摘要:

AbstractThis paper reviews the literature concerning the measurement of friction coefficients (μ) for elastomers and summarizes our data measured under static or breakaway conditions against epoxy painted steel using ∼ 176 psi contact pressure. Although largely related to missile launch system applications, the μ values presented are specific for interface pairs, normal loading force, and speed. Therefore, this article should serve as a starting point for those requiring specific friction data for selected elastom

ISSN:0021-8995    

DOI:10.1002/app.1988.070360201

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

年代:1988

数据来源: WILEY

摘要:

AbstractSilk cloth was dyed successfully by dipping it in a gold hydrosol which was prepared in the presence of a cationic surfactant, stearyltrimethylammonium chloride (SC). The color of thus dyed silk cloths is due to colloidal gold particles adsorbed on silk fibers and varies from reddish purple to dark purple according to the periods of dipping time and the amounts of SC in the gold hydrosol used. The mechanism for the adsorption of colloidal gold on the silk fibers is proposed.

ISSN:0021-8995    

DOI:10.1002/app.1988.070360202

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

年代:1988

数据来源: WILEY

摘要:

AbstractThis study examines the application of infrared (IR) spectrometry to the determination of polypropylene (PP) stereoregularity. The use of the absorption bands at 998 cm−1and 841 cm−1as indices of isotacticity and bands at 1167 cm−1and 973 cm−1as internal references have been explored. Calibration curves relating various absorption ratios to isotacticity as measured by13C nuclear magnetic resonance are reported. The ratios A998/A973and A841/A973are the most useful and provide linear correlations with isotacticity. The effect of instrument type on the calibration has been investigated for both dispersive and Fourier transform type IR spectrometers. For samples annealed at room temperature the average of measurements on the same set of PP films by five instruments provide the calibrations: A998/A973= 1.08 ± 0.02 (mm)−0.15 ± 0.03; and A841/A973= 0.84 ± 0.06 (mm)−0.04 ± 0.02. High temperature annealing increases the crystallinity of the samples and the corresponding value of the absorption ratio but is not necessary for obtaining reproducible cal

ISSN:0021-8995    

DOI:10.1002/app.1988.070360203

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

年代:1988

数据来源: WILEY

摘要:

AbstractPolymerization of methyl methacrylate and methyl, ethyl, andn‐butyl acrylates was carried out in a wide range of dose rate, 10–106rad/s by γ‐ray and electron beam irradiation. With methyl methacrylate andn‐butyl acrylate, and steady‐state kinetics in radical polymerization was maintained in an entire dose rate range at about the initial stage of the polymerization. With methyl and ethyl acrylates, the rate of polymerization increased much less markedly than expected from the square root law and the molecular weight decreased much less gradually with dose rate. In all these monomers it was found that autoacceleration of the rate of polymerization due to gel effect becomes vague at high dose rate. Two‐peaked molecular weight distribution was observed for the polymers obtained at hi

ISSN:0021-8995    

DOI:10.1002/app.1988.070360204

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe aim of the present work was to investigate the effect of fiber pretreatment, fiber content, coating concentration, and also pretreatment procedure on the tensile properties of asbestos‐epoxy composites. These composites comprise materials of considerable industrial importance. Asbestos exhibits unique properties. Occasionally it is difficult to disperse asbestos properly because the individual fibrils are very small and tend to agglomerate, but there is no evidence that asbestos is not easily wetted out by all systems. However, the higher potential aspect ratio of asbestos fibers compared with glass is not always realized in practice because the fibers break in length to fine diameters. Accordingly, the very considerable new surface created makes successful wetting difficult or impossible. For this reason, asbestos was precoated with a well adhered film of poly(hexamethylene adipamide), a polymer especially compatible with the epoxy phase. The pretreatment procedure followed was based on the principles of the interfacial polymerization involving the serial application to the asbestos of two immiscible solutions of hexamethylenediamine and adipoyl chloride. Accordingly, epoxy‐nylon‐chrysotile composites were made while varying pretreated fiber volume fraction, concentration of the polyamide coating, and reactants application order. Results obtained from tensile measurements proved quite interesting: Relative modulus of elasticity and relative ultimate strength exhibited a similar behavior when correlated with the ratio of polyamide to asbestos concentration. The corresponding curves pass through distinct maxima at which severe improvement of the material performance is effected. A thorough interpretation of these results is also inc

