In this paper, the rigid structural thermosensitive polymer （made in lab） of NBS （N-butyl styrene）, N, N-DEAM （diethyl acrylamide） and AM （acrylamide） was prepared. The influence of viscosity for copolymer sol...In this paper, the rigid structural thermosensitive polymer （made in lab） of NBS （N-butyl styrene）, N, N-DEAM （diethyl acrylamide） and AM （acrylamide） was prepared. The influence of viscosity for copolymer solution under different reaction conditions such as temperatures and inorganic salt （monovalent salt and divalent salt） was analyzed. The experiment studies the combination of polymer situation and three different types of surfactants under certain conditions of the room temperature （25℃） and the formation temperature （76℃）. At last, the influence of the surfactant kinds and concentration on the viscosity of the polymer solution are studied. The results show that： The copolymer solution, the apparent viscosity of which decreases with the increasement of temperature, but its viscosity has suddenly increased and thereafter dropped in the transition temperature. So the temperature sensitive effect ofcopolymer is very significantly. When the concentration of inorganic salt and surfactant can be controlled in certain extent, the copolymer solution, the effect increases with the increasement of the concentration, but the viscosity of which decreases with the increasement of shear rate. Shear rate can be controlled in certain extent, shearing stability properties of the copolymer solution are proved.展开更多
As the miniaturization of electronic devices and complication of electronic packaging,there are growing demands for thermal interfacial materials with enhanced thermal conductivity and the capability to direct the hea...As the miniaturization of electronic devices and complication of electronic packaging,there are growing demands for thermal interfacial materials with enhanced thermal conductivity and the capability to direct the heat toward heat sink for highly efficient heat dissipation.Pitch-based carbon fiber(CF)with ultrahigh axial thermal conductivity and aspect ratios exhibits great potential for developing thermally conductive composites as TIMs.However,it is still hard to fabricate composites with aligned carbon fiber in a general approach to fully utilize its excellent axial thermal conductivity in specific direction.Here,three types of CF scaffolds with different oriented structure were developed via magnetic field-assisted Tetris-style stacking and carbonization process.By regulating the magnetic field direction and initial stacking density,the self-supporting CF scaffolds with horizontally aligned(HCS),diagonally aligned and vertically aligned(VCS)fibers were constructed.After embedding the polydimethylsiloxane(PDMS),the three composites exhibited unique heat transfer properties,and the HCS/PDMS and VCS/PDMS composites presented a high thermal conductivity of 42.18 and 45.01 W m^(−1)K^(−1)in fiber alignment direction,respectively,which were about 209 and 224 times higher than that of PDMS.The excellent thermal conductivity is mainly ascribed that the oriented CF scaffolds construct effective phonon transport pathway in the matrix.In addition,fishbone-shaped CF scaffold was also produced by multiple stacking and carbonization process,and the prepared composites exhibited a controlled heat transfer path,which can allow more versatility in the design of thermal management system.展开更多
Silicone rubber(SR) composites are most widely used as thermal interface materials(TIMs) for electronics heat dissipation. Thermal impedance as the main bottleneck limiting the performance of TIMs is usually neglected...Silicone rubber(SR) composites are most widely used as thermal interface materials(TIMs) for electronics heat dissipation. Thermal impedance as the main bottleneck limiting the performance of TIMs is usually neglected. Herein, the thermal impedance of SR composites loaded with different levels of hexagonal boron nitride(h-BN) as TIMs was elaborated for the first time by the ASTM D 5470 standard test and finite element analysis. It was found that elastic modulus and surface roughness of SR composites increased with the increase of h-BN content, indicating that the conformity was reduced. When the assembly pressure was 0.69 MPa, there existed an optimal h-BN content at which the contact resistance was minimum(0.39 K·cm^(2)·W^(-1)). Although the decreased bond line thickness(BLT) by increasing the assembly pressure was beneficial to reduce the thermal impedance, the proper assembly pressure should be selected to prevent the warpage of the contact surfaces and the increase in contact resistance, according to the compression properties of the SR composites. This study provides valuable insights into fabrication of high-performance TIMs for modern electronic device applications.展开更多
Metallocene-catalyzed linear low-density polyethylene/polypropylene （mLLDPE/PP） blends were prepared by ultrasonic extrusion in this work. Their extrusion processing behaviors were estimated by online measured data,...Metallocene-catalyzed linear low-density polyethylene/polypropylene （mLLDPE/PP） blends were prepared by ultrasonic extrusion in this work. Their extrusion processing behaviors were estimated by online measured data, such as the die pressure and flow rate. Crystallization and mechanical properties of the blends were also investigated. The results show that the addition of PP improves the processing behaviors of mLLDPE, but has little effect on its mechanical properties. On the other hand, the addition of mLLDPE improves the impact strength of PP, but has little effect on its processing behavior. The processing behaviors and mechanical properties of mLLDPE/PP blends get further improved due to the presence of ultrasonic oscillation during extrusion. Compared with PP-rich blends, the apparent viscosity drop of mLLDPE-rich blends is more sensitive to ultrasonic oscillation. The ultrasonic oscillation affects the crystal nucleation, while barely the other crystalline behaviors of the blends.展开更多
With the rapid development of nuclear technology,nuclear protection has received extensive attention.As an important strategic resource,rare earth plays an important role in the field of nuclear shielding materials.In...With the rapid development of nuclear technology,nuclear protection has received extensive attention.As an important strategic resource,rare earth plays an important role in the field of nuclear shielding materials.In this review,the shielding principles of rare earth materials are first introduced.According to the type of matrix,the characteristics and current research status of metal-based,inorganic nonmetallic-based and polymer-based rare earth shielding materials are reviewed.Meanwhile,the future development trend of rare earth shielding materials is discussed.展开更多
The multilayered polypropylene （PP） and poly（ethylene-co-octene） （POE） sheets were prepared by the microlayered co-extrusion system. The essential work of fracture （EWF） and the impact tensile methods have bee...The multilayered polypropylene （PP） and poly（ethylene-co-octene） （POE） sheets were prepared by the microlayered co-extrusion system. The essential work of fracture （EWF） and the impact tensile methods have been successfully used to evaluate the toughening behaviors of the PP/POE multilayered blends under quasi-static and dynamic uniaxial tensile stress, respectively. The experimental results indicate that the multilayered structure plays a key role in the toughening behaviors. On increasing the layer number of the multilayered blends, the specific essential work of fracture, we, increases obviously. As for the flwp, there is no obvious variation in the multilayered blends with low POE content （6.79%）, however, obvious enhancement is observed with increasing the layer number of the high POE content multilayered blends （16.57%）. Compared with the conventional blends, the multilayered blends with 6.79% POE content are effective to increase the value of we. Additionally, the multilayered blends with high layer numbers present absolute advantage in improving the impact tensile values.展开更多
Herein,a strong extensional and shearing field was introduced to construct highly oriented hybrid networks of silicon carbide(SiC)-packed boron nitride(BN)platelets to fabricate high-performance wearresistant PA6 comp...Herein,a strong extensional and shearing field was introduced to construct highly oriented hybrid networks of silicon carbide(SiC)-packed boron nitride(BN)platelets to fabricate high-performance wearresistant PA6 composites.Results show that in-plane and through-plane thermal conductivity(TC)of the prepared PA6 composites with a total filler loading of 20 wt.%reached 1.31 and 0.35 W/(m K),352%and 25%higher than those of pure PA6,respectively.It is attributed to the highly oriented hybrid network that facilitates the formation of efficient thermal conductivity pathways.Temperature monitoring results during friction confirm that high TC favors the friction heat dissipation performance.Meanwhile,the yield strength of PA6 composites increased by 39.1%and they still have excellent ductility with an elongation at break of 207.1%.Finally,the wear rate of PA6 composites decreased sharply by 92.5%.This method can be used to manufacture advanced linear bearing and guideway parts,etc。展开更多
The molecular structure of SEBS grafted with maleic anhydride（SEBS-g-MAH） through ultrasound initiation was investigated by nuclear magnetic resonance（NMR）. It can be confirmed that the grafting groups mainly exis...The molecular structure of SEBS grafted with maleic anhydride（SEBS-g-MAH） through ultrasound initiation was investigated by nuclear magnetic resonance（NMR）. It can be confirmed that the grafting groups mainly exist on the terminus of the ultrasound initiated SEBS-g-MAH. However, it was difficult to detailedly confirm the block of the SEBS on which MAH is grafted through characterization of 1H-NMR due to the complex structure of the SEBS. Moreover, the temperaturedependent infrared spectra of the ultrasound initiated SEBS-g-MAH were also analyzed by the perturbation correlation moving window 2D（PCMW2D） correlation spectroscopy. It could confirm that the broken point existed at the joint between poly（ethylene-co-1-butene）（EB block） and polystyrene block（S block）. Therefore, the grafting groups were attached to not only the S block but also the EB block. In addition, in order to well understand the aggregation structure of the ultrasound initiated SEBS-g-MAH, the possible grafting mechanism and aggregation model of the ultrasound initiated SEBS-g-MAH at room temperature were also proposed.展开更多
Highly efficient electromagnetic shielding materials have become an increasing requirement for high-power electronic equipment.Nevertheless,there still remains a challenge in achieving excellent elec-tromagnetic inter...Highly efficient electromagnetic shielding materials have become an increasing requirement for high-power electronic equipment.Nevertheless,there still remains a challenge in achieving excellent elec-tromagnetic interference(EMI)shielding performance with low reflection.Herein,a gradient distri-bution of segregated conductive network consisting of edge-selectively carboxylated graphene(ECG)nanosheets and carboxylated multi-walled carbon nanotubes(cMWCNTs)in poly(vinylidene fluoride)(PVDF)nanocomposites was first designed to achieve outstanding low reflective electromagnetic shielding performance.The sheets of PVDF nanocomposites with different contents of hybrid ECG-cMWCNTs were stacked and further hot-pressed to fabricate the layered PVDF nanocomposites.The overall EMI shielding effectiveness(EMI SE)performance could be further improved by increasing the overall thickness and the layer number.With a fixed thickness of 2.0 mm,the PVDF@7.5wt%ECG_(1)-cMWCNTs 3 six-layered nanocom-posites exhibit excellent EMI SE reaching 79.87 dB with an absorption effectiveness(SE A)of 79.62 dB.The excellent EMI SE performance was ascribed to the multiple interface reflection of the segregated conduc-tive network.Meanwhile,the gradient distribution of ECG-cMWCNTs endows the nanocomposites with a strong absorption ability.This work provides a novel strategy for fabricating EMI shielding composites with low reflection for application in portable electronic devices.展开更多
High oxidative stress injury and bacterial infection are the main challenges that impair wound healing in diabetic patients.Therefore,a hydrogel with enhanced antimicrobial and antioxidant properties was developed for...High oxidative stress injury and bacterial infection are the main challenges that impair wound healing in diabetic patients.Therefore,a hydrogel with enhanced antimicrobial and antioxidant properties was developed for rapid healing of diabetic wounds.In this study,chitosan methacrylate-gallic acid(CSMA-GA)polymer with antioxidant activity,antimicrobial activity,and ultraviolet(UV)-triggered gelling properties was developed as a hydrogel precursor.Meanwhile,amphiphilic Pluronic F127 molecules were used to load hydrophobic chlorhexidine drug molecules to obtain F127/chlorhexidine nanoparticle(NP)with strong antibacterial activity.Subsequently,F127/chlorhexidine NPs were encapsulated in CSMA-GA hydrogel to further enhance its antibacterial activity.The hybrid hydrogel platform(CSMA-GA/F127/chlorhexidine(CMGFC))exhibited high antibacterial efficiency(>99.9%)and strong reactive oxygen species(ROS)scavenging ability(>80.0%),which effectively protected cells from external oxidative stress(upregulated superoxide dismutase(SOD)and glutathione/oxidized glutathione disulfide(GSH/GSSG)levels and downregulated malondialdehyde(MDA)levels).Moreover,in vivo results proved that the CMGFC hydrogel significantly reduced inflammatory responses(downregulated interleukin-6(IL-6)and upregulated interleukin-10(IL-10)levels),promoted angiogenesis(upregulated vascular endothelial growth factor(VEGF)and platelet endothelial cell adhesion molecule-1(CD 31)levels),and wound healing(enhanced collagen deposition and tissue remodelling).Overall,the CMGFC hydrogel with enhanced antimicrobial and antioxidant properties demonstrated significant potential to enhance diabetic wound healing.展开更多
In this work, the effects of annealing conditions on the microstructure of polypropylene（PP） precursor films and further on the porous structure and permeability of stretched membranes were investigated. Combination...In this work, the effects of annealing conditions on the microstructure of polypropylene（PP） precursor films and further on the porous structure and permeability of stretched membranes were investigated. Combinations of WAXD, FTIR, DSC and DMA results clearly showed the crystalline orientation and crystallinity of the precursor film increased with annealing temperature, while the molecular chain entanglements in the amorphous phase decreased. Changes in the deformation behavior suggested more lamellar separation occurred for the films annealed at higher temperatures. Surface morphologies of the membranes examined by SEM revealed more pore number and uniform porous structure as the annealing temperature increased. In accordance with the SEM results, the permeability of the membranes increased with annealing temperature. On the other hand, it was found that 10 min was almost enough for the annealing process to obtain the microporous membranes with an optimal permeability.展开更多
Self-lubricating polyphenylene sulfide(PPS)composites were fabricated by constructing a segregated network structure using the co-deposition method.Both carboxyl-functionalized multi-walled carbon nanotubes(CNTs)and s...Self-lubricating polyphenylene sulfide(PPS)composites were fabricated by constructing a segregated network structure using the co-deposition method.Both carboxyl-functionalized multi-walled carbon nanotubes(CNTs)and silicon carbide(SiC)were successfully coated on the surface of PPS powders with the aid of self-polymerization of dopamine(PDA)and co-polymerization between PDA and polyethyleneimine(PEI),thereby forming PPS@PDA-CNTs-SiC hierarchical reinforcing hybrids.Results showed that the thermal conductivity of PPS@PDA-CNTs-SiC(0.97 W/(m K))is about 120%higher than that of PPS/CNTs/SiC.The friction coefficient(0.193)and specific wear rate(2.50×10^(-5)mm^(3)/(N m))of PPS@PDA-CNTs-SiC are 18.9%and 50%lower than those of PPS/CNTs/SiC,respectively.The enhanced thermal conductivity of PPS@PDA-CNTs-SiC contributes to rapid dissipation of frictional heat at the sliding interface which protects the polymer substrate from being destroyed or peeled,thereby improving the tribological performance.This work provides new insights into expanding the application of self-lubricating polymer composites in the fields where efficient heat dissipation is also a primary concern.展开更多
Traditional hydrogels-based actuators are hindered by limitations such as low deliverable forces(∼2 kPa)and sluggish actuation speeds,culminating in persistent issues with low work density(∼0.01 kJ/m^(3)).Furthermor...Traditional hydrogels-based actuators are hindered by limitations such as low deliverable forces(∼2 kPa)and sluggish actuation speeds,culminating in persistent issues with low work density(∼0.01 kJ/m^(3)).Furthermore,achieving low hysteresis and high strength presents significant challenges in both their synthesis and applications.Herein,we developed poly(acrylic acid)hydrogels characterized by sparse cross-linking and high entanglement,effectively addressing these issues.Inspired by the energy conversion mechanisms of mammalian muscle fibers,the hydrogels were utilized for storing and releasing elastic potential energy in polymer network.Notably,we achieved a remarkable contractile force of 60.6 kPa,an ultrahigh work density of 30.8 kJ/m^(3),and an energy conversion efficiency of up to 53.8%.Furthermore,the hydrogels exhibit unique dual-state functionality,seamlessly transitioning between elasticity and plasticity,which paves the way for adaptable and precisely controllable energy release mechanisms.These features hold significant potential for diverse practical applications,providing a promising advancement for hydrogel actuators.展开更多
Enhanced diabetic wound repair remained a global challenge.Herein,we reported a novel hydrogel with glucose-responsive hyperglycemia regulation and antioxidant activity for enhanced diabetic wound repair.In this study...Enhanced diabetic wound repair remained a global challenge.Herein,we reported a novel hydrogel with glucose-responsive hyperglycemia regulation and antioxidant activity for enhanced diabetic wound repair.In this study,gallic acid(GA)with strong antioxidant activity was grafted onto chitosan(CS)chains by one-step synthesis,and then incorporated into poly(ethylene glycol)diacrylate(PEG-DA)hydrogel matrix to obtain a novel antioxidant hybrid hydrogel(PEG-DA/CS-GA).Meanwhile,polyethyleneimine(PEI)was modified with a unique glucose-sensitive phenylboronic acid(PBA)molecule to load insulin(PEIPBA/insulin nano-particles,PEI-PBA/insulin NPs),which could be immobilized in the PEG-DA/CS-GA hybrid hydrogel by the formation of dynamic borate bond between the phenylboronic acid groups on the PEI-PBA and the polyphenol groups on the CSGA.The results indicated that the PEG-DA/PEI-PBA/insulin/CS-GA(PPIC)hydrogel platform not only had remarkable biocompatibility,but also displayed extraordinary antioxidant properties(DPPH scavenging rate>95.0%),and effectively protected cells from oxidative damage(decreased MDA levels,increased Superoxide dismutase(SOD)levels and stable GSH/GSSG levels).Meanwhile,the PPIC hydrogel also exhibited unique glucose-responsive insulin release characteristics,and effectively regulated the blood glucose level.The in vitro and in vivo results demonstrated that our PPIC hydrogel could promoted angiogenesis(increased VEGF and CD 31 expression),reshaped the inflammatory microenvironment(decreased IL-6 and increased IL-10 level),and achieved wound closure within 20 days.All these results strongly indicated that the PPIC hydrogel represented a tough and efficient platform for diabetic wound treatment.展开更多
Anti-infection and neovascularization at the wound site are two vital factors that accelerate diabetic wound healing. However, for a wound healing dressing, the two functions need to work at different sites(inner and ...Anti-infection and neovascularization at the wound site are two vital factors that accelerate diabetic wound healing. However, for a wound healing dressing, the two functions need to work at different sites(inner and outer), giving big challenges for dressing design. In this study, we fabricated a novel sodium alginate/chitosan(SA/CS) Janus hydrogel dressing by the assembly of SA hydrogel loaded with silver nanoparticles(Ag NPs) and CS hydrogel impregnated with L-arginine loaded sodium alginate microspheres(Arg MSs) based on electrostatic interactions to combine the two functions. The outer SA-Ag NP hydrogel could prevent infection while avoiding the deposition of Ag NPs in the wound site, and the inner CS-Arg MS hydrogel on the wound surface could realize the sustained release of L-arginine and promote vascular regeneration. The composition, morphology and swelling/degradation of the SA-Ag NP/CS-Arg MS hydrogel were characterized systematically. L-Arginine release behavior has been tested and SA-Ag NP/CSArg MS hydrogel has been confirmed for excellent biocompatibility. Antibacterial and angiogenesis assays demonstrated the antibacterial and angiogenesis characteristics of the SA-Ag NP/CS-Arg MS hydrogel. Finally, in vivo diabetic wound healing assay demonstrated that the SA-Ag NP/CS-Arg MS hydrogel could significantly accelerate re-epithelialization, granulation tissue formation, collagen deposition and angiogenesis, thereby resulting in enhanced diabetic wound healing。展开更多
Nowadays, there are still many challenges to skin regeneration. As a new type of skin substitute, hydrogel has emerging gradually with its excellent properties. However, it is still a challenge to combine with biologi...Nowadays, there are still many challenges to skin regeneration. As a new type of skin substitute, hydrogel has emerging gradually with its excellent properties. However, it is still a challenge to combine with biological active agents to facilitate skin regeneration. Under the circumstance, we synthesized argininebased poly(ester amide)(Arg-PEA) and hyaluronic acid(HA-MA), and combined them into new hybrid hydrogels via photo-crosslinking. We found that the internal structure and physicochemical properties of hybrid hydrogels were greatly improved with the increase of content of Arg-PEA. Therefore, we designed hybrid hydrogels with 5 wt% and 10 wt% of Arg-PEA content, respectively. Besides, we selected the corresponding anti-inflammatory(CRP, TNF-α) indicators to detect the anti-inflammatory properties of the hybrid hydrogels at the protein level, and the corresponding antioxidant indicators(SOD, GSH/GSSG, MDA)were selected to investigate the antioxidant properties of hybrid hydrogels at the cellular level in vitro.In addition, we also selected relevant genes to test the effect of hybrid hydrogels on fibrosis and vascularization in the process of skin wound healing in vitro and verified them in vivo with a mouse dorsum wound model. The results confirmed that Arg-PEA/HA-MA(AH) hybrid hydrogel was a prospective scaffold material for skin regeneration.展开更多
文摘In this paper, the rigid structural thermosensitive polymer （made in lab） of NBS （N-butyl styrene）, N, N-DEAM （diethyl acrylamide） and AM （acrylamide） was prepared. The influence of viscosity for copolymer solution under different reaction conditions such as temperatures and inorganic salt （monovalent salt and divalent salt） was analyzed. The experiment studies the combination of polymer situation and three different types of surfactants under certain conditions of the room temperature （25℃） and the formation temperature （76℃）. At last, the influence of the surfactant kinds and concentration on the viscosity of the polymer solution are studied. The results show that： The copolymer solution, the apparent viscosity of which decreases with the increasement of temperature, but its viscosity has suddenly increased and thereafter dropped in the transition temperature. So the temperature sensitive effect ofcopolymer is very significantly. When the concentration of inorganic salt and surfactant can be controlled in certain extent, the copolymer solution, the effect increases with the increasement of the concentration, but the viscosity of which decreases with the increasement of shear rate. Shear rate can be controlled in certain extent, shearing stability properties of the copolymer solution are proved.
基金The authors are grateful for the financial support by Sichuan Science and Technology Program(2022YFH0090)the Fundamental Research Funds for the Central Universities.
文摘As the miniaturization of electronic devices and complication of electronic packaging,there are growing demands for thermal interfacial materials with enhanced thermal conductivity and the capability to direct the heat toward heat sink for highly efficient heat dissipation.Pitch-based carbon fiber(CF)with ultrahigh axial thermal conductivity and aspect ratios exhibits great potential for developing thermally conductive composites as TIMs.However,it is still hard to fabricate composites with aligned carbon fiber in a general approach to fully utilize its excellent axial thermal conductivity in specific direction.Here,three types of CF scaffolds with different oriented structure were developed via magnetic field-assisted Tetris-style stacking and carbonization process.By regulating the magnetic field direction and initial stacking density,the self-supporting CF scaffolds with horizontally aligned(HCS),diagonally aligned and vertically aligned(VCS)fibers were constructed.After embedding the polydimethylsiloxane(PDMS),the three composites exhibited unique heat transfer properties,and the HCS/PDMS and VCS/PDMS composites presented a high thermal conductivity of 42.18 and 45.01 W m^(−1)K^(−1)in fiber alignment direction,respectively,which were about 209 and 224 times higher than that of PDMS.The excellent thermal conductivity is mainly ascribed that the oriented CF scaffolds construct effective phonon transport pathway in the matrix.In addition,fishbone-shaped CF scaffold was also produced by multiple stacking and carbonization process,and the prepared composites exhibited a controlled heat transfer path,which can allow more versatility in the design of thermal management system.
基金financially supported by Sichuan Science and Technology Program (No.2022YFH0090)the Fundamental Research Funds for the Central Universities。
文摘Silicone rubber(SR) composites are most widely used as thermal interface materials(TIMs) for electronics heat dissipation. Thermal impedance as the main bottleneck limiting the performance of TIMs is usually neglected. Herein, the thermal impedance of SR composites loaded with different levels of hexagonal boron nitride(h-BN) as TIMs was elaborated for the first time by the ASTM D 5470 standard test and finite element analysis. It was found that elastic modulus and surface roughness of SR composites increased with the increase of h-BN content, indicating that the conformity was reduced. When the assembly pressure was 0.69 MPa, there existed an optimal h-BN content at which the contact resistance was minimum(0.39 K·cm^(2)·W^(-1)). Although the decreased bond line thickness(BLT) by increasing the assembly pressure was beneficial to reduce the thermal impedance, the proper assembly pressure should be selected to prevent the warpage of the contact surfaces and the increase in contact resistance, according to the compression properties of the SR composites. This study provides valuable insights into fabrication of high-performance TIMs for modern electronic device applications.
基金This work was financially supported by the Special Funds for Major State Basic Research Projects of China (No.2005CB623800)the National Natural Science Foundation of China (No. 20374037)the Open Foundation of Key Laboratory of Rubber-plastics (QUST),Ministry of Education, China and the Foundation for Youth of Sichuan University
文摘Metallocene-catalyzed linear low-density polyethylene/polypropylene （mLLDPE/PP） blends were prepared by ultrasonic extrusion in this work. Their extrusion processing behaviors were estimated by online measured data, such as the die pressure and flow rate. Crystallization and mechanical properties of the blends were also investigated. The results show that the addition of PP improves the processing behaviors of mLLDPE, but has little effect on its mechanical properties. On the other hand, the addition of mLLDPE improves the impact strength of PP, but has little effect on its processing behavior. The processing behaviors and mechanical properties of mLLDPE/PP blends get further improved due to the presence of ultrasonic oscillation during extrusion. Compared with PP-rich blends, the apparent viscosity drop of mLLDPE-rich blends is more sensitive to ultrasonic oscillation. The ultrasonic oscillation affects the crystal nucleation, while barely the other crystalline behaviors of the blends.
基金Project supported by the National Defense Science and Technology Foundation of State Key Laboratory (6142A06180102)。
文摘With the rapid development of nuclear technology,nuclear protection has received extensive attention.As an important strategic resource,rare earth plays an important role in the field of nuclear shielding materials.In this review,the shielding principles of rare earth materials are first introduced.According to the type of matrix,the characteristics and current research status of metal-based,inorganic nonmetallic-based and polymer-based rare earth shielding materials are reviewed.Meanwhile,the future development trend of rare earth shielding materials is discussed.
基金financially supported by the National Natural Science Foundation of China(Nos.51273132,51227802 and 51121001)Program for New Century Excellent Talents in Universities(No.NCET-13-0392)
文摘The multilayered polypropylene （PP） and poly（ethylene-co-octene） （POE） sheets were prepared by the microlayered co-extrusion system. The essential work of fracture （EWF） and the impact tensile methods have been successfully used to evaluate the toughening behaviors of the PP/POE multilayered blends under quasi-static and dynamic uniaxial tensile stress, respectively. The experimental results indicate that the multilayered structure plays a key role in the toughening behaviors. On increasing the layer number of the multilayered blends, the specific essential work of fracture, we, increases obviously. As for the flwp, there is no obvious variation in the multilayered blends with low POE content （6.79%）, however, obvious enhancement is observed with increasing the layer number of the high POE content multilayered blends （16.57%）. Compared with the conventional blends, the multilayered blends with 6.79% POE content are effective to increase the value of we. Additionally, the multilayered blends with high layer numbers present absolute advantage in improving the impact tensile values.
基金supported by the National Natural Science Foundation of China(No.51790501)the Sichuan Science and Technology Program(No.2022YFH0090)the Fundamental Research Funds for the Central Universities.
文摘Herein,a strong extensional and shearing field was introduced to construct highly oriented hybrid networks of silicon carbide(SiC)-packed boron nitride(BN)platelets to fabricate high-performance wearresistant PA6 composites.Results show that in-plane and through-plane thermal conductivity(TC)of the prepared PA6 composites with a total filler loading of 20 wt.%reached 1.31 and 0.35 W/(m K),352%and 25%higher than those of pure PA6,respectively.It is attributed to the highly oriented hybrid network that facilitates the formation of efficient thermal conductivity pathways.Temperature monitoring results during friction confirm that high TC favors the friction heat dissipation performance.Meanwhile,the yield strength of PA6 composites increased by 39.1%and they still have excellent ductility with an elongation at break of 207.1%.Finally,the wear rate of PA6 composites decreased sharply by 92.5%.This method can be used to manufacture advanced linear bearing and guideway parts,etc。
基金financially supported by the National Natural Science Foundation of China(Nos.51273132,50933004 and 51121001)
文摘The molecular structure of SEBS grafted with maleic anhydride（SEBS-g-MAH） through ultrasound initiation was investigated by nuclear magnetic resonance（NMR）. It can be confirmed that the grafting groups mainly exist on the terminus of the ultrasound initiated SEBS-g-MAH. However, it was difficult to detailedly confirm the block of the SEBS on which MAH is grafted through characterization of 1H-NMR due to the complex structure of the SEBS. Moreover, the temperaturedependent infrared spectra of the ultrasound initiated SEBS-g-MAH were also analyzed by the perturbation correlation moving window 2D（PCMW2D） correlation spectroscopy. It could confirm that the broken point existed at the joint between poly（ethylene-co-1-butene）（EB block） and polystyrene block（S block）. Therefore, the grafting groups were attached to not only the S block but also the EB block. In addition, in order to well understand the aggregation structure of the ultrasound initiated SEBS-g-MAH, the possible grafting mechanism and aggregation model of the ultrasound initiated SEBS-g-MAH at room temperature were also proposed.
基金support from the Sichuan Science and Technology Program(2022YFH0090)and the Fundamental Research Funds for the Central Universities.
文摘Highly efficient electromagnetic shielding materials have become an increasing requirement for high-power electronic equipment.Nevertheless,there still remains a challenge in achieving excellent elec-tromagnetic interference(EMI)shielding performance with low reflection.Herein,a gradient distri-bution of segregated conductive network consisting of edge-selectively carboxylated graphene(ECG)nanosheets and carboxylated multi-walled carbon nanotubes(cMWCNTs)in poly(vinylidene fluoride)(PVDF)nanocomposites was first designed to achieve outstanding low reflective electromagnetic shielding performance.The sheets of PVDF nanocomposites with different contents of hybrid ECG-cMWCNTs were stacked and further hot-pressed to fabricate the layered PVDF nanocomposites.The overall EMI shielding effectiveness(EMI SE)performance could be further improved by increasing the overall thickness and the layer number.With a fixed thickness of 2.0 mm,the PVDF@7.5wt%ECG_(1)-cMWCNTs 3 six-layered nanocom-posites exhibit excellent EMI SE reaching 79.87 dB with an absorption effectiveness(SE A)of 79.62 dB.The excellent EMI SE performance was ascribed to the multiple interface reflection of the segregated conduc-tive network.Meanwhile,the gradient distribution of ECG-cMWCNTs endows the nanocomposites with a strong absorption ability.This work provides a novel strategy for fabricating EMI shielding composites with low reflection for application in portable electronic devices.
基金This work was supported by the National Natural Science Foundation of China(No.51973243)Fundamental Research Funds for the Central Universities(No.191gzd35)+2 种基金Guangdong Innovative and Entrepreneurial Research Team Program(No.2016ZT06S029)Shenzhen Basic Research Project(No.JCYJ20190807155801657)Key international(regional)cooperative research projects of the National Natural Science Foundation of China(No.5181001045).
文摘High oxidative stress injury and bacterial infection are the main challenges that impair wound healing in diabetic patients.Therefore,a hydrogel with enhanced antimicrobial and antioxidant properties was developed for rapid healing of diabetic wounds.In this study,chitosan methacrylate-gallic acid(CSMA-GA)polymer with antioxidant activity,antimicrobial activity,and ultraviolet(UV)-triggered gelling properties was developed as a hydrogel precursor.Meanwhile,amphiphilic Pluronic F127 molecules were used to load hydrophobic chlorhexidine drug molecules to obtain F127/chlorhexidine nanoparticle(NP)with strong antibacterial activity.Subsequently,F127/chlorhexidine NPs were encapsulated in CSMA-GA hydrogel to further enhance its antibacterial activity.The hybrid hydrogel platform(CSMA-GA/F127/chlorhexidine(CMGFC))exhibited high antibacterial efficiency(>99.9%)and strong reactive oxygen species(ROS)scavenging ability(>80.0%),which effectively protected cells from external oxidative stress(upregulated superoxide dismutase(SOD)and glutathione/oxidized glutathione disulfide(GSH/GSSG)levels and downregulated malondialdehyde(MDA)levels).Moreover,in vivo results proved that the CMGFC hydrogel significantly reduced inflammatory responses(downregulated interleukin-6(IL-6)and upregulated interleukin-10(IL-10)levels),promoted angiogenesis(upregulated vascular endothelial growth factor(VEGF)and platelet endothelial cell adhesion molecule-1(CD 31)levels),and wound healing(enhanced collagen deposition and tissue remodelling).Overall,the CMGFC hydrogel with enhanced antimicrobial and antioxidant properties demonstrated significant potential to enhance diabetic wound healing.
基金financially supported by the National Natural Science Foundation of China(No.51273132)Chinese Scholarship Council(CSC)
文摘In this work, the effects of annealing conditions on the microstructure of polypropylene（PP） precursor films and further on the porous structure and permeability of stretched membranes were investigated. Combinations of WAXD, FTIR, DSC and DMA results clearly showed the crystalline orientation and crystallinity of the precursor film increased with annealing temperature, while the molecular chain entanglements in the amorphous phase decreased. Changes in the deformation behavior suggested more lamellar separation occurred for the films annealed at higher temperatures. Surface morphologies of the membranes examined by SEM revealed more pore number and uniform porous structure as the annealing temperature increased. In accordance with the SEM results, the permeability of the membranes increased with annealing temperature. On the other hand, it was found that 10 min was almost enough for the annealing process to obtain the microporous membranes with an optimal permeability.
基金financially supported by the China Postdoctoral Science Foundation(No.2020M673217)the National Natural Science Foundation of China(No.51703137)the Fundamental Research Funds for the Central Universities
文摘Self-lubricating polyphenylene sulfide(PPS)composites were fabricated by constructing a segregated network structure using the co-deposition method.Both carboxyl-functionalized multi-walled carbon nanotubes(CNTs)and silicon carbide(SiC)were successfully coated on the surface of PPS powders with the aid of self-polymerization of dopamine(PDA)and co-polymerization between PDA and polyethyleneimine(PEI),thereby forming PPS@PDA-CNTs-SiC hierarchical reinforcing hybrids.Results showed that the thermal conductivity of PPS@PDA-CNTs-SiC(0.97 W/(m K))is about 120%higher than that of PPS/CNTs/SiC.The friction coefficient(0.193)and specific wear rate(2.50×10^(-5)mm^(3)/(N m))of PPS@PDA-CNTs-SiC are 18.9%and 50%lower than those of PPS/CNTs/SiC,respectively.The enhanced thermal conductivity of PPS@PDA-CNTs-SiC contributes to rapid dissipation of frictional heat at the sliding interface which protects the polymer substrate from being destroyed or peeled,thereby improving the tribological performance.This work provides new insights into expanding the application of self-lubricating polymer composites in the fields where efficient heat dissipation is also a primary concern.
基金supported by China Scholarship Council(202308050028)。
文摘Traditional hydrogels-based actuators are hindered by limitations such as low deliverable forces(∼2 kPa)and sluggish actuation speeds,culminating in persistent issues with low work density(∼0.01 kJ/m^(3)).Furthermore,achieving low hysteresis and high strength presents significant challenges in both their synthesis and applications.Herein,we developed poly(acrylic acid)hydrogels characterized by sparse cross-linking and high entanglement,effectively addressing these issues.Inspired by the energy conversion mechanisms of mammalian muscle fibers,the hydrogels were utilized for storing and releasing elastic potential energy in polymer network.Notably,we achieved a remarkable contractile force of 60.6 kPa,an ultrahigh work density of 30.8 kJ/m^(3),and an energy conversion efficiency of up to 53.8%.Furthermore,the hydrogels exhibit unique dual-state functionality,seamlessly transitioning between elasticity and plasticity,which paves the way for adaptable and precisely controllable energy release mechanisms.These features hold significant potential for diverse practical applications,providing a promising advancement for hydrogel actuators.
基金supported by the National Natural Science Foundation of China(No.51973243)Fundamental Research Funds for the Central Universities(No.191gzd35)+2 种基金Guangdong Innovative and Entrepreneurial Research Team Program(No.2016ZT06S029)Shenzhen Basic Research Project(No.JCYJ20190807155801657)Key international(regional)cooperative research projects of the National Natural Science Foundation of China(No.5181001045).
文摘Enhanced diabetic wound repair remained a global challenge.Herein,we reported a novel hydrogel with glucose-responsive hyperglycemia regulation and antioxidant activity for enhanced diabetic wound repair.In this study,gallic acid(GA)with strong antioxidant activity was grafted onto chitosan(CS)chains by one-step synthesis,and then incorporated into poly(ethylene glycol)diacrylate(PEG-DA)hydrogel matrix to obtain a novel antioxidant hybrid hydrogel(PEG-DA/CS-GA).Meanwhile,polyethyleneimine(PEI)was modified with a unique glucose-sensitive phenylboronic acid(PBA)molecule to load insulin(PEIPBA/insulin nano-particles,PEI-PBA/insulin NPs),which could be immobilized in the PEG-DA/CS-GA hybrid hydrogel by the formation of dynamic borate bond between the phenylboronic acid groups on the PEI-PBA and the polyphenol groups on the CSGA.The results indicated that the PEG-DA/PEI-PBA/insulin/CS-GA(PPIC)hydrogel platform not only had remarkable biocompatibility,but also displayed extraordinary antioxidant properties(DPPH scavenging rate>95.0%),and effectively protected cells from oxidative damage(decreased MDA levels,increased Superoxide dismutase(SOD)levels and stable GSH/GSSG levels).Meanwhile,the PPIC hydrogel also exhibited unique glucose-responsive insulin release characteristics,and effectively regulated the blood glucose level.The in vitro and in vivo results demonstrated that our PPIC hydrogel could promoted angiogenesis(increased VEGF and CD 31 expression),reshaped the inflammatory microenvironment(decreased IL-6 and increased IL-10 level),and achieved wound closure within 20 days.All these results strongly indicated that the PPIC hydrogel represented a tough and efficient platform for diabetic wound treatment.
基金supported by National Natural Science Foundation of China (Nos. 51973243 and 52103039)General Program of Guangdong Natural Science Foundation (No. 2020A1515010983)Science and Technology Planning Project of Shenzhen (No.JCYJ20190807155801657)。
文摘Anti-infection and neovascularization at the wound site are two vital factors that accelerate diabetic wound healing. However, for a wound healing dressing, the two functions need to work at different sites(inner and outer), giving big challenges for dressing design. In this study, we fabricated a novel sodium alginate/chitosan(SA/CS) Janus hydrogel dressing by the assembly of SA hydrogel loaded with silver nanoparticles(Ag NPs) and CS hydrogel impregnated with L-arginine loaded sodium alginate microspheres(Arg MSs) based on electrostatic interactions to combine the two functions. The outer SA-Ag NP hydrogel could prevent infection while avoiding the deposition of Ag NPs in the wound site, and the inner CS-Arg MS hydrogel on the wound surface could realize the sustained release of L-arginine and promote vascular regeneration. The composition, morphology and swelling/degradation of the SA-Ag NP/CS-Arg MS hydrogel were characterized systematically. L-Arginine release behavior has been tested and SA-Ag NP/CSArg MS hydrogel has been confirmed for excellent biocompatibility. Antibacterial and angiogenesis assays demonstrated the antibacterial and angiogenesis characteristics of the SA-Ag NP/CS-Arg MS hydrogel. Finally, in vivo diabetic wound healing assay demonstrated that the SA-Ag NP/CS-Arg MS hydrogel could significantly accelerate re-epithelialization, granulation tissue formation, collagen deposition and angiogenesis, thereby resulting in enhanced diabetic wound healing。
基金supported by the National Natural Science Foundation of China (No. 52103039)Sichuan University postdoctoral interdisciplinary Innovation Fund。
文摘Nowadays, there are still many challenges to skin regeneration. As a new type of skin substitute, hydrogel has emerging gradually with its excellent properties. However, it is still a challenge to combine with biological active agents to facilitate skin regeneration. Under the circumstance, we synthesized argininebased poly(ester amide)(Arg-PEA) and hyaluronic acid(HA-MA), and combined them into new hybrid hydrogels via photo-crosslinking. We found that the internal structure and physicochemical properties of hybrid hydrogels were greatly improved with the increase of content of Arg-PEA. Therefore, we designed hybrid hydrogels with 5 wt% and 10 wt% of Arg-PEA content, respectively. Besides, we selected the corresponding anti-inflammatory(CRP, TNF-α) indicators to detect the anti-inflammatory properties of the hybrid hydrogels at the protein level, and the corresponding antioxidant indicators(SOD, GSH/GSSG, MDA)were selected to investigate the antioxidant properties of hybrid hydrogels at the cellular level in vitro.In addition, we also selected relevant genes to test the effect of hybrid hydrogels on fibrosis and vascularization in the process of skin wound healing in vitro and verified them in vivo with a mouse dorsum wound model. The results confirmed that Arg-PEA/HA-MA(AH) hybrid hydrogel was a prospective scaffold material for skin regeneration.
