A B S T R A C TThiol-containing antioxidants such a s 4-(mercaptoacetamido)-diphenylamine (MADA) undergo ready addition of -SH groups to the double bonds in diene rubbers in the presence of initiators. The reaction is a radical chain process leading to rubbers with improved thermooxidative resistance. The modification reaction has been carried out on high cis-polyisoprene and polybutadiene, and conditions under which the physicochemical properties (e.g., inherent viscosity, gel content, and microstructure) are less affected have been found. An oxygen absorption test and DSC were used as rapid methods for evaluation of thermooxidative stability of modified rubbers. The superiority of rubbers with MADA chemically attached (ranging from 1 to 4 phr) was shown by a circulating air oven test and by an extraction process which simulates the aggressive environments experienced by many rubbers under practical conditions. The results obtained show that a small degree of modification ( 1 phr MADA) is large enough to provide good thermooxidative stability without alteration of the molecular characteristics of the parent rubbers. At higher degrees, cistrans isomerization can occur. 52 5

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Fe43.5Mn34Al15Ni7.5 shape memory alloys (SMAs), have drawn considerable attention from the part of scientific community due to its superelastic behaviour, stable over a large thermal range (from -50 to +150°C) [1]. After cyclic heat treatment, solution treatment and ageing, the specimens became oligocrystalline and were reinforced by NiAl nanoprecipitates. The typical thermomechanical processing routine, before cyclic heat treatment of FeMnAlNi alloys, involves hot rolling, annealing and cold rolling [2]. The present paper discusses the effects of ± 1.5 at. % aluminium substitution with nickel, by correlating tensile behaviour with microstructural observations. The SMA specimens with chemical composition Fe43.5Mn34Al15±1.5Ni7.5∓1.5 were subjected to tensile tests, comprising loading-unloading cycles, based on which recoverable strain and energy storage efficiency were calculated. Considering that, in each cycle, a permanent strain was obtained, it follows that not all of the amount of stress induced martensite completely reversed to austenite, but a small part of it was accumulated in each cycle. By optical and scanning electron microscopy, the microstructural changes correlated with stress induced martensite accumulation were emphasized, while considering the effects of ± 1.5 at. % Al substitution with Ni.

The shape memory effect (SME) in binary β-Ti alloys is associated with a reversible martensitic transformation from α”- orthorhombic martensitic phase to β-bcc austenitic phase. The present paper reports the experimental results obtained on TiTa alloys, containing 25, 30, 35 and 50 mass % Ta. The specimens were processed from as-cast levitation induction melt ingots, cut by wire electric discharge, hot/cold rolled (enabling to obtain 500-mm long thin ribbons), solution treated (900°C/30 min/water quenched, W.Q.) and aged (300°C/1 h/W.Q.). From each heat treated state, samples were cut for tests meant to emphasize the presence of thermal and mechanical memory behaviour. Thermal memory was highlighted by SME-work generating training cycles, investigated by cinematographic analysis. The respective results were corroborated with those recorded by dynamic mechanical analysis (DMA). Mechanical memory was revealed by winding-unwinding and tensile tests. The winding and tensile tests offered information about the capacity of cold rolled ribbons to memorize their room temperature (RT) profile. Tensile tests were applied up to complete failure or by RT loading-unloading cycles.