摘要:

AbstractSytrene was polymerized in a 0.8‐liter vessel which was operated as an isothermal and a nonisothermal batch reactor. Styrene and n‐butyllithium conversions were determined for different reaction times. Rate equations were developed by use of the isothermal data and then used to estimate the conversions for the nonisothermal experiments. The importance of using nonisothermal data in the development of rate equations is illustra

ISSN:0021-8995    

DOI:10.1002/app.1978.070220201

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

年代:1978

数据来源: WILEY

摘要:

AbstractLinear 1,2‐polybutadiene, glass transition temperature (Tg) −18°C, is crosslinked at −10°C, to −20°C by γ irradiation while strained in simple extension, with extension, ratios (λ0) from 1.2 to 2.7. After release, the sample retracts to a state of ease (λs) at room temperature. From equilibrium stress–strain measurements up to a stretch ratio relative to the state of ease (Λ) of 1.2, together with λ0and λs, the concentration of network strands terminated by trapped entanglements (νN) is calculated. For this purpose, a three‐constant Mooney–Rivlin formulation is used, in which the entanglement network is described by Mooney–Rivlin coefficientsC1NandC2N, whereas the crosslink networks is described by the coefficientC1xonly. The ratio ψN=C2N/(C1N+C2N) is estimated from parallel studies of nonlinear stress relaxation of the uncrosslinked polymer, taking into account the thermal history before and during irradiation. For substantial degrees of crosslinking, i.e., forR0′= νx/νN>0.4 (where νNis the concentration of network strands terminated by crosslinks), and for λ0<1.8,C2Nagrees rather well with the value obtained from stress relaxation of the uncrosslinked polymer in the range of time scale where it is nearly independent of time (1.87 X 105pascals). The corresponding value of νNis 2.3 × 10−4moles/cm3, in good agreement with that obtained from viscoelastic measurements of the uncrosslinked polymer in the plateau zone (2.5 × 10−4). However, forR0′≅ 0.2, smaller values ofC2Nand νNare obtained, indicating that for low degrees of crosslinking the entanglements are not completely trapped. Also, for higher values of λ0,C2Nand νNturn out to be somewhat smaller. Similar, less extensive results were obtained previously on a 1,2‐polybutadiene with somewhat higher vinyl content and a higherTg. Crosslinked samples of both these polymers were subjected to equilibrium stress–strain measurements in simple elongation from the state of ease at higher strains up to Λ = 1.7. The results agreed closely with calcul

ISSN:0021-8995    

DOI:10.1002/app.1978.070220202

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe alkali‐catalyzed reaction ofm‐cresol with formaldehyde carried out at 65°, 70°, 75° and 80°C and at pH 7, 8, 9, 9.4, and 10 follows second‐order kinetics. The rate is found to increase with increase of pH. The overall rate constant (k) has been resolved into stepwise rate constants (k1,k2, andk3) for the formation of monomethylol, dimethylol, and trimethylol cresol, respectively. For this purpose, the rate equations for the various possible steps have been given and the concentrations of the various methylol cresols formed determined. The experimental and calculated values ofkat pH 10 and temperatures of 65°, 70°, and 80°C have been found to agree well within the experimental errors. Entropy of activation and the Arrhenius parameters for the overall reaction have also bee

ISSN:0021-8995    

DOI:10.1002/app.1978.070220203

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

年代:1978

数据来源: WILEY

摘要:

AbstractAbsorption of oxygen and degradation ofcis‐1,4‐polyisoprene by the phenylhydrazine–iron(II) chloride system was investigated at 30°C in connection with the mechanism of reclamation of vulcanized rubbers by the system. In the presence of iron(II) chloride, phenylhydrazine rapidly absorbed an equimolar amount of oxygen and evolved an equimolar amount of nitrogen. Gas‐chromatographic analysis of the reaction mixture showed the presence of benzene, phenol, and biphenyl in 37%, 35–60%, and 4–8% yields, respectively, based on phenylhydrazine. Whencis‐1,4‐polyisoprene was added to the reaction mixture, additional absorption of oxygen was observed. Molecular weight of the polymer decreased during the oxygen absorption, and the scission efficiency (i.e., number of mole scissions/mole oxyge

ISSN:0021-8995    

DOI:10.1002/app.1978.070220204

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

年代:1978

数据来源: WILEY

摘要:

AbstractDepolymerization of poly‐ϵ‐caprolactam chips was carried out at low pressures (3–15 mm Hg) and elevated temperature (225°–270°C) in the presence of sodium hydroxide as catalyst. The effects of variation of amount of sodium hydroxide, time, temperature, and pressure on ϵ‐caprolactam yield were studied. With increase in alkali content the yield increases linearly, reaching a maximum at 1% (w/w) NaOH and then falls. The yield increases with time of depolymerization up to 4 1/2 hr and then becomes practically constant. Between 240° and 250°C there is a sudden increase in depolymerization rate. Further increase in temperature has very little effect. Decrease in pressure from 15 to 3 mm Hg shows a nine‐fold increase in yield. The optimum conditions for the depolymerization were a temperature of 250°C, a pressure of 3 mm Hg, and a time 4 1/2 hr in the presence of 1% NaOH (w/w), which gave a 90.5% yield of ϵ‐caprolactam. Physical properties, IR spectra, and behavior toward polymerization of the recovered monomer indicated the presen

