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Introduction to Polymers: A Property Database OnlinePrefaceThe latest edition of Polymers: A Property Database is an improved version of an indispensable polymer reference work. The database is a comprehensive and in-depth collection of properties for a very wide range of polymers, both synthetic and natural and where polymers exist with subtle variations in structure, these are also covered in some detail. Processing grades are also described along with typical applications for each major polymer. Each polymer has a general properties section where very useful information such as chemical structure, synonyms, CAS registration numbers and monomers used in the polymerisation is given. The mechanical properties are particularly well presented and all source material is meticulously referenced. The database is well indexed (even more comprehensively in the online version) and extremely easy to use making this a very desirable addition to any researcher's library. Polymers are indexed by common name allowing ease of access even to those with only a basic knowledge of polymers, industrial/commercial names are also used where these exist. This is particularly useful for those working in industry or in multidisciplinary fields where polymers are used. IntroductionThose of us who work with polymers and polymeric materials rely heavily on data regarding solution and bulk properties, and manufacturing procedures. These parameters usually can be found spread over different handbooks, encyclopedias, and the Internet. However, Polymers: A Property Database is one-stop shopping, whereby this information is now available from a single source. Entries range from a few lines for research polymers to encyclopedic submissions for more common polymers. (An online version of the Database for simplified data retrieval and entry updates is now available from Taylor and Francis, Publishers.) To produce this comprehensive Database, which conveniently can be used as a desk reference book, a double-column format was used with small, but easy to read font with spaced-out tables. Since main-chain or common polymer names are used as headers, arranged alphabetically in dictionary style, the Database is practical to use. (IUPAC approved nomenclature is given under a separate heading). To quickly locate a polymer, a comprehensive polymer name index is available. The Database contains a listing of polymer properties that are, for the most part, associated with polymer
manufacturing, processing, and applications. As such, the Database contains other useful information in addition to polymer
properties, not found in other source books; an example of this is given for nylon 6,6, a well-studied commercial polymer:
The Database also lists many types of polysaccharides, modified cellulosics, and other important biopolymers. Different types of polymers and polymeric structures are presented, such as inorganic polymers, blends, block copolymers, graft polymers, ionomers, elastomers, fibers, hydrogels, interpenetrating networks, structural foams, polymer composites, polysiloxanes, resins, and natural rubbers. For this second edition, an introductory chapter has been added that reviews polymer complexity as it relates to polymer properties. Furthermore, tabulated lists of polymer properties are given to serve as a guide in selecting appropriate test procedures. Polymer property data are now available on the Internet in a variety of tabular forms. The advantages and convenience of having a desk reference book of the magnitude of Database cannot be overstated. No other reference handbooks contain the caveats, descriptions, and explanations that are found in Polymers: A Property Database as exemplified in the above table.
A. Importance of Polymer Properties Because of their high molecular mass, polymers, as compared to small molecules, have unique properties that are often difficult to predict. As such, some background knowledge of the physical chemistry of polymers is desirable for dealing with polymers and polymeric materials. Polymer properties, like solubility behaviour, are used as a guide on a laboratory scale when analyzing or characterizing polymers or when determining structure-property relationships. On an industrial scale, properties, such as melt viscosity or heat capacity, are important for establishing polymerization and processing conditions. A listing of properties is required for selecting polymers to meet specific applications. Polymers are ubiquitous as they are used in all applications, from consumer products to high-temperature industrial use to medical devices, under a wide-range of conditions. In modern polymer science and engineering, more complex structures, such as multilayer films, nanomaterials, electro-optical and electronic devices are being developed that require more specialized and complex testing for end-use performance evaluation. Furthermore, from knowledge of structure-property relations of polymers and polymeric materials, one can begin to design and tailor make polymers and complex polymeric structures to meet specific end-use performance requirements. It is sometimes difficult to accurately predict end-use performance characteristics of the final product using
tabulated data of individual components. As a result, accurate measurements are those made on the final product itself, rather
than using model polymers or components. In these cases, empirically derived measurements using the actual product, verified
with authentic samples, may be the best option. It should be noted that most empirically derived data are trade secrets, and,
as such, not available. Nevertheless, compilations of properties are still valuable.
Because of polymer complexity, property variability must be taken into consideration. In this section, we will discuss possible sources of polymer inconsistency and offer suggestions to recognize and reduce these errors. Chemical or compositional heterogeneity refers to the chemical or structural difference among chains of the same polymer. Thus a measured property of a chemically heterogeneous sample will be an averaged value dependent upon sample source. For chemically homogeneous samples, property variability will not be a concern. In a similar fashion, polymers that are polydisperse in molecular weight have averaged property values, while monodisperse samples will give accurate data. Obviously, samples that are both chemically homogeneous and monodisperse will give the most accurate and precise values. As compared to synthetic polymers, almost all nucleic acids and mammalian proteins are compositionally (chemically) homogeneous and monodisperse, if not there would be no life; biopolymers carry highly specific and selective information. Mammalian polysaccharides, for the most part, are also compositionally homogeneous, but are polydisperse in molecular weight; whereas plant polysaccharides are polydisperse. Chemically modified cellulose (cellulosics) are typically both compositionally heterogeneous and polydisperse in molecular weight. Starches (α-amylose and amylopectin), another major class of polysaccharides, are highly polydisperse in molecular weight, but quite compositionally homogeneous. In addition, amylopectin and many other polysaccharides are highly branched, which may further complicate listed property values. Synthetic polymers can be quite complex and, as such, tabulated and measured property data must be interpreted with care. Homogeneous synthetic polymers are those produced from condensation polymerization reactions, in which all polymer chains are chemically indistinguishable from another. Even though these types of polymers show a finite polydispersity of two, accuracy and precision will not be compromised since all samples (and reference standards) will have the same degree of polydispersity. Lastly, synthetic polymers produced by addition polymerization (i.e., ionic, complex coordination catalytic, or free-radical copolymerization), will have the greatest amount of compositional heterogeneity, and with the exception of anionically polymerized samples, will also have a large molecular weight polydispersity. For these polymers, tabulated data must be interpreted with caution, unless users establish their own data sets with reference polymers obtained from the same polymerization conditions. Sequence distribution or polymer microstructure is the next higher level of complexity in which the average arrangement of monomers along a chain is considered. The polymerization mechanism and reactivity ratios of monomers dictate this parameter. Monomers can be randomly arranged along chains in the case of statistic or random copolymers or in the extreme form a block copolymers. In any event, the microstructure of reference polymers should be defined when properties are listed. Next in line of complexity is macromolecular architecture, or polymer configuration, in which the topological nature of the chain is of interest. Thus polymer branching can take on a wide range of configurations including short- and long-chain branching, and comb, star, and dendritic structures with or without comonomer segregation or blockiness. Because of the strong influence of polymer configuration on properties, this parameter needs to be defined, and care taken when comparing tabulated data to those of actual samples. In summary, polymers may have up to two or more distributed characteristics depending on the number of different monomers used in the polymerization, the type of polymerization mechanism, and whether or not the sample was fractionated during isolation. As a rough estimate, polymer "complexity" increases exponentially with the number of distributive properties, making it more difficult to measure accurate polymer properties. Some polymers are modified after polymerization; however, this process can be somewhat difficult to control. Because polymer chain segments can influence the chemistry of a neighboring groups. Chemical modifications are done mainly on cellulosics and other polysaccharides to tailor-make specific property characteristics. Thus tabulated property data given for cellulosics and polysaccharides represent average values of the entire sample ensemble of polymer chains that differ in composition. To complicate matters further, insoluble gels, comprised of three-dimensional networks, may form if chains are allowed to chemically or physically (via hydrogen bonding) react with one another, either during or after polymerization. Post-polymerization processes are also accomplished via vulcanization, irradiation, or through the addition of a low molecular weight cross-linking agent. The resulting polymer (i.e., rubber, elastomer, resin, or gel) in essence, is one super or giant molecule approaching infinite molecular weight. These viscoelastic materials have wonderful consumer, industrial, and aerospace end-use applications when properly formulated. The next level of polymer complexity is polymer blends and multicomponent systems. To adjust the glass-transition temperature, plasticizers are added, often times at high concentrations. To increase polymer strength, reinforced polymeric materials are used that consist of added inorganic material, the most common being carbon black or glass fibers. Laminated structures are also produced for increased material strength. High-value added, specialty products with controlled molecular weight, branching, or architecture are being developed
for high-technology industries, most notably electronic and optical devices, printing inks, and coatings in the aerospace industry.
Because of their specialized uses, most of these polymeric materials are not listed in this compilation.
Most industries issue testing protocols and polymer property specifications to the trade. To ensure uniformity, national regulatory agencies have formed to deal with standardized methods and testing approaches. In the United States, ASTM is the most prominent independent agency supported by industry with about 100 test methods in place specifically for polymers and polymeric materials. API specializes in the development of procedures for petroleum products, some of which are polymeric. In Britain, BSI is the key agency for testing, while in Europe, DIN procedures are followed. Many of these agencies are overseen by ISO, a federation of national regulatory bodies. (See Table 1 for complete names and acronyms.) Governmental departments of commerce, defense, and military are also involved in issuing protocols and
specifications. For example, the FDA is responsible for establishing acceptable limits of extractable components from polymeric
materials in contact with food and drugs.
D. Reference Polymers and Specialty Materials Sources of reference polymer standards that can be used for instrument calibration and validating methods are listed in Table 2. In the United States NIST is responsible for distributing a number of well-characterized polymer standards. These standards have well-defined chemical composition and molecular weight, and are also suitable for
formulating materials for R&D. All reference standards and polymeric material should come with certificates of analysis.
(Since water content in polymers, especially hydrophilic ones and polysaccharides, may affect properties, it is advisable to vacuum
dry and properly store them to prevent moisture buildup and degradation.)
