic and can irritate the skin and mucous membranes. Swallowing may be harmful, and it can cause serious eye damage. Inhalation may lead to allergic reactions, asthma - like symptoms, or breathing difficulties.
Fire and Explosion Hazards: It is flammable. When exposed to open flames or high heat, it can catch fire and release toxic gases.
Storage and Handling
Store PMDA in a cool, dry place, away from moisture, sunlight, heat sources, and ignition sources. When handling, appropriate protective equipment such as gloves, safety glasses, and masks should be worn to avoid contact with the skin, eyes, and respiratory system.
In summary, pyromellitic dianhydride is an indispensable chemical in modern industry. Its wide range of applications and excellent performance - enhancing properties make it a preferred choice for manufacturers seeking high - quality and high - performance materials.
