Preparation of cycloaliphatic epoxy hybrids with non-conventional amine-curing agent

Cycloaliphatic epoxy resin has been successfully thermally cured using a polyamino siloxane oligomer as hardener. The curing reaction was followed by infrared spectroscopy in the near range, and thermal transitions were measured by dynamic mechanical thermal analysis. The use of accelerants and a plasticizer (dodecylphenol), and different curing schedules were explored. Cured materials showed high Tg values (around 125&-164 °C), and the analysis of laser scanning confocal microscopy images showed that they are homogeneous in the microscale.The authors would like to express their gratitude to the Dinater (MAT2007 63722) and Interfases (S 0505/MAT0227) projects for financial support

Modelling auto-acceleration in DGEBA/diamine systems

Curing of epoxy resins with aliphatic diamines at low temperatures deviates from the 4EQ mechanism (catalytic and non-catalytic dual path) at relatively low conversions, far from vitrification. Although the Horie mechanism relies on a third order reaction it is possible a more realistic approach to epoxy curing kinetics if a detailed analysis of auto-acceleration is made. A single parameter dependent only on the nature of the amine is proposed.Authors gratefully acknowledge to CAM (Pricit) and to project Epoxsil (MAT2000-0391-P4-02) for financial support

Reactive compatibilization of epoxy/polyorganosiloxane blends

A new thermoset material based on DGEBA with polyaminosiloxane curing agents is presented. The system shows reaction-induced compatibilization which prevents coalescence of polysiloxane and DGEBA rich domains, leading to gradient structured morphologies. The influence of curing temperature and/or chemical nature of the siloxane on the morphology and surface microhardness were examined. When siloxane is pre-reacted with epoxypropylphenylether (EPPE), a more homogeneous material is obtained. Microhardness profiles on the material are strongly influenced by the extension of the compositional gradients

Isotope ratio-based quantification of carbon assimilation highlights the role of plastidial isoprenoid precursor availability in photosynthesis

Abstract Background We report a method to estimate carbon assimilation based on isotope ratio-mass spectrometry (IRMS) of 13CO2 labeled plant tissue. Photosynthetic carbon assimilation is the principal experimental observable which integrates important aspects of primary plant metabolism. It is traditionally measured through gas exchange. Despite its centrality in plant research, gas exchange performs poorly with rosette growth habits typical of Arabidopsis thaliana, mutant lines with limited biomass, and accounts poorly for leaf shading. Results IRMS-based carbon assimilation values from plants labeled at different light intensities were compared to those obtained by gas exchange, and the two methods yielded similar values. Using this method, we observed a strong correlation between 13C content and labeling time (R2 = 0.999) for 158 wild-type plants labeled for 6 to 42 min. Plants cultivated under different light regimes showed a linear response with respect to carbon assimilation, varying from 7.38 nmol 13C mg−1 leaf tissue min−1 at 80 PAR to 19.27 nmol 13C mg−1 leaf tissue min−1 at 500 PAR. We applied this method to examine the link between inhibition of the 2C-methyl-d-erythritol-4-phosphate (MEP) pathway and suppression of photosynthesis. A significant decrease in carbon assimilation was observed when metabolic activity in the MEP pathway was compromised by mutation or herbicides targeting the MEP pathway. Mutants affected in MEP pathway genes 1-DEOXY-d-XYLULOSE 5-PHOSPHATE SYNTHASE (DXS) or 1-HYDROXY-2-METHYL-2-(E)-BUTENYL 4-DIPHOSPHATE SYNTHASE (HDS) showed assimilation rates 36% and 61% lower than wild type. Similarly, wild type plants treated with the MEP pathway inhibitors clomazone or fosmidomycin showed reductions of 52% and 43%, respectively, while inhibition of the analogous mevalonic acid pathway, which supplies the same isoprenoid intermediates in the cytosol, did not, suggesting inhibition of photosynthesis was specific to disruption of the MEP pathway. Conclusions This method provides an alternative to gas exchange that offers several advantages: resilience to differences in leaf overlap, measurements based on tissue mass rather than leaf surface area, and compatibility with mutant Arabidopsis lines which are not amenable to gas exchange measurements due to low biomass and limited leaf surface area. It is suitable for screening large numbers of replicates simultaneously as well as post-hoc analysis of previously labeled plant tissue and is complementary to downstream detection of isotopic label in targeted metabolite pools

Knowledge creation, integration, transference and absorption processes in industrial networks and border agents: value creation propositions

El presente trabajo propone identificar nuevas vías de generación de valor en mercados industriales caracterizados por un elevado grado de conocimiento técnico. En estas circunstancias, hemos detectado el papel positivo que tiene en la red y en los agentes frontera el rol de la absorción de conocimientos generados por los procesos de creación, integración y transferencia de conocimiento (CIT), sobre la base de unos intereses comunes, capaces de impulsar la confianza en la toma de decisiones, la innovación en los productos y la penetración en los mercados.The present work proposes to identify new ways for developing value in industrial markets, characterized by a high degree of technical knowledge. In this way, we have detected a positive role of the network and the border agents in the knowledge absorption developed by the knowledge creation, integration and transference processes (CIT), from a basis of common interests, able to impulse the trust in the decisions activities, the products innovation and the market penetration

Introduction strategy adopted by companies in euro-region Galicia-North of Portugal for reaching new markets

Tras la integración de España y Portugal en las instituciones europeas, el comercio entre Galicia y Portugal ha experimentado un crecimiento considerable. Resulta sorprendente que, siendo la portuguesa una economía de reducido tamaño en el contexto internacional, se haya convertido en el segundo cliente y proveedor de Galicia. Además, su Región Norte acapara la mayor parte de los intercambios comerciales que Portugal mantiene con Galicia. En trabajos anteriores abordamos los impulsores de estos intercambios. Esto es, la percepción de ventajas y los atractivos que ofrece el mercado de la región contigua. Y también los obstáculos más relevantes que han de afrontar las empresas de la euro-región. Sintetizaremos ahora los resultados de una encuesta realizada a 198 empresas gallegas y norteñas que realizan negocios transfronterizos y en la que concretan los modos de entrada elegidos para realizar negocios en la región vecina.Thanks to European membership, Spanish and Portuguese commerce has been increased a lot. In this sense, it is curious that the small size of Portuguese economy in the international context, has not affected to the power to rank the second level as customer and supplier in Galicia. Likewise, North of Portugal owns the most part of commercial exchanges between both countries in Iberian area. In previous studies, authors have outlined the key factors that have allowed and promoted this relationship (both advantages and obstacles). In this paper, a summary of the main results of a survey carried out in 198 Galician and North-Portuguese companies is analysed, trying to identify the main strategies used by companies for introducing their products in their neighbouring country

Pyrene Fluorescence as a Probe for the Monitoring of Polymerization Processes: Simultaneous DSC and Fluorescence Study

The polymerization of cyclohexylmethacrylate was monitored, over a wide temperature range, by simultaneous differential scanning calorimetry (DSC) and fluorimetry (FL); the equipment for both being optically coupled. Pyrene was used as a fluorescent probe. There was excellent agreement between the exothermic peak time obtained by DSC and the time at which the maximum gradient was obtained in the fluorescence intensity–time curves, but only for temperatures above 60°C, Activation energies for the gel effect onset were obtained for both, the conversion–time and intensity–time curves being concordant except for data at low temperatures, below 60°C. It was concluded that vitrification occurs at temperatures below 60°C and its presence was demonstrated by fluorimetry, by means of the conversion change associated with the fluorescence intensity jumpΔα(off-on).This research was supported by CICYT MAT93-0823

Water absorption in polyaminosiloxane-epoxy thermosetting polymers

Water absorption is a common problem in epoxy-based composites, especially in interfacial regions. In contrast to epoxy resins, silicones are hydrophobic materials. Modification of epoxy thermosets with silicones should improve physical properties because of decrease in water diffusion. Bisphenol-A diglycidyl ether (DGEBA) was cured with a synthesised aminopropyl perfunctionalised siloxane. Water absorption was analysed by different techniques, including near infrared (FTIR) water absorbance at 5200 cm−1 and gravimetry. Fick’s law diffusion coefficients were calculated. Swelling equilibrium of the resin was also analysed. Absorbed water catalyses the curing reaction strongly, allowing to reach high conversions

Mechanism of morphology development in HDGEBA/PAMS hybrid thermosets: Monte Carlo simulation and LSCM study

Reactive combinations of aliphatic epoxy resins and functional polysiloxanes form a class of hybrid thermosetting materials with properties that may come from both the organic and the inorganic phases. The two typically immiscible phases form a suspension whose morphology, composition, and thermal properties vary with curing time. The aim of this research was to elucidate the mechanism by which morphology changed with time and to simulate it through Metropolis-Monte Carlo. The selected system was hydrogenated epoxy (HDGEBA) and a synthetic polyaminosiloxane (PAMS). It was studied by DSC, FTnIR, gel point, viscometry, and in-situ laser scanning confocal microscopy. A mechanism for morphology generation was proposed and simulated, exploring a wide range of values of the "a priori" relevant variables. The essential features were captured by simulations with a reasonable agreement with experimental data. However, the complete process was more complex than the geometrical approach of the simulation. The main deviations that were found and qualitatively explained are: (i) the induction period on the rate of coalescence, and (ii) PAMS-rich domain average size increases faster than predictions.This research was funded by project PID2021-125302NB-I00 financed by the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033) and FEDER Una manera de hacer Europa, and TED2021-131847B-C21 financed by the Spanish Ministry of Science and Innovation (Refs: MCIN/AEI/10.13039/501100011033) and Union Europea NextGenationEU/PRT