In this section we discuss and list polymer properties that are included in data tables of this book. Some properties reviewed in this section are not listed in this text, but they are included for completeness. Specific properties for certain classes of polymers are not given, especially those used for optical, electronic and magnetic devices. Much of this section and the book's content is based on van Krevelen's (1976) property schemes, with modification. His book should be consulted for more detailed discussions. Other books of interest are listed at the end of this chapter. Basic information that characterizes polymers is listed in Table 3. These properties can be estimated from the expected outcome of the polymerization, measured, or calculated from group contributions (see van Krevelen, 1976). Methods for measuring these properties can be found in the reference list (for example, see Barth and Mays, 1991; Brady, 2003; Wu, 1995). Some of the more important properties will be considered here. The most useful average molecular weights are the number- (Mn), weight- (Mw), and z-averages (Mz). These
averages are easily determined from the molecular weight distribution obtained using size exclusion chromatography
(Mori and Barth, 2001). Oftentimes just the viscosity-average molecular weight (Mv) is available, which can be conveniently
determined from the measured intrinsic viscosity of the polymer in a given solvent at a specified temperature using tabulated
Mark-Houwink coefficients. Alternatively, Mw can be determined from light scattering and Mn from osmometry.
Branching, molecular topology, and comonomer sequence distribution along the chain are more difficult to estimate; these properties are best estimated by the chemistry of the polymerization procedure, with support from NMR measurements. Polymer toxicity and stability must be known or at least estimated from functional group and comonomer chemistry. It should be realized that polymer toxicity, to a first approximation, is lower, than the corresponding comonomer toxicity; because of the low polymer diffusion coefficient, macromolecules cannot readily pass through biomembranes, thus have limited bioavailability. The effect of molecular weight of a polymer in solution on its colligative properties, summarized in Table 4, is a
well-established phenomeon. These properties are dependent on the number of macromolecules in solution, independent on molecular
weight and chemical composition. In fact, the number-average molecular weight of a polymer can be determined by measuring one of its
colligative properties.
Table 5 lists volumetric properties of polymers in the liquid or solid state as a function of temperature; these properties are
related to the compactness of chains and the interaction of comonomers within and among neighboring chains. These properties
are more dependent on chemical composition, than molecular weight. Volumetric properties also depend on factors influenced by
comonomer sequence distribution, such as tacticity, branching, and polymer crystallinity.
Table 6 lists thermodynamic and calorimetric attributes of a polymer, while Table 7 deals with polymer solubility
and cohesive energy. Except for molar entropy, all these properties depend mainly of chemical composition, rather than molecular
weight. Furthermore, polymer crystallinity, in addition to the chemical nature of a polymer, plays a major role in dictating
solubility behavior. In order to effect solubility in the case of crystalline or semicrystalline polymers, the solution must be
heated near or above its melting point to break up crystalline regions.
Light scattering and inherent viscosity measurements made at infinite dilution are used to determine polymer size parameters,
conformation, 2nd virial coefficient, weight-average molecular weight, and long-chain branching parameters (Table 8).
These are fundamental parameters that allow us to probe structural features of polymer molecules. These properties are dependent
on molecular mass and shape, rather than polymer composition.
Melt index and viscosity are critical parameters needed for polymer processing. These and other polymer transport
properties are listed in Table 9. As in the case of other viscosity measurements, these properties depend mainly on higher
statistical molecular weight averages, such as Mw and Mz.
Tables 10 to 13 list polymer characteristics directly involved with end-use properties: mechanical properties (Table 10), electric and magnetic properties (Table 11), optical properties (Table 12), and polymer stability (Table 13). (A more complete discussion of these properties is given in selected references at the end of this chapter.)
Tables 10 to 13 list polymer characteristics directly involved with end-use properties: mechanical properties (Table 10), electric and magnetic properties (Table 11), optical properties (Table 12), and polymer stability (Table 13). (A more complete discussion of these properties is given in selected references at the end of this chapter.)
ConclusionsPolymer science can be viewed as an applied branch of chemistry based on deliverable properties. It is of interest to note that most of these properties depend on just four attributes: 1. polymer molecular weight, 2. crystallinity, 3. chemical composition, and 4. macromolecular topology or architecture; furthermore, these parameters interact with one another in a complex manner. By varying these parameters, polymers can be tailor-made to fit a list of desirable characteristics. It is hoped that this polymer property database will serve as a guideline to help pave the way for the development of newer materials of improved characteristics. Polymers - A Property Database on the WebTo maintain state-of-the-art property listings and to facilitate searches, Polymers - A Property Database
published online in addition to hard copy. Space considerations have precluded the inclusion of indexes other than a name
Index in the hard-copy version of the Polymer Database. In contrast, the online version contains searchable indexes on each of the
fields present in the database, covering all text and numerical fields in the following categories:
Upon entering the database you will be presented with the polymer search screen illustrated below (Fig. 1). It is from here that searches will be performed.
From the search window, design your search profile using text, numerical fields or a combination of both. Once your search has been performed the resultant hits are listed alphabetically by polymer name in the hit list window. Clicking on any one of the hits in the hit list window will result in that entry being displayed (Fig. 2).
In addition, the online version also contains a searchable monomers database. Monomers may be searched by a combination of text and structure searching via a downloadable browser plug-in (Fig. 3).
Selected References
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