Blends different chemical compositions

Certain amounts of soy sauce from different fermentation vessels are blended in the bottling process to maintain the favorite quality of soy sauce. Raw soy sauce in each fermentation vessel has different chemical compositions. Up to now, the blending ratio was decided on the basis of results of time-consuming chemical analyses of each lot of the soy sauce. At present, however, chemical compositions are analyzed automatically using the NIR. 

Besides the overall composition of blends and random copolymers, valuable information can be obtained in the case of block copolymers. If a block copolymer contains a homopolymer fraction, a shoulder or second maximum in the MMD curve can be obtained that should have a different chemical composition. Figure 9 shows the MMD of a block copolymer of methyl methacrylate and decyl methacrylate, in which a second lower molar mass maximum can be identified as poly(decyl methacrylate) (PDMA) by dual detection [37]. The increase in the PDMA content with molar mass in the main fraction is reasonable and corresponds well with what is expected from the synthesis. It is worth noticing that this type of information can only be obtained by the D-RI detector combination, because both PDMA and PMMA have a similar low response in UV. 

A blend is merely a physical mixture (no chemical bonding) of two or more phases with different chemical compositions as opposed to the copolymer where the constituent phases are actuallyjoined together by chemical bonds [7,206]. In more refined scientific sense, a polymer blend represent a class of materials [analogous to metal (stiff material)-based alloys], in which at... 

The two RMEs were blended with DF to make B7 blends. As shown in Table 13.6, the OOT of DF decreases in the presence of methyl esters (also illustrated in Fig. 13.11). The OIT of B7 l is double that of B7 2. Therefore, B7 l has a better stability to oxidation than B7 2, and both B7s are less stable than neat DF. Furthermore, the exothermal peak of DF shows a smaller oxidation slope compared with those of the two B7s. This is due to the kinetic of reaction which is slower for the oxidation of DF than in the case of B7s. This is expected because of their different chemical composition. 

Figure 5.18 Experimental phase diagram of three (AB) /(AB)p copolymer blends differing in composition and molecular weight. Molecular characteristics of the neat copolymers (as, Si, S2 and S3) are provided at the top, and regions of phase stability are denoted by the labeled symbols. (Reprinted with permission from Court, F. and Hashimoto, T. Macromolecules 34, 2536, 2001. Copyright (2001) American Chemical Society.)...

The coupling of liquid chromatography with FTIR spectroscopy provides a new and interesting method for the detailed analysis of complex polymer systems. The application of this hyphenated technique to the analysis of polymer blends shows that it is possible to identify the different blend components by their spectral characteristics. Components of different chemical compositions are determined selectively and their chemical structure is analysed through well-resolved FTIR spectra. For structure elucidation, all facilities of... 

Fig. la —c. Schematic drawing of some specific examples of polymer molecules at an interface (a) the free surface of a homopolymer, (b) the surface enrichment of one component in a miscible polymer blend, and (c) the interface between polymers of different molecular weight and/or chemical composition... 

The commercial product is actually a blend of different cements. This blending leads to a more constant quality. The chemical composition of Portland cement is typically 60% to 69% CaO, 18% to 24% Si02, 4% to 8%... 

Recent developments have allowed for more detailed studies of polymer surface morphology by ESCA. Angle-resolved ESCA (ARXPS) allows for providing chemical compositions from shallower depths. By varying the angle of incidence different depths can be probed, and procedures have been developed to arrive at three-dimensional reconstruction of the surface. An example is shown in Figure 2, where a PVC/PMMA polymer blend has been analysed using such an approach [9]. 

One practical example of demixing that might be attributed to a difference in crystallizability is the incompatibility in blends of polymers with different stereochemical compositions. The stereochemical isomers contain both chemical and geometrical similarities, but differ in the tendency of close packing. In this case, both the mixing energy B and the additional mixing entropy due to structural asymmetry between two kinds of monomers are small. However, the stereochemical differences between two polymers will result in a difference in the value of Ep. Under this consideration, most experimental observations on the compatibility of polymer blends with different stereochemical compositions [89-99] are tractable. For more details, we refer the reader to Ref. [86]. 

Some work has been done on blends of ABC and AB or AC or AB C block copolymers, such as polystyrene-b-polybutadiene-b-poly(methyl methacrylate) (PS-h-PB-fc-PMMA) triblock terpolymers with PS-h-PB or PB-h-PMMA or other systems. Besides known morphologies for these block copolymers (though at other overall compositions with respect to the different chemical... 

Therefore, polyrotaxanes can be simply defined as polymeric materials containing rotaxane units. They are different from conventional linear homopolymers because they always consist of two components, a cyclic species mechanically attached to a linear species. They also differ from polymer blends as the individual species are interlocked together and from block copolymers since the two components are noncovalendy connected. Thus new phase behavior, mechanical properties, molecular shapes and sizes, and different solution properties are expected for polyrotaxanes. Their ultimate properties depend on the chemical compositions of the two components, their interaction and compatibility. This review is designed to summarize the syntheses of these novel polymers and their properties. 

The following problems have been studied experimentally using different SFM techniques (i) the surface topography and its dependence on the preparation conditions, (ii) the chemical composition of the surface, and (iii) the role of the substrate structure in polymer demixing. Here, one has to distinguish between asymmetric blends, where one of the components concentrates at the surface and the other at the substrate interface, and symmetric blends where one of the components segregate at both interfaces. 

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