摘要:

AbstractThe radiation‐induced graft copolymerization of methyl methacrylate onto wool fibers and chemically modified (oxidized, methylated, reduced, and crosslinked) wool fibers was investigated in dimethylformamide at room temperature. The homopolymer was separated from the graft copolymer by Soxhlet extraction. The grafting increased with increase in radiation dosage from 0.5 to 1.5 Mrads. The % graft‐on depended on the nature of the wool fibers and decreased in the following order: methylated wool, reduced wool, oxidized wool, natural wool, and crosslinked wool. The molecular weights of the grafted copolymer (after separation from the wool fibers) and homopolymers were determined viscometrically. An increase in the radiation dosage reduced the molecular weights of the polym

ISSN:0021-8995    

DOI:10.1002/app.1978.070220401

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

年代:1978

数据来源: WILEY

摘要:

AbstractSmall‐angle x‐ray scattering from solid solutions of different molecular weight fractions of partially brominated polystyrene in polystyrene has been studied. The results of this study indicate that polymer chains in bulk have a radius of gyration proportional to the square root of molecular weight, which is consistent with the random coil model. However, these radii are approximately 20% larger than the unperturbed radii deduced by light scattering in dilute soluti

ISSN:0021-8995    

DOI:10.1002/app.1978.070220402

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

年代:1978

数据来源: WILEY

摘要:

AbstractStarch polyampholytes (xanthated starch amines) that contained either diethylaminoethyl or 2‐hydroxypropyltrimethylammonium ether and xanthate substituents were prepared, characterized, and evaluated as wet‐ and dry‐strength agents in paper handsheets. In aqueous solutions, these xanthated starch amines (XSA), which had degrees of substitutions (D.S.) of 0.023–0.33 amine and 0.005–0.165 xanthate, underwent intra‐ and interionic bonding at their isoelectric points to form soft flocculent precipitates. Properties of XSA resembled those of “complex coacervates.” Paper that was prepared from an unbleached kraft furnish treated with XSA (amine/xanthate molar ratios, from 1.5 to 4.0) had significantly stronger wet and dry strengths than paper treated with cationic starch amines typically used in commerc

ISSN:0021-8995    

DOI:10.1002/app.1978.070220403

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

年代:1978

数据来源: WILEY

摘要:

AbstractUnsensitized, photoinitiated polymerization reactions of glycidyl methacrylate from solutions of water and water–methanol with cotton cellulose fabrics were investigated. When several layers of cotton fabrics were immersed in solutions of glycidyl methacrylate and only the surface layer was exposed to light, polymerization reactions were initiated in this layer and also initiated in inner layers of fabrics, probably by chain transfer reactions. Photoinitiated (350 nm, 24 W, 34 min) polymerizations of glycidyl methacrylate (7.5 vol‐%) from water (43 vol‐%)–methanol (57 vol‐%) with cotton fabrics in one‐, three‐, and six‐layered configurations were: one‐layered, 32% polymer; three‐layered, 30%, 27%, and 25% polymer; and six‐layered, 29%, 25%, 22%, 20%, 14%, and 11% polymer. Electron‐microscopic examination of the distribution of poly(glycidyl methacrylate) within the cotton fibrous structure showed that polymer was distributed throughout the cross section of the fiber. At the surface of the fibers, the polymer tended to be more concentrated than within the cross section of the fibers and to encapsulate them. Photoinitiated polymerization reactivities of several vinyl monomers from solution with cotton cellulose fabrics were compared with those of glycidyl methacrylate as follows: methyl methacrylate>glycidyl methacrylate>diacetone acrylamide>1,3‐butylene dimethacrylate>methacrylic acid>acr

ISSN:0021-8995    

DOI:10.1002/app.1978.070220404

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

年代:1978

数据来源: WILEY

摘要:

AbstractMethane, ethane, propane, andn‐butane were polymerized in a plasma created by a radio‐frequency glow discharge. It was found that the kinetics of polymer deposition were similar for all monomers but methane. It is suggested that the deviation from “normal” behavior of methane may be due to the difference in mechanism of formation of reaction intermediates. The “characteristic map” for the plasma polymerization of ethane was determined. It was shown that, in addition to transparent films, powders may be formed at low pressures and low monomer flow rates and unstable discharges at high pressures and low flow rates. With increasing power input, the unstable regions are decreased while the powdery regions are increased. The rates of polymer deposition were found to depend on pressure, flow rate, and power. An empirical equation is proposed that relates the rates of deposition for ethane, propane, andn‐butane to the

ISSN:0021-8995    

DOI:10.1002/app.1978.070220405

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe properties of isocyanate‐terminated polyurethane prepolymers were optimized through the use of statistically designed experiments. A simple 2 × 2 factorial with centerpoint statistical design was used to determine the effect the diol‐to‐triol ratio and per cent free isocyanate had on the viscosity of the prepolymer. Combinations of a 1000 or 2000 molecular weight diol with either a 1500 or 4100 molecular weight triol showed that a reasonable range of viscosity could be maintained only with the 4100 molecular weight triol. A nine‐point design was then utilized to predict the best levels of free isocyanate and polyol ratio that would yield cured urethane polymers with the highest tensile strengths, moduli, and elongations. With this design, second‐order equations were computed that predict the mechanical responses of urethane polymers based on the free isocyanate and polyol ratio used in its f

