Search Results

You are looking at 1 - 8 of 8 items for

  • Author or Editor: B. Van Mele x
  • Refine by Access: All Content x
Clear All Modify Search

Modulated temperature differential scanning calorimetry

Characterization of curing systems by TTT and CHT diagrams

Journal of Thermal Analysis and Calorimetry
Authors: A. Van Hemelrijck and B. Van Mele

Abstract  

Modulated temperature differential scanning calorimetry (MTDSC) is used to study simultaneously the evolution of heat flow and heat capacity for the isothermal and non-isothermal cure of an epoxy-anhydride thermosetting system. Modelling of the (heat flow related) chemical kinetics and the (heat capacity related) mobility factor contributes to a quantitative construction of Temperature-Time-Transformation (TTT) and Continuous-Heating-Transformation (CHT) diagrams for the thermosetting system.

Restricted access

Modulated temperature differential scanning calorimetry

Considerations for a quantitative study of thermosetting systems

Journal of Thermal Analysis and Calorimetry
Authors: G. Van Assche, A. Van Hemelrijck, and B. Van Mele

Abstract  

The influence of temperature modulation and signal treatment (deconvolution procedure) of modulated temperature differential scanning calorimetry is discussed with respect to the investigation of cure kinetics of thermosetting systems. The use of a ‘dynamic’ heat capacity calibration is not important for this purpose due to normalization of the heat capacity signal in all cure experiments. The heat flow phase during isothermal and non-isothermal cure is always small, giving rise to negligible corrections on the heat capacity and reversing heat flow signals in-phase with the modulated heating rate. The evolution of the heat flow phase contains information on relaxation phenomena in the course of the chemical reactions.

Restricted access

Abstract  

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.

Restricted access

Abstract  

In this paper we compare Wollaston and silicon probes for localized thermal analysis measurements (LTA) on biaxially oriented polypropylene (BOPP) films. Up till now, no real comparison was reported in literature between the different transition temperatures measured using Wollaston and silicon probes. Using different types of probes for studying the same material proves to be very interesting. Using the Wollaston probe, the thermal properties and thickness of a 1 μm thick skin layer can be determined by through-thickness local thermal analysis measurements. The improved resolution of the silicon probes, enables the measurement of thermal properties of individual layers in a cross-sectioned film, even for layers of only 1 μm thickness. Based on the results, the silicon probes seem to be more sensitive toward the start of the melting process, since the silicon probe already penetrates at lower temperature, as compared to the Wollaston probes. This sensitivity can be exploited for studying the effect of variations in thermal history between or within samples.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: G. Scheltjens, J. Brancart, I. De Graeve, B. Van Mele, H. Terryn, and G. Van Assche

Abstract

A self-healing material for coating applications was synthesized using the Diels–Alder (DA) reaction as cross-linking reaction. The built-in reversibility allows local mobility and rearrangements in the polymeric network, which is composed of a furan functionalized epoxy-amine and a bismaleimide. The self-healing material was characterized by physical–chemical means using Fourier Transform Infrared spectroscopy, thermogravimetric analysis (TG) and rapid heat-cool differential scanning calorimetry. It has been shown that the reversibility, as a result of a change in DA/retro-DA equilibrium, occurs in a temperature window ranging from ca. 80 to 150 °C. The repeatability of the non-autonomous healing was checked by TG, showing no evaporation or degradation of the components involved in the temperature window of interest.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: G. Mosselmans, Monique Biesemans, R. Willem, J. Wastiels, M. Leermakers, H. Rahier, S. Brughmans, and B. Van Mele

Abstract  

The reaction of phosphoric acid with wollastonite has been studied for reaction mixtures with a molar ratio r=P/Ca from 0.39 up to 2.9. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) reveal the formation of the crystalline products brushite (when r is smaller than 1.4) and monetite and calcium dihydrogenphosphate monohydrate (when r is above 1). Magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) and FTIR show that amorphous silica is also formed which contains some residual calcium and hydroxyl groups. The proposed reactions are confirmed by the evolution of the reaction enthalpy measured with differential scanning calorimetry (DSC). The reaction was monitored with temperature modulated DSC (TMDSC) and dynamic mechanical analysis (DMA). The sharp increase of the elasticity modulus coincides with the onset of decrease in heat capacity. The setting of the reaction mixture does not slow down the reaction rate.

Restricted access