A new statistical theory based on the rotational isomeric state model describing the chain conformational free energy has been proposed. This theory can be used to predict different tensions of rubber elongation for c...A new statistical theory based on the rotational isomeric state model describing the chain conformational free energy has been proposed. This theory can be used to predict different tensions of rubber elongation for chemically different polymers, and the energy term during the elongation of natural rubber coincides with the experimental one.展开更多
The static properties of the lungs have been explained by energy-change considerations on the elasticity, but this article explains the elasticity of the lungs by entropy-change considerations. Entropy of the individu...The static properties of the lungs have been explained by energy-change considerations on the elasticity, but this article explains the elasticity of the lungs by entropy-change considerations. Entropy of the individual lobule was defined by application of stochastic geometry on aggregated alveolar polyhedrons. Entropy of the lungs is the result of integrating a number of lobular entropies through the fractal bronchial tree. Entropy of the lungs was thus determined by the individual lobular entropy and the connectivity of the bronchial tree to the lobular bronchioles. Thermody-namic considerations on the static conditions of the pulmonary system composed of the lungs and the chest wall have provided a theoretical approach to understand the subdivisions of lung volume as the entropy-change of lungs. Entropy-change considerations on the elasticity of the lungs have shown that alveolar collapse and subsequent alveolar induration as the primary pathway for the loss of elasticity in the lungs is an acceptable hypothesis.展开更多
The crystalline and amorphous regions were alternately arranged in the hard elastic polypropylene(PP)films with row-nucleated lamellae.In this work,their structure evolution during stretching and recovery at room temp...The crystalline and amorphous regions were alternately arranged in the hard elastic polypropylene(PP)films with row-nucleated lamellae.In this work,their structure evolution during stretching and recovery at room temperature was followed and the elastic recovery mechanism was discussed by twice cyclic tensile experiment.During the first stretching to 100%,the lamellae crystals are parallel separated and the intercrystallite crazing is formed at the first yield point.Many nano-cavities within the intercrystallite crazing appear when the strain reaches 20%.The strain-hardening process accompanies with the lamellae long period increasing and the intercrystallite crazing enlargement.After the secondary yield point,the lamellae cluster is further separated and more nano-cavities appear.The first and second recovery processes are complete overlap.During recovery,firstly,the energy elasticity provided by nano-cavities surface tension drives the shrinkage of material,and then the entropy elasticity related to amorphous chain relaxation plays a leading role when the strain is smaller than the secondary yield point.The elastic recovery process of hard elastic material is the co-contribution of energy elasticity and entropy elasticity.This work gives a clearer recognition about the source of hard elastic property and the role of amorphous region in material's deformation.展开更多
基金This project is supported by the National Natural Science Foundation of China, 863 High Technology Project and the National Basic Research Project--Macromolecular Condensed State.
文摘A new statistical theory based on the rotational isomeric state model describing the chain conformational free energy has been proposed. This theory can be used to predict different tensions of rubber elongation for chemically different polymers, and the energy term during the elongation of natural rubber coincides with the experimental one.
文摘The static properties of the lungs have been explained by energy-change considerations on the elasticity, but this article explains the elasticity of the lungs by entropy-change considerations. Entropy of the individual lobule was defined by application of stochastic geometry on aggregated alveolar polyhedrons. Entropy of the lungs is the result of integrating a number of lobular entropies through the fractal bronchial tree. Entropy of the lungs was thus determined by the individual lobular entropy and the connectivity of the bronchial tree to the lobular bronchioles. Thermody-namic considerations on the static conditions of the pulmonary system composed of the lungs and the chest wall have provided a theoretical approach to understand the subdivisions of lung volume as the entropy-change of lungs. Entropy-change considerations on the elasticity of the lungs have shown that alveolar collapse and subsequent alveolar induration as the primary pathway for the loss of elasticity in the lungs is an acceptable hypothesis.
基金supported by the National Natural Science Foundation of China(Nos.51773044 and 51603047)Research and Development Plan for Key Areas in Guangdong Province(No.2019B090914002)+1 种基金Guangdong Province Science and Technology Plan Project(No.2016A010103030)the PhD Start-up Fund of Natural Science Foundation of Guangdong Province,China(No.2016A030310344).
文摘The crystalline and amorphous regions were alternately arranged in the hard elastic polypropylene(PP)films with row-nucleated lamellae.In this work,their structure evolution during stretching and recovery at room temperature was followed and the elastic recovery mechanism was discussed by twice cyclic tensile experiment.During the first stretching to 100%,the lamellae crystals are parallel separated and the intercrystallite crazing is formed at the first yield point.Many nano-cavities within the intercrystallite crazing appear when the strain reaches 20%.The strain-hardening process accompanies with the lamellae long period increasing and the intercrystallite crazing enlargement.After the secondary yield point,the lamellae cluster is further separated and more nano-cavities appear.The first and second recovery processes are complete overlap.During recovery,firstly,the energy elasticity provided by nano-cavities surface tension drives the shrinkage of material,and then the entropy elasticity related to amorphous chain relaxation plays a leading role when the strain is smaller than the secondary yield point.The elastic recovery process of hard elastic material is the co-contribution of energy elasticity and entropy elasticity.This work gives a clearer recognition about the source of hard elastic property and the role of amorphous region in material's deformation.
