Thermal Properties of Epoxy-Based Adhesive Reinforced With Nano And MicroParticles For In-Situ Timber Bonding
—CB10TSS thixotropic and room temperature cured epoxy based adhesive specially formulated for in-situ bonding of pultruded rod into timber for repair and strengthening of timber structures. The glass transition temperature for CB10TSS is 31.7ºC which considered low for outdoor exposure. Therefore CB10TSS was modified by reinforcing it with nano-and micro-particles and denoted as Nanopox (CB10TSS/nanosilica), Albipox (CB10TSS/liquid rubber) and Timberset (CB10TSS/ceramics). Thermal properties of epoxy adhesives were studied by using dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC). Albipox showed significant improvement in the glass transition temperature but Timberset has the highest Tg, due to high modulus of ceramic particles. A second scan for all the adhesives increased Tg which shows that the room temperature cured adhesives are not fully cross-linked. In DSC scan, typical graphs of heat flow versus temperature able to describe more characteristic of the curing behavior such as a sharp and deep endothermic dip at Tg which corresponds to a rearrangement of the molecules and the wide and shallow endothermic dip at around 100°C is associated with moisture in the adhesive.
CTBN rubber phase precipitation in model epoxy resins
Abstract This study investigated the precipitation of three types of end-functionalised liquid rubber (two CTBN and one ATBN) from two homologous series of amine-cured epoxy polymers with variable cross-link density. The CTBN carboxyl endgroups strongly enhanced the curing rate through the impurity catalysis mechanism, however, the amino-terminated ATBN only retarded the reaction, possibly by dilutional effects or owing to changes in the dielectric constant of the reacting medium. The glass transition temperature (Tg) of the epoxy phase was depressed by CTBN rubber dissolved in the epoxy matrix and the Tg of the CTBN rubber was also lowered. The height of the DMTA rubber peak was a linear function of the level of CTBN and suggested that ca. 3% of the rubber was dissolved in the cured epoxy matrix. The microstructure of the rubber particles was studied by SEM and related to the kinetics and thermodynamics of phase separation.
Determination of the activation energies for α and β transitions of a system containing a diglycidyl ether of bisphenol a (DGEBA) and 1,3-bisaminomethylcyclohexane (1,3-BAC)
Using dynamic mechanical analysis (DMA) we have studied the variation with the frequency of the dynamic mechanical properties (storages modulus,E'; loss modulus,E'' and loss tangent or tan σ) for a system containg a diglycidyl ether of bisphenol A (DGEBA) and 1,3-bisaminomethylcyclohexane (1,3-BAC). These properties were measured both in the glass transition and β transition regions. An increase in frequency caused a shift of tan σ peak positions in both regions toward higher temperature. Finally, we report the activation energies of a DGEBA/1,3-BAC expoxy system for α and β transitions.ZusammenfassungMittels DMA wurde für ein System aus einem Diglycidylether von Bisphenol A (DGEBA) und 1,3-Bisaminomethylcyclohexan (1,3-BAC) die Abhängigkeit der dynamischen mechanischen Eigenschaften (SpeichermodulE' VelustmodulE'' und Verlustangens oder tan σ) von der Frequenz untersucht. Diese Eigeschaften wurden sowholh in der Glasumwandlungs- als auch in der β-Übergangsregion gemessen. Die Erhöhung der Frequenz verursacht in beiden Regionen ein Verschieben des tan σ Peaks zu höheren Temperaturen. Letztlich beschreiben wir die Aktivierungsenergie des Epoxysystems DGEBA/1.3-BAC für die α-und β-Übergänge.