摘要:

AbstractThe effects of long term exposure to dry and humid environments on carbon‐epoxy and graphite‐epoxy composites have been studied. Filament wound Naval Ordnance Laboratory rings were fabricated in 1965 and were placed in dry, distilled water and sea water for 11 years. Moisture desorption tests were conducted in order to determine the water content of specimens exposed to the water environments, The effect of the history on moisture absorption characteristics was investigated by re‐exposure of partially and completely dried specimens to two different environments: distilled water at 60°C and 98% relative humidity at 60°C. The weight gain was measured and diffusion coefficients were calculated. Horizontal shear tests and flexural tests were performed on “wet” specimens (current properties) and on partially and completely dried specimens (residual properties). The shear strength of the carbon‐epoxy composites is degraded by the exposure while that of the graphite‐epoxy composite is slightly increased. The composite flexural strengths are not degraded by the exposure. These results are discussed in terms o

ISSN:0032-3888    

DOI:10.1002/pen.760180502

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe relationship between synthesis factors and the impact resistance of high impact polystyrene (HIPS) is investigated in the light of its morphology and dynamic mechanical properties. A decrease in polymerization temperature results in an increase inTg, melt viscosity and molecular weight of the continuous polystyrene phase as characterized by gel permeation chromatography. The separated, occluded polystyrene phase however shows an invariantTgsuggesting that the grafting and/or crosslinking effect overweighs the molecular weight effect. The observed high impact strength has been correlated with the homogeneous 1‐2 μ rubber particle size distribution, a comparatively sharp rubberTgtransition at lower temperature, and a much lower occluded polystyrene content in the dispersed pha

ISSN:0032-3888    

DOI:10.1002/pen.760180503

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractData are presented for the thicknessH∞of liquid coating entrained by continuous withdrawal at speed U of a wire of radius R from the free surface of a large bath. For Newtonian fluids of viscosity μ, density ρ and surface tension σ, the data are carried out to coating speeds beyond the applicability of current theories, to Capillary numbers of nearly one hundred. In the high speed range the data, which cover several orders of magnitude in viscosity, can be well represented by the equation\documentclass{article}\pagestyle{empty}\begin{document}$$ D_\infty = H_\infty \left( {\frac{{\rho g}}{\sigma }} \right)^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} = 0.15\left( {\frac{{U\mu }}{\sigma }} \right)^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} $$\end{document}forUμ/σ=Nca>3. All data presented are at an essentially constant Goucher number of 0.08, whereNGo≡R(ρg/2σ)1/2. Data for viscoelastic fluids show phenomena quite distinct, qualitatively and quantitatively, from Newtonian observations. In particular, strongly elastic fluids show a markedly reduced ability to be entrained onto the wire. Further, the coating thickness appears to become independent of Capillary number at

ISSN:0032-3888    

DOI:10.1002/pen.760180504

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe deformation behavior of block copolymers is examined. Interdomain bridges, loops, cilia and floating chains in spherical, cylindrical and lamellar domain morphologies are considered. In the theoretical model, which is analogous to the “three‐chain” model in classical rubber elasticity theory, interdomain chains are confined between pairs of infinite, parallel impenetrable walls constructed at the surfaces of nearest neighbor domains. The domains are taken as undeformable. The quantities which are calculated are: the Young's modulus; the partial molar elastic free energy of swelling; and the stress‐strain relation for simple ex

ISSN:0032-3888    

DOI:10.1002/pen.760180505

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractPolystyrene powder was compacted in a cylindrical die at constant compaction speed. Compaction was found to be influenced by test temperature, compaction speed and void fraction of the powder bed. The stress reduction behavior of an axial stress σ1and a radial stress σ2was observed at constant void fraction after compaction. The stress reduction thus obtained was interpretable by adopting an octahedral normal stress σoctand an octahedral shear stress τoctwhich were converted from σ1and σ2. This behavior was attributable to the deformation of polystyrene around contact points and to a sliding mechanism between particles. It was ascertained that the relation between a shear stress τ and a normal stress σ obtained on compaction differed from that obtained in shear by a mechanism involving movement between polystyrene pa

ISSN:0032-3888    

DOI:10.1002/pen.760180506

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe viscosity‐shear rate functions for polysulfone (PSF) condensates ranging from 0.4RV to 0.95RV were determined using capillary rheometry, The most probable distribution of molecular weights of these resins allowed facile comparison with the polydisperse Bueche theory for viscosity, The agreement in shape of the viscosity function with theory was good but the data were displaced by a factor of 3 to 4 to higher reduced shear rate, a fairly common occurrence for melts. The high absolute value of PSF viscosity was explained with existing empirical correlations as a combination of low critical molecular weight and strong intermolecular interactions. The temperature dependence of viscosity was found to be close to that for polystyrene in the temperature range,Tg+ 90 toTg+ 190°C. The die swell, end corrections, and melt fracture characteristics were also determined. The latter was found to occur at a constant wall shear stress of about 6 × 106dynes/cm2while the die swell and end corrections were found to be sm

ISSN:0032-3888    

DOI:10.1002/pen.760180507

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractModification of a standard differential scanning calorimeter to allow irradiation of the sample material with ultraviolet light allows one to follow the course of polymerization of photocurable polymer systems. The rate and heat of polymerization are readily determined by this technique which gives it a number of very useful applications. As a quality control tool, one can use the heat of polymerization to monitor the number of reactive sites present in the prepolymer thus achieving a degree of control on the ultimate properties of the cured film. Similarly, analysis of a cured film will indicate the presence of any uncured material, thus allowing one to adjust curing conditions accordingly. The technique has numerous other applications in the study of photocurable resins, such as evaluation of initiator efficiencies, optimization of curing parameters (initiator concentration, lamp design), and the sensitivity of prepolymers to oxygen and wavelength.

ISSN:0032-3888    

DOI:10.1002/pen.760180508

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractTemperature measurements were made on the adiabatic polymerization of three urethane systems; two casting formulations, one thermoplastic and the other thermosetting, and a commercial reaction injection molding (RIM) formulation with a 10 second gel time. The data were found to fit a simple nth order overall kinetic expression. These kinetic and heat of reaction results were used to model heat transfer in a 3.8 cm diameter cylinder with an isothermal wall. Experimental temperature profiles for the two casting urethanes were in good agreement with predictions. The kinetic data on the RIM material was used to model temperature profiles1 in 3 and 6 mm thick plaque molds. Experimental measurements of temperature near the mold center agreed with the model. Temperatures measured near the wall were higher due to failure of the isothermal wall assumption.

ISSN:0032-3888    

DOI:10.1002/pen.760180509

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractA class of mathematical models for sorption of swelling solvents in glassy polymers is analyzed. The essential features of these models are the explicit consideration of the kinetics of swelling and of the driving force for swelling. It is shown that, even when all other elementary phenomena are modeled in the simplest possible way, all the experimentally observed features of the processes considered are correctly predicted.

ISSN:0032-3888    

DOI:10.1002/pen.760180510

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe strength and impact resistance of short fiber reinforced thermoplastics are greatly affected by the nature of the stress transfer interface which in turn is influenced by physico‐chemical and geometric factors. The geometric factors are controlled by the compounding technology used to manufacture the composite. This paper describes the use of several compounding technologies and a method used to infer the effectiveness of those technologies from studies of molded part mechanical properties and glass fiber length distributions. Resin systems studied were acetal copolymer, polybutylene terephalate, and nylon 6,

ISSN:0032-3888    

DOI:10.1002/pen.760180511

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY