On the use of benzaldehyde to improve the storage stability of one-pot, epoxy ionic liquid formulations

A series of adducts were prepared based on the reaction of 1-ethyl-3-methylimidazolium acetate and benzal- dehyde in various stoichiometries (from equimolar reaction to benzaldehyde in 10-fold excess) and the resulting adducts were characterized using nuclear magnetic resonance spectroscopy (¹H, ¹³C, DEPT, and HQSC experi- ments). Differential scanning calorimetry was used to examine the initiating behaviour of the adducts towards mono- and di-functional epoxy resins and the data were used to determine kinetic parameters for the poly- merization. The lower temperature peak, due to carbene formation, is sensitive to adduct concentration; the residual ionic liquid in the adduct mixture contributes towards the initiation of the curing reaction. When a monofunctional epoxy and the 1:1 adduct was subjected to a 2-week period of storage at room temperature and sub-zero temperatures in the freezer, the profiles of the thermograms for the frozen samples do not change considerably over the storage period and the formulation retains a light yellow colour (rather than the viscous, dark red appearance of the formulation stored at room temperature)

LEVANTAMENTO DAS INTOXICAÇÕES POR PARAQUAT NO ESTADO DO PARANÁ NOS ANOS DE 1998, 1999 E 2000

O paraquat é umherbicida de contato, não seletivo e pertencente ao grupo químico dos bipiridílios. Ë um dos mais específicos agentes tóxicos pulmonares conhecidos e possui uma alta taxa de mortalidade em casos de intoxicações, por isso tem sido objeto de muitas investigações em vários países. Com a finalidade de verificar a extensão da utilização do paraquat no Estado do Paraná realizamos um levantamento do número de casos e as causas das intoxicações ocorridas nos anos de 1998 (20casos), 1999 (17 casos) e 2000 (28 casos). Para isso foram utilizados dados obtidos em órgãos públicos como a Secretaria de Estado da Agricultura e Abastecimento (SEAB-PR) e oCentro de Saúde Ambiental (órgão vinculado à Secretaria DE Estado da Saúde). SURVEY ON PARAQUAT INTOXICATION IN PARANÁ STATE IN THE YEARS 1998, 1999 AND 2000 Abstract Paraquat is a contact, non-selective herbicide that belongs to the bipiridilic chemical group. It is one of the most specific toxic agent to the lungs known so far and is responsible for a high mortality rate in cases of intoxication. Because of that, paraquat has been the object of much scientific investigation in several countries. In order to know the extension of paraquat use in the Parana State, it was done a search on the number of cases and the causes of intoxication occurred in the years 1998 (20 cases), 1999 (17 cases) and 2000 (28 cases). The data were obtained from public institutions, such as Secretaria de Estado da Agricultura e Abastecimento and the Centro de Saúde Ambiental

Risk factors associated with preterm birth: identification, prediction and evaluation in the BRISA cohort

Problem: Preterm birth is the leading cause of death and can result in significant long-term loss of physical and psychological capacity among survivors.Background: An estimated 15 million babies are born preterm every year. Prediction models based on machine learning methods have reported promising results.Aims: To identify risk factors associated with preterm birth and to develop and validate a prediction model for this outcome in a Brazilian birth cohort.Methods: Cross-sectional study of all births that occurred in Ribeirão Preto-SP and of one in three births that occurred in São Luís-MA, Brazil, in 2010. Questionnaires were applied to obtain pregnancy-related data. Multivariate adaptive regression splines were used to determine the independent variables. Preterm birth, defined as birth before 37 weeks gestational age, was the dependent variable. A random forest model was developed and its performance was evaluated by ROC analysis.Findings: The preterm birth rates were 12.7% (RP) and 14.1% (SL). The prediction and validation accuracies of the RF-based model were 91.3% and 85.5% respectively. The model can be applied starting in the third month of gestation and is more effective in identifying preterm infants with GA<31 weeks and 6 days (AUC=0.98).Discussion: It was possible to build a prediction model based on easily accessible low-cost data, without the need for complementary tests, providing results similar to those of other studies.Conclusions: Previous preterm birth and prenatal care were determinants. The use of an application for individualized patient monitoring an early stage can have positive effects on the quality of life of mother and child

Investigation of structure property relationships in liquid processible, solvent free, thermally stable bismaleimide-triazine (BT) resins

Three cyanate ester monomer or oligomer species: 2,2-bis(4-cyanatophenyl)propane 1, 1-1-bis(4-cyanatophenyl)ethane (2), and the oligomeric phenolic cyanate (PrimasetTM PT30) (3), are blended in various ratios with bis(4-maleimidophenyl)methane, (4), to form binary and ternary mixtures (11 in total) and cured, in the absence of catalysts (3 K/min to 150 °C + 1 hour; 3 K/min to 200 °C + 3 hours), followed by a post cure (3 K/min to 260 °C + 1 hour). The use of liquid monomer, (2), offers the possibility of liquid processing in blends containing minority compositions of bismaleimide. Glycidylmethacrylate is explored as a reactive diluent (2.5-10 wt %) to linked interpenetrating network polymer structures comprising cyanate ester and bismaleimide components with glass transition temperatures of 267-275 ºC, depending on composition; the onset of thermo-oxidative degradation ranges from 386-397 ºC. When a binary blend of (2) and (3) (with the former in the minority) is co-cured with (4), an excellent balance of properties is achieved with liquid processing, a Tg greater than 400 C and onset of degradation of 425 ºC in static air. Kinetic analysis of DSC data using Ozawa and Kissinger methods yield activation energies of between 107- 112 kJ/mole for a binary blend of (1)90-(4)10, which is in good agreement with literature. Molecular dynamics simulation of the same blend in cured form gave a simulated glass transition temperature of 250 C that is in very close agreement with empirical DMTA data

