Chemical Properties
White powder. Soluble in some organic solvents; hydrolyzes to
the acid when exposed to moisture.
Uses
Pyromellitic dianhydride is used as a monomer in the preparation of polyimide polymers such as kapton; thermoplastics such as polyesters, polyethers, plasticizers, and expoxy resins. It is involved in the preparation of high performance coatings due to its mechanical, thermal and oxidative stability properties. It acts as a curing agent for epoxy resins which find application in adhesives, coatings and molding powders. As an intermediate, it plays an important role in polyimide based materials like printed circuit boards, tape automated bonding and magnetic wire insulation.
Uses
Pyromellitic dianhydride (PMDA) is employed as a curing agent for epoxy agent resins used for casting, laminating, the manufacture of moulding powders, adhesives and coatings.
Preparation
Pyromellitic Dianhydride is prepared by gas-phase oxidation of 1,2,4,5-tetramethylbenzene (or related tetrasubstituted benzene derivatives). An idealized equation is:
C6H2(CH3)4 + 6 O2 → C6H2(C2O3)2 + 6 H2O
In the laboratory, it can be prepared by dehydration of pyromellitic acid using acetic anhydride.
Application
Pyromellitic dianhydride (PMDA) has been used extensively as an important monomer in the preparation of a variety of thermoplastics such as polyesters, polycarbonates, polyethers polyethers, plasticizersplasticizers, expoxy resins, etc. Moreover, it is also useful in the preparation of high performance coatings that have been widely employed in many fields in our daily life beacuase of its excellent thermal, oxidative stability and excellent mechanical properties.
Pyromellitic dianhydride (PMDA) is one of several highly reactive acid anhydrides and used extensively in the production of thermoplastics and high-performance coatings. Anhydrides including PMDA are respiratory irritants and immediate-type sensitisers. Some anhydrides have been associated with occupational asthma. PMDA has also been related to occupational asthma.
General Description
Pyromellitic dianhydride (PMDA) is an acidic anhydride that can be used as a repair agent and as a chain extender in the formation of polyethylene terephthalate (PET) based chain extensions. It is mainly used in the production of thermoplastics and other coating applications.
Flammability and Explosibility
Not classified
Purification Methods
Crystallise the dianhydride from ethyl methyl ketone or dioxane. Dry, and sublime it in vacuo.[Beilstein 19 H 196, 19/5 V 407.]
