摘要:

Polymerization of acrylonitrile using Ce(IV) as initiator in the presence of hippuric acid in aqueous sulfuric acid solution catalyzed byN-cetyl trimethyl ammonium bromide (NCTAB) was studied kinetically. The polymerization experiment was carried out in the temperature range 35°-55°C. The rate of polymerization (Rp) increases with increasing concentration of NCTAB and it is found to be proportional to the concentration of acrylonitrile. Comparisons were made of the effect of different organic substrates and different miceiles on the rate of polymerization. Various effects such as effects of concentration of metal ion, ernulsi-fier, monomer, sulfuric acid, organic solvents, and inorganic salts onRpwere also investigated. The remarkable feature of the investigation involves the enhancement ofRpin the presence of micelles; a suitable mechanism for the derivation of the rate expression is proposed and optimum conditions are predicted. From the Arrhenius plot, the energy of activation (EA) was found to be 1.9805 kcal/mol.

ISSN:0360-2559    

DOI:10.1080/03602559508017209

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Electrical resistivity measurements were made for pure and doped PMMA films with TCNQ-anthracene, Li-TCNQ charge transfer solid complexes and a TCNQ-anthracene donor-acceptor system. The effect of concentration of the dopant, temperature, and light on the electrical behavior of these films was investigated and is discussed. The ultraviolet and visible spectra were also studied. The sensitivity of the PMMA doped films for photoconductivity is discussed on the basis of the conduction mechanism proposed for the charge transfer interaction in the complex systems.

ISSN:0360-2559    

DOI:10.1080/03602559508017210

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Wood-plastic composites are prepared under Co-60 γ irradiation with simul, a low-grade wood of Bangladesh using four different bulk monomers (styrene, methylmethacrylate, butylmethacry-late, and acrylamide) at different methanol concentrations in the presence of a number of additives such as NVP, TPGDA, TMPTA, sulfuric acid, urea, and lithium nitrate. The effect of copper sulfate is studied in these systems. The optimum CuSO4concentration for obtaining the highest polymer loadings is determined.

ISSN:0360-2559    

DOI:10.1080/03602559508017211

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Polymers deteriorate by a number of mechanisms. In the lifetime of a polymer, deterioration may proceed gradually or rapidly. During processing, a polymer is melted and formed to a desired shape; it undergoes some deterioration due to the extreme temperature and mechanical stress. For example, polymer chains may rupture at the molecular level as a result of high shear stress encountered during processing. When mechanical stress contributes to failure or deterioration, the process is termed mechanical degradation or stress-induced degradation. When the thermal stress contributes to failure or deterioration, the process is termed thermal degradation. The degree to which a polymer undergoes deterioration depends on the thermal and mechanical stresses the material experiences during processing. Although the deterioration process of polymers is prominent under extreme conditions of temperature and pressure, in general, these materials undergo mild deterioration under ambient conditions.

ISSN:0360-2559    

DOI:10.1080/03602559508017212

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

To use a resin for a composite, the processing conditions must be known. An engineering analysis through numerical simulation of the heat mold cure is useful for this purpose. The chemical systems studied were based in furfuryl alcohol (FA) and furfural. Sulfuric acid was used as catalyst. The kinetics of the reaction was followed by using a quasi-adiabatic calorimeter, taking into account corrections for heat losses. Kinetics parametersE, A, andnwere estimated. A mathematical model involving conservation of energy and chemical species was solved numerically for the FA system. Different types of fibers (glass and cellulose) and different volume fraction were used for the simulation. Some criteria for the process design are stated.

ISSN:0360-2559    

DOI:10.1080/03602559508017213

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A series of unsaturated polyesters (UP) based on succinic acid, adipic acid, sebacic acid, maleic anhydride, ethylene glycol, dieth-ylcnc glycol, triethylene glycol. and propylene glycol were prepared. The molecular weights of the prepared UP were determined via end group analysis. The prepared polyesters were crosslinked and their mechanical properties were measured. Sty-rene (Sty) and Sty/acrylonitrile (AN) mixtures were utilized as crosslinkers. The effect of the structure of the resins on their curing and mechanical behavior has been investigated. On the basis of the experimental results, we concluded that the flexibility increases with increasing molecular weight of the dibasic acid and increasing AN content in the monomer mixture. It has been found also, that the embodiment of PG seems to enhance the rigidity of the cured resin.

