Synergistic Effect of Functionalized Carbon Nanotubes and Micron‐Sized Rubber Particles on the Mechanical Properties of Epoxy Resin

In this study, the synergistic effect of functionalized carbon nanotubes (fCNT) and micron‐sized rubber particles in improving the thermomechanical properties of epoxy resin is demonstrated. fCNT is mixed with carboxyl‐terminated butadiene acrylonitrile toughened epoxy (CTBNTE) by ultrasonication followed by the addition of curing agent and mixing with planetary shear mixer. A significant improvement is noticed in fracture toughness (≈ 200%) and thermal stability (≈ 12 °C) of fCNT‐filled CTBNTE system but only a marginal improvement in fracture toughness and thermal stability of pristine CNT‐filled CTBNTE relative to epoxy. Dispersion of fCNT is better than pristine CNT in the epoxy matrix. Scanning electron microscope (SEM) images of fractured surface of fCNT‐filled CTBNTE reveal plastic deformation zone, stress whitening, and overall rougher surface compared to pristine CNT‐filled CTBNTE. The findings of our work show promise for use of fCNT in conjunction with a rubber toughener as filler for improving the properties of epoxy resin for advanced structural applications.

     

Hydrothermal alteration minerals in Aluto Langano geothermal wells, Ethiopia

Aluto Langano geothermal field is characterized by alteration mineral assemblages of calcite, quartz, chlorite, undifferentiated clays, hematite, biotite and epidote. The presence of garnet and sphene is also reported for one of the wells. Measured temperature for the reservoir is above 300°C. Permeability of the reservoir is highly influenced by the deposition of hydrothermal minerals.     

Risk assessment of staphylococcal poisoning due to consumption of informally-marketed milk and home-made yoghurt in Debre Zeit, Ethiopia

The objectives of the study were twofold: to prove that participatory risk assessment can be applied to informally-marketed foods, and to assess the risk of staphylococcal poisoning through consumption of raw milk and home-made yoghurt in Debre Zeit, Ethiopia. Rapid urban appraisals were combined with conventional interviews to identify and quantify formal and informal milk value chains and to collect information on consumers' food preparation and consumption behavior. Milk was sampled in 170 dairy farms and 5 milk collection centers and microbiological tests were conducted. Published data on milk fermentation in Ethiopia was combined with a growth model of Staphylococcus aureus to develop a stochastic risk model. The annual incidence rate of staphylococcal poisoning was estimated to be 20.0 (90% CI: 13.9-26.9) per 1000 people. When the effect of fermentation was removed from the model, the annual incidence rate increased to 315.8 (90% CI: 224.3-422.9) per 1000 people, showing the importance of traditional food preparation methods in risk mitigation; traditional milk fermentation reduced the risk by 93.7%. Improving the safety of milk and dairy products could be achieved through supporting appropriate traditional food preparation and consumption where an industrial risk mitigation system is not feasible. Participatory risk assessment was shown to be applicable to informal food value chain.     

Formulation of silver chloride/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (AgCl/PHBV) films for potential use in bone tissue engineering

Orthopedic implant failure due to bacterial infection has been a concern in bone tissue engineering. Here, we have formulated a composite made of biodegradable polymer, i.e., poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), and silver chloride. Ag⁺ ions released from the AgCl/PHBV film can promote an aseptic environment by promoting inhibition of bacterial growth while maintaining bone cell growth, depending on AgCl loading. The objective of this study is to formulate AgCl/PHBV film(s) of varying composition so as to evaluate the dependence of AgCl loading in the film on antimicrobial activity and cytotoxicity. The release kinetics of silver ions from AgCl/PHBV film in aqueous and Dulbecco's Modified Eagle Medium showed similarity in the initial burst of ions during the first day of desorption followed by a gradual release of ions over extended time period. The antibacterial efficacy of AgCl/PHBV film against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa was evaluated by microbiological assay, while cytotoxicity of the film toward MC3T3‐E1 cells was determined by MTT assay. For all compositions studied, a clear zone of inhibition around AgCl/PHBV film was noticed on a modified Kirby‐Bauer disk diffusion assay. We established that MC3T3‐E1 cell attachment on AgCl/PHBV film is strongly related to loading of AgCl in the film. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45162.     

Structure‐property relationship of substituted pyrrolidine functionalized CNT epoxy nanocomposite

Carbon nanotubes (CNTs) based polymer nanocomposites hold the promise of delivering exceptional mechanical properties and multifunctional characteristics. However, the realization of exceptional properties of CNT based nanocomposites is dependent on CNT dispersion and CNT‐matrix adhesion. To this end, we modified MWCNTs by Prato reaction to yield aromatic (phenyl and 2‐hydroxy‐4‐methoxyphenyl) substituted pyrrolidine functionalized CNTs (fCNT1 and fCNT2) and aliphatic (2‐ethylbutyl and n‐octyl) substituted pyrrolidine functionalized CNTs (fCNT3 and fCNT4). The functionalization of CNTs was established by Thermogravimetric analysis (TGA), Raman Spectroscopy, and XPS techniques. Optical micrographs of fCNT epoxy mixture showed smaller aggregates compared to pristine CNT epoxy mixture. A comparison of the tensile results and onset decomposition temperature of fCNT/epoxy nanocomposite showed that aliphatic substituted pyrrolidine fCNT epoxy nanocomposites have higher onset decomposition temperature and higher tensile toughness than aromatic substituted pyrrolidine fCNT epoxy nanocomposites, which is consistent with the dispersion results of fCNTs in the epoxy matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42284.