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  • 1
    Electronic Resource
    Electronic Resource
    Gas-induced damage in elastomeric composites (1990)
    Springer
    Journal of materials science 25 (1990), S. 3017-3023 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Gases may induce extensive and irreversible damage in elastomers when they are allowed to escape from the polymeric matrix. The damage is most evident as internal lacerations and also as an overall change in certain mechanical properties. The damage process, commonly termed explosive decompression failure, is really confined to gas-polymer systems which are initially equilibrated at high pneumatic stresses; greater than 107 Pa. Two interrelated facets of this phenomenon are described in the context of elastomeric composites with particular emphasis on the role of interfacial quality. The results of an optical examination of the internal cracks found during a typical gas-induced rupture cycle are described. The system is a commercial silicone elastomer-glass filler composite where the fillers have been surface modified in order to alter the adhesive strength of the interface. The data indicate that the filler particles significantly modify the stress fields in the elastomer during gas-induced rupture. Essentially, the fillers suppress the development of the characteristic large scale axially symmetrical stress fields in the composites. This visual assessment of the damage is then related to the deterioration in certain mechanical properties of this current system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584920
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  • 2
    Electronic Resource
    Electronic Resource
    Simulation of the fracture behavior of elastomeric composites: Mechanical interactions at material interfaces (1994)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 15 (1994), S. 83-90 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The fracture mechanics of multilayered elastomeric composites was simulated by the Blister Test using a polyurethane (PU)/A1 base plate interfacial assembly. In the various systems studies, and hard or soft intrposed layer (∼50 μm) separated the bulk matrix (∼ 1000 μm) from the metal counterface, with a hard-to-soft modules ratio of 1.70. Debonding was performed at a constant pressurization rate 1 × 10-8 m3/s corresponding to an average delamination rate of 0.25 m/s. Lateral hardening of the composite modules (negative transversal gradient of modulus) improved the fracture resistance (by 35%) at the material interface, in conformance with analytical predictions. Particle-dispersed and liquid-doped systems exhibited a sharp attenuation (40 to 90%) in the debond pressure. The latter results were substantiated by subjective assessement using optical microscopy, and were found consistent with stress concentration and weak conhesive fracture at the resin-substrate interface, respectively.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750150112
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  • 3
    Electronic Resource
    Electronic Resource
    Rotary injection reaction injection molding (RI-RIM). Part I: Basic design features (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 162-174 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper describes the basic design features of a new reaction injection molding (RIM) processing device, Rotary Injection RIM (RI-RIM). The new design includes a novel mixing concept which furnishes high intermaterial contact area upon shear imposed rotary injection of the RIM components for effective in situ polymerization. This system operates in low pressure and laminar flow conditions, as opposed to the high pressure and turbulent flow, found in conventional RIM systems. The mixing process is described and quantified in terms of the various forces which govern the injection process. A progressive diminution in the average size of the dispersions generated is found with increasing rate of shear, continuous-phase viscosity, and injection rate. These results are compared with those expected from traditional shear mixing (bulk convective shearing) under comparable conditions and the current system found to be more efficacious. Reaction molding experiments with RI-RIM using a model polyurethane system are described and the influence of operating conditions on the mechanical properties of the finished moldings are elucidated. A detectable change in the morphology of the system is observed following increase in the total shear strain imparted to the initial mix of the multiphase reactants. It is suggested that the observed change is affected by a segregation between the components of the segmented polymer.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760300306
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  • 4
    Electronic Resource
    Electronic Resource
