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Polymers
Published in Bryan Ellis, Ray Smith, Polymers, 2008
Equation of State: Mark-Houwink constants have been reported Latent Heat Crystallization: The ceiling temp. (Tc) for polysulfone formulation, i.e. where free energy change for the reaction is zero, varies with the parent alkene. For straight chain 1-alkenes (Tc) decreases from above 137° for ethylene to 90° for propylene, and 64° for 1-butene after this it remains reasonably constant. For alkenes Tc decreases from 2-butene (34°) to 2-pentene (8°), and 2- heptene (-38°). Branching in the side chain lowers Tc particularly at the double bond, e.g. Tc 2-for methyl-1-pentene is -34°. Polysulfones of cyclic alkenes have much higher values of Tc than the corresponding acyclic polymer, e.g. Tc of cyclopentene polysulfone is 102°, compared with 63° for 1-pentene [25,29] Transition Temperature General: Tm of alkyne/SO2 copolymers varies with MW and with crystallinity [38]. Some 1-alkene sulfones (e.g. 1-eicosene, 1-hexadecene) have liq. cryst. phases at temps. between room temp. and 100°. Softening point and clearing temp. for 1-eicosene polysulfone are 54° and 71° respectively; those for 1-hexadecene polysulfone are 65° and 70° respectively [14]
Applied Chemistry and Physics
Published in Robert A. Burke, Applied Chemistry and Physics, 2020
There are really only two alkene radicals that are important to emergency responders: the two- and three-carbon alkenes. When one hydrogen is removed from ethene, the radical formed is called vinyl. A hydrocarbon radical with two carbons and a double bond with the formula C2H3 is the “vinyl” radical. There is no rule for knowing that it is just a matter of memorizing the vinyl radical. Another important alkene used for making hydrocarbon derivatives is pentene, with one carbon removed, which becomes the “acryl” radical. So, there are three carbons in the radical with one double bond.
Synthesis of Reactants and Intermediates for Polymers
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
Dimerization of propylene is also used to produce isoprene. Several steps are involved. Initially, dimerization of propylene to 2-methyl-1-pentene occurs. Then isomerization to 2-methyl-2-pentene is effected. Finally, the 2-methyl-2-pentene is pyrolized to isoprene and methane. Another multistep synthesis starts with acetylene and acetone. Perhaps the most attractive route involves formaldehyde and isobutylene (17.42).
Effect of Molecular Structure on Laminar Flame Speeds of Three C5 Alkenes
Published in Combustion Science and Technology, 2020
In order to comprehensively use our previous experimental results to analyze the effect of molecular structure of C5 alkenes on combustion characteristics, the laminar flame speeds of 2-pentene/air mixtures were measured in a constant volume combustion bomb at T0 = 450 K, p = 0.1/0.3 MPa, and φ = 0.6–1.6. The experimental results show that the order of laminar flame speed of 1-pentene, 2-pentene, and 2-methyl-2-butene is: 1-pentene>2-pentene>2-methyl-2-butene. To better analyze the effect of molecular structure on combustion characteristics, a chemical kinetic model including 210 species and 1270 reactions for C5 alkenes combustion at high temperature was developed by a method of combining core and sub-mechanisms, and then were compared with different models. Results indicate that the chemical kinetic model developed in this paper can well predict the combustion characteristics of 1-pentene, 2-pentene, and 2-methyl-2-butene over a wide range of conditions. The chemical kinetic analyses show that the bond energies, reaction pathways, and the main reactions that are sensitive to laminar flame speeds are similar for 1-pentene and 2-pentene because their molecular structures are linear and C = C bonds are in adjacent positions. Therefore, laminar flame speeds of 2-pentene are similar to 1-pentene. However, the oxidation process of 2-methyl-2-butene with branched-chain is different from the other two C5 alkenes: Firstly, the initial reactions of 2-methyl-2-butene mainly take place at C-H bonds because the bond energy of C-C bond is much larger than C-H bond, so the reactions having crucial effect on laminar flame speed are related to dehydrogenation reactions and radical addition reactions; Secondly, the conspicuous importance of the reactions consuming H radicals and generating stable species in the 2-methyl-2-butene flame leads to slower reaction rate and laminar flame speed of 2-methyl-2-butene.