ISSN:0021-8995    

DOI:10.1002/app.1978.070220205

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

年代:1978

数据来源: WILEY

摘要:

AbstractCooligomers and ABA‐type block copolymers composed of a hydrophilic monomer, 2‐hydroxyethyl methacrylate (HEMA), and a hydrophobic monomer, styrene, were synthesized to study the relation between their microstructure and hydrophilic and hydrophobic functions. Films of cooligomers and ABA‐type block copolymers were cast from DMF solutions at 40°C. The wettability, which was determined from the contact angle with water, increased considerably when HEMA mole fraction reached around 0.8 in the cooligomer system and around 0.9 in the ABA‐type block copolymer system. The microstructures of the copolymer films were observed by electron microscopy using the osmium tetroxide fixation technique. The morphologic change in the domain structure was observed at an HEMA mole fraction of about 0.8 in the cooligomer system and about 0.9 in the ABA‐type block copolymer system. It is suggested that hydrophilic and hydrophobic functions are largely influenced by the state of aggregation of each segment, that is, the size and geometry of the hydrophilic and hydrophob

ISSN:0021-8995    

DOI:10.1002/app.1978.070220206

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

年代:1978

数据来源: WILEY

摘要:

AbstractPeanut skin, when treated with formaldehyde to polymerize tannins, is a highly efficient substrate for removal of many heavy metal ions from aqueous waste solutions. The ions Ag1+, Cd2+, Cr6+, Cu2+, Hg2+, Ni2+, Pb2+, Zn2+, as well as Ca2+and Mg2+, were contacted with formaldehyde‐treated peanut skin. Quantitative removal could be achieved with Ag1+, Cd2+, Cu2+, Hg2+, Pb2+, and Zn2+. Capacity of the substrate for ions was promising for Pb2+(2.1 meq/g substrate), Cu2+(3.0 meq/g), and Cd2+(1.3 meq/g). Sorption from a solution containing Cd2+, Cu2+, Hg2+, Ni2+, Pb2+, Zn2+, on a packed column of formaldehyde‐treated peanut skin indicated that Hg2+, Pb2+, and Cu2+were rapidly and completely bound to the packing, while Cd2+, Ni2+, and Zn2+were poorly bound until the preferred ions had been removed from solut

ISSN:0021-8995    

DOI:10.1002/app.1978.070220207

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

年代:1978

数据来源: WILEY

摘要:

AbstractIt was found previously that cast articles of transparent polymer without optical strain could be obtained efficiently in a very short time by radiation‐induced polymerization of glass‐forming monomers at low temperature. Two types of optical strain were observed in casting of these monomers: thermal stream type and remaining (inner) stress type strain. The mechanism of thermal stream‐type strain formation was investigated by following the heat and temperature change during cast polymerization in this report. It was found that the temperature difference between the upper and lower part of the sample was large and the temperature was much higher in the upper part than in the lower part under conditions of strain formation. Increase of heat removal from the sample surface decreased the temperature difference in the vertical direction and reduced the strain formation. It could be deduced that stream‐type strain formed as a result of thermal stream and it was retarded in radiation casting of glass‐forming monomers owing to high viscosity and low te

ISSN:0021-8995    

DOI:10.1002/app.1978.070220208

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

年代:1978

数据来源: WILEY

摘要:

AbstractPreviously it was found that casting could be carried out efficiently without strain formation by radiation‐induced polymerization of glass‐forming monomers. Two types of strain were observed in casting: thermal stream type, which was studied previously, and remained stress type. In this report, the effect of various factors on the formation of remaining stress‐type strain in radiation‐induced casting polymerization was studied. It was found that the molecular weight of prepolymer did not affect strain formation, while prepolymer concentration and viscosity of the system had a serious influence on strain formation. It could be deduced that this type of strain formed as a result of remaining inner stress due to poor relaxation of the shrinking stress. It was realized that less volume shrinkage of glass‐forming monomers accompanying casting polymerization reduced the strain formation of this type in radiation‐induced casting polymerization at low t

ISSN:0021-8995    

DOI:10.1002/app.1978.070220209

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

年代:1978

数据来源: WILEY

摘要:

AbstractPoly(1,3,4‐oxadiazole‐2,5‐diylvinylene) and poly(1,4‐phenylene‐1,3,4‐oxadiazole‐2,5‐diylvinylene) were prepared by polymerizing different quantities of terephthalic acid (T), maleic acid (M), and hydrazine sulfate (HS) in the presence of fuming sulfuric acid. Homopolymers of M and T and various copolymers of M:T were prepared. The polymers were characterized by viscosity, IR, UV, and elemental analysis. Their solubility in different solvents was investigated. The relative thermal stability of the polymers was evaluated

ISSN:0021-8995    

DOI:10.1002/app.1978.070220210

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

年代:1978

数据来源: WILEY