Conductivity, specialty polymers

PolyQ>phenylene sulfide) (PPS) deserves much attention as an engineering and a conductive plastic and in some cases as a specialty polymer with excellent performance. Lenz first reported that PPS is synthesized by the polycondensation of / -halothiophenolate alkali-metal salts at high temperature [83], Commercially PPS is produced by the polycondensation of -dichlorobenzene and sodium sulfide in A-methyl-2-pyrrolidone [84]. These polymerizations proceed only at high temperature and pressure, and it is difficult to remove the metal halides such as sodium chloride as by-products in order to obtain pure PPS salt contamination degrades the electric performance and moldability. 

In addition to the above-mentioned conventional polymers, several interesting developments have taken place in the preparation of nanocomposites of MMT with some specialty polymers including the N-heterocyclic polymers like poly (N-vinylcarbazole) (PNVC) [32, 33], polypyrrole (PPY) [34, 35], and polyaromatics such as polyaniline (PANI) [36-38]. PNVC is well known for its high thermal stability [39] and characteristic optoelectronic properties [40-43]. PPY and PANI are known to display electric conductivity [44-46]. Naturally, composites based on these polymers should be expected to lead to novel materials [47,48]. 

Specific blends, which could offer an interesting combination of properties with proper com-patibilization, include PPS/PSE, PEl/PPS, PA/PSE, PA/PEI, and PC/PPS. Patent activity has been noted for most of these blend combinations as well as other selected blends involving engineering polymers as noted in Table 17.3. A number of recent patent and published papers have discussed blends of engineering polymers with various specialty polymers including high temperature polymers, liquid crystalline polymers (LCP s), conductive polymers, and as matrix materials for molecular composites. These will be discussed in the following sections. 

At the present time polyaniline is without doubt the most important conducting polymer from the point of view of large scale technological use however, derivatives of polythiophene and poly(phenylenevinylene) and indeed, polypyrrole, polyacetylene and poly-paraphenylene show considerable technological promise as specialty polymers, as described later. In view of the technological importance of polyaniline, its synthesis and properties will be emphasized in this review. 

In the late 1950s, polyacrylate-based PSAs were developed [283] and gained a dominant market share in the following decades. To a smaller extent polyfvinyi ethers) are used in medical devices. For specific applications like transdermal drug delivery systems, ostomy mounts, and electrically conductive adhesives a variety of specialty polymers such as silicones, polyurethanes, and various hydrogels are applied. 

Polymeric materials have also been produced which have relatively large conductivities and behave in some cases like semiconductors and even photoconductors [28]. For example, polyphenylacetylene, polyaminoquinones, and polyacenequinone radical polymers have been reported with resistivities from 10 to 10 ohm-cm. It has been suggested that the conductivity in these organic semiconductors is due to the existence of large number of unpaired electrons, which are free within a given molecule and contribute to the conduction current by hopping (tunneling) from one molecule to an adjacent one (see Electroactive Polymers in Chapter 2 of Industrial Polymers, Specialty Polymers, and Their Applications). 

Catalysis has also had a major impact on the functional and specialty chemicals businesses, providing lower cost routes and higher performance materials than would have otherwise been possible. Major examples are from polymer syntheses including Ziegler-Natta, anionic, cationic polymerization processes, for formation of polyolefins, ABS resins, polyesters and other synthetic materials. Future materials areas include high temperature composites, electronic materials and conducting organics. 

The references noted well demonstrate the ability to utilize polymer blend technology to achieve the desired balance of mechanical properties and conductivity. The promise of electrical conductive polymers with lower cost, processability, and mechanical durability can thus be envisioned for applications such as electrical dissipative coatings, printable circuits, electromagnetic shielding, resistive heating, conductive sheathing, battery applications, elastomeric conductors, fuses, electronic uses, sensors, specialty electrical devices for corrosive atmospheres, photovoltaic devices, catalysts, optical switches, and semiconductor devices. 

BFGoodrich Specialty Chemicals produces a family of thermoplastic alloys that are inherently conductive. Alloys with 15% of the active conductive polymer differ little in surface resistivity from alloys with 25% active polymer. Further, the conductive polymer content remains relatively constant through processes such as injection molding, extrusion, and thermoforming, unlike resins containing conductive fillers. In contrast to chemical antistats, the conductive polymers are active at all humidity levels, do not lose their potency over time, and add no ionic contaminants to the surrounding atmosphere. 

Research is ongoing in the field of ECPs in order to discover various new polymers in this field, which shows the increased demand for these specialty conjugated polymers. It is necessary to use effective and stable dopants with the conducting polymers for the enhancement of their properties [1-4]. Conjugated polymers with good electronic conductivity have opened the door to various electronic devices. Various ECPs used nowadays are polyaniline, polypyrrole, polythiophene, polyacetylene, and their derivatives. The major advantages of these polymers are good electronic... 

The first successful large-scale production of a polypropylene carbonate (PPC) polymer using waste carbon dioxide (CO ) was conducted by Novomer in collaboration with specialty chemical manufacturer Albemarle Corporation (Orangeburg, SC) in May 2013 (http //energy.gov/fe/articles/recycling-carbon-dioxide-make-plastics). 

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