ISSN:0021-8995    

DOI:10.1002/app.1978.070220406

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe intrinsic properties of a yarn are brought about by its physical structure. This structure in its turn is controlled by the process conditions applied. A quantitative description is given of the effect of temperature, time, and tension during annealing on the structure of poly(ethylene terephthalate) yarns. Annealing of a yarn at elevated temperature leads to improvement of packing of the molecules within the crystals. Consequently, the crystalline density is not a constant but is largely dependent on the conditions under which crystallization has taken place. The growth of the PET crystals is not an isotropic process; the strongest growth is observed in the direction of the dipole interactions. The effects of tension and annealing time are also discussed. A prolonged annealing time causes an increase in crystallinity, while time and tension influence the growth of the crystals to some extent. However, for the experimental conditions used in this investigation, temperature is by far the most important factor. Generally speaking, PET fibers annealed at low temperature show low crystallinity built up of many small crystals. Yarn annealed at a high temperature, on the other hand, is composed of fewer big crystals together with large adjacent amorphous regions and relatively high overall crystallinity. Finally, the effect of this observed structural morphology on the dyeing behavior of PET yarns is discussed in a qualitative way. Two main effects controlling the dye uptake of PET yarn are proposed, viz., the total amount of amorphous regions and the accessibility of these regions.

ISSN:0021-8995    

DOI:10.1002/app.1978.070220407

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

年代:1978

数据来源: WILEY

摘要:

AbstractThis paper describes the results of an experimental investigation concerning the effect of polymer–solvent thermodynamics on low‐shear viscosity of copolymer soltions. Thermodynamic parameters and low‐shear solution viscosities were measured for solutions of polystyrene homopolymer and styrene–acrylonitrile copolymers in four solvents: benzene, dioxane, methyl ethyl ketone, and dimethylformamide. The thermodynamic quality of a solvent for a polymer is characterized by free‐energy‐of‐mixing parameters. These quantities are: the Flory‐Huggins thermodynamic interaction parameter χ, the second virial coefficient (from light scattering), the intrinsic viscosity, and the polymer expansion factor. The thermodynamic interaction between a solvent and a polymer in solution influences the rheological behavior of the system. At low concentrations of polymer in solvent, the low‐shear solution viscosity is larger in a good solvent than in a poor solvent. In solutions of higher concentration, the reverse may be true and the viscosity is often significantly larger in a poor solvent than in a good one. These results are not predicted quantitatively by existing theory. The parameters in existing viscosity correlation techniques are found to be solvent dependent. The so‐called entanglement concentrations for polymer solutions are not unique for a particular polymer but are related to the free energy of mixing

ISSN:0021-8995    

DOI:10.1002/app.1978.070220408

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

年代:1978

数据来源: WILEY

摘要:

AbstractCoextruded multifilms of varying chemical composition and structure were studied by the dynamic mechanical technique. The films studied were two‐ and three‐ply combinations of a polyimide (Kapton) and fluorinated ethylene–propylene copolymer (FEP) and four other two‐ply polyethylene and modified polyethylene composites: low‐density polyethylene (LDPE)–ionomer, rubber‐modified high‐density polyethylene (HDPE)–ionomer; ethylene–vinyl acetate (EVA) copolymer–LDPE, and EVA‐modified HDPE–LDPE. The mechanical spectra of individual film components were also obtained at 110 Hz between −120° and 120°C (220°C for the Kapton–FEP system). Mechanical relaxations were examined to determine the degree of interaction between adjacent films and correlate them with tensile and ulti

ISSN:0021-8995    

DOI:10.1002/app.1978.070220409

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

年代:1978

数据来源: WILEY

摘要:

AbstractThermogravimetric analysis (TGA) has been used extensively to determine the thermal stability of polymers. The present study indicates that the isothermal decomposition of polybutadienes (PBDs) is significantly different from that in the heat mode. The isothermal decomposition of PBDs is an exothermic reaction occurring at 350°–375°C. This decomposition is shown to be rapid and temperature specific. It appears to be related to the cyclization reaction reported previously by several investigators. Decomposition of PBDs in the heat mode (10°C/min) occurs at 447°–461°C. This is about 100°C higher than that observed in the isothermal mode. Further TGA experiments indicate that a period of slow heating stabilizes PBD and can eliminate the exothermic decomposition at about 360°C. This stabilization appears to be related to the ease with which both 1,2‐ and 1,4‐PBDs thermally crosslink. Heating 1,4‐PBD for 6 min at 270°C gives rise to 92% gel. 1,2‐PBD is shown to crosslink more extensively. It is shown that polymers which do not thermally crosslink or cyclize, such as polystyrene, decompose similarly in the t

ISSN:0021-8995    

DOI:10.1002/app.1978.070220410

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

年代:1978

数据来源: WILEY