A simple non-isocyanate route synthesizing thermoplastic polyurethanes（TPUs） with good thermal and mechanical properties is described. Melt transurethane polycondensation of dimethyl 1,6-hexamethylene dicarbamate wi...A simple non-isocyanate route synthesizing thermoplastic polyurethanes（TPUs） with good thermal and mechanical properties is described. Melt transurethane polycondensation of dimethyl 1,6-hexamethylene dicarbamate with 1,4-butanediol and 1,6-hexanediol was conducted at different molar ratios under the catalysis of tetrabutyl titanate. A series of crystallizable non-isocyanate TPUs with high molecular weight were prepared. The TPUs were characterized by gel permeation chromatography, FT-IR, 1 H-NMR, differential scanning calorimetry, thermogravimetric analysis, wide angle X-ray diffraction, AFM, and tensile tests. The TPUs exhibited Mn ranging from 12 500 to 26 400 g/mol, Mw from 16 700 to 56 400 g/mol, Tm up to 151.4 °C, and initial decomposition temperature over 241.8 °C. Their tensile strength reached 42.99 MPa with a strain at break of 30.00%. TPUs constructed simply with butylene, hexylene, and urethane linkages were successfully synthesized through a non-isocyanate route.展开更多
Adjusting the structure of the hard segment(HS)represents a key method for manipulating the mechanical properties of thermoplastic polyurethane(TPU).This study developed a novel molecular design strategy to tailor TPU...Adjusting the structure of the hard segment(HS)represents a key method for manipulating the mechanical properties of thermoplastic polyurethane(TPU).This study developed a novel molecular design strategy to tailor TPU's mechanical performance through altering the terminal diisocyanate structure of HS.The typical HDI-BDO based TPU was chosen as a model.Replacing HS's terminal HDI residues with aromatic PPDI,TODI,and MDI(the corresponding TPUs are named as 2P,2TO,and 2M,respectively)enabled broad tuning of TPU's Young's modulus while maintaining high tensile strength and elongation.Compared with linear PPDI and TODI,the bent and unsymmetrical MDI exhibits greater deviation from the central axis of the middle HDI-BDO segment,which reduces HS's capability of three-dimensionally ordered packing.Therefore,2P and 2TO show higher hydrogen bond content and crystallinity,stronger physical crosslinking network,and thus much higher Young's modulus than 2M(75.6 MPa).Besides geometric structure,π–πstacking between HS's terminal aromatic diisocyanates critically governs TPU's physical crosslinking network.In 2P,π–πstacking induces torsion of the middle HDI-BDO segment and disrupts the neighboring hydrogen bonds,leading to a dense network with fine hard blocks.In contrast,the lateral methyl groups in TODI hinderπ–πstacking,resulting in a sparse network with large hard blocks.Accordingly,2TO exhibits a higher Young's modulus(146.2 MPa)than 2P(124.0 MPa),but greater strain-rate sensitivity.展开更多
The continuous improvement in patient care and recovery is driving the development of innovative materials for medical applications.Medical sutures,essential for securing implants and closing deep wounds,have evolved ...The continuous improvement in patient care and recovery is driving the development of innovative materials for medical applications.Medical sutures,essential for securing implants and closing deep wounds,have evolved to incorporate smart materials capable of responding to various stimuli.This study explores the potential of thermoresponsive sutures,made from shape memory materials,that contract upon heating to bring loose stitches closer together,promoting optimal wound closure.We developed nanocomposites based on a blend of poly(lactic acid)(PLA)and thermoplastic polyurethane(TPU)—biopolymers that inherently exhibit shape memory—enhanced with carbon nanotubes(CNT)and graphene nanoplatelets(GN)to improve mechanical performance.PLA/TPU(50/50)nanocomposites were prepared with 1 and 2 wt%GN,as well as hybrid formulations combining 1 wt%CNT with 1 or 2 wt%GN,using a twin-screw extrusion process to form filaments.These filaments were characterized through differential scanning calorimetry(DSC),field emission gun scanning electron microscopy(FEG-SEM),tensile testing,and shape memory assessments.While the PLA/TPU blend is immiscible,TPU enhances the crystallinity(X_(c))of the PLA phase,further increased by the addition of CNT and GN.FEG-SEM images indicate CNTs primarily in the PLA phase and GN in the TPU phase.PLA/TPU with 1 or 2 wt%GN showed the highest potential for suture applications,with a high elastic modulus(~1000 MPa),significant strain at break(~10%),and effective shape recovery(~20%at 55℃ for 30 min).These findings suggest that these nanocomposites can enhance suture performance with controlled shape recovery that is suitable for medical use.展开更多
Polyether and polyether/ester based TPU （thermoplastic polyurethanes） were investigated with wide-angle XRD （X-ray diffraction） and SAXS （small angle X-ray scattering）. Furthermore, SAXS measurements were perfor...Polyether and polyether/ester based TPU （thermoplastic polyurethanes） were investigated with wide-angle XRD （X-ray diffraction） and SAXS （small angle X-ray scattering）. Furthermore, SAXS measurements were performed in the temperature range of 30 ℃ to 130 ℃. Polyether based polymers exhibit only one broad diffraction signal in a region of 2 θ 15° to 25°. In case of polyurethanes with ether/ester modification, the broad diffraction signal arises with small sharp diffraction signals. SAXS measurements of polymers reveal the size and shape of the crystalline zones of the polymer. Between 30 ℃ and 130 ℃ the size of the crystalline zone changes significantly. The size decreases in most of investigated TPU. In the case of Desmopan 9365D an increase of the particle size was observed.展开更多
Aluminum hypophosphite （AP） was used to prepare flame-retarded thermoplastic polyurethane （FR-TPU） composites, and their flame retardancy, thermal degradation and mechanical properties were investigated by limitin...Aluminum hypophosphite （AP） was used to prepare flame-retarded thermoplastic polyurethane （FR-TPU） composites, and their flame retardancy, thermal degradation and mechanical properties were investigated by limiting oxygen index （LOI）, vertical burning test （UL-94）, thermogravimetric analysis （TGA）, cone calorimeter （CC） test, Fourier transform infrared （FTIR） spectroscopy, scanning electron microscopy （SEM） and tensile test. TPU containing 30 wt% of AP could reach a V-0 rating in the UL-94 test, and its LOI value was 30.2. TGA tests revealed that AP enhanced the formation of residual chars at high temperatures, and slightly affected the thermal stability of TPU at high temperatures. The combustion tests indicated that AP affected the burning behavior of TPU. The peak of heat release rate （PHRR）, total heat release （THR） and mass loss rate （MLR） greatly reduced due to the incorporation of AP. The tensile test results showed that both the tensile strength and the elongation at break slightly decreased with the addition of AP. The digital photos and SEM micrographs vitrified that AP facilitated the formation of more compact intumescent char layer. Based on these results mentioned above, the flame-retarding mechanism of AP was discussed. Both the self-charring during the decomposing process of AP and its facilitation to the charring of TPU led to the great improvement in the flame retardancy of TPU.展开更多
Unsaturated polyester（UPR）/thermoplastic polyurethane（TPU）/organoclay nanocomposites were prepared by melt compounding of thermoplastic polyurethane and unsaturated polyester prepolymer,and then mixing with the hy...Unsaturated polyester（UPR）/thermoplastic polyurethane（TPU）/organoclay nanocomposites were prepared by melt compounding of thermoplastic polyurethane and unsaturated polyester prepolymer,and then mixing with the hybrids of styrene monomers and organoclay at ambient temperature.The crosslinking reaction eventually occurred through the unsaturated polyester prepolymer and styrene monomer.The morphology of the composites was investigated by scanning electron microscopy（SEM） and transmission electron microscopy（TEM）.The results show that the impact strength of UPR/TPU/organoclay nanocomposites increases obviously;the cure shrinkage decreases markedly,the glass transition temperature is enhanced and an elastic response to the deformation is prominent at the temperature above 10℃.展开更多
