摘要:

AbstractPolymers doped with low‐molecular‐weight charge‐transfer (CT) complexes exhibit interesting electrical and photoelectrical properties. On the basis of the results of thermally stimulated depolarization (TSD) for polycarbonate (PC) doped with tetracyanoethylene‐t‐stilbene complex and its components, some information about the mechanism of mutual interaction was obtained. The measurements of stress relaxation, mechanical moduli, and ultimate strength in a wide temperature range fully confirmed the predicted behavior of PCsdoped with CT complex and its components. Doping the PC with CT complex and its components lowers the glass‐transition temperature and increases the modulus in the range −60 to +60°C. The effects of doping on the mechanical properties of PC are explained in terms of α‐

ISSN:0021-8995    

DOI:10.1002/app.1979.070230501

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractA model relating the steady‐shear melt viscosity and elasticity to the molecular weight distribution in HDPE and polystyrene melts has been extended to predict the dynamic viscosity, modulus, and loss modulus. Limitations in the model as applied to the dynamic properties are discussed. The model is also applied to the transient response of stress growth during steady shearing. This application is considered useful because it may help describe nonsteady‐state flow of polymer melts in short dies and cyclic operations as employed in commercial molding equipm

ISSN:0021-8995    

DOI:10.1002/app.1979.070230502

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe advantages of carrying out reverse osmosis desalination with improved membranes at low pressures have been pointed out. Cellulose acetate (CA) semipermeable membranes developed with low air‐exposure periods by Sirkar et al. from novel Manjikian‐type casting solutions having high CA content, partial replacement of acetone by dioxane, and small amounts of ZnCl2(or none) have been tested for the following combinations of operating pressure (lb/in.2)/feed brine concentration (in ppm): 250/5000; 300/7500; 400/10,000; 600/30,000; 700/40,000; 750/50,000; 800/60,000. In the pressure range of 250‐600 lb/in.2(psig), the pure water permeability (PWP) constants of membranes for a given salt transport parameter are greater than those of similar membranes tested earlier by Sirkar et al. at 600 psig with a 5000‐ppm brine feed. The PWP constants decrease faster with pressure as the casting solution CA concentration is reduced from 32% to 30% and the dioxane content of the solvent is raised from 40% to 60%. The intrinsic performances of membranes from a 32% CA casting solution with 40% dioxane improve as the pressure is increased from 250 to 600 psig. The solution structure‐rate of evaporation concept along with the phenomenon of fingerlike cavities and protrusions in membranes from high dioxane casting solutions explain most of the observations of this work. The superior low‐pressure performance of these CA membranes provide a basis for systematically lowering the operating pressure in reverse osmosis d

ISSN:0021-8995    

DOI:10.1002/app.1979.070230503

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe crosslinking copolymerization of styrene (St)‐m‐divinylbenzene (m‐DVB) in the presence of poly(vinyl chloride) (PVC) was studied. The rate of the copolymerization decreased with the addition of PVC powder, because of the depressing of the diffusion of the monomers to the polymerizing center and the difficulty in the transfer of the polymer radicals in the swelled PVC powder. The exponential value of the benzoyl peroxide concentration and the activation energy of the copolymerization were obtained as 0.67 and 17.4 kcal/mol, respectively. The monomer reactivity ratios of St andm‐DVB were determined asr1= 0.25 andr2= 1.42 (M1: St,M2:m‐DVB). From the extraction of the resultant polymer composite with THF, both the grafting of the St‐m‐DVB copolymer onto PVC and the entanglement of PVC with St‐m‐DVB copolymer seems to occur in the St

ISSN:0021-8995    

DOI:10.1002/app.1979.070230504

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractNew binary chlorides have been obtained by reacting TiCl4with V(CO)6, Cr(CO)6, Mn2(CO)10, Mn(CO)5Cl, Ni(CO)4, Co2(CO)8, Fe(CO)5, or Mo(CO)6. The reactions yield quantitatively mixed chlorides having the general formula MCln·nTiCl3, wheren= 2 or 3 and M is a divalent or trivalent transition metal cation. MClnis generally isomorphous with the α‐ or γ‐modification of TiCl3. X‐Ray and spectroscopic investigations indicate that the mixed chlorides obtained are solid solutions. High surface area values are associated with the adducts displaying lower crystallinity. Catalyst efficiencies two or three times higher than that of AlCl3·3TiCl3were observed in the low‐pressure polymerization of ethylene (HDPE) when some binary chloride was associated with Al(i‐C4H9)3. These results allow treating the obtained solid solutions as reference systems of high‐yield catalysts for

