Curing and properties comparison of an unsaturated polyester resin, varying crosslinking reaction conditions

In this work four different curing modes were used to crosslink a general-purpose unsaturated polyester resin. Styrene was used as monomer and glass fiber mat as reinforcement. The four curing modes included a traditional convection oven, a long-wavelength infrared (IR) radiation oven, a medium-wavelength IR radiation oven, or room temperature for an open-curing condition without oven heating. Some samples were cured using initiator only, and others were cured combining initiator and promoter. For oven curing, chamber temperature was 85°C. For the samples, final curing conversion (using Fourier transform IR spectroscopy), as well as glass transition temperature (Tg), Young's modulus, impact strength, and Shore D hardness were measured and compared. The medium-wavelength IR radiation oven as curing condition offered the best option for highest conversion, Tg, and mechanical properties. © 2004 Society of Plastics Engineers

Curing kinetics and thermo-mechanical properties modelling of a general purpose unsaturated polyester resin (UPR)

Using a 3 mm thick mold trying to reproduce common industrial situations, a general purpose UPR was cured with styrene, methyl ethyl ketone peroxide (MEKP) and cobalt naphthenate. Modelling of the curing reaction (using a 2 k with 5 central points design), tensile and impact strength and glass transition temperature was accomplished. To obtain close fitting, parameters interaction was considered for modelling

Curing kinetics and thermo-mechanical properties modelling of a general purpose unsaturated polyester resin (UPR)

Using a 3 mm thick mold trying to reproduce common industrial situations, a general purpose UPR was cured with styrene, methyl ethyl ketone peroxide (MEKP) and cobalt naphthenate. Modelling of the curing reaction (using a 2 k with 5 central points design), tensile and impact strength and glass transition temperature was accomplished. To obtain close fitting, parameters interaction was considered for modelling

Elastomeric modification of an IR cured unsaturated polyester resin to improve mechanical properties

An elastomeric modification of the "core layer" in an Unsaturated Polyester Resin reinforced with two fiber glass chopped strand mats, was used to improve impact resistance. Stress-strain and rheological properties were also measured to evaluate overall performance. Prior to resin-modifier mixing, either cis-polybutadiene or 1,7 octadiene were prereacted (10 min. or 20 min.) with styrene. The reinforced three layer samples were cured in a medium wave IR oven. Results show that both modifiers impart a considerable increase in impact resistance, with a small decrease in Young's and storage moduli

lmmunocytochemical distribution of serotonin and neuropeptide Y, NPY in mouse adrenal gland

By the use of imrnunocytochetnicd staining methods. we studied the morphology and distribution of SHT and NPY immunoreactive cells and fibres in the mouse adrenal gland. The 5HT-immunoreactive cells were numerous and widely localized in the medullar tissue. These cells were arranged in three cellular types with regard to their morphological and immunocytochemical features. One of them showed cells with polygonal shape, being intensified like the typical medullary chromaffin cells. These imniunoreactive cells were observed arranged in medullar islets. The second SHT-inimi~noreactive celular type was constituted by cells with polygonal shape and strong immunoreactivity. The third one was formed by cells with irnmunoreactive prolongations. We found some islets of chromaffin nonirnmunoreactive cells surrounded by immunostained cells. We also observed some 5HT-imniunoreactive nerve fibres in the rnedullar tissue. NPY-like itlitnunoreactivity was detected in both chromaffin and ganglion cells in adrenal medulla. NPY-like imrnunoreactivity was also detected in nerve fibres at cortical level. In a few cases, we observed medullar SHT- and NPYinimunoreactive tissue in the adrenal cortex (monotremas)

Bases genéticas de las minusvalías psíquicas

Los factores genéticos juegan un papel fundamental en el origen de numerosas discapacidades psíquicas. De hecho, estas minusvalías constituyen uno de los principales motivos de petición de un asesoramiento genético. En nuestro ámbito cada vez es mayor el interés, y la necesidad, de conocer las causas que generan las afecciones hereditarias, sus mecanismos de transmisión, el riesgo de ser portador de un trastorno genético y, sobre todo, como evitar transmitirl

Motivations for committed nature conservation action in Europe

Contains fulltext : 169530.pdf (publisher's version ) (Closed access)Despite ongoing efforts to motivate politicians and publics in Europe regarding nature conservation, biodiversity continues to decline. Monetary valuation of ecosystem services appears to be insufficient to motivate people, suggesting that non-monetary values have a crucial role to play. There is insufficient information about the motivations of actors who have been instrumental in successful conservation projects. We investigated the motivations underlying these biodiversity actors using the ranking of cards and compared the results with the rankings of motivations of a second group of actors with more socially related interests. For both groups of actors, their action relating to biodiversity was supported in general by two groups of motivations related to living a meaningful life and moral values. The non-biodiversity actors also noted that their action relating to biodiversity rested more on beauty, place attachment and intrinsic values in comparison with their main non-biodiversity interests. Our results have implications for environmental policy and biodiversity conservation in that the current tendency of focusing on the economic valuation of biodiversity fails to address the motivations of successful actors, thereby failing to motivate nature conservation on an individual level.10 p