摘要:

AbstractIn this study, bis ϵ‐caprolactam bis‐diphenyl methane diisocyanate polypropylene glycol 1000 used as the macroactivator was prepared and well characterized prior to use. The anionic polymerization of ϵ‐caprolactam with the macroactivator as a function of the macroactivator concentration was adiabatically carried out. The adiabatic temperature rise method as well as the macrokinetics were used for elucidation of the kinetics of the polymerization. A nonlinear regression technique was used for determining the parameters of the macrokinetic equation. The equilibrium conversion and equilibrium time obtained were 94–96% and 2–9 min depending on the macroactivator concentration. The effects of the concentrations of macroactivator and ϵ‐caprolactam on the initial rate, apparent overall reaction rate, and the empirical parameters were studied. A side reaction induced by the transfer of the proton in the isocyanurate group of the macroactivator to caprolactam anion was found. According to this finding, a new reaction kinetic model was proposed by properly modifying the macrokinetic equation. © 1993 John

ISSN:0021-8995    

DOI:10.1002/app.1993.070501001

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

年代:1993

数据来源: WILEY

摘要:

AbstractViscoelastic deformation of an interlaminar‐toughened laminated composite was investigated, and effects of the interlaminar heterogeneity were examined. Dynamic mechanical experiments were performed on the laminates and neat matrix resins of the laminated composite in the temperature range of 82–210°C to probe linear time‐temperature behavior. The reason for using torsional shear deformation for probing was that it usually is more dominated by the matrix. In the relatively low‐temperature regime, time‐temperature superposition was applicable, and the effect of the interlaminar heterogeneity was found to be not pronounced. A methodology based on the Arrhenius activation energy approach was proposed for predictions of long‐term viscoelasticity of the heterogeneous‐phase composite. The effects of the interlaminar toughening phase became more significant at temperatures greater than theTgof the toughening phase and presented some limitations for accurate predictions of time‐dependent behavior. © 1993 Joh

ISSN:0021-8995    

DOI:10.1002/app.1993.070501002

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe precipitation values (PVs) of several organic nonsolvents in polysulfone (PSf)/solvent and polyethersulfone (PESf)/solvent systems were measured in temperatures ranging from 10 to 80°C by the direct titration method and compared with those of water in the same systems. The solvents used wereN‐methyl‐2‐pyrrolidone (NMP) andN,N‐dimethylacetamide (DMAC); the organic nonsolvents employed were methanol, ethanol, 1‐propanol, 1‐butanol, 1‐pentanol, ethylene glycol, and diethylene glycol as well as acetic acid and propionic acid. The compositions of nonsolvent, polymer, and solvent at the precipitation points for different polymer concentrations up to 10 wt % were also determined at 30°C with respect to both the polymers and six nonsolvents presented. These results were used to obtain the polymer precipitation curves in the polymer‐solvent‐nonsolvent triangular phase diagrams and to determine the theta composition of solvent‐nonsolvent for a polymer. The results show that the precipitation value of nonsolvent in polymer/solvent systems depends on both the nature of polymer, solvent, and nonsolvent used and the temperature. The effect of temperature on the precipitation value was observed to be dramatically different for different polymer/solvent/nonsolvent systems. These results were explained on the basis of polar and nonpolar interactions of the polymer, solvent, and nonsolvent system. The results indicate that the precipitation values of the type presented in this paper not only give a relative measure of the nonsolvent tolerance of the polymer/solvent system involved and the strength of solvent and nonsolvent for the polymer, but also determine the relative location of the polymer precipitation curve in the triangular phase diagram. © 199

ISSN:0021-8995    

DOI:10.1002/app.1993.070501003

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe melt‐crystallized poly(phenyl ether ether ketone) (PEEK) polymer was overlaid on crystalline zinc phosphate (Zn • Ph) conversion coating‐deposited and nondeposited coldrolled steels at 400°C in air or in N2environments. The ability of these coating systems to protect the steel against corrosion was evaluated from the rate of cathodic delamination of the coating layer from the steel. Because the cathodic reaction, H2O + 1/2O2+ 2e−= 2OH−, at the corrosion side of a defect in the coating layer creates a high pH environment at the interfacial boundary between the coating and steel, the magnitude of susceptibility of the interfacial intermediate layers to the alkali‐induced degradation played a key role in suppressing cathodic failure. The lowest level was observed in the N2‐induced PEEK/Zn • Ph/steel joint systems, thereby decreasing the rate of delamination. By contrast, oxidized PEEK induced by air in same joint systems was susceptible to the alkali‐catalyzed hydrolysis. This phenomenon significantly promoted the alkali dissolution of Zn • Ph crystals, reflecting a high rate of delamination. Nevertheless, the introduction of Zn • Ph as interfacial tailoring material into the intermediate layers markedly acted in reducing the cathodic delamination of PEEK/steel joint systems. © 19

ISSN:0021-8995    

DOI:10.1002/app.1993.070501004

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

年代:1993

数据来源: WILEY

摘要:

AbstractAverage residual stresses in polypropylene fibers, produced in a full‐scale short‐spin line, are estimated from the shift of the IR absorption peak at 975 cm‐1. Linearly polarized incident IR radiation is used to separate between stress components parallel and perpendicular to the fiber axis. For all the fibers in this study, the axial stress component is larger than the average stress perpendicular to the fiber axis. Axial and perpendicular stresses are correlated with draw ratio and polydispersity index. For narrow molecular weight distributions (Mw/Mn<4–5), the axial stress increases with increasing draw ratio. Average stress perpendicular to the fiber axis decreases with increasing draw ratio for all the molecular weight distributions in this study (Mw/Mn= 3–6). Measurements of residual stresses are consistent with other results characterizing molecular structure and mobility. An expression for estimating the stored deformation energy is discussed. © 1993 John Wiley

ISSN:0021-8995    

DOI:10.1002/app.1993.070501005

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe positronium formation and the reversibility behavior of the electric field from 31.75 to 588.24 kV/cm were studied in high‐density polyethylene (HDPE) using the positron annihilation lifetime technique. The lifetime measurements were performed using the conventional fast‐fast coincidence timing system. The observedortho‐positronium life time τ3does not show significant variation from the corresponding values measured without the electric field. On the other hand, the corresponding intensityI3increases with increasing the electric field strength in the range from ∼ 100 to 588.24 kV/cm. This result indicates a strong irreversible effect of the electric field. In addition, the effect of temperature on the sample stressed at 450 kV/cm was investigated. The structural changes on the heating and cooling cycles show reversible behavior. The thermal expansion coefficient has been deduced to be 7.53 × 10−3/°C. © 1993 John Wi

ISSN:0021-8995    

DOI:10.1002/app.1993.070501006

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

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper describes the synthesis, physical properties, and the impact modification of poly(N‐phenylnorbornene dicarboximide) (PNDI). Impact modification is carried out both by physical blending with acrylonitrile‐butadiene rubber (Hycar®) and byin situmetathesis polymerization of the monomer with the rubber. Better success is achieved byin situmetathesis polymerization. A copolymer, poly(N‐phenylnorbornene dicarboximide) ‐co‐poly(norbornene nitrile) containing Hycar rubber (PNDI/PNN/Hycar), is prepared with a good balance of high‐heat impact and flexural properties. The melt viscoelastic behavior of PNDI/PNN/Hycar is evaluated and the energy of activation for viscous flow (Ea) was found to be 42 kcal/mol. © 1993 John Wi

ISSN:0021-8995    

DOI:10.1002/app.1993.070501007

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe removal and recovery of gallium ion (Ga+3) from a solution with the high cross‐linked amphoteric starches containing the phosphate anionic group and the quaternary ammonium or tertiary amine cationic group was investigated. The adsorption capacity of tertiary amine phosphate starch (TAP) and quaternary ammonium phosphate starch (QAP) is 0.54 and 0.48 meq/g, respectively. The adsorption process has been found to be concentration dependent and endothermic, and follows the Langmuir isothermal adsorption. The heat of adsorption (ΔH) is equal to 7.65 kcal/mol for the QAP and equal to 7.65 kcal/mol for the TAP. The percentage of adsorbed Ga+3ion decreases when HCl, H2SO4, NaCl, or Na2SO4is added to the solution. The Ga+3ion adsorbed on the adsorbents can be recovered by treating with an NaOH or HCl solution (1Mand 3M); the maximum percentage of recovery is about 70% when 1MNaOH solution is used. © 1993 John Wiley&Sons,

ISSN:0021-8995    

DOI:10.1002/app.1993.070501008

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

年代:1993

数据来源: WILEY

摘要:

AbstractBiodegradation of cellulose acetate and cellulose propionate was conclusively established with a naturally derived mixed microbial culture derived from activated sludge and14C labeled cellulose esters. Radiolabeled cellulose esters were synthesized with either [1‐14C]‐acetate or [1‐14C]‐propionate and back hydrolyzed to the desired degree of substitution (DS) ranging from 1.77 to 2.64. Biodegradation was measured in anin vitroaerobic culture system that was designed to capture14CO2produced by the aerobic microbial metabolism of the cellulose esters. Microorganisms were able to extensively degrade cellulose [1‐14C]‐acetate (CA) with DS ranging from 1.85 to 2.57 over periods of 14–31 days. More than 80% of the original14C‐polymeric carbon was biodegraded to14CO2for CA substrates with a DS of 1.85. CA polymers with a DS of 2.07 and 2.57 yielded over 60% conversion to14CO2. The amount of biodegradation that was observed with cellulose [1‐14C]‐propionate with DS of 2.11, 2.44, and 2.64 were lower than the corresponding acetyl ester and ranged from 0.09 to 1.1%. However, cellulose [1‐14C]‐propionate with a DS of 1.77 and 1.84 underwent very rapid degradation in the mixed culture system, with 70 to over 80% conversion of labeled polymeric carbon metabolized to14CO2in 29 days. The high level of microbial utilization of carbon from both cellulose esters and its conversion to CO2confirms the biodegradability of these polymers and the potential they have for total mineralization in natural microbiologically active environments. © 1

ISSN:0021-8995    

DOI:10.1002/app.1993.070501009

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

年代:1993

数据来源: WILEY

摘要:

AbstractMixtures of PET and PVC were prepared in three different compositions by a solution blending technique. A plasma surface modification method was applied to PET powder surfaces in order to enhance the miscibility of both components because of their mutual insolubility. The intrinsic viscosities of blends were measured in a phenol/tetrachloroethanemixed solvent system. The degree of compatibility of blends was characterized by the use of the parameter Δb, as derived by Krigbaum and Wall. © 1993 John Wiley&Sons, In

ISSN:0021-8995    

DOI:10.1002/app.1993.070501010

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

年代:1993

数据来源: WILEY