Based on three dimensional （3D） Discrete Element Method （DEM）, the paper presents simulation results of undrained tests on loose assemblies of polydisperse spheres under axisymmet- ric compression and plane strain...Based on three dimensional （3D） Discrete Element Method （DEM）, the paper presents simulation results of undrained tests on loose assemblies of polydisperse spheres under axisymmet- ric compression and plane strain conditions using a periodic cell. In the present work, undrained tests were modelled by deforming the samples under constant volume conditions. The undrained （effective） stress paths are shown to be qualitatively similar to experimental results in literature. A microscopic parameter in terms of redundancy factor （RF） is used to identify the onset of lique- faction （or temporary liquefaction）, with the condition of RF equal to unity defining the transition from ＇solid-like＇ to ＇liquid-like＇ behaviour. It is found that the undrained behaviour is governed by the evolution of redundancy factor under both undrained axisymmetric compression and plane strain conditions, and a reversal of deviatoric stress in stress path for medium loose systems oc- curs due to the fact that the system becomes a structural mechanism （RF 〈 1） transiently at the microscopic level during the evolution.展开更多
Alloying and nanocompositing are two most effective techniques by which isotactic polypropylene(iPP), one of the most promising polymers of the 21 st century, can be endowed with high performance for ever-demanding hi...Alloying and nanocompositing are two most effective techniques by which isotactic polypropylene(iPP), one of the most promising polymers of the 21 st century, can be endowed with high performance for ever-demanding high-end applications. Thanks to the continuous advancement of catalyst technology, the technological trend for iPP alloy and nanocomposite fabrication has been projected to be in-reactor synthesis, the performance and economic advantages of which are beyond doubt. In this paper, we review two recent key developments in the iPP in-reactor alloy and in-reactor nanocomposite technology in our laboratory that will have profound influence on the continuing development of the prestigious iPP modification art. The first is the simultaneous EPR(ethylene-propylene random copolymer) cross-linking chemistry for controlling its physical growth pattern during in-reactor alloying, which helps to remove the compositional cap on EPR that so far greatly limits the iPP in-reactor alloying technique. The second is the nanofiller support fabrication strategy for simultaneously controlling both the phase morphology of the nanofiller dispersion and the polymer particle granule morphology of synthesized nanocomposites, which resolves the critical scale-up issue surrounding the iPP in-reactor nanocompositing technique. Based on these new developments, new advancements of iPP materials are envisaged.展开更多
Enabling thermoplastic polyamides with significant room temperature phosphorescent(RTP)performance holds great application potential,but remains challenging.Herein,we develop an efficient crystallization-mediated appr...Enabling thermoplastic polyamides with significant room temperature phosphorescent(RTP)performance holds great application potential,but remains challenging.Herein,we develop an efficient crystallization-mediated approach to fabricate RTP-active bio-based polyamide 56(PA56)that simultaneously achieves an exceptional phosphorescence lifetime of 1.214 s and maintains robust mechanical properties with a tensile yield strength exceeding 80 MPa.Comprehensive characterization demonstrates that the material's RTP characteristics can be precisely tuned through controlled crystallization,where the synergistic effects of electron-rich carbonyl group aggregation(functioning as phosphorescent centers)and interchain hydrogen-bonding networks effectively suppress non-radiative decay pathways.This crystallization-dependent modulation enables systematic optimization of PA56's phosphorescent properties.Furthermore,we successfully demonstrate practical applications leveraging these unique RTP features,including advanced information encryption/anti-counterfeiting systems and innovative visualization techniques for real-time moisture monitoring and mechanical load assessment in PA56 products.This work establishes a general design strategy for engineering thermoplastic polyamides with tailorable phosphorescence,opening new avenues for smart material development.展开更多
基金supported by the Guangdong Natural Science Foundation, China (No. 10151503101000006)the Engineering and Physical Sciences Research Council, UK (No. GR/R91588)
文摘Based on three dimensional （3D） Discrete Element Method （DEM）, the paper presents simulation results of undrained tests on loose assemblies of polydisperse spheres under axisymmet- ric compression and plane strain conditions using a periodic cell. In the present work, undrained tests were modelled by deforming the samples under constant volume conditions. The undrained （effective） stress paths are shown to be qualitatively similar to experimental results in literature. A microscopic parameter in terms of redundancy factor （RF） is used to identify the onset of lique- faction （or temporary liquefaction）, with the condition of RF equal to unity defining the transition from ＇solid-like＇ to ＇liquid-like＇ behaviour. It is found that the undrained behaviour is governed by the evolution of redundancy factor under both undrained axisymmetric compression and plane strain conditions, and a reversal of deviatoric stress in stress path for medium loose systems oc- curs due to the fact that the system becomes a structural mechanism （RF 〈 1） transiently at the microscopic level during the evolution.
基金supported by the National Natural Science Foundation of China(21574143,51373178)
文摘Alloying and nanocompositing are two most effective techniques by which isotactic polypropylene(iPP), one of the most promising polymers of the 21 st century, can be endowed with high performance for ever-demanding high-end applications. Thanks to the continuous advancement of catalyst technology, the technological trend for iPP alloy and nanocomposite fabrication has been projected to be in-reactor synthesis, the performance and economic advantages of which are beyond doubt. In this paper, we review two recent key developments in the iPP in-reactor alloy and in-reactor nanocomposite technology in our laboratory that will have profound influence on the continuing development of the prestigious iPP modification art. The first is the simultaneous EPR(ethylene-propylene random copolymer) cross-linking chemistry for controlling its physical growth pattern during in-reactor alloying, which helps to remove the compositional cap on EPR that so far greatly limits the iPP in-reactor alloying technique. The second is the nanofiller support fabrication strategy for simultaneously controlling both the phase morphology of the nanofiller dispersion and the polymer particle granule morphology of synthesized nanocomposites, which resolves the critical scale-up issue surrounding the iPP in-reactor nanocompositing technique. Based on these new developments, new advancements of iPP materials are envisaged.
基金supported by the Young Elite Scientists Sponsorship Program by Beijing Association for Science and Technology(BAST)(BYESS2023086)the Fundamental Research Funds for the Central Universities(buctrc202225)the Scientific Research Projects of China National Petroleum Corporation(PRIKY23093)。
文摘Enabling thermoplastic polyamides with significant room temperature phosphorescent(RTP)performance holds great application potential,but remains challenging.Herein,we develop an efficient crystallization-mediated approach to fabricate RTP-active bio-based polyamide 56(PA56)that simultaneously achieves an exceptional phosphorescence lifetime of 1.214 s and maintains robust mechanical properties with a tensile yield strength exceeding 80 MPa.Comprehensive characterization demonstrates that the material's RTP characteristics can be precisely tuned through controlled crystallization,where the synergistic effects of electron-rich carbonyl group aggregation(functioning as phosphorescent centers)and interchain hydrogen-bonding networks effectively suppress non-radiative decay pathways.This crystallization-dependent modulation enables systematic optimization of PA56's phosphorescent properties.Furthermore,we successfully demonstrate practical applications leveraging these unique RTP features,including advanced information encryption/anti-counterfeiting systems and innovative visualization techniques for real-time moisture monitoring and mechanical load assessment in PA56 products.This work establishes a general design strategy for engineering thermoplastic polyamides with tailorable phosphorescence,opening new avenues for smart material development.
