Structure-property relationships in nylon 6 nanocomposites based on octaphenyl-, dodecaphenyl-POSS, montmorillonite, and their combinations

Binary and ternary nanocomposites were produced by incorporating, via melt compounding, two types of octa-and dodecaphenyl substituted polyhedral oligomeric silsesquioxanes (POSS), montmorillonite (MMT), and combinations of POSS with MMT into nylon 6. The tensile, flexural, and dynamic thermo-mechanical properties of these materials were characterized and their structure-property relationships discussed. The results show that the losses in ductility and toughness experienced after inclusion of MMT into nylon 6 can be balanced out by co-mixing MMT with the dodecaphenyl- POSS to produce a ternary nanocomposite. This trend however was less pronounced in the ternary MMT/octaphenyl-POSS system. Analysis of the microstructure organization in these materials using XRD and SEM sheds some light on understanding the differences in behavior. Both types of POSS particles mixed alone in nylon 6 were found to be polydisperse (500 nm to a few microns in size) and locally aggregated, yielding materials with similar mechanical performance. The co-mixing of MMT with the octaphenyl- POSS served to break down the POSS crystal aggregates, enhancing their micro-mechanical reinforcing action. On the other hand, the POSS crystals were not affected in the MMT/dodecaphenyl-POSS system, which led to improving their toughening ability.

Monitoring corrosion of reinforced concrete beams in a chloride containing environment under different loading levels

Corrosion has significant adverse effects on the durability of reinforced concrete (RC) structures, especially those exposed to a marine environment and subjected to mechanical stress, such as bridges, jetties, piers and wharfs. Previous studies have been carried out to investigate the corrosion behaviour of steel rebar in various concrete structures, however, few studies have focused on the corrosion monitoring of RC structures that are subjected to both mechanical stress and environmental effects. This paper presents an exploratory study on the development of corrosion monitoring and detection techniques for RC structures under the combined effects of external loadings and corrosive media. Four RC beams were tested in 3% NaCl solutions under different levels of point loads. Corrosion processes occurring on steel bars under different loads and under alternative wetting - drying cycle conditions were monitored. Electrochemical and microscopic methods were utilised to measure corrosion potentials of steel bars; to monitor galvanic currents flowing between different steel bars in each beam; and to observe corrosion patterns, respectively. The results indicated that steel corrosion in RC beams was affected by local stress. The point load caused the increase of galvanic currents, corrosion rates and corrosion areas. Pitting corrosion was found to be the main form of corrosion on the surface of the steel bars for most of the beams, probably due to the local concentration of chloride ions. In addition, visual observation of the samples confirmed that the localities of corrosion were related to the locations of steel bars in beams. It was also demonstrated that electrochemical devices are useful for the detection of RC beam corrosion.

Aggression-related alcohol expectancies and barroom aggression among construction tradespeople

INTRODUCTION AND AIMS: Few studies have investigated the relationship of barroom aggression with both general and barroom-specific alcohol expectancies. The present study investigated these associations in a rarely studied and high-risk population: construction tradespeople. DESIGN AND METHODS: Male construction tradespeople (n = 211) aged 18-35 years (M = 21.91, SD = 4.08 years) participated in a face-to-face questionnaire assessing general and barroom-specific alcohol expectancies and perpetration of physical and verbal barroom aggression as well as control variables, age, alcohol consumption and trait aggression. RESULTS: Sequential logistic regression analyses revealed that general alcohol-aggression expectancies of courage or dominance were not predictive of either verbal or physical barroom aggression after controlling for age, alcohol consumption and trait aggression. However, barroom-specific alcohol expectancies were associated with both verbal and physical barroom aggression, with positive associations found for expected hyper-emotionality and protective effects for expected cognitive impairment. DISCUSSION AND CONCLUSIONS: In a population where rates of risky drinking and barroom aggression are high, specific expectations about the effects of drinking in bars may influence subsequent aggressive behaviour in bars. [Zinkiewicz L, Smith G, Burn M, Litherland S, Wells S, Graham K, Miller P. Aggression-related alcohol expectancies and barroom aggression among construction tradespeople. Drug Alcohol Rev 2015;00:000-00].