Polyimide raw materials mainly involve two types of core monomers: dianhydrides (such as pyromellitic dianhydride PMDA and biphenyl dianhydride BPDA) and diamines (such as p-phenylenediamine PDA and 4,4'-diaminodiphenyl ether ODA).
These monomers form polyamic acid (PAA) through polycondensation reactions, which is then subjected to high-temperature imidization or chemical imidization to remove water molecules, ultimately producing polyimide (PI). The following analysis covers four dimensions: raw material characteristics, process relevance, application scenarios, and industry standards:
Raw Material Characteristics and Selection Criteria
Dianhydride Monomers: PMDA is commonly used in general-purpose PI films (such as Kapton) due to its low cost and high reactivity; BPDA, due to its rigid structure which improves heat resistance, is often used in high-end electronic packaging materials. The purity of dianhydrides must be ≥99.5%, otherwise it will affect the molecular weight distribution of PI.
Diamine Monomers: PDA provides high strength but is easily oxidized; ODA improves flexibility and is often compounded with PDA. Aromatic diamines generally have melting points between 100-150℃, requiring strict temperature control during storage to prevent clumping.
Solvent systems: N,N-dimethylacetamide (DMAc) and N-methylpyrrolidone (NMP) are the mainstream solvents. Their high boiling points (>200℃) prevent pre-iminolation volatilization, but a corresponding waste gas treatment system is required.
