Generic polymers

In this chapter we introduce the main engineering polymers. They form the basis of a number of major industries, among them paints, rubbers, plastics, synthetic fibres and paper. As with metals and ceramics, there is a bewilderingly large number of polymers and the number increases every year. So we shall select a number of "generic" polymers which typify their class others can be understood in terms of these. The classes of interest to us here are ... 

In summary, then, design with polymers requires special attention to time-dependent effects, large elastic deformation and the effects of temperature, even close to room temperature. Room temperature data for the generic polymers are presented in Table 21.5. As emphasised already, they are approximate, suitable only for the first step of the design project. For the next step you should consult books (see Further reading), and when the choice has narrowed to one or a few candidates, data for them should be sought from manufacturers data sheets, or from your own tests. Many polymers contain additives - plasticisers, fillers, colourants - which change the mechanical properties. Manufacturers will identify the polymers they sell, but will rarely disclose their... 

The number-average molecular weight of a polymer may be controlled by offsetting the stoichiometry of two dissimilar mutually reactive difunctional monomers. The polymer will have the same endgroup functionality as that of the monomer used in excess. For a generic polymer made from a difunctional monomer AA with A functional groups and an excess of difunctional monomer BB widt B functional groups, r is defined as... 

The ADMET reaction is shown below in Eq. 1, which generically displays an a,oo-acyclic diene being condensed into its requisite generic polymer plus a small molecule. 

MATERIALS. Selection of a base polymer thermoplastic resin from which a molded substrate is produced is influenced by factors of price and performance. Secondary considerations include supplier preference. Given the uniqueness of each product application, standardization of generic polymers is unlikely. In fact, the selection possibilities are likely to grow with continued diversification of application requirements/specifications. 

TABLE 17.4 The power-law index, shear viscosity, and other useful properties of a number of neat generic polymers [14]... 

Figure 1.3 Effect of crystallinity on modulus-temperature curves. The two curves refer to the same generic polymer, differing only in rate of cooling from the melt. Both samples show a 7g...

Consider the case of amorphous polypropylene as a generic polymer, the ideal plastic response and cavitation response of which have been simulated in considerable detail (Mott et al. 1993a, 1993b) under imposed pure shear deformation and under pure dilatation, respectively. As stated by those investigators, the otherwise ideal plastic shear resistance r and the ideal cavitation resistance a were determined to be... 

Despite the shorter destabilisation time and faster growing modes of a fully conducting polymer compared to a perfect dielectric, the patterning process is reminiscent of the well-studied case of generic polymers [33-35], thus confirming the same underlying physical mechanism. 

The generic polymer based process that yields oxygen containing silicon carbide fibers consists of five steps. (1) Polydimethylsilane, or PDMS, is synthesized. (2) PDMS is rearranged into polycarbosilane, or PCS. (3) PCS is melt spun and yields a solid, green, or... 

In Table 6.2 a number of rheological and thermal properties have been tabulated for several important generic polymers. These data have been gathered from numerous sources, including the author s own measurements. The data should be used as estimates only, because measurement techniques may differ and because considerable differences in properties can occur in one particular polymer as a result of variations in molecular weight distribution, additives, thermomechanical history, etc. Actual measurement of polymer properties should always be preferred above published data. However, actual measurement is not always possible, in which case the table may provide useful information. 

Table 6.2 Useful Properties of a Number of Generic Polymers...

Figure 14.2 Click reaction between a generic polymer functionalized with a triple bond (red) and azide (blue). Triazole is synthesized by their chemical interaction.

Fig. 11 Solvated generic polymer molecule in atomistic and CG solvent in the same simulation box. Blue filed circles represent the CG beads and blue circles with tetrahedral molecule in it represent the solvent molecules in the transition region. The generic polymer (in red) is solvated in the atomistic solvent.

A generic polymer chain of length i is produced through i -1 propagation reactions, after which the chain becomes inactive by termination (by disproportionation) or transfer. One can start by defining the probability of propagation, q, as shown in Equation 1.46 ... 

The gradient energy coefficient, k, is selected as 6.9e-ll J m [52] for a generic polymer material, while the diffusivity, D = le-20 m s, is chosen as a typical value for polymers. The mobility of the system can then be evaluated, using the relationship [53] ... 

The compositions of the protective materials with the same generic polymer name are not necessarily the same. The basic materials usually have different additives, which affect the material properties. Also, the composition of the basic material may differ. For example, nitrile rubber is acrylonitiile-butafliene copolymer. The proportions of the acrylonitrile and butadiene monomers often fliffer between nitrile gloves. Thus, the protective properties can be quite flifferent for two separate glove products even if the same manufacturer makes them. 

In determining the appropriateness of a sealant or caulk for an application, many factors need to be considered. The generic polymer technology, the physical form, sealant classification, specifications and performance properties are all important features of a sealant or caulk. Table 22 outlines some basic performance properties of the sealant types reviewed in this chapter. As seen in Table 22, most of these sealant types are utilized in construction applications. As described earlier in this chapter, sealants and caulks can be classified in low, medium, and high movement categories, and selection is primarily decided on the basis of movement capability, adhesion, life expectancy, and material cost. Table 23 reviews the typical applications for these types of sealants and caulks. 

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