Advances in Polycarbonates: An Overview - ACS Symposium Series

Chapter 1

Advances in Polycarbonates: An Overview Daniel J. Brunelle

Downloaded by 146.185.202.118 on December 4, 2016 | http://pubs.acs.org Publication Date: March 8, 2005 | doi: 10.1021/bk-2005-0898.ch001

G E Global Research, 1 Research Circle, Niskayuna, NY 12309

Polycarbonates (1) are an interesting and commercially successful class of polymers. Known for useful properties such as high heat capability, optical clarity, and incredible toughness, polycarbonates continue to generate academic interest as well as finding new avenues for commercial utilization. Although aromatic polycarbonates were first reported in the literature just over 100 years ago, the number of patents and publications continues to climb each year. The field of polycarbonate research is very diverse, with novel work covering the entire range of theoretical calculations, synthesis, physical measurements and analysis, as well as new additives, blends and applications. This volume is based on a symposium, "Advances in Polycarbonates," held at the National A C S Meeting in New Orleans, in March, 2003. It collects chapters from a variety of authors describing recent work or reviews on an assortment of polycarbonate topics.

The polycarbonate from bisphenol A (BPA) was first prepared in 1953 by chemists Daniel Fox at G E (!) and Herman Schnell at Bayer, A G , (2) while working independently at their respective companies. The glassy material was immediately recognized to have unique characteristics, including clarity, a relatively high softening temperature (glass transition temperature, T - 155°C), g

© 2005 American Chemical Society Brunelle and Korn; Advances in Polycarbonates ACS Symposium Series; American Chemical Society: Washington, DC, 2005.

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2 and remarkable impact toughness. Within a decade, both companies had built production facilities, and were selling B P A polycarbonate. Most of the early work on polycarbonate was targeted at developing efficient processes for its manufacture, and in scoping of other monomers similar to B P A to see if additional benefits could be gained. Despite a significant amount of research, only the polycarbonate from B P A proved commercially successful for more than 2 decades. During the 1970's and 1980's, B P A polycarbonate became a major item of commerce, and research was carried out on the full range of its properties, including optical characteristics, electrical properties, chemical and hydrolytic stability, flame retardant behavior, processing and rheology, thermal oxidative stability, the full range of mechanical properties, etc. Because of its ability to be modified and tailored to specific applications, the polycarbonate market is very broad, with over 500 different formulations being sold. Many types of additives, fillers, and blends were reported as well, and many of these (for example blends with poly (butylene terephthalate) or with ABS) became commercial successes in their own right. In the late 1980's, and into the mid-1990's, a great deal of effort on polycarbonate was centered on optimization and control of manufacturing processes, as the market for this material grew from hundreds of millions to billions of kilograms. One of the principal developments was implementation of melt processes for its manufacture, which avoided use of solvent or phosgene. Other areas of intensive research during that time (some of which continue today) were the preparation of oligomeric cyclics and their conversion by ringopening polymerization into very high molecular weight polycarbonates, (3) and solid-state polymerization (SSP) (4) as a means to increase molecular weight beyond that achievable via conventional processes. In Chapter 7, Kiserow, et al discuss use of supercritical C 0 to enhance the SSP process. A description of the processes used for preparation of polycarbonate is presented in Chapter One, along with experimental techniques for several laboratory methods. As melt polycarbonate techniques were examined anew, leading to commercialization of a solvent- and phosgene-free process for making B P A polycarbonate, the importance of monomer quality became very apparent. Pressman, et al in Chapter 3 review the chemistry of the two major compoents of the melt reaction, B P A and diphenyl carbonate. Over the past ten years, another renaissance in polycarbonate chemistry has been occurring, with several activities. New monomers which can enhance ductility even further, lead to higher T polymers, or improved solvent resistance are being incorporated into polycarbonates. Karbach, et al, of Bayer present details on the enhanced properties of 4,4 -biphenol/BPA copolycarbonates in chapters 8 and 9. Work on copolymers, both random and block has progressed, affording far greater than incremental improvements in properties. G E has recently introduced Lexan® E X L , a block polycarbonate2

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Brunelle and Korn; Advances in Polycarbonates ACS Symposium Series; American Chemical Society: Washington, DC, 2005.

3 dimethylsiloxane copolymer, which has greatly improved low temperature ductility and resistance to hydrolysis. (5) Polycarbonates can be easily endfunctionalized, by either melt or interfacial processes, and a summary of recent work on end-functionalized oligomers is presented in chapters 4-6. Research on the use of catalysis to use C O or C 0 for the formation of polycarbonates has been very successful, especially in the area of aliphatic polycarbonates. (6, 7) Although the vast majority of polycarbonates produced today are BPA-based, many of these new materials are reaching commercial acceptance as value-added polymers. In Chapter 16, Acar and Brunelle report their work on aliphatic polycarbonates based on tetramethylcyclobutanediol. Mullen, et al. in Chapter 17 report their recent work on functionalization of aliphatic polycarbonates with pendent olefin or epoxide groups. Polycarbonate has long been used as an unbreakable window glassreplacement material. Specialty laminated glazing materials are capable of withstanding gunfire, even point-blank shotgun blasts, and are used for security installations and military canopies. With the advent of the digital recording industry, it became apparent that B P A polycarbonate was the polymer of choice for compact discs, opening a major new market. Use of polycarbonate for storage of digital data has continued to grow, with many developments in use of new monomers in polycarbonates, as the storage density increases from C D ' s to D V D ' s and beyond. (8) Because of its high refractive index, clarity, U V absorption characteristics, and toughness, polycarbonate is ideal for eyewear, including the ophthalmic market for corrective lenses, sunglasses, and safety eyewear. Very recently, weatherable polycarbonate compositions, which can retain both mechanical and esthetic properties after long-term outdoor aging have been developed and commercialized. Lexan® S L X , a block polycarbonate-resorcinol polyarylate was designed for weatherable applications, utilizing a UV-light induced photo-Fries rearrangement to form a polymeric UV-absorbant coating, in a self-protecting system. (9)


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Lexan® SLX Since its invention, B P A polycarbonate has been an object of theoretical interest, in attempts to understand the source of its exceptional ductility. Direct evidence of molecular motion can be seen in a large low temperature (-100°C) loss peak measured by dynamic mechanical analysis. Understanding these molecular motions, and how they might absorb and disperse the energy of an impact has been the object of study of several groups. A variety of molecular



4 motions, including spinning, cis-trans isomerization about the carbonate bond, have been identified and studied. By understanding the source of the dramatic ductility of B P A polycarbonate, it is hoped that such properties can be incorporated into other polymers. With increased computational capability, modelling work has reached the point of predictive ability for designing new monomers. Bendler and Boyles have presented work suggesting that the cross-sectional area and aspect ratio of monomers used for polycarbonates may be a key factor controlling high ductility. Their computational and experimental work is presented in Chapters 10 and 11. Jones, et al. have used density functional/Monte Carlo calculations to study the mechanism of transesterification in ring opening of cyclic oligomers, and the effects of various catalysts on that reaction. That work was extended to study the effects of catalyst structure on degree of branching in polycarbonates prepared at high temperatures in the melt, presented in Chapter 15. Hagenaars, et al. has extended the characterization techniques for studying polycarbonate, and reports on use of molecular weight fractionation methods in chapter 14. Because polycarbonate is very tough, and easily molded, new applications are always being sought. Polycarbonate highly filled with carbon black can be made slightly conductive, conducive to powder-coating and other operations. Potschke, el al. have found that multi-walled carbon nanotubes can be dispersed in polycarbonate, leading to highly conductive, filled polymers at loadings of less than 2% nanotubes. Her work in that area, and on the study of nanotubefilled polycarbonate/polyethylene blends appears in Chapters 12 and 13. Polycarbonate is an unusual polymer in that is has a wide variety of applications in several families of formulations. Clear, transparent grades are popular for optical or glass-replacements. Opaque or highly colored grades are common for business machines, sporting goods, etc. Many filled or reinforced grades are also used for high modulus applications. Because of the multiple market applications, recycle of polycarbonate has been little exploited. In Chapter 18, Mormann and Spitzer report on a technique for chemical recycling of polycarbonate, using ammonia. In summary, although polycarbonate should be considered a mature area of research, because of the breadth of applications available to such a unique material, research continues unabated in both industry and academics. With new techniques for controlling chemical structure and morphology of the polymer, and with the number of potential additives growing with the onset of the nanotechnology era, it appears that polycarbonate will remain an item of interest for some time to come.


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References 1. 2. 3. 4.


5. 6. 7. 8.

9.

Fox, D.W. U.S. Pat. 3, 144,432 asigned to the General Electric Company. 1964. Schnell, H . Angew. Chem. 1956, 68, p. 633. Schnell, H . Ind. Eng. Chem. 1959, 51, p. 157. Brunelle, D . J., Shannon, T. G., Macromolecules, 1991, 24, 30333044. Schulz, J. M., Fakirov, S. Solid State Behavior of Linear Polyester and Polyamides, Prentice Hall 1990. Davis, G. C, Wisnudel, M. B., Dris, I., US Patent 6,492,481, to General Electric, 2001. Beckman, E. J., Polym. Prep., 2003, 44(1), 734. Moore, D . R., Allen, S. D., Goates, G . W. Polym. Prep.,2003, 44(1), 35. Davis, G.C., Davis, I. Wisnudel, M. B., Boven, G., Johannes, J., van Ginneken, C., Goewey, C., US Patent 6,395,364, to General Electric, 2002. Suriano, J. A . , Siclovan, T. M., Pickett, J. E., Brunelle, D. J., O'Neil, G. A . , Zhou, H., Polym. Prep.,2003, 44(1), 748.


Advances in Polycarbonates: An Overview - ACS Symposium Series

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