Synthesis and modification of water-soluble hyperbranched poly(amidoamine)s

The multi-step syntheses of two water-soluble AB(_2) monomers, N-acryloyl-1,2- diaminoethane hydrochloride and N-acryloyl-1,2-daminoethane, are reported. The melt polymerisation at 210 ºC for 4 hours of N-acryloyl-1,2-diaminoethane hydrochloride gave, by Michael additions of the terminal ammonium salts (B(_2) groups) of a monomer molecule or growing oligomer with the unreacted vinyl double bond (A group) of another monomer molecule or growing oligomer, hyperbranched macromolecules. High degrees of conversion, determined using (^1)H NMR spectroscopy, were obtained and a degree of branching, determined using (^15)N NMR spectroscopy, was found to be equal or close to 1. However, this method proved difficult to reproduce and the alternative aqueous solution polymerisation at 100 ºC for 10 days of this monomer was investigated. The use of ampoules closed with Teflon taps as reactors lead to polymers displaying random signs of free radical polymerisation and high degrees of conversion due to such side-reaction, whereas, the alternative use of sealed Carius tubes lead to lower DP materials displaying no significant signs of free radical side-reactions. The kinetic study of this polymerisation allowed the determination of the rate constant associated with the oligomer growth and the MALDI analysis of these polymers revealed an evolution with time of the oligomer molecular weight distribution with time in agreement with the theoretical prediction. This last study also revealed that at least 70% of the molecules were not cyclised. On the other hand, the aqueous solution polymerisation of the corresponding free base monomer, N-acryloyl-1,2- diaminoethane, at 100 ºC for 90 minutes lead to hyperbranched macromolecules with high DP values. The kinetic study did not allow a precise determination of the rate constant associated with the oligomer growth due to the high reactivity of the free terminal amino groups. The MALDI analysis of these polymer samples showed that the evolution with time of the oligomer molecular weight distribution did not follow the theoretical prediction and that these macromolecules were cyclised

The use of positron emission particle tracking (PEPT) to study milling of roll-compacted microcystalline cellulose ribbons

© 2015. Milling is a critical process for controlling the properties of the granules produced by roll compaction. In the current study, the positron emission particle tracking (PEPT) technique was used to examine the milling kinematics of roll-compacted ribbons at various milling speeds. Microcrystalline cellulose (MCC, Avicel PH-102) was used as the model feed material and a radioactive particle (tracer) was mixed with the MCC powder and roll-compacted to form sample ribbons. They were then milled using an oscillating mill at various speeds and the kinematics of the ribbons (trajectory, velocity, and occupancy) were quantitatively determined using PEPT. A close examination of the PEPT data reveals that, for milling MCC PH-102 ribbons using the oscillating mill considered in this study, the milling speed plays an important role: at low values, the milling process is dominated by cooperative motion of the ribbons with the blade (i.e. the speeds of the ribbons and the blade are similar, and the ribbons move along with the blade) and the ribbons are milled primarily by abrasion; as the speed increases the ribbons undergo more random motion involving collisions that results in an increase in ribbon breakage and hence an increase in the milling efficiency. It is shown that the PEPT technique is a useful technique for examining milling kinematics of roll-compacted ribbons

The Application of Positron Emission Particle Tracking (PEPT) to Study Inclusions in the Casting Process

The behavior of inclusions in castings was studied using radioactive labeling of oxide particles located by Positron Emission Particle Tracking (PEPT). This uses the isotope18F, which has a half-life of 110 minutes, and allows particle detection within an accuracy of a few mm. Alumina and glass particles with a size range of 110 to 600 μm were made radioactive by an ion-exchange/surface adsorption process involving irradiated water. Individual radioactive particles were placed in resin-bonded sand moulds at known initial positions, and the moulds were filled with Al alloy, causing the particle to be entrained into the metal stream during the casting process. A modular γ-ray positron camera was used to track the paths of the particles within the mould, demonstrating the applicability of the technique to the study of inclusion behaviour in castings.</jats:p