In this work,a morphology transition mode is revealed in ultra-high molecular weight polyethylene(UHMWPE)when stretching at 120℃:moving from the slightly deformed region to the necked region,the morphology transfers ...In this work,a morphology transition mode is revealed in ultra-high molecular weight polyethylene(UHMWPE)when stretching at 120℃:moving from the slightly deformed region to the necked region,the morphology transfers from small spherulites to a mixture of transcrystalline and enlarged spherulites,and finally to pure transcrystalline;meanwhile,the lamellae making up the transcrystalline or spherulite were fragmented into smaller ones;spatial scan by wide-angle X-ray scattering(WAXS)and small angle X-ray scattering(SAXS)revealed that the crystallinity is increased from 25.3%to 30.1%and the crystal orientation was enhanced greatly,but the lamellae orientation was quite weak.The rise of enlarged spherulites or a mixture of transcrystalline and spherulites can also be found in UHMWPE stretched at 140 and 148℃,whereas absent in UHMWPE stretched at 30℃.In situ WAXS/SAXS measurements suggest that during stretching at 30℃,the crystallinity is reduced drastically,and a few voids are formed as the size increases from 50 nm to 210 nm;during stretching at 120℃,the crystallinity is reduced only slightly,and the kinking of lamellae occurs at large Hencky strain;during stretching at 140 and 148℃,an increase in crystallinity with stretching strain can be found,and the lamellae are also kinked.Taking the microstructure and morphology transition into consideration,a mesoscale morphology transition mode is proposed,in the stretching-induced crystallization the fragmented lamellae can be rearranged into new supra-structures such as spherulite or transcrystalline during hot stretching.展开更多
Poly(butylene adipate-co-terephthalate)(PBAT)is a promising biodegradable flexible polymer but suffers from slow crystallization rate,making it less attractive for some applications like the injection-molded products ...Poly(butylene adipate-co-terephthalate)(PBAT)is a promising biodegradable flexible polymer but suffers from slow crystallization rate,making it less attractive for some applications like the injection-molded products in comparison with low-density polyethylene(LDPE).This work aimed to accelerate the crystallization of PBAT by adding a self-assembly nucleating agent octamethylenedicarboxylic dibenzoylhydrazide(OMBH).PBAT/OMBH composites with various OMBH contents(0 wt%,0.5 wt%,0.7 wt%,1 wt%,2 wt%,3 wt%and 5 wt%)were prepared through melt-mixing.The effect of OMBH on the crystallization behavior,morphologies and mechanical properties of PBAT was investigated.The highest nucleation efficiency value of 59.6%was achieved for PBAT with 0.7 wt%OMBH,much higher than that of 22.7%for PBAT with 0.7 wt%talc.Atomic force microscopy results showed that OMBH formed fine fibers and induced the formation of transcrystalline layers of PBAT.Fourier transform infrared spectroscopy(FTIR)combined with two-dimensional correlation spectra suggested that the intermolecular dipole-dipole N—H…O=C interactions but not hydrogen bond between OMBH and PBAT promoted the crystallization of PBAT in the initial period of crystallization.The presence of OMBH did not change the crystal form of PBAT but had positive contribution in enhancing its crystallinity and mechanical properties.This work is essential for preparing PBAT with high crystallization rate,enhancing its potential applications in injection-molded products.展开更多
Herein,isotactic polypropylene films with smallβ-nucleating agent content were fabricated via a melt-extrusion-stretched technology with intended"shear-free"in barrel and die.Compared with neat films,the te...Herein,isotactic polypropylene films with smallβ-nucleating agent content were fabricated via a melt-extrusion-stretched technology with intended"shear-free"in barrel and die.Compared with neat films,the tensile strength,elongation at break and strain energy density at break of i PP film with 0.05 wt%β-nucleating agent are significantly improved by 13.8%,39.6%and 90.6%,respectively,indicating the simultaneously enhanced toughness and strength.Additionally,theβ-crystal content gradually increases with increasingβ-NA content,while the relative total daughter content ofα-andβ-crystal exhibits opposite tendency.Moreover,nucleation and crystal growth induced by variousβ-NA contents are different.This work proves an efficient strategy to enhance mechanical properties of isotactic polypropylene film via controlling elongation flow and addition of appropriateβ-NA content.展开更多
