Polymer macrostructure

The tetraphenylborate ion-doped polypyrrole electrode was sensitive to zinc ions [464, 465], and its sensitivity was dependent on the polymer macrostructure. 

It can be concluded that it is very difficult to predict the result from a polymer macrostructure, but it is relatively easy to measure the secondary species generated on irradiation by using known analytical techniques, such as measuring swelling, tensile tests, analysis using nuclear magnetic resonance (NMR), etc. The yield is then expressed by the G value, which represents the number of cross-links, scissions, double bonds, etc., produced for every 100 eV (1.6 X 10 J) dissipated in the material. For example, G (cross-links), abbreviated G(X), = 3.5 means that 3.5 cross-links are formed in the polymer per 100 eV under certain irradiation conditions. Similarly, the number of scissions formed is denoted by G(S). In order to determine the number of crosslinks or G(X), the number of scissions or G(S), etc., it is necessary to know the dose or dose rate and the time of exposure for these irradiation conditions. From the product yields it is possible to estimate what ratio of monomer units in a polymer is affected by irradiation. ... 

Before reviewing elastomer characteristics required to meet any given set of tire performance parameters, it is appropriate to identify two means by which the materials scientist may describe a polymer polymer macrostructure... 

The authors collected the test data shown in Table X. From these data it can be noted that the number-average molecular weight, or of a commercial emulsion SBR such as IISRP 1500 or 1712 is typically 90,000 to 175,000. The primary molecular weight of a solution-polymerized polymer produced with an anionic lithium catalyst can, in contrast, be increased toward 250,000 without gelation. In addition, emulsion-polymerized SBR contains only about 92% rubber hydrocarbon as a result of the presence of residues from the production process solution polymers tend to be near 100% hydrocarbon. As a consequence, the authors concluded that the number-average molecular weight can be considered the key parameter of polymer macrostructure, particularly with respect to the hysteretic characteristics of a tread formulation. Hence the differences in macrostructure between emulsion- and solution-polymerized polymers will dictate many of their properties in a tire tread compound. 

In addition to polymer composition and microstructure, molecular weight, molecular weight distribution (MWD) and chain architecture (collectively referred to as polymer macrostructure) are considered to... 

A review on drag-reducing polymers is given in the literature [1359]. It has been suggested that drag reduction occurs by the interactions between elastic macromolecules and turbulent-flow macrostructures. In turbulent pipe flow, the region near the wall, composed of a viscous sublayer and a buffer layer, plays a major role in drag reduction. 

Anionically formed polymers of /3-Iactones have helical macrostructures, in which the ester groups are approximately in the planar configuration. Copolymers of different /3-lactones have the same basic structure but show variations of other properties (73AG(E)432, 77MI51301, 78MI51302, 74CJC3742). 

The information on physical properties of radiation cross-linking of polybutadiene rubber and butadiene copolymers was obtained in a fashion similar to that for NR, namely, by stress-strain measurements. From Table 5.6, it is evident that the dose required for a full cure of these elastomers is lower than that for natural rubber. The addition of prorads allows further reduction of the cure dose with the actual value depending on the microstructure and macrostructure of the polymer and also on the type and concentration of the compounding ingredients, such as oils, processing aids, and antioxidants in the compound. For example, solution-polymerized polybutadiene rubber usually requires lower doses than emulsion-polymerized rubber because it contains smaller amount of impurities than the latter. Since the yield of scission G(S) is relatively small, particularly when oxygen is excluded, tensile... 

In the final chapter "Principles of Statistical Chemistry as Applied to Kinetic Modeling of Polymer Obtaining Processes" by Semion Kuchanov (Lomonosov Moscow State University, Moscow, Russia), the contemporary problems of bridging models of micro- and macrostructure are discussed. The hierarchical analysis of chemical correlation functions (so-called chemical correlators) is a subject of the author s special interest. These problems are presented conceptually stressing that the problem of crucial importance is revealing the relation between the process mode and the chemical structure of polymer products obtained. 

It is clear, however, that a s is not quantitatively equal to a because the macrostructural looseness (A) of the polymer in the two cases is not the same A for (Sty), x(DVB)x is given by [(1/x)1 3 — (l/x)o 3], as defined in Eq. 20, whereas A for the non-crosslinked polymer varies with the class of liquid, which determines y and the distribution of the self-associated domains that comprise y as noted above. It may be possible, however, to establish a quantitative relationship of a with oc9 for a given class of liquids, which could then be used in turn to establish the corresponding a/ocs for other P-L systems in that liquid classification. 

So far most of the pertinent literature interprets interactions between polymer and a second sorbed component on the basis of the colligative properties of the system. This information is summarized in Sect. 2 of this review. From those reports, I inferred that some sort of association of the small penetrant molecules with the repeat unit of the polymer is a prerequisite condition for the sequential changes described above. This implies that the magnitude of polymer swelling should be directly related to how well the molecular structure of the small molecule can be accommodated by the molecular structure of the polymer repeat unit in view of the macrostructure of that polymer (i.e. the crosslink density). The results obtained in our laboratory, which are summarized in Sect. 3 of this Review, are thoroughly consistent with that hypothesis. In Sect. 4 these interpretations are extended to correlate the colligative properties of Sect. 2. 

The physico-mechanical properties of aminoplasts in the articles are determined by the degree of hardening and macrostructural defects. In the cooling of the articles down to room temperature reactive groups in the polymer are still retained, but their interaction is made difficult due to the loss of mobility caused by the molecules of the reticular polymer because of the latter s vitrification. Simultaneously a nonequilibrium supramolecular structure is recorded. Heat treatment of the articles does not alter the supramolecular structure, the latter remaining invariable. Heat treatment at a temperature below the vitrification temperature may only cause either a certain additional hardening of the binder or increase the... 

In order to establish and evaluate quantitatively the relation between the morphology and the properties of foamed polymers the basic macrostructural parameters must be determined. These parameters include relative number of open and closed cells, volumetric weight or apparent density cell size, shape, wall thickness, cell distribution according to size and shape in a given volume and specific surface area of the foamed plastic material. 

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