Poly apparent heat capacity

FIGURE 4.9 Apparent heat capacity and optical microscopy measurement (% light transmission) of a 75/25 poly(oxyethylene)/poly(ether sulfone) blend. (From Dreezen, G., Groen-inckx, G., Swier, S., and Van Mele, B., Polymer, 42, 1449, 2001. With permission.)... 

Figure 4.49 shows the results of adiabatic calorimetry, standard DSC and quasi-isothermal MTDSC for poly-/ -dioxanone (—CH2—CH2— O—CH2—COO—)x, (PPDX). The ordinate is labelled as apparent heat capacity since in the transition region, latent heat contributions may increase the heat capacity. Up to 250 K, the heat capacity is practically fiilly vibrational as is typical for glassy and crystalline solids. The skeletal and group vibrational contributions are then extrapolated to higher temperature, as is discussed with Figure 4.1 for polyethylene. The sample analysed with... 

Figure 4.49. Apparent heat capacity of poly-p-dioxanone (PPDX) using adiabatic calorimetry by calculation of Cp = (AT/corrected for heat loss/A corrected for temperature drift)p,n Standard DSC using Eq. (10), and quasi-isothermal MTDSC evaluated with Eq. (11). The data were...

Poly(ethylene oxide) of high molar mass behaves similarly to the PET and PTT and other polymers analysed, although special effects are seen for many analysed polymers [78,82]. Figure 4.80 represents an example of PEO of a molar mass of 35,000 Da. As before, at low temperature, standard DSC and quasi-isothermal MTDSC give the same result. Most of the melting is irreversible and shows only in the total apparent heat capacity. A small amount, however, is reversing. The irreversible melting occurs at a temperature expected for 4 folds per molecule [52]. 

Figure 9.4 Characteristic temperatures of meltiug and heat of fusion from the evaluation of apparent heat capacity versus temperature for semicrystalhne poly(lactic acid) (PLA).

Figure 9.5 Deconvolution of apparent heat capacity of semicrystalline poly(lactic acid) in the melting region based on heat of fusion, conformation, anharmonic, and vibration contributions [22].

Figure 9.7 Advanced thermal analysis of melting process for estimation of heat of fusion from apparent heat capacity, Cp(exp) of semicrystaUine poly(trimethylene teraphthalate) PTT [28]. (See color insert.)...

Figure 9.12 Analysis of the experimental apparent heat capacity of copolymer of poly(oligoamide-a/t-oligoether) (PEBA) in melting areas [33].

Figure 9.35 Comparison of the reversing (by TMDSC) and apparent heat capacity (by DSC) of semicrystalline poly(oxy-2,6-dimethyl-l,4-phenylene) (PPO) [57].

Glass transitions involve mainly the onset or freezing of cooperative, large-amplitude motion and can be studied using thermal analysis. Temperature-modulated calorimetry, TMC, is a new technique that permits to measure the apparent, fiequency-dependent heat capacity. The method is described and a quasi-isodiermal measurement method is used to derive kinetic parameters of the glass transitions of poly(ethylene terephthalate) and polystyrene. A first-order kinetics expression can describe the approach to equilibrium and points to the limits caused by asymmetry and cooperativity of the kinetics. Activation energies vary from 75 to 350 kJ/mol, dependent on thermal pretreatment. The preexponential factor is, however, correlated with the activation energy. 

Figure 4.24. Apparent specific heat capacity of a poly(oligoamide-12- //-oligooxytetramethylene) copolymer. Copolymer is analysed with a quantitative baseline based on heat capacity.

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