Description of complementary actions of mineral and organic additives in thermoplastic polymer composites by Flame Retardancy Index

This work visualizes the complementary actions of organic and mineral additives in model thermoplastic polymer composites in terms of Flame Retardancy Index (FRI). Thermal and flame retardancy behaviors of ethylene‐vinyl acetate copolymer (EVA) composites containing calcium carbonate (CC) mineral and ammonium polyphosphate (APP) organic additives were studied varying composition of additives in the 80/20 EVA/(xCC + (20 ? x)APP) composites with x denoting 0, 5, 10, 15, and 20 wt%. Thermogravimetric analysis (TGA) revealed that the onset temperature of composites and the remaining residue were increased by combination of APP and CC, while cone calorimetry results were indicative of a promising flame retardancy performance at a given composition of APP and CC. Based on FRI values, we made distinguished samples from flame retardancy performance viewpoint, where the best flame retardancy was obtained by combination of 15 wt% APP and 5 wt% CC, as reflected in FRI value of 3.08. By contrast, samples containing only APP or CC revealed low resistance against flame, as signaled by FRI values of 0.99 and 0.89, respectively. X‐ray diffraction (XRD) analysis was made on remaining residue collected at the end of cone calorimetry measurements. Moreover, Raman analysis confirmed barrier effect of flame retardancy for EVA/(5APP + 15CC) sample, featured by a higher graphitization level as well as a thicker yet more homogenous char layer. Mechanical behavior analysis of composites revealed an acceptable level of properties, particularly high elongation at break, which was almost independent of formulation. However, a minor loss in yield stress was observed, especially for EVA(10CC + 10APP) sample.     

Variations des caracteristiques dielectriques des resines epoxydes au cours de leur reticulation sous microondes

The dielectric loss factor of epoxy resin cured by amine is measured all along the curing, performed under a microwave field (2,45 GHz). A linear hypothesis based on the dielectric contributions of all known constituents allows to show a polar intermediate state; the formation of this state is reversible. An interpretation taking into account hydrogen bonds is proposed. The evolution of dielectric constants during curing brings evidences that microwaves are a peculiarly convenient means of energy transfer to chemical processes as cross-linking reactions.     

Elementaranalyse durch Reduction

Ohne ZusammenfassungAus dem Holländischen übersetzt von der Redaction.     

Ueber die Verzuckerung der St?rke durch die Amylase des Malzes

Ohne Zusammenfassung     

Farbenreaktionen verschiedener Aminok?rper in Gegenwart von Minerals?uren und Kaliumbichromat

Ohne Zusammenfassung     

Sur les transformations analytiques des domaines cerclés et semi-cerclés bornés

Sans résumé     

Synthesis of α‐alkenyl‐β‐hydroxy adducts by α‐addition of unprotected 4‐bromocrotonic acid and amides with aldehydes and ketones by chromium(II)‐mediated reactions

The regioselective and diastereoselective chromium(II)‐mediated reactions of 4‐bromocrotonic acid or amides with aldehydes and ketones can proceed without the need to protect protic sites to generate the respective α‐alkenyl‐β‐hydroxy adducts, i.e. formally the addition of the α‐anion of a carboxylic acid or amide to an oxo‐compound is featured. Copyright © 2016 John Wiley & Sons, Ltd.     

Topical Issue on Thermal Non-Equilibrium Phenomena in Soft Matter

The European Physical Journal E - The transmission and the reflection of a shock wave by one or several impurities in viscoelastic bead chains is studied in the present paper. There is only one...     

Thermal analysis and high heat flux testing of unidirectional carbon–carbon composite for infrared imaging diagnostic

Carbothermic reduction of chromite in the presence of nickel as the alloying element was investigated in a wide temperature range up to 1500 °C using thermogravimetric analysis coupled with continuous off-gas analysis (TG-DSC-MS). Both isothermal and non-isothermal linear heating tests were performed for the kinetic study with the calculation of activation energies. In order to further elucidate the reduction mechanism, the reduced products were characterized by SEM–EDS and XRD. It was concluded that the reduction sequence followed a multi-stage mechanism, reflected partly by the dependency of the activation energy on the extent of reduction. With the progress of reduction, refractory oxide layers gradually formed on/close to the surface of each chromite particle, causing the shift of the rate-limiting factor from chemical control to diffusion control. The promoting effect from the addition of Ni was evident at temperatures higher than 1300 °C due to the formation of alloys of lower melting point.