Supercritical Propylene Research Articles

Solubility of Subcritical and Supercritical Propylene in the Semicrystalline Polyethylenes

Solubility of Subcritical and Supercritical Propylene in the Semicrystalline Polyethylenes

Solubility of Subcritical and Supercritical Propylene in Semicrystalline Polypropylene

The solubility of propylene in semicrystalline isotactic polypropylene (iPP) was measured at temperatures from (348.15 to 383.15) K and pressures up to 8 MPa by a pressure-decay method. The results demonstrated that solubility of propylene in iPP is increased with elevated pressure and decreased with elevated temperature. The results could be correlated using the Sanchez−Lacombe equation of state (SL EOS) with temperature-dependent binary interaction parameters kij. It was shown that the SL EOS can well predict the solubility of propylene in polypropylene over a wide range even above the critical temperature and pressure. The deviations between experimental data and calculated results were within 5 %. It is important to point out that the value of kij varied almost linearly with respect to temperature, and the solubility of propylene in semicrystalline polypropylene in other conditions can be estimated.

Hydroformylation of propylene in supercritical CO 2 + H 2O and supercritical propylene + H 2O

Hydroformylation of propylene has been carried out in supercritical CO 2 + H 2O and in supercritical propylene + H 2O mixtures using Rh(acac)(CO) 2 and triphenylphosphine trisulfonate trisodium salt (TPPTS), P( m-C 6H 4SO 3Na) 3, as catalyst. Visual observation of the reaction mixtures indicates that in both systems a single phase is present at supercritical temperatures and pressures so that the reaction occurs under homogeneous conditions. After reaction is complete, a biphasic system is formed when the pressure and temperature are reduced to ambient. This facilitates separation of the products in the organic phase and the rhodium catalyst in the aqueous phase. The rhodium concentration in the organic phase was found to be negligible (∼1.0 × 10 −6 mg/ml). Furthermore, compared with traditional hydroformylation technology, the supercritical reactions also show better activity and selectivity.

Fractionation of poly(ethylene-co-vinyl acetate) in supercritical propylene: Towards a molecular understanding of a complex macromolecule

A commercial low-density polyethylene copolymer, poly(ethylene-co-vinyl acetate) (EVA), synthesized via the high-pressure free-radical polymerization process, was fractionated with supercritical propylene by isothermal increasing pressure profiling and critical, isobaric, temperature rising elution fractionation (CITREF™). Extensive characterization of the fractions by nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC) in combination with low-angle laser light scattering (LALLS), and differential scanning calorimetry (DSC) was used to map not only the molecular-weight and chemical composition distributions of the parent copolymer, but also its short-chain branch (SCB) and long-chain branch (LCB) distributions. Fractionation by increasing pressure profiling confirmed the broad molecular-weight distribution and the narrow acetate-branch distribution expected for this random copolymer but revealed the presence of a small amount (∼ 2 wt %) of low molecular-weight amorphous species containing a high level of alkyl SCBs (80 branches/1000 C). The LCB density estimated from the Zimm-Stockmayer relationship using the GPC data monotonically increases with increasing molecular weight above 60,000 g/mol, in agreement with the kinetics of free-radical polymerization. CITREF™ was found to fractionate this copolymer by crystallinity, which is influenced by both the alkyl SCBs and the acetate branches. Up to 18% difference in total branch density (<5% in crystallinity) between EVA molecules was identified using CITREF™. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2015–2030, 1997

Density-tuned polyolefin phase equilibria. 1. Binary solutions of alternating poly(ethylene-propylene) in subcritical and supercritical propylene, 1-butene, and 1-hexene. Experiment and Flory-Patterson model

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDensity-tuned polyolefin phase equilibria. 1. Binary solutions of alternating poly(ethylene-propylene) in subcritical and supercritical propylene, 1-butene, and 1-hexene. Experiment and Flory-Patterson modelShean Jer Chen and Maciej RadoszCite this: Macromolecules 1992, 25, 12, 3089–3096Publication Date (Print):June 1, 1992Publication History Published online1 May 2002Published inissue 1 June 1992https://doi.org/10.1021/ma00038a011RIGHTS & PERMISSIONSArticle Views302Altmetric-Citations58LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts