Differential scanning calorimetry semicrystalline polymers

Because of the usual experimental ranges of crystallinity, the appearance of the baselines in the study of semicrystalline polymers is not very frequent [36, 37]. Therefore, the crystalline volume fraction should be obtained by other alternative techniques such as, for example, differential scanning calorimetry. In this way, if the crystallinity in volume is known, it is possible to obtain the lost baseline [37, 38]. However, if the crystallinity is either low or high, it is possible to directly obtain the baseline for which it is foreseen that the morphology is solved [36]. For example, Vonk and Pijpers and Vonk and Koga worked at high crystallinities and they observed the aforementioned baselines [39]. 

The glass-transition temperature, melting point, heat distortion temperature, thermal degradation temperature, ete. are important parameters affecting the application and processing of semicrystalline polymer materials. These thermal parameters can be obtained via differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, etc. 

Within the past few years, many investigators have observed an increase in the degree of crystallinity or crystallite size of semicrystalline polymer-CNT composites due to the addition of CNTs. Differential scanning calorimetry (DSC) melting endotherms have been frequently employed to demonstrate this effect (Table 35.3). Recently, Coleman et al. [69] investigated this induced crystallization effect, and related it to the mechanical properties of the composite. The results highlight a fundamental difference between CNT-polymer composites and carbon fiber—polymer composites with CNT composites the interface dominates all other effects due to the vast surface area/volume ratio that CNTs have relative to carbon fibers (Fig. 35.2). 

Differential scanning calorimetry. DSC is used to obtain the glass transition temperature, but not the melt points, for amorphous polymers. Melt points are created in the crystalline segment of semicrystalline polymers. 

To determine crystallinity in a semicrystalline polymer, diffraction, thermodynamic, and spectroscopic methods can be used. Diffraction method is mainly used with waxd methods. Thermodynamic methods include dilatometiy, differential scanning calorimetry (dsc), etc, while ir and nuclear magnetic resonance (nmr), and other spectroscopic methods can also be used. 

For many years, the thermodynamic description of macromolecules lagged behind other materials because of the unique tendency of pol5nneric systems to assume nonequilibrium states. Most standard sources of thermodynamic data are, thus, almost devoid of polymer information (1-7). Much of the aversion to include polymer data in standard reference sources can be traced to their nonequilibrium nature. In the meantime, polymer scientists have learned to recognize equilibrium states and utilize nonequilibrium states to explore the history of samples. For a nonequilibrium sample it is possible, for example, to thermally establish how it was transferred into the solid state (determination of the thermal and mechanical history). More recently, it was discovered with the use of temperature-modulated differential scanning calorimetry (TMDSC) that within the global, nonequilibrium structure of semicrystalline polymers, locally reversible melting and crystallization processes are possible on a nanophase level (8). 

Copolymer [8o,5-CPPo.5]-Leu(6)o 75-Lys(Bz)o.25 (Table 1) with Mw = 82 000 Da and polydispersity (PDI) = 1.66 was isolated with 76 % yield. As a result, the incorporation of 50% CPP-unit in sebacic acid based PEA raised the Tg from 22 to 44°C. An additional sharp melting endotherm in differential scanning calorimetry (DSC) curves at 286°C was also observed, indicating a semicrystalline nature of the co-polymer. The polymer is soluble in chlorinated nonpolar and aprotic polar solvents, but not in ethanol. Because of its high hydrophobicity, the CPP-co-polymer does not swell in aqueous media, and equilibrium water content is about 2-3% w/w. 

Fillers and pigment can, in some cases, nucleate crystallization of semicrystalline polymers including PE, PP, PA6, PA6,6, PBT, and PEEK. The effect is normally measured by differential scanning calorimetry (DSC), which detects crystallization. Nucleation results in crystals starting to form at higher temperature as the melt cools and this can be... 

In this chapter, the basics of differential scanning calorimetry (DSC) analysis and its correlation to polymer morphology for semicrystalline polymeric materials are presented. After a brief review of fundamental concepts, the utility of the technique is illustrated by a series of practical applications. 

This chapter describes the basic principle, recent developments, and selected applications of some commonly used experimental techniques (i.e., optical microscopy, electron microscopy, atomic force microscopy, nuclear magnetic resonance, diffraction and scattering (X-ray, neutron, and light), and differential scanning calorimetry) for characterization of semicrystalline polymers. Many excellent reviews for each technique and their usage exist, and the listed references only represent the exem-... 

In order to evaluate the application of modulated-temperature differential scanning calorimetry (M-TDSC) to the study of the crystallisation kinetics of semicrystalline polymers, isothermal crystallisation kinetics in poly(e-caprolactone)-SAN blends are investigated. The temperature dependence of d In G/dT (G =crystal growth rate), determined by M-TDSC agrees approximately with previous experimental data and theoretical values. These were obtained from direct measurements of spherulite growth rate by optical microscopy. Here, theoretical and M-TDSC experimental results show that the d In G/dT versus temperature plots are not sensitive to the noncrystalline component in the poly(e-caprolactone)-SAN blends. 15 refs. 

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