ISSN:0021-8995    

DOI:10.1002/app.1979.070230505

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractBinary chlorides described in part I yielded very active catalyst systems for HDPE synthesis when they were associated with (i‐C4H9)3Al. Very high initial polymerization rates were observed for systems bases on MnCl2·TiCl3, MnCl2·2TiCl3, or FeCl2·2TiCl3(III), but high yields, i.e., above 30 kg polymer/g Ti, could be reached only using moderate pressure of ethylene. Hydrogen consumption during ethylene polymerization was observed in the case of catalysts based on AlCl3·3TiCl3, CrCl3·3TiCl3, and other binary chlorides containing elements of the VIII group. Relevant amounts of ethane were found in the case of systems III, V, and VIII. All the mixed chlorides studied were able to reduce cyclohexene in the presence of H2and (i‐C4H9)3Al, even though with different kinetic courses. Compounds II, III, V, and VIII and (MgCl2)1.5·TiCl3and AlCl3·3TiCl3were very active. The results have been explained on the basis of solubilization processes involving the heterogeneous catalysts which actually were experimentally verified during cyclohexene reduction. Analogous processes may occur also during HDPE

ISSN:0021-8995    

DOI:10.1002/app.1979.070230506

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe feasibility of chromium(VI) to induce graft polymerization of methyl methacrylate onto silk was investigated. The rate of grafting was determined by varying monomer concentration, chromium(VI) concentration, temperature, acidity of the medium, nature of the silk, reaction medium, and redox system. The graft yield increased with increasing monomer concentration up to 0.65M, and with further increase of monomer the graft yield decreased. The graft yield increased with increasing chromium(VI) concentration. The grafting is considerably influenced by chemical modification of silk prior to grafting. The graft yield is influenced by thiourea concentration, decreasing with increasing thiourea concentration. The effect of certain inorganic salts and anionic surfactants on the rate of grafting was investigated.

ISSN:0021-8995    

DOI:10.1002/app.1979.070230507

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractIn order to elucidate the reaction mechanism involved in the photocrosslinking of epoxide resins containing the 4,4′‐dioxychalcone functional group as part of the polymer backbone, the behavior of the monomeric model compound, namely, the digylcidyl ether of 4,4′‐dihydroxychalcone, when subjected to UV irradiation has been studied in some detail. The initial photochemical reaction is trans‐cis isomerization to a photostationary state, the trans/cis ratios in this state being wavelength dependent. This is followed by a slow dimerization to dimers of the truxillic and truxinic type, the products being mainly formed from the trans isomer under our conditions of irradiation (λ = 350 nm). GPC studies on the irradiated products also reveal the formation of low molecular weight oligomers. Irradiation in the solid phase resulted in the conversion of 37% of the reacted monomer into polymer, whereas irradiation in the solution phase led to 23% of the reacted monomer being converted into low molecular weight polymer. A slow depolymerization of the dimer into the monomeric chalcone is also believed to occur on irradiation

ISSN:0021-8995    

DOI:10.1002/app.1979.070230508

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractUltrafiltration has been evaluated as a method for the purification of of polymeric dyes. Transport data for solvent and solutes were obtained for several polymer‐impurity mixtures and different membrane types. Relatively low molecular weight impurities were found to be significantly rejected by these membranes. A critical concentration of sodium chloride or sodium hydroxide was found to be necessary to effect efficient transport of these species. Gel permeation chromatography was used to monitor these separations and characterize the purity of the polymeric dyes produced. Impurity concentrations in the final product were typically less than 500 pp

ISSN:0021-8995    

DOI:10.1002/app.1979.070230509

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractQuaternary phosphonium compounds have been found to be extremely effective latent accelerators for anhydride‐cured bisphenol A epoxy resins; at concentrations from 0.01% to 0.25%, fast gel times are found in the temperature range of 135°–200°C combined with very good storage properties at ambient temperatures. Using these materials as accelerators, it is possible to formulate long‐life, one‐component epoxy resins. From gel time data, Arrhenius plots were made for some of these phosphonium compounds, and results indicate low activation energy values of the order of 16.1 kcal/mole. Reaction mechanisms are proposed to explain the effectiveness of these phosphonium compounds as latent accelerators. The initiation mechanism probably involves the formation of hydrogen‐bonded phosphonium–epoxy or phosphonium–anhydride complexes which rearrange on the application of heat to form activated species resulting in polymerization of the epoxy–anhydride components. The transfer of a proton from the phosphonium complex(es) to other epoxy or anhydride molecules would appear to be the rate‐determining step in this initiation mechanism. Comparison of other well‐known accelerators used for the anhydride cure of bisphenol A epoxy resins shows quaternary phosphonium compounds to be among the most effective accelerat

ISSN:0021-8995    

DOI:10.1002/app.1979.070230510

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY