Iria Fraga

Escola Universitària Salesiana de Sarrià | EUSS · Formació Bàsica

It has been shown, for three different polymer layered silicate (PLS) nanocomposite systems, how Differential Scanning Calorimetry (DSC) can identify the different reactions of homopolymerisation and of crosslinking that occur in the intra- and extra-gallery regions of these nanocomposites, respectively, and hence how DSC can be used to assess the...

Polymer layered silicate nanocomposites have been prepared with diglycidyl ether of bisphenol-A (DGEBA) epoxy resin as the matrix and organically modified momtmorillonite (MMT) as the clay nanofiller. Resin-clay mixtures with different clay contents (0, 2, 5 and 10 wt%) were cured, both isothermally and non-isothermally, using a poly(ethyleneimine)...

The isothermal cure of a highly reactive tri-functional epoxy resin, tri-glycidyl para-amino phenol (TGAP), with diamino diphenyl sulphone (DDS), at two different cure temperatures T-c has been studied by both conventional differential scanning calorimetry (DSC) and by a stochastic temperature modulated DSC technique, TOPEM. From a series of isothe...

MATLAB is a software package used primarily in the field of engineering for signal processing, numerical data analysis, modeling, programming, simulation, and computer graphic visualization. In the last few years, it has become widely accepted as an efficient tool, and, therefore, its use has significantly increased in scientific communities and ac...

The processes of vitrification and devitrification that occur in an epoxy resin when it cures non-isothermally with a hardener are studied in terms of their frequency dependence and as a function of the heating rate. A novel modulated DSC technique, TOPEM, has been used which permits the evaluation of the frequency dependence for a single sample in...

The processes of vitrification and devitrification that occur during the non‐isothermal cure of a cross‐linking system are studied in terms of their dependence on frequency. Experimental results are obtained by TOPEM, a new multi‐frequency temperature modulated differential scanning calorimetry (TMDSC) technique, and a simulation with MATLAB was us...

The rheological behaviour of the materials diglycidil ether of bisphenol A (n = 0), 1, 2 diamine-cyclohexane and the epoxy reactive diluent vinylcyclohexane dioxide have been studied both separately and mixed before the beginning of the curing reaction. Different kinds of tests such as: preshear and time sweep, flow curve and stress sweep experimen...

Vitrification during the isothermal cure of a thermoset, which is monitored by dynamic techniques such as temperature‐modulated differential scanning calorimetry (TMDSC) or dielectric analysis (DEA), is analyzed in terms of its dependence on frequency. A simulation was used to obtain the vitrification time as a function of frequency, considering it...

The process of vitrification that occurs during the isothermal cure of a cross-linking system at temperatures below T g∞, the glass transition temperature of the fully cured resin, has been studied by TOPEM, a new temperature modulated DSC (TMDSC) technique based upon the use of stochastic temperature pulses. A comparison is made between TOPEM and...

The diffusive, calorimetric and thermal degradation behavior of different epoxy-amine systems was investigated during water sorption at different temperatures (23, 40 and 70°C). Experimental results showed that the water absorption at these temperatures fitted well to Fick’s law. Influence of water immersion during different periods of time on the...

TOPEM is a new temperature modulated DSC technique, introduced by Mettler-Toledo in late 2005, in which stochastic temperature modulations are superimposed on the underlying rate of a conventional DSC scan. These modulations consist of temperature pulses, of fixed magnitude and alternating sign, with random durations within limits specified by the...

Differential scanning calorimetry was used to study the influence of an epoxy reactive diluent, vinylcyclohexane dioxide, on the curing reaction of a polymeric system composed of diglycidyl ether of bisphenol A (n=0) and 1,2-diaminecyclohexane (DCH). Heat evolution and glass transition temperature, were measured in terms of the added diluent percen...

The thermal degradation of an epoxy system consisting of a diglycidyl ether of bisphenol A (DGEBA, n=0) and m-xylylenediamine (m-XDA) was studied by both thermogravimetric analysis (TG) and dielectric analysis (DEA). It has been checked a deviation of the typical behaviour in the Arrhenius plot expected for this kind of systems, owing to the therma...

The study of the degradation of a polymer is important because it can determine the upper temperature limit, the mechanism of a solid-state process, and the life-time for this system. Since the behavior of thermosets is affected by the selection of the curing cycle, it is important to investigate the changes which take place during the thermal degr...