Stereocomplex formation of high-molecular-weight polylactide: A low temperature approach

Polymer ◽  
2012 ◽  
Vol 53 (24) ◽  
pp. 5449-5454 ◽  
Author(s):  
Rui-Ying Bao ◽  
Wei Yang ◽  
Wen-Rou Jiang ◽  
Zheng-Ying Liu ◽  
Bang-Hu Xie ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Temperature ◽  
High Molecular Weight ◽  
Stereocomplex Formation

Application of ultra-high molecular weight polyethylene in a hydraulic drive

2020 ◽  
pp. 77-78
Keyword(s):  
Molecular Weight ◽  
Low Temperature ◽  
High Molecular Weight ◽  
Hydraulic Drive ◽  
Control Valve ◽  
Hydraulic Control ◽  
Hydraulic Motor ◽  
Hydraulic Pump ◽  
Hydraulic Oil ◽  
Ultra High Molecular Weight

The use of ultra-high molecular weight polyethylene (UHMW PE) for the manufacture of various parts, in particular cuffs for hydraulic drives, is proposed. The properties and advantages of UHMW PE in comparison with other polyethylene materials are considered. Keywords ultra-high molecular weight polyethylene, hydraulic pump, hydraulic motor, hydraulic control valve, hydraulic oil, low temperature. [email protected]

Low temperature synthesis of high molecular weight polyaniline

Polymer ◽  
1996 ◽  
Vol 37 (15) ◽  
pp. 3411-3417 ◽  
Author(s):  
P.N. Adams ◽  
P.J. Laughlin ◽  
A.P. Monkman ◽  
A.M. Kenwright
Keyword(s):  
Molecular Weight ◽  
Low Temperature ◽  
High Molecular Weight ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis

scholarly journals Tandem Synthesis of Ultra-High Molecular Weight Drag Reducing Poly-α-Olefins for Low-Temperature Pipeline Transportation

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3930
Author(s):  
Ilya E. Nifant’ev ◽  
Alexander N. Tavtorkin ◽  
Alexey A. Vinogradov ◽  
Sofia A. Korchagina ◽  
Maria S. Chinova ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Temperature ◽  
High Molecular Weight ◽  
Petroleum Products ◽  
Additional Treatment ◽  
Reaction Products ◽  
Pipeline Transportation ◽  
Stage Synthesis ◽  
Reaction Media ◽  
Ultra High Molecular Weight

Ultra-high molecular weight poly-α-olefins are widely used as drag reducing agents (DRAs) for pipeline transportation of oil and refined petroleum products. The synthesis of polyolefin DRAs is based on low-temperature Ziegler–Natta (ZN) polymerization of higher α-olefins. 1-Hexene based DRAs, the most effective at room temperature, typically lose DR activity at low temperatures. The use of 1-hexene copolymers with C8–C12 linear α-olefins appears to offer a solution to the problem of low-temperature drag reducing. The present work aims to develop two-stage synthesis of polyolefin DRAs that is based on selective oligomerization of ethylene in the presence of efficient chromium/aminodiphosphine catalysts (Cr-PNP), followed by polymerization of the olefin mixtures, formed at oligomerization stage, using efficient titanium–magnesium ZN catalyst. We have shown that oligomerization of ethylene in α-olefin reaction media proceeds faster than in saturated hydrocarbons, providing the formation of 1-hexene, 1-octene, and branched C10 and C12 olefins; the composition and the ratio of the reaction products depended on the nature of PNP ligand. Oligomerizates were used in ZN polymerization ‘as is’, without additional treatment. Due to branched character of C10+ hydrocarbons, formed during oligomerization of ethylene, resulting polyolefins demonstrate higher low-temperature DR efficiency at low polymer concentrations (~1 ppm) in comparison with benchmark polymers prepared from the mixtures of linear α-olefins and from pure 1-hexene. We assume that faster solubility and more efficient solvation of the polyolefins, prepared using ‘tandem’ ethylene-based process, represent an advantage of these type polymers over conventional poly(1-hexene) and linear α-olefin-based polymers when used as ‘winter’ DRAs.

Natural and Synthetic Rubber. II. Reduction of Isoprene by Na-Nh3

1929 ◽  
Vol 2 (3) ◽  
pp. 452-452
Author(s):  
Thomas Midgley ◽  
Albert L. Henne
Keyword(s):  
Molecular Weight ◽  
Double Bond ◽  
Low Temperature ◽  
High Molecular Weight ◽  
Liquid Ammonia ◽  
Volatile Hydrocarbon ◽  
Hydrogen Addition ◽  
Synthetic Rubber ◽  
Reaction Proceeds ◽  
Natural And Synthetic

Abstract The reduction of isoprene by sodium in liquid ammonia was attempted to determine: (1) whether reduction would take place in preference to polymerization and (2) the location of the added hydrogen. Isoprene was added to sodium dissolved in liquid ammonia and a 60% yield of 2-methyl-2-butene resulted. No other volatile hydrocarbon was found. High molecular weight hydrocarbons were formed but were not investigated. It is thus shown: (1) that the predominant reaction proceeds in accordance with the equation C5C8+2Na+2NH3=C5C10+2NaNH2 and (2) that hydrogen adds to isoprene in the 1,4-position, in agreement with Thiele's theory. The hydrogen addition is similar to the bromination of isoprene at low temperature. If properly conducted the latter reaction stops after 2 atoms of bromine have been added to 1 molecule of isoprene; the resulting compound, 1,4-dibromo-2-methyl-2-butene, is characterized b the inactivity of its double bond toward bromine. Similarly, 2-methyl-2-butene obtained by reduction of isoprene is not reduced to isopentane by an excess of Na—NH3 reagent.

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