Kinetic studies of polyamide-imide synthesis

Abstract

To understand the kinetic of synthesis of polyamide‐imide (PAI) via p‐chlorophenol‐(PCP) blocked 4,4′‐diphenyl methane diisocyanate (MDI) with trimellitic anhydride (TMA), a series of reactions of blocked MDI with excess phthalic anhydride (PA) and benzoic acid are designed. PCP‐blocked phenyl isocyanate (BPI) which also released isocyanate at higher temperatures was used as a model compound for BMDI. The dissociation constants of BPI and BMDI in the presence of excess PA or BA was measured by collecting the evolved CO2. The effect of the catalyst concentration and temperatures were combined by a Hostettler equation. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1703–1710, 1997

On the Versatility of Urethane/Urea Bonds: Reversibility, Blocked Isocyanate, and Non-isocyanate Polyurethane

“…43 The minimum temperature at which detectable turbidity from carbonate precipitation appears is taken as the minimum deblocking temperature. Ho et al 165 followed the kinetics of deblocking by weighing the evolved CO 2 in the U shaped tube. The CO 2 evolution methods are only qualitative and relatively subjective.…”

Structure-property relationship of blocked diisocyanates: synthesis of polyimides using imidazole-blocked isocyanates

“…Although polyimides can be prepared successfully by a one‐step reaction of free diisocyanates and dianhydrides,24 we have synthesized them using imidazole blocked‐diisocyanates with PMDA in the presence of 4‐DMAP as a catalyst in DMPU. Compared to the use of alcohol and phenol‐blocked isocyanate in the preparation of polyimides,19, 20, 25, 26 the present approach is relatively new and experimentally more viable because the blocking agent released is basic and can accelerate the imidization reaction 24. Farrissey and co‐workers25, 27 examined the reaction of isocyanate and anhydride, and found that high temperatures were required in non‐polar solvents such as diglyme and dioctylphthalate.…”

“…The polymerization reaction of diisocyanates and dianhydrides has been known for three decades 18. Chen and Ho19, 20 have recently described the imide formation reaction of blocked isocyanate with anhydride. Even though blocked isocyanates have a number of advantages over isocyanates and amines, they have not been studied extensively in connection with polyimides.…”

Synthesis of polyamide-imide-montmorillonite-nanocomposites via new approach of in situ polymerization and solvent casting

“…At the initial reaction temperature of 80 • C 4,4 -methylene diphenyl diisocyanate (MDI) and the anhydride group of TMA form a carboxylic acid ended polyimide oligomer [10]. At the second stage around 120 • C amide groups are formed from the condensation of acid groups with the rest of MDI which combines the polyimide oligomers through the formation of amide and increases the overall molecular weight [10]. The PAI structure obtained by diisocyanate route has been characterized extensively by NMR techniques [11][12][13].…”

“…The challenge for the protection agent is the requirement of a very low deblocking temperature below 80 • C in order to enable the first reaction step imide oligomer formation. Our concept to realize in situ polymerization via protection of MDI was inspired by works of Ho and Chen [10,17]. They investigated a PAI synthesis derived from p-chlorphenole-blocked MDI.…”