ISSN:0360-2559    

DOI:10.1080/03602559508017214

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Hydroperoxide groups are widely believed to be critical intermediates in the oxidative degradation of many polymers, especially commodity polyolefins [34, 5 1-53]. Trace amounts of hydroperoxides in polyolefins such as polyethylene (PE) may be formed inadvertently during polymerization and processing. It is found that hydroperoxides are formed almost quantitatively from the oxygen absorbed by the polymer during its induction period [26,27,44]. Moreover, it has baeen suggested that the stability of articles made from polyolefins depends largely on the concentration of hydroperoxides formed during storage of the nascent polymer before any stabilizer is added 1701.

ISSN:0360-2559    

DOI:10.1080/03602559508017215

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Delamination of three different automotive epoxy adhesives (A, B, and D) from two different steel substrates (cold-rolled steel and electrodeposited zinc steel) upon exposure to distilled water and a 1.0 M NaCl solution was studied using DC-resistance measurements. The DC-resistance measurements were taken on sandwich adhesive bonded specimens having different combinations of adhesive and steel metal substrates upon exposure to a test solution. The measurements were taken on: (i) electrodeposited zinc steel substrates bonded by adhesives A and D in distilled water; (ii) electrodeposited zinc steel substrates bonded by adhesives B and D in a 1.0 M NaCl solution: and (iii) cold-rolled steel substrates bonded by adhesives A and D in a 1.0 M NaCl solution. Four stages of the resistance change across the metal/adhesive/metal specimens were proposed, corresponding to the different stages of bonding degradation. It was found that the initial resistance decrease across an adhesive-bonded specimen was governed by the concentration of the electrolyte produced in the adhesive matrix. The more the water-soluble fillers dissolved in water inside the adhesive, the higher the concentration of the electrolyte and the lower the resistance across the specimen. Hence, the amount of water required to dissolve the water-soluble fillers was governed by the water absorption rate and the rate of adhesive degradation. Adhesive delamination occurred when sharp resistance fluctuations were detected across an adhesive-bonded specimen. The sharp resistance fluctuations were a result of the consecutive breakdown and formation phenomenon of the interfacial secondary oxide or hydroxide film. The magnitude of the resistance fluctuations increased with the degree of adhesive delamination and the area of oxide or hydroxide film breakdown. Anodic delamination was found to occur in the metal/adhesive/ metal specimens according to the crevice corrosion mechanism. The degree of anodic delamination depended on the nature of the secondary oxide or hydroxide film at the adhesive/substrate interface.

ISSN:0360-2559    

DOI:10.1080/03602559508017216

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The effect of carbon black particle size and structure on the equilibrium volume swelling and elastic recovery of polychloroprene rubber immersed in hydraulic oil and subjected to uniaxial compression stress was investigated in this study.

ISSN:0360-2559    

DOI:10.1080/03602559508017217

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The Third International Conference on Fire Retardancy of Polymeric Materials was held in Atlanta, Georgia, USA, on December 7–8, 1993. The conference focused upon the latest developments in zero- and lowhalogen additives and polymers used to minimize flammability, smoke, fume, and toxicity problems. This was an intensive and executive-level meeting for compounders and technical specialists using fire retardants (FR) in plastics, textiles, wire and cable, and furniture applications; business development managers who follow specialty chemical and additive markets; health, safety, insurance, and regulatory affairs managers; and materials, equipment, and testing/measurement specialists in the fire safety industry. An exhibition of fire retardant additives and instruments was arranged within the framework of the conference. The participants took this opportunity to discuss their needs with the exhibitors and to discover new sources of equipment, materials, and services.

ISSN:0360-2559    

DOI:10.1080/03602559508017218

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor