Wiley
0022-3832
1542-6238
Cơ quản chủ quản: N/A
Lĩnh vực:
Phân tích ảnh hưởng
Thông tin về tạp chí
Các bài báo tiêu biểu
Improved relationships for diffusion and sedimentation constants and for viscosity and streaming birefringence of solutions of polymers Abstract For the description of the practical properties of a large number of linear polymer molecules as well as for the discussion of the various mean parameters of the individual chain molecule, the model usually employed to represent the molecule consists of N m A m A m
Tập 14 Số 74 - Trang 193-208 - 1954
Effect of x‐rays and γ‐rays on synthetic polymers in aqueous solution Abstract A study has been made of the effect of ionizing radiation (x‐ and γ‐rays) on aqueous solution of the following vinyl polymers: polymethacrylic acid, polyacrylic acid, polyacrylamide, polystyrene sulfonate, polyvinylpyrrolidone, and polyvinyl alcohol. In dilute solutions (<0.3% for the samples of polymer used) all the polymers are degraded by main chain fracture although in some cases dissolved oxygen has to be present. In others, degradation occurs in carefully deoxygenated solution but is increased by the presence of oxygen. The breakdown of polystyrene sulfonate is independent of oxygen. At higher concentration, crosslinking becomes the dominant action for all the polymers studied with the exception of polymethacrylic acid and ionized polyacrylic acid, which degrade at all concentrations. The dose of radiation necessary to produce a gel has been studied as a function of concentration and passes through a minimum. No gel formation occurs below a minimum polymer concentration of about 0.4%. The results cannot be explained on the basis that indirect action by the free radicals formed in the water leads to degradation while direct energy uptake by the polymer itself produces crosslinking. Other possible mechanisms are examined. The manner by which added substances reduce the effectiveness of irradiation (i.e. , protect) is discussed briefly.
Tập 23 Số 103 - Trang 355-375 - 1957
Infrared spectrophotometric studies on polyethylene. II. Oxidation Abstract Polyethylene can be heat‐oxidized in air when temperatures in excess of 125°C. are employed or photo‐oxidized when exposed to ultraviolet radiation during weathering. Infrared spectrophotometric studies show that during these types of oxidation carbonyl groups are formed and the concentrations of the three types of carbon to carbon double bond groups present are altered. Grating spectra in the 5.6–6.0 micron region reveal that the carbonyl groups formed by heat‐oxidation are mainly ketonic (5.81 microns) although some aldehyde (5.77 microns) and acid (5.84 microns) groups are also present. In photo‐oxidized samples, the carbonyl groups are rather well distributed among the aldehyde, acid and ketone forms. For oxidized samples showing intense carbonyl absorptions, there is a small increase in the concentration of RHCCHR groups (10.35 microns) for both types of oxidation. At this same degree of oxidation both the heat‐and photo‐oxidized samples show decreases in the concentration of RRCCH2 groups (11.25 microns). However, this decrease is considerably more pronounced in the photo‐oxidized samples. Finally, there is a small decrease in the concentration of RHCCH2 groups (10.07 and 11.00 microns) in the heat‐oxidized samples which stands in contrast to a large increase in concentration of RHCCH2 groups produced by photo‐oxidation. The presence of an absorption maximum at 2.81 microns as the heat‐oxidation of polyethylene is occuring is indicative of unstable hydroperoxide groups.
Tập 13 Số 72 - Trang 535-547 - 1954
Viscosity and glass temperature relations for polymer‐diluent systems Abstract Expressions are derived from free volume considerations which predict the concentration dependence of viscosity and glass temperature for polymer‐diluent systems. Experimental data for several systems were examined and general agreement with theory was found over broad ranges of concentration. Particular emphasis is placed on the limited amount of information required for the application of these expressions to describe the viscous properties of polymer‐diluent systems.
Tập 50 Số 154 - Trang 549-556 - 1961
Disulfide interchange in polysulfide polymers Abstract A study has been made on the effect of thiols and disulfides on lowering the molecular weight of polysulfide polymers. It was shown that in the presence of aqueous sodium disulfide there is an interchange of chain segments. This effect is observable if a simple organic disulfide is present in the system, resulting in a lower molecular weight. Co‐polymers can be prepared by heating together in the presence of sodium disulfide, aqueous dispersions of two different polysulfide polymers. When thiols are present in the system, interchange of disulfide groups occurs in the absence of sodium disulfide. The results show that disulfide/disulfide redistribution and thiol/disulfide interchange take place in polysulfide polymers. The occurrence of these same reactions has recently been recognized by workers in the biochemical field. A literature survey of thiol/disulfide reactions showed that results formerly attributed to oxidation/reduction reactions could be also explained by an interchange mechanism.
Tập 19 Số 91 - Trang 17-27 - 1956
Nitrogen‐containing monomers. I. Copolymerization reactions of <i>N</i>‐alkyl maleamic acids and <i>N</i>‐alkyl maleimides Abstract The polymerization reactions of some N ‐alkyl maleamic acids and N ‐alkyl maleimides have been described and a number of copolymers have been characterized. The N ‐alkyl maleamic acids do not homopolymerize under the conditions employed but do copolymerize with styrene, acrylonitrile, and methacrylates. N ‐Alkyl maleimides form homopolymers readily and copolymerize with a variety of vinyl monomers. Reactivity ratios of N ‐butyl maleimide with styrene and methyl methacrylate have been determined, and Q and e values have been calculated.
Tập 38 Số 133 - Trang 241-245 - 1959
Kinetics of polymerization of vinylene carbonate Abstract The kinetics of polymerization of vinylene carbonate have been studied as a function of the concentration of initiator, the concentration of monomer, and the temperature. In acetone solution, the order of reaction with respect to the concentration of initiator is equal to 0.5, independent of the monomer concentration ((M ) = 4.15 and 14.7 mole/l.); moreover any thermal polymerization is absent at 70°C. Contrary in ethylbenzoate ((M ) = 3.41 mole/l. at 77°C.) the apparent order with respect to the initiator is 0.77; in agreement with the results of Scanlan in the case of vinylacetate. This behavior is interpreted on the basis of an efficiency factor q , corresponding to the fraction of solvent radicals able to reinitiate a growing chain. In ethylbenzoate solution this factor q is equal to 0.45 and 0.80 for vinylene carbonate and vinylacetate, respectively. With respect to the monomer concentration, the order of the reaction is 1 in the presence of ethylene carbonate as solvent over the total range of concentrations. The transfer constant with this solvent is negligible because it results from molecular weight determinations at constant initiator concentration. In acetone and in benzene the apparent order of reaction is 1, only in dilute solutions; in concentrated solutions small amounts of solvent cause a strong decrease of the rates of reactions. This behavior has been interpreted on the basis of a general kinetic scheme, in which the cross‐termination rate constant Φ and the chain transfer constant with the solvent are the predominant factors. In ethylbenzoate the reaction is characterized by a partial degradative chain transfer. The overall activation energy of the polymerization of vinylene carbonate is 22.2 kcal./mole and the coefficient A of the Arrhenius equation is equal to 3.0 × 10−9 .
Tập 29 Số 119 - Trang 257-274 - 1958
Copolymerization of vinylene carbonate Abstract The copolymerization of vinylene carbonate VC (M2 ) with several vinyl monomers (M1 ) has been examined. The reactivity ratios r 2 and r 1 have been determined in the system VC‐vinyl acetate (0.27 and 3.0), VC‐vinyl chloride (0.09 and 5.2), VC‐vinylpyrrolidone (0.4 and 0.7), VC‐methyl methacrylate (<0.01 and ∼70). These values indicate for vinylene carbonate in the Alfrey‐Price scheme a reactivity Q equal to 0.012 and a polarity e of −0.6. From the r 1 and r 2 parameters of the system vinyl acetatevinylpyrrolidone (0.38 and 0.44, respectively) the Q and e values of vinylpyrrolidone have also been determined: Q = 0.11 and e = −1.6. The copolymers of vinylene carbonate and vinyl acetate yield on hydrolysis polyalcohols (CH2 CHOH)x y
Tập 27 Số 115 - Trang 275-283 - 1958
Copolymérisation de l'Anhydride Maléique avec Différents Monomères Vinyliques Abstract Die Mischpolymerisation von Maleinsaeure Anydrid mit verschiedenen Vinyl‐Verbindungen wie Methakrylsaeure, Methylester, Vinylchlorid, Vinylazetat und Isopropenylazetat wurde untersucht. Die Verhaeltnisse der Geschwindigkeits‐Konstanten r 1 und r 2 wurden fuer jeden dieser Faelle festgestellt. Die Mischpolymerisation mit Monomeren, die eine elektronreiche Doppelverbindung enthalten, zeichnet sich durch eine hohe Selektivitaet aus. In diesen Faellen koennen die Ergebnisse nicht gaenzlich durch das Alfrey‐Price Schema erklaert werden.
Tập 5 Số 2 - Trang 253-258 - 1950