The hydrolytic condensation of a precursor synthesized by the reaction of equimolar amounts of (3-aminopropyl)triethoxysilane
and phenylglycidylether led to a distribution of polyhedral oligomeric silsesquioxanes (POSS) containing 8–11 Si atoms, functionalized
with amine groups. About 57% of the NH functionalities were active for reaction with epoxy groups. The multifunctional amine-POSS
was used to modify an epoxy network obtained by the homopolymerization of diglycidylether of bisphenol A initiated by benzyldimethylamine.
The main effect of POSS modification was an increase in both the glassy and rubbery modulus explained, respectively, by the
increase in cohesive energy and crosslink densities.
Authors:F. Fraga, V. Soto, E. Rodríguez-Núñez, J. Martínez-Ageitos and V. Rodríguez
The study of the cure reaction of the epoxy
network diglycidyl ether of bisphenol A with amantidine is a useful tool to
characterize the industrial behaviour of this material. The total enthalpy
of reaction, the glass transition temperature and the partial enthalpies at
different cured temperatures have been determined using differential scanning
calorimetry in dynamic and isothermal mode. Two models, one based on chemical
kinetics and the other accounting for diffusion were used and compared with
experimental data. It can be seen that the inclusion of a diffusion factor
in the kinetic model is negligible.
Epoxy resins of DGEBA type were thermally cured with diaminodiphenylmethane as crosslinking agent, and then analysed by Differential Scanning calorimetry (DSC) at various heating rates in order to determine the glass transition temperatureTg of the final networks. First it was shown that during cyclingTg is shifted towards higher values up to a maximum or
. Such a change is attributed to an increasing extent of cure which develops during the thermal analysis, and also to relaxation processes thermally activated inside the polymeric matrix. Then the dependence of
on the heating rateq imposed by the DSC apparatus was presented forq changing from 0.1 to10‡C min−1. At heating rates exceeding 3‡C min−1 only the classical temperatureTg was detected, but at smallerq values, an additional endothermic transition was revealed, located at higher temperature and linked to a physical aging-like phenomenon, which takes place at low heating rates. The plot of
against logq is divided into two quasi-linear parts on each side ofq=3‡C min−1. In conclusions, an equation was given to describe the
vs. logq function.
Authors:F. Fraga, V. Soto, J. Blanco-Méndez, A. Luzardo-Alvarez, E. Rodríguez-Núñez, J. Martínez-Ageitos and M. Pérez
Knowledge of the the kinetic study of chitosan/genipin
allow to know the different effects that time and temperature have on the
cure reaction of the material.
The total enthalpy of reaction,
the glass transition temperature and the partial enthalpies have been determined
using DSC in dynamic mode. Two models, one based on chemical kinetics and
the other accounting for diffusion were used. The incorporation of the diffusion
factor in the second model allowed for the cure kinetics to be predicted the
whole range of conversion.
Authors:M. A. García del Cid, M. G. Prolongo, C. Salom, C. Arribas, M. Sánchez-Cabezudo and R. M. Masegosa
with aromatic diamines, decreases in the T g of the epoxynetwork have been frequently reported [ 5 , 14 , 17 – 19 ]. This fact has been attributed to the plasticization of the epoxynetwork by the hydrocarbon chains of the alkylammonium cations [ 5
Authors:C. Arribas, Rosa Masegosa, C. Salom, E. Arévalo, S. Prolongo and Margarita Prolongo
Diglycidyl ether of bisfenol-A (DGEBA)/polybenzyl methacrylate (PBzMA)
blends cured with 4,4’-diaminodiphenylmethane (DDM) were studied. Miscibility,
phase separation, cure kinetics and morphology were investigated through differential
scanning calorimetry (DSC) and scanning electron microscopy (SEM). Non-reactive
DGEBA/PBzMA blends are miscible over the whole composition range. The addition
of PBzMA to the reactive (DGEBA+DDM) mixture slows down the curing rate, although
the reaction mechanism remains autocatalytic. On curing, initially miscible
(DGEBA+DDM)/PBzMA blends phase separate, arising two glass transition temperatures
that correspond to a PBzMA-rich phase and to epoxy network. Cured epoxy/PBzMA
blends present different morphologies as a function of the PBzMA content.
In this work the curing kinetics behaviour of a rubber modified epoxy amine system is investigated through calorimetric analysis.
This study is part of a wider investigation on new epoxy formulations to be used as matrices of composite materials. The aim
is to enhance both the processing behaviour and the mechanical properties of the matrix in order to obtain higher performance
composites for more demanding applications. The epoxy system is blended with a high molecular mass rubber containing functional
groups reactive towards the epoxies. The formation of a rubber/epoxy network can be achieved by means of a 'pre-reaction'
between the epoxy monomers and the rubber functional groups, carried out in the presence of a suitable catalyst and before
the resin is cured with the amino hardener. In this work the influence of both the rubber and the catalyst on the resin cure
kinetics is analysed.
Authors:S. Montserrat, P. Cortés, Y. Calventus and J. Hutchinson
Structural relaxation in different epoxy-anhydride and epoxy-diamine resins has been investigated by differential scanning
calorimetry using annealing and cooling rate experiments. The annealing experiments lead to the determination of enthalpy
loss,δH, at an equivalent annealing temperatureTa=Tg-20, and for periods of annealing time, ta, between 1 h and 4 months. The variation ofδH with logta, defines a relaxation rate per decade,rrpd, which is very sensitive to changes of the epoxy network. The cooling rate experiments allow the determination of the apparent
activation energy,δh*. The effect of the degree of crosslinking, the addition of a reactive diluent, which acts as flexibilizer, and the length
of cross-link onrrpd and δh* was studied.
Authors:M. Núñez, M. Villanueva, B. Rial and L. Núñez-Regueira
The thermal degradation of the epoxy systems diglycidyl ether of bisphenol A (BADGE n=0)/1, 2 diamine cyclohexane (DCH) and diglycidyl ether of bisphenol A (BADGE n=0)/1, 2 diaminecyclohexane (DCH) containing calcium carbonate filler immersed and not immersed in hydrochloric acid have
been studied by thermogravimetric analysis in order to compare their decomposition processes and to determine the reaction
mechanism of the degradation processes. The value of the activation energies, necessary for this study, were calculated using
various integral and differential methods. Analysis of the results suggests that hydrochloric acid does not affect the decomposition
of the epoxy network and that the reaction mechanisms produce sigmoidal-type curves for the systems not immersed in HCl and
deceleration curves for the same systems immersed.
Authors:Margarita Prolongo, C. Arribas, Catalina Salom and Rosa Masegosa
ether of bisfenol-A (DGEBA)/poly(vinyl acetate) (PVAc)/poly(4-vinyl phenol)
brominated (PVPhBr) ternary blends cured with 4,4’-diaminodiphenylmethane
(DDM) were investigated by differential scanning calorimetry (DSC), dynamic
mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM).
Homogeneous (DGEBA+DDM)/PVPhBr networks with a unique Tg
are generated. Ternary blends (DGEBA+DDM)/PVAc/PVPhBr are initially miscible
and phase separate upon curing arising two Tgs
that correspond to a PVAc-rich phase and to epoxy network phase. Increasing
the PVPhBr content the Tgof
the PVAc phase move to higher temperatures as a consequence of the PVAc-PVPhBr
interactions. Different morphologies are generated as a function of the blend