Authors:Jiawu Gao, Lin Li, Yanping Deng, Zongming Gao, Changhua Xu, and Mingxi Zhang
A new method for determining the degree of conversion of gelation (αgel) and gel time (tgel) at gel point using a single technology, DSC, is discussed in this work. Four kinds of thermoset resins are evaluated. It
is found that the mutation points of reduced reaction rate (Vr) vs. reaction conversion (α) curves, corresponding with the changes of reaction mechanism, represents the gelation of the
reaction. The α at the mutation point is defined as αgel. From isothermal DSC curves, the point at αgel is defined astgel. Traditional techniques (ASTM D3532 and DSC method) are also used to determine αgel andtgel in order to demonstrate this new method. We have found that the results obtained from this new method are very consistent
with the results obtained from traditional methods.
Authors:A. Cadenato, J. Salla, X. Ramis, J. Morancho, L. Marroyo, and J. Martin
In the present work, gelation and vitrification experimental data are obtained by TMA and DMTA techniques using the same thermoset
based on an epoxy-amine system. The results show that the times obtained are not equivalent and depend on the technique used.
An attempt has been made to compare both determinations using the degree of cure obtained by means of DSC technique. The principal
conclusion that we want to emphasize is that it is the conversion degree and not the time of the phenomenological changes
that take place during cure, that is the link to connect and interrelate the results obtained with different techniques. A
method is also described for constructing the TTT diagram with only DSC and TMA or DMTA data.
Authors:G. Van Assche, E. Verdonck, and B. Van Mele
The free radical cross-linking copolymerization of an unsaturated polyester resin with styrene is studied in isothermal conditions using temperature modulated differential scanning calorimetry (TMDSC) and dynamic rheometry. The dynamic rheometry measurements show that gelation occurs at a conversion below 5%, while TMDSC measurements show that an important autoacceleration starts near 60% conversion, giving rise to a maximum cure rate closely before the (partial) vitrification of the system near 80%. This indicates that the autoacceleration is not due to the sharp increase in bulk viscosity at gelation, but rather to a change in molecular mobilities at higher conversion.
structure. At low temperature (below 1150 °C) the material transforms to the monoclinic structure, which is a thermodynamically stable phase [ 4 , 5 ].
Different methods have been adopted for the preparation of phase pure Zirconia. The sol–gel route
Authors:Barbara Bellich, Massimiliano Borgogna, Michela Cok, and Attilio Cesàro
role of hydrogels in many applications is the duality between the polymer network constituting the gel matrix and the diffusible active molecules in the presence of an excess of solvent, most commonly water [ 1 ]. In order to achieve a hydrogel system
Authors:Karina Ilona Hidas, Csaba Németh, Lien Phuong Le Nguyen, Anna Visy, Adrienn Tóth, László Friedrich, and Ildikó Csilla Nyulas-Zeke
for industrial purposes. Liquid egg yolk (LEY) is a popular ingredient in the food industry because of its gelling, emulsifying, colouring, and coagulating properties, high nutritional value, and unique sensory characteristics. It is often used as a
Authors:Hasan Demir, Moghtada Mobedi, and Semra Ülkü
and adsorptive, shape and size of pores, etc. Aristov et al. [ 8 ] obtained sorption behavior of water vapor on Fuji RD silica gels which have 820 m 2 g −1 BET surface areas and particle size between 0.3 and 1.0 mm using CAHN 2000 thermo