Polyamide-Imide Film
Polyamide-imide “single pass, heavy gauge films are made by first applying a polyamic acid solution as a single, wet, precursor layer on a substrate. This is followed by an initial heating step, to remove a large percentage of the solvent from the cast precursor layer, at temperatures between 80.degree. and 110.degree.C, preferably in a non-circulating oven at a relative humidity up to about 60 percent. Conversion to the solid amide-imide film then proceeds rapidly by curing at temperatures between about 130.degree. and 350.degree.C to remove the rest of the solvent and condensation water. The film is sufficiently dry at about 130.degree. to 150.degree.C to be stripped from the substrate by hand or other suitable means, and while final curing, the stripped film is stretched between 0.5 and 150 percent but preferably between 5 and 125 percent of its original length, at temperatures between about 200.degree. and 350.degree.C. This stretching orients the film to a certain degree, reduces the amount of amorphous material and thus improves the film's fold endurance and elongation.”
Recent Journal Articles
Polyamide–imide membranes with surface immobilized cyclodextrin for butanol isomer separation via pervaporation
(1470–1484)AIChE Journal 57 #6 (2011)
Wang, Chung and Wang of the National University of Singapore, China, synthesized a novel cyclodextrin (CD) derivative, m-xylenediamine-β-cyclodextrin (m-XDA-β-CD) which was grafted to a membrane surface for the pervaporation separation of butanol isomers. The as-fabricated novel CD-grafted polyamide-imide (PAI) membranes show homogeneous morphology and significant improved separation performance as compared to the unmodified PAI membranes and PAI/CD mixed matrix membranes made of physical blends. The optimal separation performance can be found with the CD-grafted PAI membrane cast from a 22 wt % dope concentration, which exhibits a total butanol flux of 15 g/m2/h and a separation factor of 2.03. This newly developed membrane with surface-immobilized CD may open new perspective for the development of next-generation high-performance pervaporation membranes for liquid separations. (RDC 5/5/2011)