1, polyimide mainly by two yuan anhydride and two amine synthesis, compared with many other heterocyclic polymers, such as poly-phenyl imidazole, Polyphenylene and Matt, poly-benzene and thiazole, and poly-quinoline, the monomer has a wide source of raw materials and is easy to synthesize. A wide variety of anhydride, diamine, different combinations can obtain different properties of polyimide.
2, polyimide can be two anhydride and two amine in polar solvents, such as DMF,DMAC,NMP or the/methanol mixed solvent in the first low temperature polycondensation, obtain soluble polyamide acid, film or spinning after heating up to 300 ℃ to the dehydration of the ring to polyimide; it can also add acetic anhydride and tertiary amine catalysts to polyamide acid. , the chemical dehydration is done, and the polyimide solution and powder are obtained. Diamine and two anhydride can also be used in high boiling point solvents, such as phenol solvent heating polycondensation, one-step to obtain polyimide. In addition, the four-yuan acid of two yuan ester and two-amine reaction to obtain polyimide, can also be converted from polyamide acid to poly-Imide, and then converted to polyimide. These methods are convenient for processing, the former is called the PMR method, can obtain the low viscosity, the high solid solution, has the low melt viscosity in the processing the window, specially is suitable for the composite material manufacture, the latter has increased the solubility, does not release the low molecule compound in the transformation process.
3, as long as two anhydride (or four acid) and two amine purity qualified, no matter what the condensation method, it is easy to get high enough molecular weight, adding a unit of anhydride or cell amine can also easily regulate the molecular weight.
4, to two anhydride (or four acid) and two amine polycondensation, as long as the first-class molar ratio, in the vacuum heat treatment, can be solid low molecular weight prepolymer of the molecular weight of a large increase, so that processing and powder to bring convenience.
5. It is easy to introduce reactive groups to form active low polymer on the chain end or chain to get thermosetting polyimide.
6, the use of polyimide in the carboxyl group, esterification or salt, the introduction of photosensitive groups or long chain alkyl to obtain amphiphilic polymers, can be photoresist or for the preparation of LB films.
7, the general synthesis of polyimide process does not produce inorganic salts, for the preparation of insulating materials is particularly beneficial.
8, as a monomer of two anhydride and two amine in a high vacuum easily sublimation, so easy to use vapor deposition method in the workpiece, especially the surface of rugged devices on the formation of polyimide film.
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