Levels Of Chain Branching Research Articles

Economical and Efficient Hybrid Surfactant with Low Fluorine Content for the Stabilisation of Water-in-CO2 Microemulsions

The relationship between the tail architecture and performance of hybrid AOT analogue surfactants has been investigated. Three hybrid surfactants were synthesised using hydrocarbon CO2-philic tails with different levels of chain branching. The performance of each surfactant was investigated via high-pressure phase behaviour, UV-visible spectroscopy, and air–water (a/w) surface tension measurements. Notably, the incorporation of hydrocarbon CO2-philic tails with a high degree of branching has been found to significantly boost CO2-philicity, allowing the surfactant to stabilise water-in-CO2 (w/c) microemulsions at low cloud pressures, Ptrans. The newly synthesised hybrid CF2/SIS1 (sodium (4H, 4H, 5H, 5H, 5H-pentafluoropenyl-5,7,7-trimethyl-2-(1,3,3-trimethyl-buthyl)-octyl)-2-sulfosuccinate) is a CO2-philic surfactant that contains the lowest amount of fluorine (15.01 wt%) and exhibits the highest efficiency of any di-chain surfactant to date. High-pressure phase behaviour studies provided a maximum water-to-surfactant molar ratio (wmax) of wmax=39, which is usually only observed from surfactants with long fluorocarbon chains. The present results are beneficial for expanding the pool of economical, effective, and efficient surfactants available for CO2-based technology.

Thermo-Mechanical Chain Branching of Commercial High Density Polyethylene during Extrusion

Two different phenomena may affect average molecular weight (Mw) of molten polyethylene during extrusion process. The first is crosslinking, which can be divided to two categories of chain branching and network formation, leading to an increase in Mw. The second is chain scission which leads to a decrease in the average Mw. In this work, chain branching of molten stabilized pipe grade high density polyethylene (HDPE) and unstabilized one, extruded in industrial twin screw extruder, has been studied. Therefore a series of analytical techniques including melt flow rate (MFR), capillary rheometer, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and Fourier transform infrared spectroscopy (FTIR) were employed. The unstabilized samples' MFR were lower than stabilized ones' which showed a higher melt viscosity of unstabilized samples due to their higher Mw. By applying rheometry test in different modes, the unstabilized PE samples showed a higher shear viscosity in comparison with stabilized ones agreeing with MFR results. DSC results showed a difference in degree of crystallinity between samples. This difference was verified by DMA result of solid state which showed a higher shear storage modulus for stabilized samples. Also, DMA results confirmed the obtained results from rheometry test in melt state. Additionally, FTIR results of stabilized and unstabilized samples demonstrated the difference between their chemical structures. Although it seems that the level of chain branching in this grade of HDPE is low howover, all techniques' results are in a good agreement which makes the provided results and data reliable. Moreover, a combination of the applied methods in this work can be helpful to determine the validity and efficiency of antioxidants.