Thermograms, component polymers

Tan 6 curves from dmta thermograms of blends based on combinations of HPL/PVA(> 0) are shown in Figure 5 (10). The tan 6 transition, which is another measure of Ts, is broadened by the presence of HPL component, and it increases above that of the parent polymers consistent with dsc data. This can again be explained with the presence of strong interactions between the amorphous components which coexist in a closely associated state. 

Tg of either polymer components. In addition to the two distinguishable Tg signals, the melting endotherm and cold-crystallization exotherm of CA are both detectable for every blend at almost the same temperature positions as those for the CA (DS = 2.95) alone, with a proportional reduction of the respective peak areas. In contrast to the result, the thermograms compiled in Fig. 9a for the pair of CA (DS = 2.70) and P(VP-co-VAc) (VP/VAc = 0.51/0.49) (combination A) indicate a definitely single Tg that shifts to the higher temperature side with increasing CA content. As summarized in Fig. 8, CA/PVAc blends are immiscible irrespective of the DS of the CA component, while PVP forms a miscible monophase with CAs unless the acetyl DS exceeds a value of... 

Figure 2.13. (a) TGA thermograms of pristine polymer as well as nanocomposites containing varying amounts of nanotubes and (b) degradation temperatures of side and main chain components of the polymer in the composites. Reproduced from reference 52 with permission from American Chemical Society. 

Below the melting point the situation is more complicated. As mentioned above the dynamics now depends on the thermal history. Quenched samples exhibit relatively fast chain motions conqiarable to those in the nematic melt. For annealed samples two components are observed, which we assign to a LC and a crystalline phase. Decomposition of various relaxation curves into two components yields a crystallinity of 55% 5y practically independent of ten ierature [10, 96, 175]. A similar heterogeneity is observed for ordinary polymers, which exhibit amorphous and crystalline phases [176]. Accordingly, melt and glass transitions are detected in the DSC thermograms of both types of polymers [96, 177]. 

Figure 2.7 displays differential scanning calorimetry (DSC) thermograms of A-PS/T-PBMA = 50/50 blends, where the A-PS and T-PBMA components contain various contents of VBA and VBT, respectively [68]. The binary blend of PS and PBMA exhibits two glass transition temperatures located at the same temperatures as those of their respective pure polymers, revealing... 

Dynamic mechanical analyzer n. An instrument that can test in an oscillating-flexural mode over a range of temperature and frequency to provide estimates of the real , i.e., in-phase, and imaginary , i.e., out-of-phase parts of the complex modulus. The real part is the elastic component, the imaginary part is the loss component. The square root of the sum of their squares is the complex modulus. With polymers, the components and the modulus are usually dependent on both temperature and frequency. ASTM D 4065 spells out the standard practice for reporting dynamic mechanical properties of plastics. An example of a DMA thermogram of different Perkin-Elmer Inc., manufactures the Diamond DMA instrument. Polymer films is shown. Sepe MP (1998) Dynamic mechanical analysis. Plastics Design Library, Norwich, New York. 

Fig. 1 A schematic thermogram showing various possible transitions of a system with a polymer component.

Although it can be seen that there are distinct advantages to these hyphenated combinations, these only really extend over the portion of the TGA thermogram that deals with the organic components in a polymer sample (i.e. stage 1 in Section 6.2.1). Once all of the organic components have been removed by volatilisation or pyrolysis, only carbonaceous... 

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