Browsing by Author "Mondragon, I."
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Correlations between rheological and thermal behaviour of TGDDM/m-PDA epoxy systems(1994-05) Imaz, J. J.; Valea, A.; Cortazar, M.; Mondragon, I.; Centros PRE-FUSION TECNALIA - (FORMER)Isothermal variation of viscosity has been investigated at various temperatures for an epoxy-aromatic amine system (TGDDM/m-PDA system). The variation of the extent of reaction during the curing process has been also determined by means of differential scanning calorimetry. Two different models were used to predict the viscosity during cure: a model based on a modified Williams-Landel-Ferry equation, and a percolation-gelation analogy. This analysis reflects that the reaction mechanism does not change with temperature in the studied range.Item Influence of migration of plasticizer during melt mixing on the transitions and properties of PC/CAB blends(1990-06) Jurado, M. J.; Gaztelumendi, M.; Nazabal, J.; Mondragon, I.; Tecnalia Research & InnovationStatic and dynamic mechanical properties, morphology, and thermal behavior of polycarbonate (PC)/plasticized cellulose acetobutyrate (CAB) blends were investigated to determine whether the plasticizer of the CAB modifies the miscibility of the blend and the mechanical properties of this essentially incompatible blend. In spite of the lack of transparency of the blends, both dynamic mechanical and thermal analysis results show the presence, at all blend compositions studied, of a single glass transition temperature which varies with the composition of the blend. Considering the ternary nature of the blends, we propose that plasticizer migration and the difficulty of discerning the presence of one or two peaks in a narrow temperature range may account for the observed behavior. Scanning electron microscopy confirms the immiscibility of the blends. The blends show large positive deviations of the tensile moduli from linearity and very low ductility. The reported tensile strength data are discussed in terms of several different equations for composites. This mechanical behavior is explained as a consequence of the migration of the plasticizer and of its subsequent antiplasticizing effect on the properties of the blend.Item Physical and mechanical behavior of tetraglycidyl diaminodiphenyl methane (TGDDM)/m‐phenylene diamine (m‐PDA) epoxy systems(1992-09-05) Imaz, J. J.; Jurado, M. J.; Corcuera, M. A.; Mondragon, I.; Tecnalia Research & InnovationThe rheological behavior of a tetraglycidyl diaminodiphenyl methane with a tetrafunctional aromatic diamine has been studied in terms of the influence of curing agent content and temperature. In this work, critical times corresponding to gelation are used as a measure of activation energy. The dynamic mechanical behavior has been used to analyze the curing extent of these epoxy systems with different amine contents before and after thermal posttreatment. The β‐relaxation peak temperature is found to increase with the curing agent content and also after thermal posttreatment. This has been related to the rise of crosslinking extent. Dependence of flexural mechanical properties on curing agent content and the postcure process has also been determined.Item Rheological characterization of tetraglycidyl 4,4′-diaminodiphenylmethane/m-phenylene diamine systems(1992-03) Imaz, J. J.; Markaide, N.; Jurado, M. J.; Corcuera, M. A.; Mondragon, I.; Tecnalia Research & InnovationAn epoxy resin/hardener system, TGDDM/m-PDA, has been studied. A series of isothermal rheological runs provided information about the kinetics of curing over a temperature range. Both important parameters of the curing reaction (resin/hardener stoichiometry and temperature) were varied and their influence on viscosity was investigated. The dependence of viscosity on temperature was described by using Williams-Landel-Ferry treatment and the gelation process was studied using viscosity profiles during curing cycles.