Deformation-induced phase transition of FormⅡto FormⅠin polybutene-1(PB-1)has been investigated by time-resolved Fourier transform infrared(FTIR)spectroscopy over a wide temperature range from 25℃to 105℃.The initi...Deformation-induced phase transition of FormⅡto FormⅠin polybutene-1(PB-1)has been investigated by time-resolved Fourier transform infrared(FTIR)spectroscopy over a wide temperature range from 25℃to 105℃.The initial film sample containing orientated lamellae is prepared by pre-stretching of PB-1 melt followed by solidification.This is to realize a homogeneity of subsequent deformation at the mesoscale of lamellar stacks by avoiding large-scale spherulites.The deformation induced phase transition is recognized to occur with two stages:first,FormⅡundergoes the lamellar fragmentation,slipping or local melting after yielding to activate its transition to FormⅠ,which may be realized by releasing the restrictions on chains translational movements in crystalline phase;second,the phase transition proceeds with a continuous dissipation of external work and determines the tensile mechanical response of film.To quantify the relationship between crystalline transition of FormⅡto FormⅠand external tensile field,a simple kinetic equation is well established based on FTIR measurement.The equation can describe not only the dependence of crystal transitional degree on applied specific work,but also the retardation effect of elevating temperature on phase transition.展开更多
The coronavirus disease 2019(COVID-19)caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) has posed severe threats to human health,public safety,and the global economy.Metal nutrient elements can dir...The coronavirus disease 2019(COVID-19)caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) has posed severe threats to human health,public safety,and the global economy.Metal nutrient elements can directly or indirectly take part in human immune responses,and metal-related drugs have served as antiviral drugs and/or enzyme inhibitors for many years,providing potential solutions to the prevention and treatment of COVID-19.Metal-based drugs are currently under a variety of chemical structures and exhibit wide-range bio activities,demonstrating irreplaceable advantages in pharmacology.This review is an intention to summarize recent progress in the prevention and treatment strategies against COVID-19 from the perspective of metal pharmacology.The current and potential utilization of metal-based drugs is briefly introduced.Specifically,metallohydrogels that have been shown to present superior antiviral activities are stressed in the paper as potential drugs for the treatment of COVID-19.展开更多
Poly(lactic acid) (PLA) is a promising bio-based environmentally-friendly plastic. Nevertheless, the physical aging-induced brittleness of PLA limits its widespread applications. Blending with immiscible ductile polym...Poly(lactic acid) (PLA) is a promising bio-based environmentally-friendly plastic. Nevertheless, the physical aging-induced brittleness of PLA limits its widespread applications. Blending with immiscible ductile polymer is an effective way to toughen PLA. However, the underlying details of the toughening mechanism and, in particular, the effect of physical aging are not well understood. Herein, atomic force microscopy (AFM) based nanomechanical mapping technology was utilized to visualize the differences in the deformation mechanisms between unaged and aged PLA/poly(ε-caprolactone) (PCL) blend upon uniaxial drawing. Results show that physical aging has a significant effect on the microscopic Young’s modulus and its distribution of PLA matrix, resulting in a highly heterogeneous response of the PLA/PCL blend to external stress and affecting the mechanical properties of the PLA phase under different extensions. This work provides a new experimental basis for understanding the effect of physical aging on the mechanical properties of PLA-based materials.展开更多
Although there has been rapid advancement in piezoelectric sensors,challenges still remain in developing wearable piezoelectric sensors by a one-step,continuous and environmentally friendly method.In this work,a 1D fl...Although there has been rapid advancement in piezoelectric sensors,challenges still remain in developing wearable piezoelectric sensors by a one-step,continuous and environmentally friendly method.In this work,a 1D flexible coaxial piezoelectric fiber was directly fabricated by melt extrusion molding,whose core and sheath layer are respectively slender steel wire(i.e.,electrode)and PVDF(i.e.,piezoelectric layer).Moreover,such 1D flexible coaxial piezoelectric fiber possesses short response time and high sensitivity,which can be used as a selfpowered sensor for bending and vibration sensing.More interestingly,such 1D flexible coaxial piezoelectric fiber(1D-PFs)can be further endowed with 3D helical structure.Moreover,a wearable and washable motion monitoring system can be constructed via braiding such 3D helical piezoelectric fiber(3D-PF)into commercial textiles.This work paves a new way for developing 1D and 3D piezoelectric fibers through a one-step,continuous and environmentally friendly method,showing potential applications in the field of sensing and wearable electronics.展开更多
Flexible strain sensor has promising features in successful application of health monitoring, electronic skins and smart robotics, etc.Here, we report an ultrasensitive strain sensor with a novel crack-wrinkle structu...Flexible strain sensor has promising features in successful application of health monitoring, electronic skins and smart robotics, etc.Here, we report an ultrasensitive strain sensor with a novel crack-wrinkle structure(CWS) based on graphite nanoplates(GNPs)/thermoplastic urethane(TPU)/polydimethylsiloxane(PDMS) nanocomposite. The CWS is constructed by pressing and dragging GNP layer on TPU substrate,followed by encapsulating with PDMS as a protective layer. On the basis of the area statistics, the ratio of the crack and wrinkle structures accounts for 31.8% and 9.5%, respectively. When the sensor is stretched, the cracks fracture, the wrinkles could reduce the unrecoverable destruction of cracks, resulting in an excellent recoverability and stability. Based on introduction of the designed CWS in the sensor, the hysteresis effect is limited effectively. The CWS sensor possesses a satisfactory sensitivity(GF=750 under 24% strain), an ultralow detectable limit(strain=0.1%) and a short respond time of 90 ms. For the sensing service behaviors, the CWS sensor exhibits an ultrahigh durability(high stability>2×10^(4) stretching-releasing cycles). The excellent practicality of CWS sensor is demonstrated through various human motion tests,including vigorous exercises of various joint bending, and subtle motions of phonation, facial movements and wrist pulse. The present CWS sensor shows great developing potential in the field of cost-effective, portable and high-performance electronic skins.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52003249,12072325 and 52273027)the Natural Science Foundation of Henan(No.242300421236).
文摘In this work,a morphology transition mode is revealed in ultra-high molecular weight polyethylene(UHMWPE)when stretching at 120℃:moving from the slightly deformed region to the necked region,the morphology transfers from small spherulites to a mixture of transcrystalline and enlarged spherulites,and finally to pure transcrystalline;meanwhile,the lamellae making up the transcrystalline or spherulite were fragmented into smaller ones;spatial scan by wide-angle X-ray scattering(WAXS)and small angle X-ray scattering(SAXS)revealed that the crystallinity is increased from 25.3%to 30.1%and the crystal orientation was enhanced greatly,but the lamellae orientation was quite weak.The rise of enlarged spherulites or a mixture of transcrystalline and spherulites can also be found in UHMWPE stretched at 140 and 148℃,whereas absent in UHMWPE stretched at 30℃.In situ WAXS/SAXS measurements suggest that during stretching at 30℃,the crystallinity is reduced drastically,and a few voids are formed as the size increases from 50 nm to 210 nm;during stretching at 120℃,the crystallinity is reduced only slightly,and the kinking of lamellae occurs at large Hencky strain;during stretching at 140 and 148℃,an increase in crystallinity with stretching strain can be found,and the lamellae are also kinked.Taking the microstructure and morphology transition into consideration,a mesoscale morphology transition mode is proposed,in the stretching-induced crystallization the fragmented lamellae can be rearranged into new supra-structures such as spherulite or transcrystalline during hot stretching.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.52073261 and U1704162).
文摘Poly(butylene adipate-co-terephthalate)(PBAT)is a promising biodegradable flexible polymer but suffers from slow crystallization rate,making it less attractive for some applications like the injection-molded products in comparison with low-density polyethylene(LDPE).This work aimed to accelerate the crystallization of PBAT by adding a self-assembly nucleating agent octamethylenedicarboxylic dibenzoylhydrazide(OMBH).PBAT/OMBH composites with various OMBH contents(0 wt%,0.5 wt%,0.7 wt%,1 wt%,2 wt%,3 wt%and 5 wt%)were prepared through melt-mixing.The effect of OMBH on the crystallization behavior,morphologies and mechanical properties of PBAT was investigated.The highest nucleation efficiency value of 59.6%was achieved for PBAT with 0.7 wt%OMBH,much higher than that of 22.7%for PBAT with 0.7 wt%talc.Atomic force microscopy results showed that OMBH formed fine fibers and induced the formation of transcrystalline layers of PBAT.Fourier transform infrared spectroscopy(FTIR)combined with two-dimensional correlation spectra suggested that the intermolecular dipole-dipole N—H…O=C interactions but not hydrogen bond between OMBH and PBAT promoted the crystallization of PBAT in the initial period of crystallization.The presence of OMBH did not change the crystal form of PBAT but had positive contribution in enhancing its crystallinity and mechanical properties.This work is essential for preparing PBAT with high crystallization rate,enhancing its potential applications in injection-molded products.
基金financially supported by the National Natural Science Foundation of China(Nos.11432003 and 11572290)Young Teacher Project of Zhongyuan University of Technology(No.2019XQG05)。
文摘Herein,isotactic polypropylene films with smallβ-nucleating agent content were fabricated via a melt-extrusion-stretched technology with intended"shear-free"in barrel and die.Compared with neat films,the tensile strength,elongation at break and strain energy density at break of i PP film with 0.05 wt%β-nucleating agent are significantly improved by 13.8%,39.6%and 90.6%,respectively,indicating the simultaneously enhanced toughness and strength.Additionally,theβ-crystal content gradually increases with increasingβ-NA content,while the relative total daughter content ofα-andβ-crystal exhibits opposite tendency.Moreover,nucleation and crystal growth induced by variousβ-NA contents are different.This work proves an efficient strategy to enhance mechanical properties of isotactic polypropylene film via controlling elongation flow and addition of appropriateβ-NA content.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51803189,51503186)the Postdoctoral Science Foundation of China(No.2018M630832).
文摘Deformation-induced phase transition of FormⅡto FormⅠin polybutene-1(PB-1)has been investigated by time-resolved Fourier transform infrared(FTIR)spectroscopy over a wide temperature range from 25℃to 105℃.The initial film sample containing orientated lamellae is prepared by pre-stretching of PB-1 melt followed by solidification.This is to realize a homogeneity of subsequent deformation at the mesoscale of lamellar stacks by avoiding large-scale spherulites.The deformation induced phase transition is recognized to occur with two stages:first,FormⅡundergoes the lamellar fragmentation,slipping or local melting after yielding to activate its transition to FormⅠ,which may be realized by releasing the restrictions on chains translational movements in crystalline phase;second,the phase transition proceeds with a continuous dissipation of external work and determines the tensile mechanical response of film.To quantify the relationship between crystalline transition of FormⅡto FormⅠand external tensile field,a simple kinetic equation is well established based on FTIR measurement.The equation can describe not only the dependence of crystal transitional degree on applied specific work,but also the retardation effect of elevating temperature on phase transition.
基金Hunan Provincial Key Laboratory of Micro&Nano Materials Interface Sciencethe National Natural Science Foundation of China(Nos.21773311 and 21972169)Hunan Provincial Science and Technology Plan Project,China(No.2019TP1001)。
文摘The coronavirus disease 2019(COVID-19)caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) has posed severe threats to human health,public safety,and the global economy.Metal nutrient elements can directly or indirectly take part in human immune responses,and metal-related drugs have served as antiviral drugs and/or enzyme inhibitors for many years,providing potential solutions to the prevention and treatment of COVID-19.Metal-based drugs are currently under a variety of chemical structures and exhibit wide-range bio activities,demonstrating irreplaceable advantages in pharmacology.This review is an intention to summarize recent progress in the prevention and treatment strategies against COVID-19 from the perspective of metal pharmacology.The current and potential utilization of metal-based drugs is briefly introduced.Specifically,metallohydrogels that have been shown to present superior antiviral activities are stressed in the paper as potential drugs for the treatment of COVID-19.
基金the National Natural Science Foundation of China(No.52073261).
文摘Poly(lactic acid) (PLA) is a promising bio-based environmentally-friendly plastic. Nevertheless, the physical aging-induced brittleness of PLA limits its widespread applications. Blending with immiscible ductile polymer is an effective way to toughen PLA. However, the underlying details of the toughening mechanism and, in particular, the effect of physical aging are not well understood. Herein, atomic force microscopy (AFM) based nanomechanical mapping technology was utilized to visualize the differences in the deformation mechanisms between unaged and aged PLA/poly(ε-caprolactone) (PCL) blend upon uniaxial drawing. Results show that physical aging has a significant effect on the microscopic Young’s modulus and its distribution of PLA matrix, resulting in a highly heterogeneous response of the PLA/PCL blend to external stress and affecting the mechanical properties of the PLA phase under different extensions. This work provides a new experimental basis for understanding the effect of physical aging on the mechanical properties of PLA-based materials.
基金the National Natural Science Foundation of China(No.51873199)Program for Innovative Research Team(in Science and Technology)in University(No.20IRTSTHN002)。
文摘Although there has been rapid advancement in piezoelectric sensors,challenges still remain in developing wearable piezoelectric sensors by a one-step,continuous and environmentally friendly method.In this work,a 1D flexible coaxial piezoelectric fiber was directly fabricated by melt extrusion molding,whose core and sheath layer are respectively slender steel wire(i.e.,electrode)and PVDF(i.e.,piezoelectric layer).Moreover,such 1D flexible coaxial piezoelectric fiber possesses short response time and high sensitivity,which can be used as a selfpowered sensor for bending and vibration sensing.More interestingly,such 1D flexible coaxial piezoelectric fiber(1D-PFs)can be further endowed with 3D helical structure.Moreover,a wearable and washable motion monitoring system can be constructed via braiding such 3D helical piezoelectric fiber(3D-PF)into commercial textiles.This work paves a new way for developing 1D and 3D piezoelectric fibers through a one-step,continuous and environmentally friendly method,showing potential applications in the field of sensing and wearable electronics.
基金financially supported by the National Natural Science Foundation of China (Nos. 51773183 and U1804133)National Natural Science Foundation of China-Henan Province Joint Funds (No. U1604253)+1 种基金Henan Province University Innovation Talents Support Program (No. 20HASTIT001)Innovation Team of Colleges and Universities in Henan Province(No. 20IRTSTHN002)。
文摘Flexible strain sensor has promising features in successful application of health monitoring, electronic skins and smart robotics, etc.Here, we report an ultrasensitive strain sensor with a novel crack-wrinkle structure(CWS) based on graphite nanoplates(GNPs)/thermoplastic urethane(TPU)/polydimethylsiloxane(PDMS) nanocomposite. The CWS is constructed by pressing and dragging GNP layer on TPU substrate,followed by encapsulating with PDMS as a protective layer. On the basis of the area statistics, the ratio of the crack and wrinkle structures accounts for 31.8% and 9.5%, respectively. When the sensor is stretched, the cracks fracture, the wrinkles could reduce the unrecoverable destruction of cracks, resulting in an excellent recoverability and stability. Based on introduction of the designed CWS in the sensor, the hysteresis effect is limited effectively. The CWS sensor possesses a satisfactory sensitivity(GF=750 under 24% strain), an ultralow detectable limit(strain=0.1%) and a short respond time of 90 ms. For the sensing service behaviors, the CWS sensor exhibits an ultrahigh durability(high stability>2×10^(4) stretching-releasing cycles). The excellent practicality of CWS sensor is demonstrated through various human motion tests,including vigorous exercises of various joint bending, and subtle motions of phonation, facial movements and wrist pulse. The present CWS sensor shows great developing potential in the field of cost-effective, portable and high-performance electronic skins.