ISSN:0021-8995    

DOI:10.1002/app.1988.070360205

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe crystallization and polymerization behavior of a crystalline LaRC‐TPI powder at elevated temperatures have been studied. The characterization methods include differential scanning calorimetry and the measurements of inherent viscosity, ηinh, and viscoelastic properties of the fully imidized samples. The as‐Received material possesses an initial crystal melting peak temperature of 272°C. For the material annealed at temperatures below 320°C, a semicrystalline polymer can be obtained. On the other hand, a purely amorphous structure is realized in the samples annealed at temperatures above 320°C. Isothermal crystallization kinetics are studied by means of the simple. Avrami equation. The likely nucleation path is attributed as an intermolecular oligomer nucleation type. The isothermal polymerization behavior is quantified by inherent viscosity measurements. A single cure is found to correlate values ofTgand ηinhfor samples experiencing different thermal histories. Fully imidized amorphous and semicrystalline LaRC‐TPI samples are successfully molded based on the information obtained from thermal analyses. The viscoelastic properties of these samples are als

ISSN:0021-8995    

DOI:10.1002/app.1988.070360206

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe thermal and crystallization behavior of blends of glass fiber reinforced polyphenylene sulfide (PPS) with polyethylene terephthalate (PET) has been reported. The blends showed two overlapping melting peaks and two separate crystallization peaks. The heat of crystallization of PPS was found to decrease continuously with increasing PET content, whereas the heat of crystallization of PET was found to increase with increasing PPS content. This indicates that the degree of crystallinity of PPS is reduced whereas that of PET is increased as a result of blending. It is interesting to note that the combined heats of fusion of the blends were marginally higher than those calculated by proportional additivity rule in spite of the drop in the heat of crystallization of PPS. The temperature onset of crystallization of PET in the blends shifted to higher temperature whereas there was no significant change in the crystallization temperature of PPS. The increase in the temperature of crystallization of PET indicates enhanced nucleation. The isothermal crystallization studies of the component polymers revealed that both the component polymers crystallized at a relatively faster rate in the blend. The crystallization rate of PPS was found to increase significantly with increasing PET content. A significant increase in the rate of crystallization of PET was also observed in the blends. The acceleration of crystallization rate of PET in the blends was more pronounced as compared to that of PPS. The acceleration in the PET crystallization rate was attributed to the presence of glass fibers and crystallized PPS.

ISSN:0021-8995    

DOI:10.1002/app.1988.070360207

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

年代:1988

数据来源: WILEY

摘要:

AbstractWe present here a method for superposing creep measurements on polymer concrete (PC), taken at different temperatures, imposed stresses, and resin contents, onto master curves, which describe the respective responses of various PC systems and their resin binders, to compressive, tensile, and flexural loads. This treatment is extended to systems reinforced with chopped glass fiber and montmorillonite (MMT). The general applicability of this superposition is tested with creep measurements by other investigators under tensile, compressive, and flexural loads. The results make it possible to predict the long‐term creep behavior of unfilled as well as reinforced glassy polymer systems at different temperatures and load conditions from limited, short‐term data. Success of the multiple superposition suggests a generalized constitutive equation, which describes the creep compliance of these systems as a product of separable functions of each parameter in the form of shift factors for temperature (αT), stress (ασ), resin content (αυ), fiber reinforcement (αF), and MMT reinforcement (αM):J(PC) =JrαTασαυαFαMtm, whereJris an appropriately chosen reference creep compliance. The time exponentmdoes not depend on the chemical nature of t

ISSN:0021-8995    

DOI:10.1002/app.1988.070360208

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

年代:1988

数据来源: WILEY

摘要:

AbstractTwo types of interpenetrating polymer networks based on polyamide (nylon 12) and a polyurethane formed in the polyamide melt were prepared. The first type (A), which could be regarded as a semi‐2‐IPN, consisted of a polyurethane component crosslinked with trimethylolpropane whereas for the second type (B), which would meet the definition of a thermoplastic IPN, the polyurethane component was chain‐extended with butane‐1,4‐diol only. The phase morphologies of these IPNs were investigated using electron microscopy, dynamic mechanical analysis, tensile testing, and sonic velocity measurements. Electron micrographs were compared by using the conventional TEM technique and a Robinson‐type backscattered electron detector in combination with a SEM. It was concluded that the materials are phase separated, but with a fine continuous‐dispersed phase structure. For a 44 wt % polyurethane IPN a cocontinuous phase structure with a subcellular texture was indicated. One physically blended sample was compared with the analogous IP

ISSN:0021-8995    

DOI:10.1002/app.1988.070360209

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe paper presents studies on the influence of temperature and atmosphere composition on the thermal degradation products evolved from flexible polyurethane foam. The experiments have been carried on within the temperature range 200–700°C in air atmosphere and oxygen–nitrogen–helium mixtures. The main volatile toxic products and weight losses during thermal degradation of the polyurethane foam have been determined. The test results have been presented graph

ISSN:0021-8995    

DOI:10.1002/app.1988.070360210

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

年代:1988

数据来源: WILEY