Halloysite nanotubes(HNTs)have been considered as a promising flame retardant fillers for polymers.In this work,the polyhedral oligomericsilsesquioxane(POSS)containing amino group was covalently grafted on the surface...Halloysite nanotubes(HNTs)have been considered as a promising flame retardant fillers for polymers.In this work,the polyhedral oligomericsilsesquioxane(POSS)containing amino group was covalently grafted on the surface of HNTs with 3-(2,3-epoxypropoxy)propytrimethoxysilane as a chemical bridge.The POSS modified HNTs(HNTs-POSS)dispersed uniformly in the thermoplastic polyurethane(TPU)matrix and endowed TPU nanocomposites with enhanced tensile properties and fire safety.Cone calorimeter tests revealed that the introduction of 2 wt%HNTs-POSS to TPU matrix remarkably reduced the peak of heat release rate(PHRR)and total heat release(THR)by 60.0%and 18.3%,respectively.In addition,the peak CO production rate and total smoke release(TSR)could be significantly suppressed by the addition of HNTsPOSS.The well dispersed HNTs in combination with the ceramified silicon network from the thermal decomposition of POSS contributed to the formation of a continuous and compact char layer,exhibiting a tortuous effect by inhibiting heat diffusion and evaporation of volatile gaseous.In addition,the released crystal water from HNTs could dilute the combustible volatiles and then decline the combustion intensity.The tensile tests demonstrated that introduction of 2 wt%HNTs-POSS would enhance the maximum stress of TPU nanocomposite with a slight decrease of elongation at break.The combination of HNTs and POSS through the construction of effective interfacial interactions provides a feasible way to effectively enhance the fire safety of TPU nanocomposites without scarifying ductility.展开更多
A simple non-isocyanate route is developed for synthesizing crystallizable aliphatic thermoplastic poly（ester urethane） elastomers （TPEURs） with good thermal and mechanical properties. Three prepolymers of 1,6-bis...A simple non-isocyanate route is developed for synthesizing crystallizable aliphatic thermoplastic poly（ester urethane） elastomers （TPEURs） with good thermal and mechanical properties. Three prepolymers of 1,6-bis（hydroxyethyloxycarbonylamino） hexane （BHCH）, i.e. PrePBHCHs, were prepared through the self-transurethane polycondensation of BHCH. A poly（butylene adipate） prepolymer （PrePBA） with terminal HO-- groups was prepared and used as a polyester glycol. A series of TPEURs were prepared by the co-polycondensation of the PrePBHCHs with PrePBA at 170 ℃under a reduced pressure of 399 Pa. The TPEURs were characterized by gel permeation chromatography, FTIR, 1H-NMR, differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffraction, atomic force microscopy, and tensile test. The TPEURs exhibited Mn up to 23300 g/mol, Mw up to 51100 g/mol, Tg ranging from -33.8 ℃ to -3.1 ℃, Tm from 94.3 ℃ to 111.9 ℃, initial decomposition temperature over 274.7℃, tensile strength up to18.8 MPa with a strain at break of 450.0%, and resilience up to 77.5%. TPU elastomers with good crystallization and mechanical properties were obtained through a non-isocyanate route.展开更多
Black phosphorus(BP),as one of the most promising fillers for flame retarding polymer,has been seriously limited in practical application,due to the agglomeration and poor structural stability challenges.Here,the BP w...Black phosphorus(BP),as one of the most promising fillers for flame retarding polymer,has been seriously limited in practical application,due to the agglomeration and poor structural stability challenges.Here,the BP was modified by MXene and polydopamine(PDA)via ultrasonication and dopamine modification strategy to improve the structural stability and dispersibility in the matrix.Then,the obtained(BP-MXene@PDA)nanohybrid was employed to promote the mechanical performance,thermal stability,and flame retardancy of thermoplastic polyurethane elastomer(TPU).The resultant TPU composite containing 2 wt.%of BP1-MXene2@PDA showed a 19.2%improvement in the tensile strength and a 13.8%increase in the elongation at break compared to those of the pure TPU.The thermogravimetric analysis suggested that BP-MXene@PDA clearly enhances the thermal stability of TPU composites.Furthermore,the introduction of the BP-MXene@PDA nanohybrids could considerably improve the flame retardancy of TPU composite,i.e.,64.2%and 27.3%decrease in peak heat release rate and total heat release,respectively.The flame-retardant mechanisms of TPU/BP-MXene@PDA in the gas phase and condensed phase were investigated systematically.This work provides a novel strategy to simultaneously enhance the fire safety and mechanical properties of TPU,thus expanding its industrial applications.展开更多
The microstructural evolution of a thermoplastic polyurethane(TPU)with low hard segment content has been monitored utilizing in situ real-time synchrotron small angle X-ray scattering(SAXS)and time-domain nuclear magn...The microstructural evolution of a thermoplastic polyurethane(TPU)with low hard segment content has been monitored utilizing in situ real-time synchrotron small angle X-ray scattering(SAXS)and time-domain nuclear magnetic resonance(NMR)measurements.The TPU is composed of 23 wt% of[4,4-methylenediphenyl diisocyanate(MDI)]-[1,4-butanediol(BD)]chain segments,which form hard domains,as[polytetrahydrofuran(PTHF)]forming soft domains.The number and distribution of monomer units in hard blocks is determined by the successive self-nucleation and annealing thermal fractionation technique.In situ SAXS method reveals heating-induced increase in the spacing of hard and soft domains,while time-domain ^(1)H-NMR characterizes the changes in the phase composition and chain dynamics in these domains.A glassy fraction of short MDI-BD chain segments in hard domains passes through T_(g) above ambient temperature.At higher temperatures,MDI-BD nanocrystals start to melt.Sequence length distribution of MDI-BD chain segments causes a distribution in crystal sizes and wide melting temperature range.The melting is accompanied by the mixing of MDI-BD with PTHF segments in soft domains,and by increase in segmental mobility in these domains.Above 180℃,the TPU melt is homogeneous on the scale above nanometers according to SAXS data.展开更多
Stimulus-responsive polymers containing dynamic bonds enable fascinating properties of self-healing,recycling and reprocessing due to enhanced relaxation of polymer chain/network with labile linkages.Here,we study the...Stimulus-responsive polymers containing dynamic bonds enable fascinating properties of self-healing,recycling and reprocessing due to enhanced relaxation of polymer chain/network with labile linkages.Here,we study the structure and properties of a new type of thermoplastic polyurethanes(TPUs)with trapped dynamic covalent bonds in the hard-phase domain and report the frustrated relaxation of TPUs containing weak dynamic bond andπ-πinteraction in hard segments.As detected by rheometry,the aromatic TPUs with alkyl disulfide in the hard segments possess the maximum network relaxation time in contrast to those without dynamic bonds and alicyclic TPUs.In situ FTIR and small-angle scattering results reveal that the alkyl disulfide facilitates stronger intermolecular interaction and more stable micro-phase morphology inπ-πinteraction based aromatic TPUs.Molecular dynamics simulation for pure hard segments of model molecules verify that the presence of disulfide bonds leads to strongerπ-πstacking of aromatic rings due to both enhanced assembling thermodynamics and kinetics.The enhancedπ-πpacking and micro-phase structure in TPUs further kinetically immobilize the dynamic bond.This kinetically interlocking between the weak dynamic bonds and strong molecular interaction in hard segments leads to much slower network relaxation of TPU.This work provides a new insight in tuning the network relaxation and heat resistance as well as molecular self-assembly in stimulus-responsive dynamic polymers by both molecular design and micro-phase control toward the functional applications of advanced materials.展开更多
Aluminum hypophosphite microspheres(AHP) were synthesized by hydrothermal method using NaH2PO2·H2O and AlCl3·6H2O as raw materials, and then the AHP microspheres were polymerized by surface polymerization of...Aluminum hypophosphite microspheres(AHP) were synthesized by hydrothermal method using NaH2PO2·H2O and AlCl3·6H2O as raw materials, and then the AHP microspheres were polymerized by surface polymerization of micro-nanospheres with cyclic cross-linked poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol)(PZS). A new organic-inorganic poly(phosphonitrile)-modified aluminum hypophosphite microspheres(PZS-AHP) were synthesized by encapsulation and applied to flame retardant thermoplastic polyurethane(TPU). The microstructure and chemical composition of the PZS-AHP microsphere were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray spectroscopy. The thermal stability of PZS-AHP microsphere was explored with thermogravimetric analysis. Thermogravimetric data indicate that the PZS-AHP microspheres have excellent thermal stability. The thermal and flame-retarding properties of the TPU composites were evaluated by thermogravimetric(TG), limited oxygen index tests(LOI), and cone calorimeter test(CCT). The TPU composite achieved vertical burning(UL-94) V-0 grade and LOI value reached 29.2% when 10 wt% PZS-AHP was incorporated. Compared with those of pure TPU, the peak heat release rate(pHRR) and total heat release(THR) of TPU/10%PZS-AHP decreased by 82.2% and 42.5%, respectively. The results of CCT indicated that PZS-AHP microsphere could improve the flame retardancy of TPU composites.展开更多
Medical devices-related infections pose a great threat to patients and cause an increased morbidity and mortality. Herein, we prepare an antibacterial composite(TPU-x) through blending medical grade thermoplastic poly...Medical devices-related infections pose a great threat to patients and cause an increased morbidity and mortality. Herein, we prepare an antibacterial composite(TPU-x) through blending medical grade thermoplastic polyurethane(TPU) and the complex(PL-DOSS) of ε-polylysine(ε-PL) and docusate sodium(DOSS). >99% reduction of colony forming unit(CFU) can be obtained in TPU-x composite films even at relatively low content of PL-DOSS, e.g. 0.13% for Methicillin resistant S. aureus(MRSA) and 0.5% for E. coli. The excellent antibacterial activity is mainly attributed to the formation of PL-DOSS nanoparticles that are uniformly dispersed in the TPU matrix with a size of ~100 nm. TPU-x composite films exhibit long-term stability in saline and good biocompatibility, and retain mechanical properties of TPU.展开更多
All-solid-state lithium batteries(ASSLB) are promising candidates for next-generation energy storage devices.Nevertheless,the large-scale commercial application of high energy density AS S LB with the polymer electrol...All-solid-state lithium batteries(ASSLB) are promising candidates for next-generation energy storage devices.Nevertheless,the large-scale commercial application of high energy density AS S LB with the polymer electrolyte still faces challenges.In this study,a thin solid polymer composite electrolyte(SPCE) is prepared through a facile and cost-effective strategy with an infiltration of thermoplastic polyurethane(TPU),lithium salt(LiTFSI or LiFSI),and halloysite nanotubes(HNTs) in a porous framework of polyethylene separator(PE)(TPU-HNTs-LiTFSI-PE or TPU-HNTs-LiFSI-PE).The composition,electrochemical performance,and especially the effect of anions(TFSI-and FSI-) on cycling performance are investigated.The results reveal that the flexible TPU-HNTs-LiTFSI-PE and TPU-HNTs-LiFSI-PE with a thickness of 34 μm exhibit wide electrochemical windows of 4.9 and 5.1 V(vs.Li+/Li) at 60℃,respectively.Reduction in FSI-tends to form more LiF and sulfur compounds at the interface between TPU-HNTs-LiFSI-PE and Li metal anode,thus enhancing the interfacial stability.As a result,cell composed of TPU-HNTs-LiFSI-PE exhibits a smaller increase in interfacial resistance of solid electrolyte interphase(SEI) with a distinct decrease in charge-transfer resistance during cycling.Li|Li symmetric cell with TPU-HNTs-LiFSI-PE could keep its stable overpotential profile for nearly 1300 h with a low hysteresis of approximately39 mV at a current density of 0.1 mA cm-2,while a sudden voltage rise with internal cell impedance-surge signals was observed within 600 h for cell composed of TPU-HNTs-LiTFSI-PE.The initial capacities of NCMITPU-HNTs-LiTFSIPEILi and NCMITPU-HNTs-LiFSI-PEILi cells were 149 and 114 mAh g-1,with capacity retention rates of 83.52% and89.99% after 300 cycles at 0.5 C,respectively.This study provides a valuable guideline for designing flexible SPCE,which shows great application prospect in the practice of ASSLB.展开更多
The aim of the present study was to develop sugar palm fiber(SPF)reinforced thermoplastic polyurethane(TPU)composites and to investigate the effects of fiber surface modification by 2%silane treatment and fiber loadin...The aim of the present study was to develop sugar palm fiber(SPF)reinforced thermoplastic polyurethane(TPU)composites and to investigate the effects of fiber surface modification by 2%silane treatment and fiber loading(0,10,20,30,40 and 50 wt%)on the mechanical and thermal properties of the obtained composites.Surface treatment was employed to improve the fiber-matrix interface,which was expected to boost the mechanical strength of the composites,in terms of tensile,flexural and impact properties.Thermal properties were also investigated by thermal gravimetric analysis(TGA)and dynamic mechanical analysis(DMA)to assess the thermal stability of the developed composites.Furthermore,scanning electron microscopy(SEM)was used to study the tensile fracture samples of composites with a view towards evaluating the effects of fiber surface treatments on the fiber/matrix interfacial bonding.The findings of this study reveal that the silane treatment has determined good bonding and linkage of the cellulose fiber to the TPU matrix,hence contributing to enhanced mechanical and thermal properties of the composites.The composite formulation with 40 wt%sugar palm fiber loading showed optimum values such as 17.22 MPa for tensile,13.96 MPa for flexural,and 15.47 kJ/m^2 for impact strength.Moreover,the formulations with higher fiber content exhibited satisfactory values of storage modulus and thermal degradation,while their good interfacial adhesion was evidenced by SEM images.展开更多
This study aimed to investigate the effect of artificial weathering test on the photoaging behavior of TPU films. Changes in mechanical properties, morphology and chemical structures are studied by tensile test, scann...This study aimed to investigate the effect of artificial weathering test on the photoaging behavior of TPU films. Changes in mechanical properties, morphology and chemical structures are studied by tensile test, scanning electron microscopy, atomic force microscopy, Fourier-transformed infrared, and X-ray photoelectron spectroscopy. The results show that the photoaging negatively affects the initial modulus and stress at break values of TPU films. The surface of the specimen that is exposed to irradiation becomes rough, and some visible micro-defects such as blisters and voids can be detected. The morphology of the fracture surfaces illustrates that irradiation reduces the plasticity but increases the brittleness of the TPU films. The chemical structure analyses of the accelerated aged films prove that chemical structural changes in TPU films occur. The irradiation may break the long molecular chains on the surface of the specimens and form the lowmolecular weight oxygen-containing groups. The number of chain scissions increases with the increase in exposure time.展开更多
Poly <span style="font-family:Verdana;">(</span><span style="font-family:Verdana;">Lactic Acid</span><span style="font-family:Verdana;">)</span><spa...Poly <span style="font-family:Verdana;">(</span><span style="font-family:Verdana;">Lactic Acid</span><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;"> (PLA) is a biodegradable polymer which originates from natural resources such as corn</span><span style="font-family:Verdana;"> and</span><span style="font-family:Verdana;"> starch</span><span style="font-family:Verdana;">,</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> offering excellent strength, biode</span><span style="font-family:Verdana;">gradability</span></span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> nevertheless its inherent brittleness and low impact resistance</span><span style="font-family:Verdana;"> properties ha</span><span style="font-family:Verdana;">ve</span><span style="font-family:Verdana;"> limited its application. On the other hand</span><span style="font-family:Verdana;">,</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> Thermoplastic Polyu</span><span style="font-family:Verdana;">rethane (TPU) has high toughness, durability and flexibility</span></span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> which </span><span style="font-family:Verdana;">is</span><span style="font-family:Verdana;"> one of</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> the </span><span style="font-family:Verdana;">most potential alternatives for enhancing the flexibility and mechanical</span><span style="font-family:Verdana;"> strength of Poly </span></span><span style="font-family:Verdana;">(</span><span style="font-family:Verdana;">Lactic Acid</span><span style="font-family:Verdana;">)</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> (PLA) by blending it with a compati</span><span style="font-family:Verdana;">bilizer. With the aim to improve the mechanical and thermal properties of</span><span style="font-family:Verdana;"> Poly </span></span><span style="font-family:Verdana;">(</span><span style="font-family:Verdana;">Lactic Acid</span><span style="font-family:Verdana;">)</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> (PLA) </span><span style="font-family:Verdana;">meltblown nonwovens, The Thermoplastic Polyurethane (TPU) was melt</span><span style="font-family:Verdana;"> blend</span></span><span style="font-family:Verdana;">ed with Poly </span><span style="font-family:Verdana;">(</span><span style="font-family:Verdana;">Lactic Acid</span><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;"> (PLA) at the different corresponding proportions for toughening the Poly </span><span style="font-family:Verdana;">(</span><span style="font-family:Verdana;">Lactic Acid</span><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;"> and the corresponding PLA/TPU MBs (meltblown nonwovens) were also manufactured. Joncryl ADR 4400 </span><span style="font-family:Verdana;">is</span><span style="font-family:Verdana;"> mixed </span><span style="font-family:Verdana;">in</span><span style="font-family:Verdana;">to the PLA matrix during processing. It was found that Joncryl had </span><span style="font-family:Verdana;">a </span><span style="font-family:;" "=""><span style="font-family:Verdana;">much higher chain extension that substantially in</span><span style="font-family:Verdana;">creased the molecular weight of the PLA matrix. SEM study revealed that Joncryl ADR 4400 is a good compatibi</span><span style="font-family:Verdana;">lizer</span></span><span style="font-family:Verdana;">.</span><span style="font-family:Verdana;"> Moreover, in this study</span><span style="font-family:Verdana;">,</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> the crystallization, thermal and rheological behaviors </span><span style="font-family:Verdana;">of the corresponding PLA and TPU blends were also investigated. PLA/TPU</span><span style="font-family:Verdana;"> MBs were also characterized by</span> <span style="font-family:Verdana;">morphology and mechanical properties. The rheological property of the</span><span style="font-family:Verdana;"> PLA/TPU meltblown nonwoven revealed that the viscosity </span><span style="font-family:Verdana;">is increasing as the amount of TPU is increasing in the blend, PLA/TPU</span><span style="font-family:Verdana;"> melt</span></span><span style="font-family:Verdana;">blown nonwovens exhibited excellent mechanical properties;they are soft, </span><span style="font-family:;" "=""><span style="font-family:Verdana;">elas</span><span style="font-family:Verdana;">tic, and have certain tensile strength. New materials have potential applica</span><span style="font-family:Verdana;">tions in the medical and agri</span><span style="font-family:Verdana;">cultural field</span></span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;">. Joncryl ADR 4400 compatibilized blends showed higher</span><span style="font-family:Verdana;"> strength than simple PLA/TPU blends at the same PLA/TPU ratio.</span>展开更多
Viscoelastic properties of thermoplastic polyurethane(TPU)is of fundamental importance for its processing.In this work,we prepared different TPUs from polycaprolactone(PCL)diol,diphenylmethane-4,4′-diisocyanate(MDI),...Viscoelastic properties of thermoplastic polyurethane(TPU)is of fundamental importance for its processing.In this work,we prepared different TPUs from polycaprolactone(PCL)diol,diphenylmethane-4,4′-diisocyanate(MDI),and 1,4-butanediol(BDO),and investigated the viscoelastic behavior of three TPUs with different hard segment content during thermal annealing process.The storage modulus(G′)of TPU increases over time in a medium annealing temperature(T_(a))region,but remains unchanged at both high and low temperature regions.The growth of loss modulus(G″)over time is slower than that of G′.At medium T_(a),both G′and G″increase during the repeating frequency(ω)sweep,due to the gradual crystallization of hard segments.This indicates that the crystallites primarily restrain the relaxation of unit with large size.The increments of G′and G″are weakened when the content of hard segment in TPU is decreased.For TPU with high content of hard segments,a complete high elastic platform with a width of 3 orders of magnitude was observed only through one frequency scan test at medium T_(a).In addition,the crystallites of hard segments grow up continuously during frequency scan test(isothermal annealing treatment)and cause the extreme increase in G′and G″withωin lowωregion.展开更多
The hydrogen bond percentage and its temperature dependence of the three TPU samples synthesized from polytetrahydrofuran, 4,4'-diphenylmethane diisocyanate, N -methyl diethanol amine or 1,4-butane diol were stud...The hydrogen bond percentage and its temperature dependence of the three TPU samples synthesized from polytetrahydrofuran, 4,4'-diphenylmethane diisocyanate, N -methyl diethanol amine or 1,4-butane diol were studied by means of IR thermal analysis. The enthalpy and the entropy of the hydrogen bond dissociation were determined by the Van't Hoff plot.展开更多
Thermoplastic polycarbonate polyurethanes(PCUs) are multiblock copolymers that have been applied for medical devices for long time. Aliphatic diols are common chain extenders(CE) involved in the composition of the har...Thermoplastic polycarbonate polyurethanes(PCUs) are multiblock copolymers that have been applied for medical devices for long time. Aliphatic diols are common chain extenders(CE) involved in the composition of the hard segments of PCU. However, limited knowledge was discovered about how the chemical structure of CE affects the hydrogen bonding organization within PCUs and their mechanical properties.To investigate this problem, a group of PCUs were synthesized respectively by extending the polymer chain with 1,4-butanediol(BDO),aminoethanol(MEA), ethanediol(EO) as three kinds of chain extenders. Tiny differences in the CE chemical structure results in remarkable variations in phase separation, condensed morphologies, thermal and mechanical properties, which are characterized by Fourier transform infrared spectrometer, atomic force microscopy, small-angle X-ray scattering, differential scanning calorimetry, and tensile tests. The microstructural evolution during unilateral deformation and the different mechanism induced by the different CEs was probed and unveil by in situ wide-and small-angle X-ray diffraction. Symmetry of CE can improve the organization of the hydrogen bonding. The coherence strength of the urethane/urea group also plays a key role by comparing the two PCUs with ethanediol and aminoethanol.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.21244006 and 50873013)the Beijing Natural Science Foundation(No.2182056)
文摘A simple non-isocyanate route synthesizing thermoplastic polyurethanes（TPUs） with good thermal and mechanical properties is described. Melt transurethane polycondensation of dimethyl 1,6-hexamethylene dicarbamate with 1,4-butanediol and 1,6-hexanediol was conducted at different molar ratios under the catalysis of tetrabutyl titanate. A series of crystallizable non-isocyanate TPUs with high molecular weight were prepared. The TPUs were characterized by gel permeation chromatography, FT-IR, 1 H-NMR, differential scanning calorimetry, thermogravimetric analysis, wide angle X-ray diffraction, AFM, and tensile tests. The TPUs exhibited Mn ranging from 12 500 to 26 400 g/mol, Mw from 16 700 to 56 400 g/mol, Tm up to 151.4 °C, and initial decomposition temperature over 241.8 °C. Their tensile strength reached 42.99 MPa with a strain at break of 30.00%. TPUs constructed simply with butylene, hexylene, and urethane linkages were successfully synthesized through a non-isocyanate route.
基金financially supported by the CAS Project for Young Scientists in Basic Research(No.YSBR-023)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.Y2022068)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDC06020301)。
文摘Adjusting the structure of the hard segment(HS)represents a key method for manipulating the mechanical properties of thermoplastic polyurethane(TPU).This study developed a novel molecular design strategy to tailor TPU's mechanical performance through altering the terminal diisocyanate structure of HS.The typical HDI-BDO based TPU was chosen as a model.Replacing HS's terminal HDI residues with aromatic PPDI,TODI,and MDI(the corresponding TPUs are named as 2P,2TO,and 2M,respectively)enabled broad tuning of TPU's Young's modulus while maintaining high tensile strength and elongation.Compared with linear PPDI and TODI,the bent and unsymmetrical MDI exhibits greater deviation from the central axis of the middle HDI-BDO segment,which reduces HS's capability of three-dimensionally ordered packing.Therefore,2P and 2TO show higher hydrogen bond content and crystallinity,stronger physical crosslinking network,and thus much higher Young's modulus than 2M(75.6 MPa).Besides geometric structure,π–πstacking between HS's terminal aromatic diisocyanates critically governs TPU's physical crosslinking network.In 2P,π–πstacking induces torsion of the middle HDI-BDO segment and disrupts the neighboring hydrogen bonds,leading to a dense network with fine hard blocks.In contrast,the lateral methyl groups in TODI hinderπ–πstacking,resulting in a sparse network with large hard blocks.Accordingly,2TO exhibits a higher Young's modulus(146.2 MPa)than 2P(124.0 MPa),but greater strain-rate sensitivity.
基金This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoalde Nível Superior-Brasil(CAPES)-Finance Code 001.
文摘The continuous improvement in patient care and recovery is driving the development of innovative materials for medical applications.Medical sutures,essential for securing implants and closing deep wounds,have evolved to incorporate smart materials capable of responding to various stimuli.This study explores the potential of thermoresponsive sutures,made from shape memory materials,that contract upon heating to bring loose stitches closer together,promoting optimal wound closure.We developed nanocomposites based on a blend of poly(lactic acid)(PLA)and thermoplastic polyurethane(TPU)—biopolymers that inherently exhibit shape memory—enhanced with carbon nanotubes(CNT)and graphene nanoplatelets(GN)to improve mechanical performance.PLA/TPU(50/50)nanocomposites were prepared with 1 and 2 wt%GN,as well as hybrid formulations combining 1 wt%CNT with 1 or 2 wt%GN,using a twin-screw extrusion process to form filaments.These filaments were characterized through differential scanning calorimetry(DSC),field emission gun scanning electron microscopy(FEG-SEM),tensile testing,and shape memory assessments.While the PLA/TPU blend is immiscible,TPU enhances the crystallinity(X_(c))of the PLA phase,further increased by the addition of CNT and GN.FEG-SEM images indicate CNTs primarily in the PLA phase and GN in the TPU phase.PLA/TPU with 1 or 2 wt%GN showed the highest potential for suture applications,with a high elastic modulus(~1000 MPa),significant strain at break(~10%),and effective shape recovery(~20%at 55℃ for 30 min).These findings suggest that these nanocomposites can enhance suture performance with controlled shape recovery that is suitable for medical use.
文摘Polyether and polyether/ester based TPU （thermoplastic polyurethanes） were investigated with wide-angle XRD （X-ray diffraction） and SAXS （small angle X-ray scattering）. Furthermore, SAXS measurements were performed in the temperature range of 30 ℃ to 130 ℃. Polyether based polymers exhibit only one broad diffraction signal in a region of 2 θ 15° to 25°. In case of polyurethanes with ether/ester modification, the broad diffraction signal arises with small sharp diffraction signals. SAXS measurements of polymers reveal the size and shape of the crystalline zones of the polymer. Between 30 ℃ and 130 ℃ the size of the crystalline zone changes significantly. The size decreases in most of investigated TPU. In the case of Desmopan 9365D an increase of the particle size was observed.
基金financially supported by the National Natural Science Foundation of China(Nos.50933005 and 51121001)the Program for Changjiang Scholars and Innovative Research Teams in Universities of China(IRT 1026)
文摘Aluminum hypophosphite （AP） was used to prepare flame-retarded thermoplastic polyurethane （FR-TPU） composites, and their flame retardancy, thermal degradation and mechanical properties were investigated by limiting oxygen index （LOI）, vertical burning test （UL-94）, thermogravimetric analysis （TGA）, cone calorimeter （CC） test, Fourier transform infrared （FTIR） spectroscopy, scanning electron microscopy （SEM） and tensile test. TPU containing 30 wt% of AP could reach a V-0 rating in the UL-94 test, and its LOI value was 30.2. TGA tests revealed that AP enhanced the formation of residual chars at high temperatures, and slightly affected the thermal stability of TPU at high temperatures. The combustion tests indicated that AP affected the burning behavior of TPU. The peak of heat release rate （PHRR）, total heat release （THR） and mass loss rate （MLR） greatly reduced due to the incorporation of AP. The tensile test results showed that both the tensile strength and the elongation at break slightly decreased with the addition of AP. The digital photos and SEM micrographs vitrified that AP facilitated the formation of more compact intumescent char layer. Based on these results mentioned above, the flame-retarding mechanism of AP was discussed. Both the self-charring during the decomposing process of AP and its facilitation to the charring of TPU led to the great improvement in the flame retardancy of TPU.
基金supported by the Natural Science Foundation of Guangdong Province(No.39172)
文摘Unsaturated polyester（UPR）/thermoplastic polyurethane（TPU）/organoclay nanocomposites were prepared by melt compounding of thermoplastic polyurethane and unsaturated polyester prepolymer,and then mixing with the hybrids of styrene monomers and organoclay at ambient temperature.The crosslinking reaction eventually occurred through the unsaturated polyester prepolymer and styrene monomer.The morphology of the composites was investigated by scanning electron microscopy（SEM） and transmission electron microscopy（TEM）.The results show that the impact strength of UPR/TPU/organoclay nanocomposites increases obviously;the cure shrinkage decreases markedly,the glass transition temperature is enhanced and an elastic response to the deformation is prominent at the temperature above 10℃.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0302300)the International Collaboration Programs of Guangdong Province(No.2020A0505100010)+4 种基金the Fundamental Research Funds for the Central Universities(No.2019MS062)the Natural Science Foundation of Guangdong Province(No.2021A1515012425)the Overseas Famous Scholar Funds of Guangdong Province(No.2020A1414010372)City University of Hong Kong(No.9678103)the Opening Project of Key Laboratory of Polymer Processing Engineering(South China University of Technology),Ministry of Education of China(No.KFKT1904)。
文摘Halloysite nanotubes(HNTs)have been considered as a promising flame retardant fillers for polymers.In this work,the polyhedral oligomericsilsesquioxane(POSS)containing amino group was covalently grafted on the surface of HNTs with 3-(2,3-epoxypropoxy)propytrimethoxysilane as a chemical bridge.The POSS modified HNTs(HNTs-POSS)dispersed uniformly in the thermoplastic polyurethane(TPU)matrix and endowed TPU nanocomposites with enhanced tensile properties and fire safety.Cone calorimeter tests revealed that the introduction of 2 wt%HNTs-POSS to TPU matrix remarkably reduced the peak of heat release rate(PHRR)and total heat release(THR)by 60.0%and 18.3%,respectively.In addition,the peak CO production rate and total smoke release(TSR)could be significantly suppressed by the addition of HNTsPOSS.The well dispersed HNTs in combination with the ceramified silicon network from the thermal decomposition of POSS contributed to the formation of a continuous and compact char layer,exhibiting a tortuous effect by inhibiting heat diffusion and evaporation of volatile gaseous.In addition,the released crystal water from HNTs could dilute the combustible volatiles and then decline the combustion intensity.The tensile tests demonstrated that introduction of 2 wt%HNTs-POSS would enhance the maximum stress of TPU nanocomposite with a slight decrease of elongation at break.The combination of HNTs and POSS through the construction of effective interfacial interactions provides a feasible way to effectively enhance the fire safety of TPU nanocomposites without scarifying ductility.
基金financially supported by the National Natural Science Foundation of China(Nos.21244006 and 50873013)
文摘A simple non-isocyanate route is developed for synthesizing crystallizable aliphatic thermoplastic poly（ester urethane） elastomers （TPEURs） with good thermal and mechanical properties. Three prepolymers of 1,6-bis（hydroxyethyloxycarbonylamino） hexane （BHCH）, i.e. PrePBHCHs, were prepared through the self-transurethane polycondensation of BHCH. A poly（butylene adipate） prepolymer （PrePBA） with terminal HO-- groups was prepared and used as a polyester glycol. A series of TPEURs were prepared by the co-polycondensation of the PrePBHCHs with PrePBA at 170 ℃under a reduced pressure of 399 Pa. The TPEURs were characterized by gel permeation chromatography, FTIR, 1H-NMR, differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffraction, atomic force microscopy, and tensile test. The TPEURs exhibited Mn up to 23300 g/mol, Mw up to 51100 g/mol, Tg ranging from -33.8 ℃ to -3.1 ℃, Tm from 94.3 ℃ to 111.9 ℃, initial decomposition temperature over 274.7℃, tensile strength up to18.8 MPa with a strain at break of 450.0%, and resilience up to 77.5%. TPU elastomers with good crystallization and mechanical properties were obtained through a non-isocyanate route.
基金supported by the National Natural Science Foundation of China(No.21908031)Scientific Research Funds of Yunnan Education Department(No.2021Y111)。
文摘Black phosphorus(BP),as one of the most promising fillers for flame retarding polymer,has been seriously limited in practical application,due to the agglomeration and poor structural stability challenges.Here,the BP was modified by MXene and polydopamine(PDA)via ultrasonication and dopamine modification strategy to improve the structural stability and dispersibility in the matrix.Then,the obtained(BP-MXene@PDA)nanohybrid was employed to promote the mechanical performance,thermal stability,and flame retardancy of thermoplastic polyurethane elastomer(TPU).The resultant TPU composite containing 2 wt.%of BP1-MXene2@PDA showed a 19.2%improvement in the tensile strength and a 13.8%increase in the elongation at break compared to those of the pure TPU.The thermogravimetric analysis suggested that BP-MXene@PDA clearly enhances the thermal stability of TPU composites.Furthermore,the introduction of the BP-MXene@PDA nanohybrids could considerably improve the flame retardancy of TPU composite,i.e.,64.2%and 27.3%decrease in peak heat release rate and total heat release,respectively.The flame-retardant mechanisms of TPU/BP-MXene@PDA in the gas phase and condensed phase were investigated systematically.This work provides a novel strategy to simultaneously enhance the fire safety and mechanical properties of TPU,thus expanding its industrial applications.
基金financially supported by the National Natural Science Foundation of China (No. 22161132007)BASF within the framework of NAO (Network for Advanced Materials Open Research)。
文摘The microstructural evolution of a thermoplastic polyurethane(TPU)with low hard segment content has been monitored utilizing in situ real-time synchrotron small angle X-ray scattering(SAXS)and time-domain nuclear magnetic resonance(NMR)measurements.The TPU is composed of 23 wt% of[4,4-methylenediphenyl diisocyanate(MDI)]-[1,4-butanediol(BD)]chain segments,which form hard domains,as[polytetrahydrofuran(PTHF)]forming soft domains.The number and distribution of monomer units in hard blocks is determined by the successive self-nucleation and annealing thermal fractionation technique.In situ SAXS method reveals heating-induced increase in the spacing of hard and soft domains,while time-domain ^(1)H-NMR characterizes the changes in the phase composition and chain dynamics in these domains.A glassy fraction of short MDI-BD chain segments in hard domains passes through T_(g) above ambient temperature.At higher temperatures,MDI-BD nanocrystals start to melt.Sequence length distribution of MDI-BD chain segments causes a distribution in crystal sizes and wide melting temperature range.The melting is accompanied by the mixing of MDI-BD with PTHF segments in soft domains,and by increase in segmental mobility in these domains.Above 180℃,the TPU melt is homogeneous on the scale above nanometers according to SAXS data.
基金financially supported by the National Natural Science Foundation of China(No.21774135)。
文摘Stimulus-responsive polymers containing dynamic bonds enable fascinating properties of self-healing,recycling and reprocessing due to enhanced relaxation of polymer chain/network with labile linkages.Here,we study the structure and properties of a new type of thermoplastic polyurethanes(TPUs)with trapped dynamic covalent bonds in the hard-phase domain and report the frustrated relaxation of TPUs containing weak dynamic bond andπ-πinteraction in hard segments.As detected by rheometry,the aromatic TPUs with alkyl disulfide in the hard segments possess the maximum network relaxation time in contrast to those without dynamic bonds and alicyclic TPUs.In situ FTIR and small-angle scattering results reveal that the alkyl disulfide facilitates stronger intermolecular interaction and more stable micro-phase morphology inπ-πinteraction based aromatic TPUs.Molecular dynamics simulation for pure hard segments of model molecules verify that the presence of disulfide bonds leads to strongerπ-πstacking of aromatic rings due to both enhanced assembling thermodynamics and kinetics.The enhancedπ-πpacking and micro-phase structure in TPUs further kinetically immobilize the dynamic bond.This kinetically interlocking between the weak dynamic bonds and strong molecular interaction in hard segments leads to much slower network relaxation of TPU.This work provides a new insight in tuning the network relaxation and heat resistance as well as molecular self-assembly in stimulus-responsive dynamic polymers by both molecular design and micro-phase control toward the functional applications of advanced materials.
基金Supported by the Opening Project of Hubei Three Gorges Laboratory (No.SK213008)the Innovation Fund of Key Laboratory of Green Chemical Process of Ministry of Education (No.GCXP202109)。
文摘Aluminum hypophosphite microspheres(AHP) were synthesized by hydrothermal method using NaH2PO2·H2O and AlCl3·6H2O as raw materials, and then the AHP microspheres were polymerized by surface polymerization of micro-nanospheres with cyclic cross-linked poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol)(PZS). A new organic-inorganic poly(phosphonitrile)-modified aluminum hypophosphite microspheres(PZS-AHP) were synthesized by encapsulation and applied to flame retardant thermoplastic polyurethane(TPU). The microstructure and chemical composition of the PZS-AHP microsphere were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray spectroscopy. The thermal stability of PZS-AHP microsphere was explored with thermogravimetric analysis. Thermogravimetric data indicate that the PZS-AHP microspheres have excellent thermal stability. The thermal and flame-retarding properties of the TPU composites were evaluated by thermogravimetric(TG), limited oxygen index tests(LOI), and cone calorimeter test(CCT). The TPU composite achieved vertical burning(UL-94) V-0 grade and LOI value reached 29.2% when 10 wt% PZS-AHP was incorporated. Compared with those of pure TPU, the peak heat release rate(pHRR) and total heat release(THR) of TPU/10%PZS-AHP decreased by 82.2% and 42.5%, respectively. The results of CCT indicated that PZS-AHP microsphere could improve the flame retardancy of TPU composites.
基金the National Natural Science Foundation of China(Nos.51773201 and 51973212)the Bureau of Science and Technology of Changchun(No.19SS005)+1 种基金the Department of Science and Technology of Jilin Province(No.20200301017RQ)the Joint Program of CAS-Jilin Province(No.2019SYHZ0002).
文摘Medical devices-related infections pose a great threat to patients and cause an increased morbidity and mortality. Herein, we prepare an antibacterial composite(TPU-x) through blending medical grade thermoplastic polyurethane(TPU) and the complex(PL-DOSS) of ε-polylysine(ε-PL) and docusate sodium(DOSS). >99% reduction of colony forming unit(CFU) can be obtained in TPU-x composite films even at relatively low content of PL-DOSS, e.g. 0.13% for Methicillin resistant S. aureus(MRSA) and 0.5% for E. coli. The excellent antibacterial activity is mainly attributed to the formation of PL-DOSS nanoparticles that are uniformly dispersed in the TPU matrix with a size of ~100 nm. TPU-x composite films exhibit long-term stability in saline and good biocompatibility, and retain mechanical properties of TPU.
基金financially supported by the National Natural Science Foundation of China(No.21673051)the Department of Science and Technology of Guangdong Province,China(No.2019A050510043)。
文摘All-solid-state lithium batteries(ASSLB) are promising candidates for next-generation energy storage devices.Nevertheless,the large-scale commercial application of high energy density AS S LB with the polymer electrolyte still faces challenges.In this study,a thin solid polymer composite electrolyte(SPCE) is prepared through a facile and cost-effective strategy with an infiltration of thermoplastic polyurethane(TPU),lithium salt(LiTFSI or LiFSI),and halloysite nanotubes(HNTs) in a porous framework of polyethylene separator(PE)(TPU-HNTs-LiTFSI-PE or TPU-HNTs-LiFSI-PE).The composition,electrochemical performance,and especially the effect of anions(TFSI-and FSI-) on cycling performance are investigated.The results reveal that the flexible TPU-HNTs-LiTFSI-PE and TPU-HNTs-LiFSI-PE with a thickness of 34 μm exhibit wide electrochemical windows of 4.9 and 5.1 V(vs.Li+/Li) at 60℃,respectively.Reduction in FSI-tends to form more LiF and sulfur compounds at the interface between TPU-HNTs-LiFSI-PE and Li metal anode,thus enhancing the interfacial stability.As a result,cell composed of TPU-HNTs-LiFSI-PE exhibits a smaller increase in interfacial resistance of solid electrolyte interphase(SEI) with a distinct decrease in charge-transfer resistance during cycling.Li|Li symmetric cell with TPU-HNTs-LiFSI-PE could keep its stable overpotential profile for nearly 1300 h with a low hysteresis of approximately39 mV at a current density of 0.1 mA cm-2,while a sudden voltage rise with internal cell impedance-surge signals was observed within 600 h for cell composed of TPU-HNTs-LiTFSI-PE.The initial capacities of NCMITPU-HNTs-LiTFSIPEILi and NCMITPU-HNTs-LiFSI-PEILi cells were 149 and 114 mAh g-1,with capacity retention rates of 83.52% and89.99% after 300 cycles at 0.5 C,respectively.This study provides a valuable guideline for designing flexible SPCE,which shows great application prospect in the practice of ASSLB.
文摘The aim of the present study was to develop sugar palm fiber(SPF)reinforced thermoplastic polyurethane(TPU)composites and to investigate the effects of fiber surface modification by 2%silane treatment and fiber loading(0,10,20,30,40 and 50 wt%)on the mechanical and thermal properties of the obtained composites.Surface treatment was employed to improve the fiber-matrix interface,which was expected to boost the mechanical strength of the composites,in terms of tensile,flexural and impact properties.Thermal properties were also investigated by thermal gravimetric analysis(TGA)and dynamic mechanical analysis(DMA)to assess the thermal stability of the developed composites.Furthermore,scanning electron microscopy(SEM)was used to study the tensile fracture samples of composites with a view towards evaluating the effects of fiber surface treatments on the fiber/matrix interfacial bonding.The findings of this study reveal that the silane treatment has determined good bonding and linkage of the cellulose fiber to the TPU matrix,hence contributing to enhanced mechanical and thermal properties of the composites.The composite formulation with 40 wt%sugar palm fiber loading showed optimum values such as 17.22 MPa for tensile,13.96 MPa for flexural,and 15.47 kJ/m^2 for impact strength.Moreover,the formulations with higher fiber content exhibited satisfactory values of storage modulus and thermal degradation,while their good interfacial adhesion was evidenced by SEM images.
