Polyamides and Polyimides

In short, the microwave energy was successfully applied for the first time for the rapid synthesis of condensation polymers such as polyimides and polyamides from the salt monomers (and co-amino acids) by using a simple domestic microwave oven. The rapid polymer formation is caused by the efficient internal heating of the reactants. This compares favorably with the long reaction time required for the conventional thermal polycondensation with external heating. 

A series of novel polyimides were prepared from diaminophthalide 288 and four anhydrides 289 for the investigation of water-permeable membranes. Of the polymer products 290, the best permeability was associated with bulky groups (trifluoromethyls) on the polyimide chains <2005JAPS2047>. There are other variants of diaminophthalide 288 used to prepare polyimides and polyamides. A fluorinated variation 291 has been used for polyimide synthesis <2004MI979> as has 292, derived from o-cresolphthalein 284 <1999PSA455>. 

In this paper we use dielectric measurements to calculate the polarizability of absorbed water in a series of aromatic polyimides and polyamide-imides. In the relatively non-polar polyimides, the absorbed water has a dipole moment close to that of free water (/i - 1.88 Debyes). This value drops to less than 0.4/x for polyamide-imides. The decrease may be attributed to hydrogen-bonded water in the very polar polyamide-imides. In addition, the "group" dipole moment for amide is calculated and found to be greater than the dipole moment of free water. 

Dielectric measurements were used to calculate the relative polarizability of absorbed water in a series of polyimides and polyamide-imides. The effective dipole moment of the absorbed water varied from 1.8 Debyes to 0.7 Debyes. This corresponds to... 

Aromatic polyimides and polyamides exhibit outstanding thermal stability and strength, two properties responsible for the industrial importance of these materials. The macroscopic properties are controlled to a large extent by the state of aggregation of the macromolecules and their relative orientation. Photophysical measurements, aimed at detecting polarization properties and the formation of excited-state charge transfer (CT) states have proven extremely useful tools to elucidate the microstructure of these materials. 

The polyimides and polyamide-imides are produced by condensation reactions which give off volatile low-molecular-weight by-products. The polybismalemimides may however be produced by rearrangement polymerization with no formation of by-products. The starting materials in this case are the bismaleimides, which are synthesized by the reaction of maleic anhydride with diamines (Figure 4.21). 

The Kinel materials produced by Rhone-Poulenc are polybismaleinimides of the type shown in Figure 4.22. These materials have chain-end double bonds, as explained previously, can be processed like conventional thermosetting plastics. The properties of the cured polymers are broadly similar to the polyimides and polyamide-imides. Molding temperatures are usually from 200°C to 260°C. Post-curing at 250°C for about 8 h is necessary to obtain the optimum mechanical properties. 

Polyimide and polyamide-imide Excellent thermal properties Good composite properties Good electrical properties Good fire properties Restricted choice of color Arc resistance Acid and alkali resistance... 

Matty polymers may be used for produetion of wire and cable. These include polyethylene, crosslinked polyethylene, chlorosnlfonated polyethylene, ethylene-propylene rubber, polyvinylchloride, bntyl robber, styrene bntadiene rubber, silicone rubber, natural robber, polyisoprene robber, polyurethane, nitrile butadiene rubber, polychloroprene, polysulfone, thermoplastie elastomers, polyimide, and polyamides. Selection of polymer(s) depends on projected conditions of service such as temperature, presence of corrosive liquids, surrounding temperature, quality of insulation, etc. 

There are examples of poly(arylene ether)s, polyimides, and polyamides having l,l -binaphthy-lene-2,2 -diyl or biphenylene units that introduce chiral twists in the polymer chain. The chiral groups are expected to make the entire chain take a helical conformation. Earlier studies based on similar molecular designs are cited in Mi et... 

The thermal degradation kinetics of Ticona s Vectra, BP-Amoco s Xydar, EHiPont s Zenite, and Mitsui s polyimide and polyamide LCPs are analyzed below. 

In both types of continuous systems the maximum processing speed ( line speed ) is determined by the required residence time in the plasma to get the proper treatment. The present data show that, for reasonable power densities and existing equipment, clean polymers (e.g. polyethylene, polyimide, and polyamide) can be treated in less than 10 seconds residence time. This gives a line speed of 150 m/min (500 ft/min) or more. 

S.H. Hsiao, C.P. Yang, S.C. Huang, Preparation and properties of new polyimides and polyamides based on l,4-fcis(4-amino-2- trifluorometh-ylphenoxy)naphthalene, J. Polym. Sci. Part A Polym. Chem. 42 (10) (2004) 2377-2394. 

In this method, the PBIs are prepared by the thermal rearrangement of the precursor polyimides and polyamides. A general procedure of the preparation of PBIs from a precursor polyimide is given below. 

D.N. Khanna, W.H. Mueller, New high temperature stable positive photoresists based on hydroxy polyimides and polyamides containing the hexafiuoroisopropylidene (6-E) linking group, Polym. Eng. Sci. 29 (14) (1989) 954-959. 

There is also commercially available a class of polymers related to both polyimides and polyamides. These polymers are called poly(amide4mide)s. One such material is prepared from trimellitic anhydride (as the acid chloride) and 4,4 -diaminodiphenylmethane as follows ... 

Method 3.6 Determination of Amino Groups in Aromatic Polyamides, Polyimides and Polyamides-imides. Potassium Hydroxide Fusion Gas Chromatography [158, 159]... 

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