Rheology Impact of Various Hydrophilic-Hydrophobic Balance (HLB) Index Non-Ionic Surfactants on Cyclopentane Hydrates

In this study, series of non-ionic surfactants from Span and Tween are evaluated for their ability to affect the viscosity profile of cyclopentane hydrate slurry. The surfactants; Span 20, Span 40, Span 80, Tween 20, Tween 40 and Tween 80 were selected and tested to provide different hydrophilic–hydrophobic balance values and allow evaluation their solubility impact on hydrate formation and growth time. The study was performed by using a HAAKE ViscotesterTM 500 at 2 °C and a surfactant concentration ranging from 0.1 wt%–1 wt%. The solubility characteristic of the non-ionic surfactants changed the hydrate slurry in different ways with surfactants type and varying concentration. The rheological measurement suggested that oil-soluble Span surfactants was generally inhibitive to hydrate formation by extending the hydrate induction time. However, an opposite effect was observed for the Tween surfactants. On the other hand, both Span and Tween demonstrated promoting effect to accelerate hydrate growth time of cyclopentane hydrate formation. The average hydrate crystallization growth time of the blank sample was reduced by 86% and 68% by Tween and Span surfactants at 1 wt%, respectively. The findings in this study are useful to understand the rheological behavior of surfactants in hydrate slurry.

LaRC ™-SI: A Soluble Aromatic Polyimide

LaRC™-SI (NASA Langley Research Center-Soluble poly Imide) is a wholly aromatic, high-performance thermoplastic with a unique combination of physical, mechanical and adhesive properties. LaRC™-SI is synthesized from equimolar amounts of the dianhydrides 4, 4′-oxydiphthalic anhydride (ODPA) and 3, 3′, 4, 4′-biphenyltetracarboxylic dianhydride (BPDA); 3, 4′-oxydianiline (3, 4′-ODA) and phthalic anhydride (PA) as an endcapping reagent. The most unique property of LaRC™-SI is its initial solubility in conventional high-boiling aprotic solvents. However, when exposed to temperatures above its softening point of 250 °C it becomes insoluble yet retains its melt processability. This allows LaRC™-SI to be solution processed as both a polyamic acid and a polyimide. In addition to this solubility characteristic and high softening point, LaRC™-SI is extremely tough and fracture resistant with G1c and K1c values of 4.6 kJ m−2 and 4.4 MN m−3/2 respectively. As a melt extruded film, LaRC™-SI has been used as a hot melt adhesive to bond titanium and aluminium with lap shear strengths for titanium and cleavage strengths for aluminium exceeding 43 MPa and 16.9 MPa respectively at 23 °C.