    Rotary injection reaction injection molding (RI-RIM). Part II: Interfacial segregation of release systems (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 175-186 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper describes the shear imposed interfacial segregation of release systems for the facilitated attenuation of polyurethane (PU) adhesion to metal coun-terfaces using a RI-RIM system. It is shown that the migration rate of the dispersed release additives due to a shear imposed stress in the resin fluid is much greater than that arising from Fickian diffusion, thereby removing a vital constraint from conventional practice. The novel rotary injection RIM system is presented to simulate the on-line injection and shear induced interfacial segregation in model PU/abherent systems. A wide range of recipes comprising single (liquids or solids) and multicomponent (liquid-liquid and solid-liquid) release materials were injected into the polymerizing resin mixture to provide cohesively weak and friable “particle” boundary layer assemblies at the PU/metal interface. An instrumented Blister Test was employed to evaluate the quality of the molded interfaces in terms of adhesion and the concentration distribution of the injected species in the final cured moldings was determined through high pressure liquid chromatography (HPLC). A comparison of the results on the shear modified and the compounded interfaces confirm an accentuated lateral migration of the additives to the interface resulting in an appreciable diminution in the adhesion of the system. Finally, transport models are suggested to account for the observed augmented transport.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760300307
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  • 5
    Electronic Resource
    Electronic Resource
    Sorption and dilation of silicone elastomer composites at high gas pressures: The role of interfacial quality (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 959-969 
    Details
    ISSN: 0887-6266
    Keywords: composites of silicone elastomer and glass blends, interfacial quality and sorption of gas in ; sorption of gas in glass bead filled silicone elastomer, interfacial quality and dilation ; interfacial quality and gas sorption in silicone elastomer composites ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In elastomers the crosslink density, the presence of filler particles, and the volumetric confinement toward sorptive dilation can influence the extent of gas mass uptake. In this study the effects of filler particles on the high-pressure gas mass sorption and the volumetric dilation of a silicone elastomer matrix has been investigated. Glass beads, ca. 30 μm radii, with different surface treatments were incorporated as inclusions in various specimens at relatively low concentrations of ca. 10% by volume. The high-pressure gases used were N2 and CO2 up to a maximum ambient pressure of ca. 25 MPa at ca. 20°C and 42°C, respectively. The gas mass sorption was determined by a vibrating reed technique. The sorptive dilation was measured by an ultrasonic transducer operating as a displacement probe. In certain systems the absorbed CO2 gas was able to disrupt the internal interfaces. This led to an increased gas mass uptake in the corrupted specimen. The N2 gas did not affect the interfacial bonds. The amount of penetrant uptake was found generally to be reduced when the internal interfaces were not disrupted. The presence of various internal interfaces restrained the sorptive dilation of the elastomeric matrix. These hindrances to the natural sorptive dilation of the elastomer network suppressed the extent of the gas sorption process. This effect has also been investigated separately in detail using model ‘poker chip’ type of specimens of various aspect ratios. The sorptive dilational characteristics have been correlated with the mechanical properties of similar specimens. The influence of an almost complete volumetric confinement on the gas sorption capacity of the silicone elastomer specimen has also been studied. © 1992 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1992.090300904
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  • 6
    Electronic Resource
    Electronic Resource
    Interaction of CO2 gas with silicone elastomer at high ambient pressures (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 989-999 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Interaction of high-pressure CO2 gas with a silicone elastomer, and to a lesser extent, with a nitrile rubber and a PTFE have been investigated. Sorptive dilations of the polymers were measured with the help of custom-made piezoelectric ultrasonic transducers under gas pressures of up to ca. 22 MPa at 42°C. The gas mass sorption was determined by a vibrating reed probe. For the silicone elastomer system the dilation isotherm mimics the sorption isotherm. The partial molar volume (PMV) of the absorbed CO2 gas in the silicone elastomer has been computed. A significant drop in the PMV value is observed when the CO2 gas becomes supercritical. In the transition region, the transmission of ultrasonic signals through the specimen indicated the formation of discrete small (estimated as about 60 μm in diameter) high density zones of CO2 in the rubber matrix. The plasticization effects of the absorbed high pressure CO2 gas have been identified from the interpretation of the changes in the acoustic longitudinal modulus obtained from ultrasonic transmission measurements. The effects of rapid gas decompression on the structural integrity of the various polymers have also been determined. Significant inflation of certain specimens occur toward the latter stages of the decompression cycle. The initiation and development of internal cracks or bubbles was followed by monitoring the ultrasonic signal attenuation.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1991.090290809
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