The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
M.s. Hamada - One of the best experts on this subject based on the ideXlab platform.
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A Bayesian analysis of the Compression Set and stress–strain behavior in a thermally aged silicone foam
Polymer Degradation and Stability, 2006Co-Authors: J. E. Coons, M.d. Mckay, M.s. HamadaAbstract:Data obtained from an archived nine-year aging study on S5370 foam were used to develop Compression Set and stress–strain aging models. Compression Set was characterized using a first order kinetic model and the stress–strain relationship was analyzed using a material model previously described by Rusch for flexible foams. The models were fitted to data from the aging study using Bayesian methods, which easily accommodate uncertainties in the test conditions and provide probability distributions of the model parameters. The parameter distributions were sampled using a Markov chain Monte Carlo algorithm and incorporated to effect prediction intervals and compared to data obtained from independent studies for the purpose of validation. Compression Set data from the short time study of Patel and Skinner are shown to predict significantly higher Compression Sets, which are attributed to additional crosslinking reactions and other phenomena that do not dominate the long term aging behavior. Using data from the nine-year study, the time period required to achieve a given Compression Set at 25 °C is increased by 20 years or more over the predictions of Patel and Skinner. The activation energy applicable near room temperature is similar to that reported by Patel and Skinner, which is consistent with numerous physical and catalyzed chemical mechanisms. Finally, load retention predictions from the stress–strain aging model agree with independent studies at test gaps that are larger than or equal to a zero gradient test gap limit.
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a bayesian analysis of the Compression Set and stress strain behavior in a thermally aged silicone foam
Polymer Degradation and Stability, 2006Co-Authors: J. E. Coons, M.d. Mckay, M.s. HamadaAbstract:Data obtained from an archived nine-year aging study on S5370 foam were used to develop Compression Set and stress–strain aging models. Compression Set was characterized using a first order kinetic model and the stress–strain relationship was analyzed using a material model previously described by Rusch for flexible foams. The models were fitted to data from the aging study using Bayesian methods, which easily accommodate uncertainties in the test conditions and provide probability distributions of the model parameters. The parameter distributions were sampled using a Markov chain Monte Carlo algorithm and incorporated to effect prediction intervals and compared to data obtained from independent studies for the purpose of validation. Compression Set data from the short time study of Patel and Skinner are shown to predict significantly higher Compression Sets, which are attributed to additional crosslinking reactions and other phenomena that do not dominate the long term aging behavior. Using data from the nine-year study, the time period required to achieve a given Compression Set at 25 °C is increased by 20 years or more over the predictions of Patel and Skinner. The activation energy applicable near room temperature is similar to that reported by Patel and Skinner, which is consistent with numerous physical and catalyzed chemical mechanisms. Finally, load retention predictions from the stress–strain aging model agree with independent studies at test gaps that are larger than or equal to a zero gradient test gap limit.
Martin Strangwood - One of the best experts on this subject based on the ideXlab platform.
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Compression Set of thermoplastic polyurethane under different thermal–mechanical-moisture conditions
Polymer Degradation and Stability, 2011Co-Authors: Carl Slater, C. L. Davis, Martin StrangwoodAbstract:Abstract Elastomeric materials are used in the manufacture of structural dampeners due to their high damping coefficient and ease of production. However, elastomers, and in particular thermoplastic polyurethanes (TPU), are susceptible to degradation from environmental conditions. Samples of TPU were investigated, in terms of their mechanical properties, under the influence of four factors; time (up to 10 weeks thermal exposure), temperature (20–80 °C), strain (10% and 25%) and moisture (pre-soak/testing in water). Compression, hardness and Compression Set tests were used to determine the major contributors to the degradation process. It was found that pure thermal loading at 70 °C for 10 weeks did not result in any changes in material properties, other than an initial drying phase causing an increase in hardness of 2–3 Shore D. The Compression Set values were found to be heavily dependent on the test temperature, with a significant increase in Compression Set being seen between 70 and 80 °C. The presence of water (introduced by testing in water) acted as a plasticiser and resulted in a larger amount of Compression Set, than testing in the absence of water. The level of Compression Set was shown to be insensitive to the strain level. Overall, it was found, for the conditions tested, that temperature was the major driving force behind the Compression Set of the TPU material.
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Compression Set of thermoplastic polyurethane under different thermal mechanical moisture conditions
Polymer Degradation and Stability, 2011Co-Authors: Carl Slater, C. L. Davis, Martin StrangwoodAbstract:Abstract Elastomeric materials are used in the manufacture of structural dampeners due to their high damping coefficient and ease of production. However, elastomers, and in particular thermoplastic polyurethanes (TPU), are susceptible to degradation from environmental conditions. Samples of TPU were investigated, in terms of their mechanical properties, under the influence of four factors; time (up to 10 weeks thermal exposure), temperature (20–80 °C), strain (10% and 25%) and moisture (pre-soak/testing in water). Compression, hardness and Compression Set tests were used to determine the major contributors to the degradation process. It was found that pure thermal loading at 70 °C for 10 weeks did not result in any changes in material properties, other than an initial drying phase causing an increase in hardness of 2–3 Shore D. The Compression Set values were found to be heavily dependent on the test temperature, with a significant increase in Compression Set being seen between 70 and 80 °C. The presence of water (introduced by testing in water) acted as a plasticiser and resulted in a larger amount of Compression Set, than testing in the absence of water. The level of Compression Set was shown to be insensitive to the strain level. Overall, it was found, for the conditions tested, that temperature was the major driving force behind the Compression Set of the TPU material.
J. E. Coons - One of the best experts on this subject based on the ideXlab platform.
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A Bayesian analysis of the Compression Set and stress–strain behavior in a thermally aged silicone foam
Polymer Degradation and Stability, 2006Co-Authors: J. E. Coons, M.d. Mckay, M.s. HamadaAbstract:Data obtained from an archived nine-year aging study on S5370 foam were used to develop Compression Set and stress–strain aging models. Compression Set was characterized using a first order kinetic model and the stress–strain relationship was analyzed using a material model previously described by Rusch for flexible foams. The models were fitted to data from the aging study using Bayesian methods, which easily accommodate uncertainties in the test conditions and provide probability distributions of the model parameters. The parameter distributions were sampled using a Markov chain Monte Carlo algorithm and incorporated to effect prediction intervals and compared to data obtained from independent studies for the purpose of validation. Compression Set data from the short time study of Patel and Skinner are shown to predict significantly higher Compression Sets, which are attributed to additional crosslinking reactions and other phenomena that do not dominate the long term aging behavior. Using data from the nine-year study, the time period required to achieve a given Compression Set at 25 °C is increased by 20 years or more over the predictions of Patel and Skinner. The activation energy applicable near room temperature is similar to that reported by Patel and Skinner, which is consistent with numerous physical and catalyzed chemical mechanisms. Finally, load retention predictions from the stress–strain aging model agree with independent studies at test gaps that are larger than or equal to a zero gradient test gap limit.
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a bayesian analysis of the Compression Set and stress strain behavior in a thermally aged silicone foam
Polymer Degradation and Stability, 2006Co-Authors: J. E. Coons, M.d. Mckay, M.s. HamadaAbstract:Data obtained from an archived nine-year aging study on S5370 foam were used to develop Compression Set and stress–strain aging models. Compression Set was characterized using a first order kinetic model and the stress–strain relationship was analyzed using a material model previously described by Rusch for flexible foams. The models were fitted to data from the aging study using Bayesian methods, which easily accommodate uncertainties in the test conditions and provide probability distributions of the model parameters. The parameter distributions were sampled using a Markov chain Monte Carlo algorithm and incorporated to effect prediction intervals and compared to data obtained from independent studies for the purpose of validation. Compression Set data from the short time study of Patel and Skinner are shown to predict significantly higher Compression Sets, which are attributed to additional crosslinking reactions and other phenomena that do not dominate the long term aging behavior. Using data from the nine-year study, the time period required to achieve a given Compression Set at 25 °C is increased by 20 years or more over the predictions of Patel and Skinner. The activation energy applicable near room temperature is similar to that reported by Patel and Skinner, which is consistent with numerous physical and catalyzed chemical mechanisms. Finally, load retention predictions from the stress–strain aging model agree with independent studies at test gaps that are larger than or equal to a zero gradient test gap limit.
Thomas S. Wilson - One of the best experts on this subject based on the ideXlab platform.
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3D Printed Silicones with Shape Memory
Scientific Reports, 2017Co-Authors: Amanda S Wu, Taylor M. Bryson, Thomas R. Metz, Stephanie E. Schulze, Emily Cheng, Ward Small, Eric B Duoss, Thomas S. WilsonAbstract:Direct ink writing enables the layer-by-layer manufacture of ordered, porous structures whose mechanical behavior is driven by architecture and material properties. Here, we incorporate two different gas filled microsphere pore formers to evaluate the effect of shell stiffness and T_g on compressive behavior and Compression Set in siloxane matrix printed structures. The lower T_g microsphere structures exhibit substantial Compression Set when heated near and above T_g, with full structural recovery upon reheating without constraint. By contrast, the higher T_g microsphere structures exhibit reduced Compression Set with no recovery upon reheating. Aside from their role in tuning the mechanical behavior of direct ink write structures, polymer microspheres are good candidates for shape memory elastomers requiring structural complexity, with potential applications toward tandem shape memory polymers.
