Synthesis of 2,4,6-Trinitrotoluene (TNT) Using Flow Chemistry.

This paper describes the nitration of 2,4-dinitrotoluene (DNT) and its conversion to 2,4,6-trinitrotoluene (TNT) at a gram scale with the use of a fully automated flow chemistry system. The conversion of DNT to TNT traditionally requires the use of highly hazardous reagents like fuming sulfuric acid (oleum), fuming nitric acid (90-100%), and elevated temperatures. Flow chemistry offers advantages compared to conventional syntheses including a high degree of safety and simpler multistep automation. The configuration and development of this automated process based on a commercially available flow chemistry system is described. A high conversion rate (>99%) was achieved. Unlike established synthetic methods, ordinary nitrating mixture (65% HNO3/98% H2SO4) and shorter reaction times (10-30 min) were applied. The viability of flow nitration as a means of safe and continuous synthesis of TNT was investigated. The method was optimized using an experimental design approach, and the resulting process is safer, faster, and more efficient than previously reported TNT synthesis procedures. We compared the flow chemistry and batch approaches, including a provisional cost calculation for laboratory-scale production (a thorough economic analysis is, however, beyond the scope of this article). The method is considered fit for purpose for the safe production of high-purity explosives standards at a gram scale, which are used to verify that the performance of explosive trace detection equipment complies with EU regulatory requirements.

Development of Inert, Polymer-Bonded Simulants for Explosives Detection Systems Based on Transmission X-ray.

Explosives detection systems (EDS) based on X-ray are used at airports to screen baggage for the presence of explosives. In Europe and the United States, EDS equipment is tested extensively by specialist test centres prior to approval for operational use in airports. Once EDS are installed in airports, however, it can be challenging to test the EDS equipment and verify that it continues to perform at the highest level, because of the impracticality of introducing bulk explosives into civil aviation airports. We have developed inert, non-toxic polymer-bonded simulants and validated them against real explosives using EDS equipment. The accuracy of our simulants is within 1% of the target bulk density, and within 2% of the target effective atomic number, and the materials have a stability of at least 4 years, with an uncertainty of 0.5%. The simulants generate alarms in almost 100% of cases on a wide range of commercial EDS models, and we consider the simulants fit for purpose for use during testing of EDS equipment at airports.

Surfactant kinetics and their importance in nucleation events in (mini)emulsion polymerization revealed by quartz crystal microbalance with dissipation monitoring.

Surfactants are vital components of almost all heterogeneous polymerizations for maintaining colloidal stability, but they also play an important role in the kinetics and mechanism of particle nucleation. Despite many decades of research, the knowledge of adsorption-desorption surfactant kinetics and their application in (mini)emulsion polymerization is largely based on qualitative arguments. In this paper we show that the use of a quartz crystal microbalance with dissipation monitoring can provide quantitative information on both the adsorption equilibrium of ionic and nonionic surfactants, and also the kinetics of adsorption/desorption, that can be applied to the understanding of nucleation processes in (mini)emulsion polymerization. We show that surfactant dynamics and nucleation phenomena in (mini)emulsion polymerization are not dominated by diffusion phenomena linked to molecular size of surfactant as previously thought but rather are driven by the large differences in the rate of surfactant adsorption and desorption at the polymer-water interface. Finally, we show the application of this knowledge to explain the differences between nucleation processes for ionic and nonionic surfactants in emulsion polymerization.

Study of the interactions of proteins with a solid surface using complementary acoustic and optical techniques.

Membrane water treatment processes suffer severely from (bio)fouling phenomena, defined as an undesired deposition and build-up of adsorbed materials, which alters the membrane performance. The control of membrane (bio)fouling is directly related to first the (bio)foulant agent-membrane surface interactions arising at a much earlier stage during the process. This study aims at real time characterization of interaction between proteins and polymeric membrane surface. The adsorbed organic mass, water content, and the corresponding viscoelastic properties of adsorbed proteins on the polymeric membrane surface were investigated by combining the acoustic quartz crystal microbalance with dissipation monitoring technique with the optical surface plasmon resonance technique. Bovine serum albumin (BSA) and avidin were used as model protein, and a polysulfone (PSU) was included as reference polymeric membrane. The results showed that both proteins tested were irreversibly adsorbed on the spin-coated polysulfone surface. The "dry" amount of irreversible BSA and avidin adsorbed on the PSU surface was found to be 292 and 380 ng/cm(2), respectively, and the corresponding water contents were 50% and 58%. Consequently, BSA adsorption on the PSU surface yielded a thinner, flat, and more compact (rigid) layer while avidin adsorbed in a thicker layer with higher surface mass density, a more diffuse, viscoelastic layer, and in addition, it undergoes larger conformational/orientational changes.