摘要:

AbstractBurning rates of glass‐reinforced poly(methyl methacrylate) candles were measured under limiting conditions using an oxygen index apparatus modified to allow weighing of the candle as it burns. The limiting oxygen index was found to increase slightly with increasing concentration of glass in the candle for all samples tested. Burning rates were found to be a function of both glass concentration and orientation with respect to the propagating flame front. The burning rates of candles constructed from randomly oriented glass mats were found to increase with mat concentration by a factor of nearly 3 as mat content was increased to 70% by volume. The burning rates of candles constructed with unidirectionally oriented fibers, parallel to the flame propagation direction, were found to decrease by a factor of 2 as the glass concentration increased to 40% by volume. Erratic burning rates were observed for candles constructed with oriented fibers perpendicular to the flame propagation direction. These results are correlated by extension of existing thermally thin flame spread theories through consideration of composite solid‐state energetics and the relative tendencies of the glass reinforcements to act as wicks for supplying the flame with degraded polymer liq

ISSN:0021-8995    

DOI:10.1002/app.1977.070210201

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

年代:1977

数据来源: WILEY

摘要:

AbstractMeasurements are reported on the acoustic attenuation and velocity of dry and wet samples of poly(methyl methacrylate) over a temperature range of 5° to 70°C and over a frequency range of 5 to 35 MHz. Lowering of the glass transition temperature with increase in water content was reflected in an increase in the acoustic attenuation and a lowering of the velocity at high temperature. Comparison of the infrared spectra of wet and dry thin films indicates that water exhibits spectroscopic characteristics of isolated rather than highly clustered molecules. A study of the temperature dependence of the diffusion coefficient of water into the polymer matrix provided an activation energy for the migration process. The data suggest that water plasticizes poly(methyl methacrylate) via specific local interactions with the backbon

ISSN:0021-8995    

DOI:10.1002/app.1977.070210202

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

年代:1977

数据来源: WILEY

摘要:

AbstractThermal analysis of cotton samples grafted with acrylamide, acrylonitrile, methyl acrylate, and methyl methacrylate individually and in mixture compositions has been carried out. Additional endothermic peaks in the DTA curves characteristic of the polymers grafted were observed. Graft copolymerization of acrylamide and acrylonitrile makes cotton thermally more stable, while in the case of methyl acrylate‐and methyl methacrylate‐grafted cottons, the initial decomposition starts at higher temperatures, but subsequent decomposition is faster and the overall thermal stability is lowered. In the case of binary mixtures of acrylamide and acrylonitrile, inception of decomposition starts earlier, but subsequent decomposition takes place at much higher temperatures than for individual monomer‐grafted cottons. Interaction between monomers during grafting is indicated. When fabric samples containing polyacrylamide grafts are methylolated and subsequently cross‐linked, there is a reduction in the thermal stability of the treated

ISSN:0021-8995    

DOI:10.1002/app.1977.070210203

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe behavior of ions in a cellulose acetate membrane was discussed from the standpoint of mobilities obtained from the membrane potentials. The mobilities of univalent ions larger in radius or divalent ions relative to Na+ion mobility in the membrane are much different from those in aqueous solutions. The order of the mobilities of ions in the membrane is shown quantitatively. The mobilities of the ions with radii larger than a certain value in the membrane decrease with increase in their size. This could be explained by the physical friction between the ion and the membrane wall. This friction is of importance as the ionic radius comes close to the intermolecular gaps between polymer chains. The mobilities of Na+anyd 1−ions in the membrane are (2–3) × 10−7cm2/sec‐V and are about three to four orders of magnitude less than those in aqueous s

ISSN:0021-8995    

DOI:10.1002/app.1977.070210204

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

年代:1977

数据来源: WILEY

摘要:

AbstractAn experimental study was carried out to investigate the moldability of polymer blends which form two phases in the molten state and the effect of mixing on the morphology and mechanical porperties of molded specimens. Blends of polystyrene with polypropylene and blends of polystyrene with high‐density polyethylene were used for this study. A plunger‐type injection molding machine (Van Dorn) was employed for molding specimens. To improve the mixing performance of the plunger machine, a Static Mixer (Kenics Corp., Super Nozzle) was installed between the heating cylinder and the sprue. A number of different molding conditions (injection pressure, temperature, injection time, cooling time) were varied, and molded specimens were collected under each molding condition. The specimens were used for studying the degree of dispersion in the blends and for determining the mechanical properties. A differential thermal analysis (DTA) experiment was also carried out to determine the degree of dispersion of the blends in molded specimens. It was found that a linear correlation exists between the blend composition and thermal spectra area of the blends tes

ISSN:0021-8995    

DOI:10.1002/app.1977.070210205

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe effect of the degree of chemical crosslinking of cellulose with two bifunctional crosslinking agents dimethylol ethylene are (DMEU) and bis (hydroxyethyl) sulfur (BHES), on the equilibrium absorption of the direct dyes Chlorazol Sky Blue FF (C.I. Direct Blue 1) and Chrysophenine G (C.I. Direct Yellow 12) has been reported. The results show the increasing reduction of equilibrium dye absorption with increasing crosslink density. However, the maximum loss of absorption is about less than half of the amount absorbed by uncrosslinked cellulose. The results have been interpreted by reference to the parameters affecting the free energy of dyeing and the relevant models (pore model and gel model) available for explaining the fine structure of swollen cellulose.

ISSN:0021-8995    

DOI:10.1002/app.1977.070210206

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe effect of crosslinking in the dry state on the rate of dyeing of cellophane with two direct dyes, Chrysophenine G and Chlorazol Sky Blue FF, has been studied. Dimethylolethyleneurea and bis(hydroxyethyl) sulfone were the crosslinking agents. It was found that the rate of dyeing was reduced at high degree of crosslinking by more than 90%, whereas the amount of dye absorbed at equilibrium was reduced by only 40%. It was concluded that the major factor in the practical undyeability of the crosslinked cellulose fibers in commerce is the reduction of the rate of dyeing rather than that of the absorption at final equilibrium. The average diffusivities of the dyes in the cellulose film were calculated from the rate data. The diffusion coefficients as functions of the dye concentration in the films were estimated from the diffusivity values. The two models of swollen cellulose, the pore model and the gel model, were applied to explain the effect of crosslinking on the diffusion coefficients. The pore model offers a satisfactory explanation by assuming that crosslinking reduces the average pore diameter and therefore increases the drag and also the tortuosity. The gel model offers an equally satisfactory explanation by assuming that crosslinking reduces the free volume by increasing the rigidity and concentration of the cellulose chains in the cellulose gel.

ISSN:0021-8995    

DOI:10.1002/app.1977.070210207

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

年代:1977

数据来源: WILEY

摘要:

AbstractA computerized and automated torsional pendulum has been used to characterize amorphous poly(methyl methacrylates) at about 1 Hz in the temperature sequence 473° → 93° → 473°K. The effects of thermal prehistory, temperature cycling, water content, and tacticity are demonstrated. In particular, a comparison of the out‐of‐phase shear modulus (G″) versus temperature for “syndiotactic,” “atactic,” and “isotactic” polymer specimens shows that the intensity of the glassy‐state β loss peak decreases with increasing isotactic content while the temperature of its location remains the same. Extrapolation suggests that completely isotactic polymer would not display a β loss peak. The shape and location of theG″data at low temperatures indicate that the basic mechanism of the β process is the same for the three polymer samples and support the validity of the extrapolation. The effect of tacticity is reflected also in the glass transition region; the isotactic sample has itsTgabout 65°C lower with greater intensi

ISSN:0021-8995    

DOI:10.1002/app.1977.070210208

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

年代:1977

数据来源: WILEY

摘要:

AbstractStarch‐g‐polystyrene copolymers have been prepared by the simultaneous60Co‐irradiation of starch–styrene mixtures, and copolymers have been characterized with respect to weight per cent polystyrene (% add‐on) and also the molecular weight and molecular weight distribution of polystyrene grafts. In a typical polymerization, 4 g each of starch and styrene were blended with 1 ml water and 1.5 ml of an organic solvent; the resulting semisolid paste was irradiated to a total dose of 1 Mrad. With ethylene glycol, acetonitrile, ethanol, methanol, acetone, and dimethylformamide as the organic solvent, values for % add‐on ranged from 24% to 29%. The highest % add‐on (43%) and the highest conversion of styrene to grafted polymer (76%) were obtained when the organic solvent was omitted, and water alone was used. When water was also omitted, polymerization of styrene was negligible; however, graft copolymer was formed in the absence of water when either ethylene glycol or ethanol was added. Attempts were unsuccessful to achieve a % add‐on greater than 43% by doubling the amount of styrene in the polymerization recipe. Mixtures of equal weights of starch and styrene are relatively nonvicious, but these mixtures thicken when either water or ethylene glycol is blended in. Reasons for this thickening action and the possible influence of thickening on the graft polymerization reactio

ISSN:0021-8995    

DOI:10.1002/app.1977.070210209

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

年代:1977

数据来源: WILEY

摘要:

AbstractThree aspects of vapor pressure osmometry were examined: drop size, solute volatility, and the constancy of the calibration factor. It was shown that there is a drop size effect which is dependent on the solute concentration. Solutes having vapor pressures as low as 0.3 mm Hg under the operating conditions were found to give unsatisfactory results. The calibration factor was determined using eight compounds in the molecular weight range of 128 to 883 in chloroform, toluene, and methyl ethyl ketone at several temperatures; a small but significant dependence of the calibration factor on molecular weight was demonstrated. The results fitted, with a high degree of accuracy, the relation logM̄n=a+blog (ΔV/C)C= 0, whereaandbare constants for a given solvent/temperature combination. However, measurements with standard polystyrene samples, using extrapolations of this relationship to higher molecular weights, revealed considerable discrepancies in results for the one compound under different solvent/temperature combination

ISSN:0021-8995    

DOI:10.1002/app.1977.070210210

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

年代:1977

数据来源: WILEY