Deformation and Strength of Polymers

Бартенев, Г. М.; Zuyev, Yu.S.

doi:10.1016/b978-0-08-003110-1.50006-6

Cited by 2 publications

(2 citation statements)

References 16 publications

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“…This state is called the viscoelastic or rubbery state. The transition temperature from the frozen state to the viscoelastic state is the glass transition. , Just above the viscoelastic state in temperature, the branch mobility increases, and at the flow temperature, T f , the molecules enter the viscofluid state and start flowing. In the viscofluid state, molecular motion may be activated, and the molecules do not have the fluidity of a true liquid but possess sufficient thermal mobility to move past one another.…”

Section: Resultsmentioning

confidence: 99%

Effectiveness of Low-Field NMR to Assess the Molecular Dynamics of Fatty Esters around the Glass Transition

Bouzidi

Narine

2022

Ind. Eng. Chem. Res.

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The molecular dynamics involved in the emergence of solidity in glass-forming organic esters are poorly understood. Some branched esters are examples of organic materials that do not crystallize under typical thermal protocols but form glasses at low temperatures. The present work investigates the solid-to-liquid phase transition of three fatty branched esters, which are synthetic mimics of compounds found in jojoba oil (so-called jojoba-like esters or JLEs), using low-field 1H NMR and differential scanning calorimetry (DSC). Spin–lattice and spin–spin relaxation times (T 1 and T 2, respectively) measured from the solid-arrested state to the fluid state provided information about the dynamics and structures of the JLEs below and above the glass transition temperature (T g). The T 1 and T 2 state diagrams indicated that the transition involves an intermediary viscoelastic state similar to that observed in polymers. 1H NMR detected the transition because the backbone is “arrested” at the viscoelastic–fluid transition. T g measured by DSC recorded the “arrest” of the molecules when the branches enter the glassy state deep in the viscoelastic state matching the lowest temperature singularity in the T 1 and T 2 state diagrams. The rotational correlation time determined using the Bloembergen–Purcell–Pound (BPP) theory indicated an Arrhenius function for T > T g with an activation energy of 26.1 kJ·mol–1 similar to those of other organic glass formers. The minimum of the coupling constant × T 1 (KT 1) technique and simultaneous solution of the BPP expressions showed that the distance between neighboring protons remains constant in the glassy state (r g = 2.09 Å) and increases almost linearly in the viscoelastic and fluid states.

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Section: Resultsmentioning

confidence: 99%

Effectiveness of Low-Field NMR to Assess the Molecular Dynamics of Fatty Esters around the Glass Transition

Bouzidi

Narine

2022

Ind. Eng. Chem. Res.

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“…Discrete distribution of amber particles may indicate discrete distribution of the applied energy during grinding. The discrete set of weak points of the amber structure before grinding with different strength is also a cause for discrete particle size range of the grinded amber [14].…”

Section: Resultsmentioning

confidence: 99%

Archive of Mechanical Engineering

Chornyi

Kharchenko

Mysiura

et al. 2021

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Investigation of particle size distribution of grinded amber by electropulse discharges in a liquid mediumThe article presents the study results of electropulse grinding of amber in aqueous and alcoholic media at different amounts of supplied energy.Description of the electropulse grinding laboratory installation, the mechanism of the destruction process of amber particles and methods of statistical processing of experimental data are given. It was established that alcohol medium has a greater impact on the efficiency of crushing than water. Thus, under the same conditions of energy supply, in the aqueous medium the weighted average particle size of amber was 601.6 ± 688.9 µm, and in an alcohol medium -368.0 ± 269.6 µm. In an aqueous medium, the particle size decreased to 1/13.6 of raw sample, and in an alcoholic medium to 1/22.3 of raw sample compared to the initial size of raw amber. We found that in the aqueous medium the ratio of large to small fractions is mainly the same with the coefficient of alignment of particles with a size of 1.09. In an alcoholic medium, this ratio significantly differs, with the coefficient of alignment of amber particles of a size of 1.67 with the amount of supplied energy of 125 kJ.

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Deformation and Strength of Polymers

Cited by 2 publications

References 16 publications

Effectiveness of Low-Field NMR to Assess the Molecular Dynamics of Fatty Esters around the Glass Transition

Effectiveness of Low-Field NMR to Assess the Molecular Dynamics of Fatty Esters around the Glass Transition

Archive of Mechanical Engineering

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