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Thermal Aging Study of a Dow Corning SE 1700 Porous Structure Made by Direct Ink Writing: 1-Year Results and Long-Term Predictions
2015Co-Authors: Ward Small, Eric B Duoss, Mark A. Pearson, Amitesh Maiti, Thomas Metz, Thomas S. WilsonAbstract:Dow Corning SE 1700 (reinforced polydimethylsiloxane) porous structures were made by direct ink writing (DIW). The specimens (~50% porosity) were subjected to various compressive strains (15, 30, 45%) and temperatures (room temperature, 35, 50, 70°C) in a nitrogen atmosphere (active purge) for 1 year. Compression Set and load retention of the aged specimens were measured periodically during the study. Compression Set increased with strain and temperature. After 1 year, specimens aged at room temperature, 35, and 50°C showed ~10% Compression Set (relative to the applied compressive deflection), while those aged at 70°C showed 20-40%. Due to the increasing Compression Set, load retention decreased with temperature, ranging from ~90% at room temperature to ~60-80% at 70°C. Long-term Compression Set and load retention at room temperature were predicted by applying time-temperature superposition (TTS). The predictions show Compression Set relative to the compressive deflection will be ~10-15% with ~70-90% load retention after 50 years at 15-45% strain, suggesting the material will continue to be mechanically functional. Comparison of the results to previously acquired data for cellular (M97*, M9760, M9763) and RTV (S5370) silicone foams suggests that the SE 1700 DIW porous specimens are on par with, or outperform, the legacy foams.
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Compression Set in gas-blown condensation-cured polysiloxane elastomers
Polymer Degradation and Stability, 2010Co-Authors: Mogon Patel, Thomas S. Wilson, Robert S. Maxwell, Sarah C. Chinn, Stephen A. BirdsellAbstract:Accelerated thermal ageing studies on foamed condensation cured polysiloxane materials have been performed in support of life assessment and material replacement programmes. Two different types of filled hydrogen-blown and condensation cured polysiloxane foams were tested; commercial (RTV S5370), and an in-house formulated polysiloxane elastomer (Silfoam). Compression Set properties were investigated using Thermomechanical (TMA) studies and compared against two separate longer term ageing trials carried out in air and in dry inert gas atmospheres using Compression jigs. Isotherms measured from these studies were assessed using time-temperature (T/t) superposition. Acceleration factors were determined and fitted to Arrhenius kinetics. For both materials, the thermo-mechanical results were found to closely follow the longer term accelerated ageing trials. Comparison of the accelerated ageing data in dry nitrogen atmospheres against field trial results showed the accelerated ageing trends over predict, however the comparison is difficult as the field data suffer from significant component to component variability. Of the long term ageing trials reported here, those carried out in air deviate more significantly from field trials data compared to those carried out in dry nitrogen atmospheres. For field return samples, there is evidence for residual post-curing reactions influencing mechanical performance, which would accelerate Compression Set. Multiple quantum-NMR studies suggest that Compression Set is not associated with significant changes in net crosslink density, but that some degree of network rearrangement has occurred due to viscoelastic relaxation as well as bond breaking and forming processes, with possible post-curing reactions at early times.
Carl Slater - One of the best experts on this subject based on the ideXlab platform.
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Compression Set of thermoplastic polyurethane under different thermal–mechanical-moisture conditions
Polymer Degradation and Stability, 2011Co-Authors: Carl Slater, C. L. Davis, Martin StrangwoodAbstract:Abstract Elastomeric materials are used in the manufacture of structural dampeners due to their high damping coefficient and ease of production. However, elastomers, and in particular thermoplastic polyurethanes (TPU), are susceptible to degradation from environmental conditions. Samples of TPU were investigated, in terms of their mechanical properties, under the influence of four factors; time (up to 10 weeks thermal exposure), temperature (20–80 °C), strain (10% and 25%) and moisture (pre-soak/testing in water). Compression, hardness and Compression Set tests were used to determine the major contributors to the degradation process. It was found that pure thermal loading at 70 °C for 10 weeks did not result in any changes in material properties, other than an initial drying phase causing an increase in hardness of 2–3 Shore D. The Compression Set values were found to be heavily dependent on the test temperature, with a significant increase in Compression Set being seen between 70 and 80 °C. The presence of water (introduced by testing in water) acted as a plasticiser and resulted in a larger amount of Compression Set, than testing in the absence of water. The level of Compression Set was shown to be insensitive to the strain level. Overall, it was found, for the conditions tested, that temperature was the major driving force behind the Compression Set of the TPU material.
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Compression Set of thermoplastic polyurethane under different thermal mechanical moisture conditions
Polymer Degradation and Stability, 2011Co-Authors: Carl Slater, C. L. Davis, Martin StrangwoodAbstract:Abstract Elastomeric materials are used in the manufacture of structural dampeners due to their high damping coefficient and ease of production. However, elastomers, and in particular thermoplastic polyurethanes (TPU), are susceptible to degradation from environmental conditions. Samples of TPU were investigated, in terms of their mechanical properties, under the influence of four factors; time (up to 10 weeks thermal exposure), temperature (20–80 °C), strain (10% and 25%) and moisture (pre-soak/testing in water). Compression, hardness and Compression Set tests were used to determine the major contributors to the degradation process. It was found that pure thermal loading at 70 °C for 10 weeks did not result in any changes in material properties, other than an initial drying phase causing an increase in hardness of 2–3 Shore D. The Compression Set values were found to be heavily dependent on the test temperature, with a significant increase in Compression Set being seen between 70 and 80 °C. The presence of water (introduced by testing in water) acted as a plasticiser and resulted in a larger amount of Compression Set, than testing in the absence of water. The level of Compression Set was shown to be insensitive to the strain level. Overall, it was found, for the conditions tested, that temperature was the major driving force behind the Compression Set of the TPU material.