Derakene is a vinyl ester resin largely employed as matrix for polymeric based composite systems. In this work, the performance of such polymeric system was evaluated considering the effect of hygrothermal aging. The mechanical and thermal properties were examined for the processed material before and after ageing in water at 60 °C for a maximum period of 64 days. Both analyses indicated the occurrence of post cure of the system after 16 days due to exposition at 60 °C in water, which was also confirmed by analyses in samples with post cure treatment. Moreover, it was observed plasticizing of resin after 36 and 64 days of ageing. Micro structural and fracture surface analyses were carried out in order to characterize the samples. The appearance of surface voids was also observed.

Industry has been challenged to provide riser systems which are more cost effective and which can fill the technology gaps with respect to water depth, riser diameter and high temperatures left open by flexibles, steel catenary risers (SCRs) and hybrid risers. Composite materials present advantages over conventional steel risers because composite materials are lighter, more fatigue and corrosion resistant, better thermal insulators and can be designed for improving the structural and mechanical response. This paper contains a study of the toughening mechanism of an epoxy resin under rubber addition by means of fractographic analysis and its relation with the fracture process and increase of strength of a composite riser employing this polymeric matrix. Initially, an epoxy resin system was toughened by rubber CTBN addition (10 wt. (%)) as a way of improving the flexibility of future risers. Mechanical and thermal analyses were carried out for characterizing the polymeric systems. Later, composite tubes were prepared and mechanically characterized. The influence of matrix toughening on the mechanical behavior of the tubes was also studied. Split-disk tests were used to determine the hoop tensile strength of these specimens. The results indicate that the matrix plays an important role in composite fracture processes. The adding rubber to the polymeric matrix promoted a simultaneous increase of stress and elongation at fracture of the tubes manufactured herein, which is not often reported. These results, probably, is function of better adhesion between fibers and polymeric matrix observed in the CTBN-modified composite rings, which was evidenced in the fractografic analysis by SEM after the split-disk tests.

Este trabalho apresenta um método multirresíduo de extração por dispersão da matriz em fase sólida (MSPD) para quantificação de dois inseticidas organofosforados (malation e paration metílico) e um organoclorado (β-endosulfan) em arroz por cromatografia gasosa de alta resolução com detector por captura de elétrons. Experimentos foram realizados com adição de pesticidas na amostra, variando quantidades de amostra e de suporte, tipo de suporte e solvente de eluição. A eficiência do método proposto foi demonstrada pelos valores médios de recuperação entre 75,5% e 116,0%, com valores de desvio padrão relativo entre 0,5% e 10,9%, obtidos nas análises de recuperação com amostras fortificadas nos níveis de 0,5 a 10,0 mg kg -1 . Os limites de detecção foram de 20 a 105 pg para os pesticidas estudados. Arroz comercial foi analisado para a aplicação do método.This work reports a multi-residue extraction method based on matrix solid-phase dispersion (MSPD) and capillary gas chromatography -electron capture detection for quantification of two widely used organophosphorus insecticides (malathion and parathion-methyl) and an organochlorine pesticide (β-endosulfan) in rice. A set of experiments was done with a spiked matrix with a standard mix, varying sample and solid phase amounts, solid phase and eluting solvent. Analyses of fortified rice samples were performed at different levels (0.5-10.0 mg kg -1 ). Mean recoveries from three replicates ranged from 75.5% to 116.0%, with coefficients of variation from 0.5% to 10.9%. The limit of detection was in the range of 20 to 105 pg for the pesticides. Commercial rice was analyzed for method application.

Epoxy resins are considered as one of the most important class of thermosetting polymers and find extensive use in various fields. However, these materials are characterized by a relatively low toughness. In this respect, many efforts have been made to improve the toughness of cured epoxy resins. In this work, samples of epoxy resin diglycidyl ether of bisphenol‐A and fiber glass‐reinforced composite of this polymer with and without liquid carboxyl‐terminated butadiene acrylonitrile (CTBN) copolymer were prepared to assess the effect of CTBN rubber on the properties of polymeric and composite laminate specimens. The addition of CTBN into the polymeric specimens led to a decrease in the glass transition temperature, fracture stress (from 70.39 to 56.34 MPa), and tensile elasticity modulus (from about 3.51 to 2.65 GPa), accompanied by an increase in elongation (from 2.47 to 5.64%). However, the degradation temperature of the polymeric system was not modified. Infrared analysis evidenced the occurrence of chemical reaction between the two components, and scanning electron microscopy results suggested rubber particles deformation as the prevailing toughening mechanism. The rubber addition in the composite specimens, promoted an increase simultaneous in fracture stress and in elongation at fracture. The elasticity tensile modulus has not changed. This probably results from the increased deformation capacity of the matrix, which prevents its premature cracking, and better adhesion between fibers and matrix observed in the CTBN‐modified composite laminates. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers