Fluorescence method using labeled chromophores to study the curing kinetics of a polyurethane system

Journal of Colloid and Interface Science

Aznar³

et al. 2004

Self Cite

The analysis of the fluorescen response from the dansyl moiety as a function of temperature has been used to estimate the thermal transi-tions in silica particle/epoxy-based composite materials. Silica particles were surface-coated with 3-aminopropyltriethoxysilane (APTES) and 3-aminopropylmethyldiethoxysilane (APDES). 5-Dimethylamino-1-naphtalenesulfonyl chloride (DNS) and 5-dimethylaminonaphthalene-1-(2-aminoehyl)) sulfonamide (DNS-EDA) were selectively attached to the silanized silica particles and to the epoxy matrix respectively. The fluoresce ce results, interpreted in terms of the model of interpenetrating polymer networks, suggest that (i) independent of the silane coating, the interfacial region is slightly more rigid and heterogeneous than the epoxy bulk and (ii) the interface generated with APTES seems to be more flexibl than that obtained with APDES.

Section: Introductionmentioning

confidence: 99%

Fluorescent labels to study thermal transitions in epoxy/silica composites

Albalá

Journal of Colloid and Interface Science

Aznar³

et al. 2004

Self Cite

“…However, those works only show the potential utility of the method and deeper studies should be carried out. For instance, it is necessary: (i) to perform the studies with real systems, glass f bers instead of glass plates; (ii) to fi d dyes whose f uorescent response is stable at the temperature used for curing and at the wavelength used for its excitation-for example, the nitrostilbene moiety has been demonstrated to be not very stable when used to monitor cure processes [21]; (iii) to fin specifi photophysical parameters whose values perfectly correlates with epoxy conversion; and (iv) to understand the relation between surface characteristics of the reinforcement and curing at the interface.…”

Section: Introductionmentioning

confidence: 99%

Kinetic study of epoxy curing in the glass fiber/epoxy interface using dansyl fluorescence

Journal of Colloid and Interface Science

Aznar

Baselga

et al. 2003

The fluorescenc response of the dansyl chromophore has been used to study the kinetic of epoxy curing processes. With this new method, comparison between the curing at the interface of a glass fiber/epox and in the epoxy bulk of a composite material was studied. The effect of two glass fibe surface treatments was investigated. Commercial E-glass fi ers were surface coated with 3-aminopropyltriethoxysilane (APTES) and 3-aminopropylmethyldiethoxysilane (APDES). Fluorimetry (using fluorescen labels) and FT-NIR (Fourier transformed infrared spectroscopy in the near range) techniques were used to monitor the curing process in these composite materials. From the analysis of the data obtained, different simple kinetic models were discussed and apparent activation energies were obtained. Furthermore, from those techniques the respective results were compared to obtain complementary information. Independently of the sample and the technique used for the kinetic analysis, no variation of the activation energy of the epoxy curing reaction was found, which suggests that there are no changes in the mechanism of the reaction along the process. Fluorescence from dansyl located at the glass fiber/epox interface reflecte that the kind of reinforcement treatment clearly affects the epoxy curing process exactly in that region. However, when analytical response comes from the whole system the mechanism of the reaction does not seem to change with the silane coating used although is quite different in comparison with the process at the interface.

“…(see b) Bands shifts in terms of an absorbance ratio method based on that proposed by Vatanparast et al [15,16] .…”

Section: Analytical Approximationsmentioning

confidence: 99%

A Near‐Infrared Spectroscopy Study on Thermal Transitions of PMMA and PMMA/SiO₂ Nanocomposites

Sanchez

Redondo

Macromolecular Symposia

et al. 2014

Summary: In this work infrared spectroscopy in the near infrared (NIR) range is used to study the dynamics of polymethylmethacrylate (PMMA) as a pure polymer and when it is modified with silica nanoparticles. Different ways of analyzing FT-NIR spectra were explored taking the temperature as the variable of the systems: i) bands shifts in terms of the first moment of the wavenumber; ii) bands shifts in terms of an absorbance ratio method and iii) absorbance variations in terms of the integrated absorbance. The spectroscopic analysis allowed to study thermal transitions in PMMA and PMMA based nanocomposites. In particular the method based on the use of an absorbance ratio is the most sensible to analyze the thermal transitions. All bands considered could be used to detect thermal transitions reflecting how the vibrations of the groups CH 2 ; CH 3 and C¼O are affected by changes in the free volume of the PMMA. It seems that the PMMA dynamics is more driven by the lateral groups than the backbone of the polymer. The presence of silica nanoparticles, at least when 1% by weight is used, restrains the PMMA motion increasing the relaxation temperatures that can be associated with the glass transitions.