Melting peak, multiple

Similar heat treatment of the blends also yielded multiple melting peaks (Table II). Because the specific heats of blends are influenced by the thermal histories of the samples, only two mixtures containing 40 and 60% terpolymer, respectively, were selected for quantitative Cp measurements. Each sample experienced the same thermal history as the two component polymers, namely, cooling at 40°C/min from 140° to — 90°C. The Cp curves of the two mixtures are also shown in Figure 9. In the liquid state, the Cp of the blend was found to be the weight average of... 

The melting behavior of the i-PS material seems to indicate the presence of two crystalline forms, with two melting temperatures marked H and L in Figure 2. The behavior of the multiple melting peaks in i-PS is actually quite complex, and as the crystallization temperature,... 

Like other crystalline polymers, liquid crystalline polymers can also exhibit multiple melting peaks when studied with DSC. Multi-melting is common to crystalline polymers including single crystals of polyethylene. For example, Bair et al. (1967) found the single crystals of PE grown... 

FIGURE 3 Multiple melting peaks exhibited by PHBSHHx, which was isothermally crystallized at 112°C. 

Multiple melting peaks are observed when the polymer exhibits polymorphism like nylon 6, 6 and isotactic poly(propylene) (/-PP). 

The next thermal analyses are for solution-grown dendrites, hedrites, and melt-grown lamellae, represented by Eigs. 6.93 and 6.94. The dendrites melt at much lower temperatures than the extended-chain crystals and show multiple melting peaks. 

The development of the new crystal structures was aecompanied by the appearance of new HS melting peaks in the DSC traces. For the HDO polymer, the new peak for the contracted form appeared at a higher temperature than that for the original extended form for the BDO and PDO polymers the new peaks for the extended forms appeared at lower temperatures than those for the contraeted forms. Only a single peak was seen for the polymer extended with EG, for which only one crystal structure was detected for the HS. These results indicated that the development of polymorphic crystal structures have to be considered in the interpretation of the multiple melting phenomena seen for the hard domains in PUs. 

Although the ternary blends did not give multiple melting peaks due to the existence of two crystallisable phases, all crystalline blends (with 50 wt % or... 

PBT often displays multiple melting peaks in DSC measurements [60-63]. The DSC scans of PBT are influenced both by the heating and cooling rate, as well as by the thermal history of the sample and require very careful interpretation of the obtained results. This phenomenon of double melting behavior may be due to the formation of crystals of different sizes and distribution as well as because of repeated fusion/recrystallization processes during DSC measurement [63, 64]. 

Again, we remark on the linear relationship between and observed at water contents below the pre-region. This indicates that the molar melting enthalpy for the freezable interlamellar water is nearly the same for 5 < A < 8. However, this result does not agree with our analysis because the multiple-component deconvolutions of the ice-melting peak for the freezable interlamellar water suggest the existence of water molecules in different hydrogen bond modes. 

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