Impact-induced glass transition in elastomeric coatings

Bogoslovov, R. B.; Roland, C. M.; Gamache, Raymond M.

doi:10.1063/1.2745212

Cited by 151 publications

(134 citation statements)

References 7 publications

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“…10 Of interest herein is the effect of nanoparticle reinforcement on the local segmental dynamics. These motions underlie many important properties of polymers 11 and also function as the precursor to the larger length scale chain motions associated with processing and flow. 12 Constraints from nanoparticles may affect segmental mobility, at least of chains near the particle surface, and it has been proposed that immobilization of such interfacial chains induces glassy behavior at temperatures above the bulk T g .…”

Section: Introductionmentioning

confidence: 99%

Effect of Silica Nanoparticles on the Local Segmental Dynamics in Poly(vinyl acetate)

et al. 2008

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The effect of nanosized silica particles on the properties of poly(vinyl acetate) (PVAc) was investigated for a range of silica concentrations encompassing the percolation threshold. The quantity of polymer adsorbed to the particles ("bound rubber") increased systematically with silica content and was roughly equal to the quantity shielded from shear stresses ("occluded rubber"). This bound and occluded polymer attained a level of ∼12% at a silica volume content of 28%; nevertheless, the glass transition properties of the PVAc, including the glass transition temperature, local segmental relaxation function and relaxation times, and the changes in thermal expansion coefficient and heat capacity at T g , were unaffected by the interfacial material. That is, there is no indication that the local segmental dynamics of the chains adjacent to silica particles differ from the motions of the bulk chains. Interestingly, the volume sensitivity of the segmental dynamics, as determined from the scaling exponent γ in the relation T g ∼ V g -γ in which V g is the specific volume at the glass transition, becomes stronger with increasing silica concentration. Moreover, this dependence of γ increases abruptly at the filler percolation threshold. The implication of this result and possible directions for new research are considered.

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Section: Introductionmentioning

confidence: 99%

Effect of Silica Nanoparticles on the Local Segmental Dynamics in Poly(vinyl acetate)

et al. 2008

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“…This work shows that the PU elastomer, which is known to convert to a glassy state under impact loading (ε g 10 5 s -1 ), 2 responds differently to moderate strain rates of ca. 500 s -1 or less.…”

Section: Discussionmentioning

confidence: 87%

Structure Evolution in a Polyurea Segmented Block Copolymer Because of Mechanical Deformation

et al. 2008

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Extensional stress-strain measurements on a polyurea (PU) were carried out at strain rates up to 830 s -1 , in combination with ex post facto small-angle X-ray scattering (SAXS) measurements and temperaturedependent SAXS. The elastomer is of interest because of its application as an impact-resistant coating. The highest strain rates used herein fall within the softening, or transition, zone of the viscoelastic spectrum and are thus relevant to the working hypothesis that the performance of a polyurea impact coating is related to its transition to the glassy state when strained very rapidly. While quasi-static and slow deformation of the PU gives rise to irrecoverable strain and anisotropic SAXS patterns, when stretched at high rates the PU recovers completely and the scattering is isotropic. Thus, the deformation of the hard domains observed at low rates is absent at high strain rates. Linear dynamic mechanical measurements were also carried out, with the obtained segmental relaxation times in good agreement with dielectric relaxation measurements on this material. The PU exhibits the usual breakdown of time-temperature superposition in the transition zone. This thermorheological complexity underlies the fact that published time-temperature shift factors for this material are unrelated to the segmental dynamics, and therefore use of these shift factors to predict the onset of glassy dynamics during impact loading of the PU will be in error.

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“…The particular polymers employed have segmental dynamics occurring on the time scale of the ballistic impact (ca. 10 − 5 s), so that the impact induces a rubber-to-glass viscoelastic phase change [38]. This phase transition corresponds to the mechanical regime in which polymers are most energy dissipative.…”

Section: Introductionmentioning

confidence: 99%

Elastomer-metal laminate armor

et al. 2016

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• Polymer-aluminum laminates on the strike-face of steel plates enhance ballistic performance.• With judicious selection of substrate and laminate, a broad range of performance and weight combinations can be obtained.• There is both a reduction in magnitude of the substrate deformation and spatial dispersion of the impact.• The main function of the metallic layers is to stiffen the polymer without affecting the latter's viscoelasticity response. A study was carried out of pressure wave transmission and the ballistic penetration of steel substrates incorporating a front-face laminate, the latter consisting of alternating layers of thin metal and a soft polymer; the latter undergoes a viscoelastic phase transition on impact. The ballistic properties of laminate/steel structures are substantially better than conventional military armor. This enhanced performance has three origins: large energy absorption by the viscoelastic polymer, a significant strain-hardening of the material, and lateral spreading of the impact force. These mechanisms, active only at high strain rates, depend on the chemical structure of the polymer but not on the particular metal used in the laminate. G R A P H I C A L A B S T R A C T a b s t r a c t a r t i c l e i n f oPublished by Elsevier Ltd.

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Impact-induced glass transition in elastomeric coatings

Cited by 151 publications

References 7 publications

Effect of Silica Nanoparticles on the Local Segmental Dynamics in Poly(vinyl acetate)

Effect of Silica Nanoparticles on the Local Segmental Dynamics in Poly(vinyl acetate)

Structure Evolution in a Polyurea Segmented Block Copolymer Because of Mechanical Deformation

Elastomer-metal laminate armor

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