Improving the hydrolytic stability of aryl cyanate esters by examining the effects of extreme environments on polycyanurate copolymers

Three cyanate ester monomer or oligomer species: 2,2-bis(4-cyanatophenyl)propane 1, 1-1-bis(4-dicyanatophenyl)ethane 2, and the oligomeric phenolic cyanate 3, are blended in various ratios to form binary mixtures (18 in total), formulated with copper(II) acetylacetonate (200 ppm) in dodecylphenol (1 % w/v active copper suspension) and cured (3 Kmin-1 to 150 °C + 1 hour; 3 Kmin-1 to 200 °C + 3 hours) followed by a post cure (3 Kmin-1 to 260 °C + 1 hour). Cured copolymers were exposed to environments of elevated relative humidity (75 % RH) and parallel immersion testing in H2O, H2SO4 (10 %) and NaOH (10 %) at 25 °C for a period of up to 2 years and accelerated ageing in boiling water (14 days). Periodic measurements are made of moisture gain along with infrared spectra and compared with cured homopolymers. Changes in mass are recorded periodically throughout exposure, prior to destructive thermo-mechanical analyses. Dynamic mechanical thermal analysis data comparing neat and exposed blends demonstrate the detrimental effect of moisture ingress whilst data from thermogravimetric analysis demonstrate no change in degradation onset between neat and exposed materials. An optimised blend of 1:1 of monomer units 1 and 2 was found to absorb less moisture than blends of different stoichiometry or between other respective monomeric units, consequently limiting the deleterious effect of moisture ingress

Examining the nature of the network formation during epoxy polymerization initiated using ionic liquids

A commercial diglycidyl ether of bisphenol A monomer (Baxxores™ ER 2200, eew 182 g/mole, DGEBA) is thermally polymerized in the presence of an ionic liquid, 1-ethyl-3-methylimidazolium acetate at a variety of loadings (5–45 wt %). The loss modulus data for cured samples, containing 5 wt % initiator, display at least two thermal transitions and the highest storage modulus occurs in the sample that has been cured for the shortest time at the lowest temperature. Samples that are exposed to higher temperatures (140, 150 °C) yield more heterogenous networks, whereas following exposure to a much shorter/lower temperature cure schedule (80 °C) exhibits a considerably higher damping ability than the other samples, coupled with a lower glass transition temperature. Differential scanning calorimetry reveals that the latter sample achieves a conversion of 95%, while crosslink densities for the DGEBA samples containing 5 wt % and 15 wt % are respectively 9.5 × 10-3 mol. dm-3 and 1.2 × 10-3 mol. dm-3 (when cured to 80 °C) and 2.0 × 10-2 mol. dm-3 and 2.4 × 10-3 mol. dm-3 (when cured to 140 °C)

Examining the Influence of Anion Nucleophilicity on the Polymerisation Initiation Mechanism of Phenyl Glycidyl Ether

The reaction of phenyl glycidyl ether (PGE) with 1-ethyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium thiocyanate to initiate the polyetherification reaction was examined using thermal and spectral analysis techniques. The influence of the nucleophilicity of the anions on the deprotonation of the 1-ethyl-3-methylimidazolium cation determined the reaction pathway. The thermal degradation of the ionic liquid liberated the acetate ion and led, subsequently, to the deprotonation of the acidic proton in the imidazole ring. Thus, polymerisation of PGE occurred via a carbene intermediate. The more nucleophilic thiocyanate anion was not sufficiently basic to deprotonate the 1-ethyl-3-methylimidazolium cation, and thus proceeded through direct reaction with the PGE, unless the temperature was elevated and a competing carbene mechanism ensued

Investigating the mechanism through which ionic liquids initiate the polymerisation of epoxy resins

The mechanism of reaction between 1-ethyl-3-methylimidazolium acetate and the difunctional diglycidyl ether of bisphenol A (DGEBA) is explored using thermal and spectroscopic methods. Investigation of the 1,3-dialkylimidazolium based ionic liquids comprising the common cation (1-ethyl-3-methylimidazolium) and different anions (acetate, diethyl phosphate, dicyanamide or thiocyanate) via thermogravimetric analysis revealed 1-ethyl-3-methylimidazolium acetate to be the least thermally stable, both in air and nitrogen, and 1-ethyl-3-methylimidazolium dicyanamide to be the most thermally stable. Dynamic differential scanning calorimetry reveals the formulations comprising DGEBA and ionic liquid where it was revealed that the lowest and highest temperature for the onset of reaction were observed for formulations with 1-ethyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium dicyanamide respectively. 1-Ethyl-3-methylimidazolium acetate was shown, via nuclear magnetic resonance (NMR) spectroscopy and residual gas analysis, to degrade at 150 °C to yield dealkylated products including methyl acetate and ethyl acetate as well as 1-methylimidazole and 1- ethylimidazole. The dealkylated imidazole ring is proposed as a route for initiation of the epoxy ring. Adduct formation between 1-ethyl-3-methylimidazoloium acetate and benzaldehyde at room temperature was observed leading to the proposal of the generation of a carbene species as a route for initiation of the epoxy ring in formulations with the acetate anion. NMR analysis of formulations comprising 1-ethyl-3-methylimidazolium thiocyanate and epoxy are believed, at room temperature, to initiate via reaction of the thiocyanate anion with the epoxy ring.At elevated temperatures, it is proposed that a second, competing reaction, involving deprotonation of the imidazolium ring, also becomes active. The three proposed reaction pathways, namely the carbene route, the imidazole route and the counter-ion route, are all proposed to occur when an ionic liquid is used to initiate an epoxy resin