C Differential Scanning Calorimetry

Cure kinetics of thermosets are usually deterrnined by dsc (63,64). However, for phenohc resins, the information is limited to the early stages of the cure because of the volatiles associated with the process. For pressurized dsc ceUs, the upper limit on temperature is ca 170°C. Differential scanning calorimetry is also used to measure the kinetics and reaction enthalpies of hquid resins in coatings, adhesives, laminations, and foam. Software packages that interpret dsc scans in terms of the cure kinetics are supphed by instmment manufacturers. 

Plato. C. Differential scanning calorimetry as a general method for determining purity and heat of fusion of high-purity organic chemicals, Ana/ Cfiero, 44(8) 1531-1534, 1972. 

The Thermoelastic 125 (30% by weight of polystyrene) has been studied by Canter132 as a function of temperature using a specimen moulded at 150 °C. Differential scanning calorimetry has revealed the presence of two transitions. The lower transition temperature corresponds to Tg of polybutadiene chains and the upper transition temperature corresponds to Tg of styrene chains. The upper transition has also been studied by temperature dependence of the torsional modulus. 

Eagle, S. C., Barry, B. W. and Scott, R. C. Differential scanning calorimetry and permeation studies to examine surfactant damage to human skin. Journal of Toxicology—Cutaneous and Ocular Toxicology /7(l) 77-92, 1992. 

Clas, S.-D. Dalton, C.R. Hancock, B.C. Differential Scanning calorimetry applications in drug development. Pharm. Sci. Technol. Today 1999, 2, 311-320. 

Equilibrium moisture content 2-3% w/w at ambient temperature and humidity ( 25°C, 40% RH). See also Figure 1. Glass transition temperature 113 2°C (differential scanning calorimetry dried sample)... 

List some of the factors that influence (a) thermogravimetry curves, (b) differential thermal analysis curves, and (c) differential scanning calorimetry curves, indicating which are most important for the various techniques. 

Bruylants, G. Wouters, J. Michaux, C. Differential scanning calorimetry in life science Thermodynamics, stability, molecular recognition and application in drug design. Current Medicinal Chemistry, 2005,12, 2011-2020. 

After a PEM is cooled at very low temperatures (e.g., less than -50°C) differential scanning calorimetry (DSC) shows an endothermic peak at around 0°C as the temperature scans up. This seems to indicate that the PEM contains water that freezes af the water freezing temperature. From the peak area the amount of such "freezable" water can be determined, and its difference from the total amount of water within the membrane that is pre-determined by weighing is used to represent the amount of water that is not freezable (called non-freezable water). For example, Hou et al. found that fully hydrated Nation 212 membrane in liquid water at 25°C contains 5.3 and 15.2 freezable and non-freezable water molecules per -SOjH group, respectively while the same membrane hydrated in water vapor at 75% RH and 25°C contains 0 and 6.2 freezable and non-freezable water per -SO3H group, respectively (Hou 2008). 

Ultraviolet-visible absorption spectra of polymers and model compounds were measured on a Beckman ACTA MVI spectrophotometer. Fluorescence spectra of compounds in dilute solution were recorded using an Aminco-Bowman spectrophotofluorometer at 20 C. Differential scanning calorimetry (DSC) was performed using a Perkin-Elmer DSC-2 scanning calorimeter. Melting points were determined on a Perkin-Elmer DSC-II at a 5 C/min. heating rate. Elemental analyses were by Galbraith Laboratories, Knoxville, Tennessee. 

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