摘要:

AbstractThe supermolecular structure and viscoelastic and diffusion properties of a perfluorinated polymer containing sulfonic acid (Nafion) were investigated. The breakdown of time–temperature super‐position for the dry salt and and acid in the presence of 0.5 H2O/SO3H as well as the results of small‐angle x‐ray scattering suggest that the ions in this material are clustered. Above 180°C, the reestablishment of the time–temperature superposition in the salt suggests that ions in the clusters become mobile. Dynamic mechanical studies were performed over a temperature range from −190°C to above the glass transition temperaturesTgof the materials. TheTgof the salts is found at ca. 220°C, while in the acid it occurs at 110°C. A β peak in the acid is found at ca. 20°C, while in the salts it occurs between 140°C and 160°C. The β peak shifts to a lower temperature with the addition of water in both the acid and the salts, while the α and γ peaks are unaffected. The latter is located at ca. −110°C at 1 Hz. Dielectric behavior has also been studied as a function of water content for the acid sample and the potassium salt at frequencies of 100 Hz to 10 kHz. Two relaxations with different activation energies were observed. The position of both peaks shifts to a lower temperature as the water content increases. Finally, the diffusion of water in Nafion in the acid form has been determined. The diffusion coefficient can be represented by the equation\documentclass{article}\pagestyle{empty}\begin{document}$ D = 6.0 \times 10^{ - 3} \exp ( - 4.8{\rm kcal}/{\rm RT}){\rm c

ISSN:0021-8995    

DOI:10.1002/app.1977.070210401

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

年代:1977

数据来源: WILEY

摘要:

AbstractAn electron‐microscopic diffraction technique has been described to record with ease diffraction patterns of cotton cellulose with 3–5 sec exposure time, which is suited to determined the crystallinity of cellulose. The % crystallinity index for cotton and ramie determined by this technique amounted to 81% and 85%, respectiv

ISSN:0021-8995    

DOI:10.1002/app.1977.070210402

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

年代:1977

数据来源: WILEY

摘要:

AbstractSodium bisulfite‐initiated polymerization of methyl methacrylate (MMA) in water medium was carried out in the absence and in the presence of cupric oxide and manganese dioxide using various initiator concentrations at various temperatures ranging from 30° to 60°C. It seems that the metal oxide–water interface plays an important role, as it has been found that both oxides accelerate the rate of polymerization. Cupric oxide was found to be more effective than manganese dioxide. The cupric oxide was found to have nearly the same catalytic effect as the cuprous oxide, and manganese dioxide was found to be somewhat more effective than titanium dioxide. The initial rate of polymerization increased from 2.3 × 10−5mole/(l.sec) to 3.4 × 10−4mole/(l.sec) and to 6.6 × 10−5mole/(l.sec) when the metal oxide concentration increased from 0 to 3 g/l. in case of cupric oxide and manganese dioxide, respectively. The initial rate of polymerization increased from 3.7 × 10−4mole/(l.sec) to 4.2 × 10−4mole/(l.sec) and from 7.2 × 10−5to 2.2 × 10−4mole/(l.sec) when the temperature was raised from 30° to 60°C in the presence of cupric oxide and manganese dioxide, (9 g/l.), respectively. Both the rate of polymerization and the number‐average molecular weights were found to increase with increase the monomer concentration; the rate values were higher while the number‐average molecular weights were lower in case of cupric oxide than in case of manganese dioxide. For example, the rate of polymerization increased from 2 × 10−5mole/(l.sec) to 8.1 × 10−5mole/(l.sec) and from 1.9 × 10−5mole/(l.sec) to 6.9 × 10−5mole/(l.sec); and the number‐average molecular weight increased from 0.7 × 105to 2.2 × 105and from 1.5 × 105to 4.9 × 105in the presence of cupric oxide and manganese dioxide (10 g/l.), respectively, when the monomer concentration was increased from 23.5 g to 94 g/1. water. The apparent energy of activation for the polymerization of methyl methacrylate in water medium between 40° and 50°C was found to be 0.8 and 4.3 kcal/mole when using cupri

ISSN:0021-8995    

DOI:10.1002/app.1977.070210403

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe thermal properties of some new higher molecular weight UV absorbers of the 2‐hydroxy‐benzophenone type have been studied using DTA and TG methods, and the obtained results have been compared with the thermal properties of 2‐hydroxy‐4‐n‐octyloxybenzophenone. The DTA, TG, and DTG curves and initial and maximum rate temperatures are given. The maximum rates of active decomposition and residues were als

ISSN:0021-8995    

DOI:10.1002/app.1977.070210404

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

年代:1977

数据来源: WILEY

摘要:

AbstractReverse osmosis (RO) composite polymer membranes were prepared from the organic monomers 3‐butenenitrile, propyleneimine, 4‐vinylpyridine, and allylamine by plasma polymerization in a radio‐frequency discharge. RO performance data (water flux and salt rejection) were obtained as a function of discharge power and deposition time. Membranes were subject to RO testing at 45°C for up to 150 hr to investigate membrane deterioration. No appreciable degradation was observed. Water flux increased significantly with time at 45°C, and improved salt rejection at 45°C was observed in mo

ISSN:0021-8995    

DOI:10.1002/app.1977.070210405

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

年代:1977

数据来源: WILEY

摘要:

AbstractA study of the effect of a series of fire retardants upon the crystallization behavior and morphology of polypropylene suggests three categories: (1) “Insolubilized nucleating additives”—these remain insolubilized at the premelting temperature of polypropylene, resulting in very high nucleation density which leads to numerous irresolveable small spherulites. (2) “Solubilized nucleating additives”—these are soluble at the premelting temperature of polypropylene but recrystallize before and/or simultaneously with the crystallization of polypropylene; the subsequent lower nucleation density results in medium‐size spherulites of a fairly heterogeneous distribution. (3) “Nonnucleating additives”—these remain solubilized in the polymer matrix throughout the course of crystallization of polypropylene. The nonnucleating nature and low viscosity of these solubilized additives results in large volume‐filling spherulites crystallized at a much faster growth than the u

ISSN:0021-8995    

DOI:10.1002/app.1977.070210406

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

年代:1977

数据来源: WILEY

摘要:

AbstractA series of polymer blends of commercial poly(vinyl chloride) (suspension‐polymerized powder) and an ethylene–vinyl acetate copolymer (EVA with 45 wt % VA) containing 2–10 wt % EVA were prepared by mixing at room temperature (0) and by milling at 160°C for 15 min (I) and then heat treated at 170°C for 20 min (II) and 40 min (III). Wide‐line NMR measurements for protons at room temperature show a broad band (assigned to PVC phase) and a superimposed narrow band (assigned to mobile EVA phase). The 0‐samples had a narrow band intensity corresponding to the total EVA content; the I‐samples had a less intense narrow band than expected, indicating that 2–3% EVA was included in the rigid PVC phase. Heat treatment for 20 min (II) and 40 min (III) increased the narrow band intensity toward the 0‐samples showing phase separation except for milled blends containing 2 wt % EVA, which had no separable narrow band and remained so. These results indicate that about 2 wt % EVA is compatible with the PVC phase and in equilibrium, while milled blends with more than 2 wt % E

ISSN:0021-8995    

DOI:10.1002/app.1977.070210407

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

年代:1977

数据来源: WILEY

摘要:

AbstractTensile mechanical properties of synthetic polymer–paper laminates were measured. The laminates were constructed by hot pressing a sandwich made of a sheet of paper between polymer films. There is complete penetration of the polymer inside the paper; no voids are left. Two different polymer matrices were used: poly(methyl methacrylate) and polyethylene. Several paper samples were utilized: an unoriented holocellulose paper (a strong paper), a highly oriented holocellulose paper, and an unoriented Whatman filter paper (a weak paper). The laminates contain from 0% to 50% of paper. Young's moduli and breaking strengths of the unoriented holocellulose paper laminates can be theoretically predicted from the properties of their constituents using laws of mixtures. The mechanical properties of the Whatman paper laminates are significantly higher than those predicted from the laws of mixtures. This indicates that the polymer increases the strength of the fiber‐to‐fiber bonds of the weaker sheets, although it does not change the bond strength of a stronger paper such as the holocellulose paper. For the oriented paper laminates, changes in Young's modulus with angle of measurement are explained by the composite materials theories if the angular variations in shear modulus are taken in to account. Changes in breaking strength with angle for the oriented laminates can be analyzed by Tsai and Azzi's theory for composite mate

ISSN:0021-8995    

DOI:10.1002/app.1977.070210408

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

年代:1977

数据来源: WILEY

摘要:

AbstractSolar energy‐absorbing coatings have been prepared from commercially available polymers of acrylonitrile and butadiene by coating films of these polymers on aluminum panels and heating them at 600°F. These coatings are more selective and, therefore, of higher theoretical efficiency than black paints presently used a solar thermal absorbers. Our results show that the selectivity of the absorber is a function of its thickness, and the optimum thickness is below 0.30 mils. This discovery opens a new line of possible research in the design of polymer films as solar energy absorbe

ISSN:0021-8995    

DOI:10.1002/app.1977.070210409

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe thermal degradation of poly(vinyl chloride) (PVC) was studied by following the rates of dehydrochlorination at temperatures between 180°C in pure nitrogen and air flow. Iron oxide accelerates the elimination of hydrogen chloride from PVC. The accelerating effect depends on the concentration of the oxide, and it has a maximum. This work tried to explain these behaviors. A mechanism of dehydrochlorination is suggested for polymer containing iron oxide

ISSN:0021-8995    

DOI:10.1002/app.1977.070210410

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

年代:1977

数据来源: WILEY