Diffusion measurements of isopentane, 1‐hexene, cyclohexane in polyethylene particles by the intelligent gravimetric analyzer

Abstract

The diffusion coefficients of isopentane (i-C 5 H 12 ), 1-hexene (C 6 H 12 ), cyclohexane (C 6 H 14 ) in polyethylene particles were measured by a highly sensible microbalance-intelligent gravimetric analyzer, using the desorption method with N 2 as a bypassing gas. Both the effective diffusion coefficients (D eff ) and dilute diffusion coefficients (D $ eff ) were measured simultaneously. It was found that D $ eff was about one magnitude smaller than D eff and the logarithmic form of D $ eff was linear with that of D eff . In addition, the effects of particle size and distribution, polymer properties (e.g., the crystallinity and melt index), and operating conditions (e.g., temperature and pressure) on D eff were systematically investigated. The results showed that D eff increased linearly with the increase of the square of particle size. The diffusion behaviors of hydrocarbons in polyethylene are of great importance in the polymerization and purging processes.

Solubility measurement of hydrogen, ethylene, and 1‐hexene in polyethylene films through an intelligent gravimetric analyzer

“…The sorption experiments were carried out in an IGA (model IGA‐003, Hiden Analytical, Warrington, UK), a weighing instrument with a highly sensitive (1 μg) microbalance and an ultra‐high‐vacuum. The measurement system has been well described in our previous work . An additional vapor inlet of 1‐hexene was added to the original system in this work, and a gas distributor was adopted for the uniform mixing of multi‐components, as shown in Figure .…”

Nanocomposite materials based on zinc sulfide nanoparticles reinforced chlorinated styrene butadiene rubber

“…It can be seen that the solvent uptake of composites decreases with an increase in the size of the solvent molecules from petrol to diesel. Due to the lowest molecular mass, petrol shows maximum uptake, while diesel, with the highest molecular mass, shows the lowest mol uptake . This is clarified through the free volume theory, in which the rate of sorption of different solvents through the samples depends on the rate of solvent uptake of the samples are in accordance with the extent of polymer segments exchange the voids with the penetrant molecules.…”

“…Due to the lowest molecular mass, petrol shows maximum uptake, while diesel, with the highest molecular mass, shows the lowest mol uptake. 41 This is clarified through the free volume theory, in which the rate of sorption of different solvents through the samples depends on the rate of solvent uptake of the samples are in accordance with the extent of polymer segments exchange the voids with the penetrant molecules. Hence, the exchange of positions in a polymer chain becomes difficult for higher molecular weight solvents, which agrees with work reported by Hwang et al and Tung et al 42,43 The mol uptake of solvents generally increases with the increase in temperatures.…”

Investigation of the extraction process in gel‐spinning technology for ultrahigh‐molecular‐weight polyethylene fibers by low‐field nuclear magnetic resonance

“…In general, diffusion processes in the polymers can also be measured by holographic techniques, inverse gas chromatography, and nuclear magnetic resonance (NMR) apart from the conventional gravity weighing method . The transport parameter obtained by the first three methods is the self‐diffusion coefficient, whereas that determined by the weighing method is the mutual D .…”

“…In general, diffusion processes in the polymers can also be measured by holographic techniques, 21,22 inverse gas chromatography, 23,24 and nuclear magnetic resonance (NMR) 25,26 apart from the conventional gravity weighing method. 27,28 The transport parameter obtained by the first three methods is the selfdiffusion coefficient, whereas that determined by the weighing method is the mutual D. The two Ds are not identical but can be correlated. 29 The holographic approaches are commonly limited by the need for transparent solutions; on the other hand, the size of the UHMWPE fiber is too large to be coated in the column for inverse gas chromatography.…”