Polyimide polymer, properties

Cycloahphatic diamines react with dicarboxyUc acids or their chlorides, dianhydrides, diisocyanates and di- (or poly-)epoxides as comonomers to form high molecular weight polyamides, polyimides, polyureas, and epoxies. Polymer property dependence on diamine stmcture is greater in the linear amorphous thermoplastic polyamides and elastomeric polyureas than in the highly crosslinked thermo set epoxies (2—4). 

Table 18.13 Typical properties of fabricated unfilled and 15% graphite-loaded polyimide polymers...

Thus, the ease of polymer synthesis, the facile handling of soluble precursors, the ready thermal or chemical conversion to the final polyimide structures, and the often unprecedented polymer properties that can be obtained collectively make polyimides highly desirable for a wide range of applications. 

Attaching thin adherent titania films to polyimide polymers demonstrates the promise of such coatings as barrier layers. Potential applications must examine the effect of the deposition process on the mechanical and thermal properties of the polymer and the requisite thickness of the ceramic layer. Nevertheless, the low-cost and convenience of LPD coatings, their mild conditions and their lack of line-of-site limitations, recommend their use. 

Cyclotrimerization of polyfunctional aryl acetylenes offers a unique route to a class of highly aromatic polymers of potential value to the micro-electronics industry. These polymers have high thermal stability and improved melt planarization as well as decreased water absorption and dielectric constant, relative to polyimides. Copolymerization of two or more monomers is often necessary to achieve the proper combination of polymer properties. Use of this type of condensation polymerization reaction with monomers of different reactivity can lead to a heterogeneous polymer. Accordingly, the relative rates of cyclotrimerization of six para-substituted aryl acetylenes were determined. These relative rates were found to closely follow both the Hammett values and the spectroscopic constants A h and AfiCp for the para substituents. With this information, production of such heterogeneous materials can be either avoided or controlled. 

The polymers and copolymers described in this chapter were derived fi"om the novel anhydride-terminated disiloxane, 5,5 -bis(l,l,3,3-tetra-methyl-1,3-disiloxanediyl)norbornane-2,3-dicarboxylic anhydride (DiSiAn) (14). Both siloxane-polyimide polymers and copolymers based on DiSiAn and its polysiloxane derivatives were investigated. This chapter describes the synthesis, characterization, and physical properties of these materials. 

Table II. Tensile Properties of DiSiAn-Polyimide Polymers and Copolymers...

Polymer properties are highly sensitive to temperature with transitions between physical states typically occurring over many tens of degrees Celsius (A). Additionally, the properties are sensitive to the rate at which the temperature changes. For example, the apparent glass transition temperature of a given polymer sample increases with the rate of temperature scan. For thermosets (such as epoxies and polyimides) the thermal history is especially important because of its coupled effect on the physical state of the polymer and the reaction kinetics (11). 

The information for the polymer properties was adapted from Sun and Kwok" and Becker and Gartner. The polymers listed include polyfdimethylsiloxane) (PDMS), polymethyl methacrylate (PMMA) and polyimide (PI). The information for the glass properties was obtained from the Schott website, specifically BOROFLOAT 33. 

V.L. Bell, B.L. Stump, H. Gager, Polyimide structure-property relationships. II. Polymers from isomeric diamines, J. Polym. Sci., Part A Polym. Chem. 14 (9) (1976) 2275-2291. 

X. Chen, P. Chen, K.I. Okamoto, Synthesis and properties of novel side-chain-type sulfonated polyimides, Polym. Bull. 63 (1) (2009) 1-14. 

D.F. Sanders, R. Guo, Z.P. Smith, K.A. Stevens, Q. Liu, J.E. McGrath, D.R. Paul, B.D. Freeman, Influence of polyimide precursor synthesis route and ortho-position functional group on thermally rearranged (TR) polymer properties pure gas permeability and selectivity, J. Membr. Sci. 463 (2014) 73-81. 

This methodology is quite general and can be utilized to prepare several types of polymers such as polyamides, polyimides, polyurethanes, polyethers etc. The polymer properties depend on the type of functional groups that link the polymer building blocks. Further modulation is achievable by varying the nature of the difimctional monomer within each class of polymers. It is not always necessary to condense two difunctional monomers. Some polymers such as polyethers are prepared by the oxidative coupling of the corresponding phenols. A few examples of polymers that can be prepared by the condensation reactions are shown in Fig. 1.2. 

New polyimide polymers have been prepared by the Diels-Alder reaction. An exocyclic 1,3-diene system provided monomers and polymers that had very low solubilities and inconsistent composition. These polyimides did form good films, but exhibited no detectable Tg. To enhance the monomer and polymer solubility and to alter the reactivity of the monomer, the 1,3-diene-ring structure was opened. Three new systems were evaluated before a polymer of known composition and with good properties was obtained that provided films with Tg s in the range of 200-260 C. 

Ghosh A., Mistri E. A., and Banerjee S. 3—Fluorinated polyimides Synthesis, properties, and applications. In Baneijee S (ed). Handbook of Specialty Fluorinated Polymers, pp. 97-185. Chadds Ford, Pennsylvania, USA William Andrew Publishing, 2015. 

Keywords Degradation Fuel cells Polymer synthesis Proton exchange membranes Structure Sulfonated polyimides Transport properties... 

BiaxiaHy oriented films have excellent tensile strength properties and good tear and impact properties. They are especially well regarded for their brilliance and clarity. Essentially all poly(ethylene terephthalate) film is biaxiaHy oriented, and more than 80% of polypropylene film is biaxiaHy oriented. Polystyrene film is oriented, and a lesser amount of polyethylene, polyamide, poly(vinyl chloride), and other polymers are so processed. Some of the specialty films, like polyimides (qv), are also oriented. 

Polyimides (PI) were among the eadiest candidates in the field of thermally stable polymers. In addition to high temperature property retention, these materials also exhibit chemical resistance and relative ease of synthesis and use. This has led to numerous innovations in the chemistry of synthesis and cure mechanisms, stmcture variations, and ultimately products and appHcations. Polyimides (qv) are available as films, fibers, enamels or varnishes, adhesives, matrix resins for composites, and mol ding powders. They are used in numerous commercial and military aircraft as stmctural composites, eg, over a ton of polyimide film is presently used on the NASA shuttle orbiter. Work continues on these materials, including the more recent electronic apphcations. 

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