基金Funded by the Fundamental Research Funds for the Central Universities(No.HIT.KISTP.201408)
文摘This study aimed to investigate the effect of artificial weathering test on the photoaging behavior of TPU films. Changes in mechanical properties, morphology and chemical structures are studied by tensile test, scanning electron microscopy, atomic force microscopy, Fourier-transformed infrared, and X-ray photoelectron spectroscopy. The results show that the photoaging negatively affects the initial modulus and stress at break values of TPU films. The surface of the specimen that is exposed to irradiation becomes rough, and some visible micro-defects such as blisters and voids can be detected. The morphology of the fracture surfaces illustrates that irradiation reduces the plasticity but increases the brittleness of the TPU films. The chemical structure analyses of the accelerated aged films prove that chemical structural changes in TPU films occur. The irradiation may break the long molecular chains on the surface of the specimens and form the lowmolecular weight oxygen-containing groups. The number of chain scissions increases with the increase in exposure time.
文摘Poly <span style="font-family:Verdana;">(</span><span style="font-family:Verdana;">Lactic Acid</span><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;"> (PLA) is a biodegradable polymer which originates from natural resources such as corn</span><span style="font-family:Verdana;"> and</span><span style="font-family:Verdana;"> starch</span><span style="font-family:Verdana;">,</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> offering excellent strength, biode</span><span style="font-family:Verdana;">gradability</span></span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> nevertheless its inherent brittleness and low impact resistance</span><span style="font-family:Verdana;"> properties ha</span><span style="font-family:Verdana;">ve</span><span style="font-family:Verdana;"> limited its application. On the other hand</span><span style="font-family:Verdana;">,</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> Thermoplastic Polyu</span><span style="font-family:Verdana;">rethane (TPU) has high toughness, durability and flexibility</span></span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> which </span><span style="font-family:Verdana;">is</span><span style="font-family:Verdana;"> one of</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> the </span><span style="font-family:Verdana;">most potential alternatives for enhancing the flexibility and mechanical</span><span style="font-family:Verdana;"> strength of Poly </span></span><span style="font-family:Verdana;">(</span><span style="font-family:Verdana;">Lactic Acid</span><span style="font-family:Verdana;">)</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> (PLA) by blending it with a compati</span><span style="font-family:Verdana;">bilizer. With the aim to improve the mechanical and thermal properties of</span><span style="font-family:Verdana;"> Poly </span></span><span style="font-family:Verdana;">(</span><span style="font-family:Verdana;">Lactic Acid</span><span style="font-family:Verdana;">)</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> (PLA) </span><span style="font-family:Verdana;">meltblown nonwovens, The Thermoplastic Polyurethane (TPU) was melt</span><span style="font-family:Verdana;"> blend</span></span><span style="font-family:Verdana;">ed with Poly </span><span style="font-family:Verdana;">(</span><span style="font-family:Verdana;">Lactic Acid</span><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;"> (PLA) at the different corresponding proportions for toughening the Poly </span><span style="font-family:Verdana;">(</span><span style="font-family:Verdana;">Lactic Acid</span><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;"> and the corresponding PLA/TPU MBs (meltblown nonwovens) were also manufactured. Joncryl ADR 4400 </span><span style="font-family:Verdana;">is</span><span style="font-family:Verdana;"> mixed </span><span style="font-family:Verdana;">in</span><span style="font-family:Verdana;">to the PLA matrix during processing. It was found that Joncryl had </span><span style="font-family:Verdana;">a </span><span style="font-family:;" "=""><span style="font-family:Verdana;">much higher chain extension that substantially in</span><span style="font-family:Verdana;">creased the molecular weight of the PLA matrix. SEM study revealed that Joncryl ADR 4400 is a good compatibi</span><span style="font-family:Verdana;">lizer</span></span><span style="font-family:Verdana;">.</span><span style="font-family:Verdana;"> Moreover, in this study</span><span style="font-family:Verdana;">,</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> the crystallization, thermal and rheological behaviors </span><span style="font-family:Verdana;">of the corresponding PLA and TPU blends were also investigated. PLA/TPU</span><span style="font-family:Verdana;"> MBs were also characterized by</span> <span style="font-family:Verdana;">morphology and mechanical properties. The rheological property of the</span><span style="font-family:Verdana;"> PLA/TPU meltblown nonwoven revealed that the viscosity </span><span style="font-family:Verdana;">is increasing as the amount of TPU is increasing in the blend, PLA/TPU</span><span style="font-family:Verdana;"> melt</span></span><span style="font-family:Verdana;">blown nonwovens exhibited excellent mechanical properties;they are soft, </span><span style="font-family:;" "=""><span style="font-family:Verdana;">elas</span><span style="font-family:Verdana;">tic, and have certain tensile strength. New materials have potential applica</span><span style="font-family:Verdana;">tions in the medical and agri</span><span style="font-family:Verdana;">cultural field</span></span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;">. Joncryl ADR 4400 compatibilized blends showed higher</span><span style="font-family:Verdana;"> strength than simple PLA/TPU blends at the same PLA/TPU ratio.</span>
文摘Viscoelastic properties of thermoplastic polyurethane(TPU)is of fundamental importance for its processing.In this work,we prepared different TPUs from polycaprolactone(PCL)diol,diphenylmethane-4,4′-diisocyanate(MDI),and 1,4-butanediol(BDO),and investigated the viscoelastic behavior of three TPUs with different hard segment content during thermal annealing process.The storage modulus(G′)of TPU increases over time in a medium annealing temperature(T_(a))region,but remains unchanged at both high and low temperature regions.The growth of loss modulus(G″)over time is slower than that of G′.At medium T_(a),both G′and G″increase during the repeating frequency(ω)sweep,due to the gradual crystallization of hard segments.This indicates that the crystallites primarily restrain the relaxation of unit with large size.The increments of G′and G″are weakened when the content of hard segment in TPU is decreased.For TPU with high content of hard segments,a complete high elastic platform with a width of 3 orders of magnitude was observed only through one frequency scan test at medium T_(a).In addition,the crystallites of hard segments grow up continuously during frequency scan test(isothermal annealing treatment)and cause the extreme increase in G′and G″withωin lowωregion.
基金Supported by the Key Subject Construction Project of Shanghai Educational Com mittee(No. 13980 70 2 )
文摘The hydrogen bond percentage and its temperature dependence of the three TPU samples synthesized from polytetrahydrofuran, 4,4'-diphenylmethane diisocyanate, N -methyl diethanol amine or 1,4-butane diol were studied by means of IR thermal analysis. The enthalpy and the entropy of the hydrogen bond dissociation were determined by the Van't Hoff plot.
基金financially supported by the National Natural Science Foundation of China (No.21774135)。
文摘Thermoplastic polycarbonate polyurethanes(PCUs) are multiblock copolymers that have been applied for medical devices for long time. Aliphatic diols are common chain extenders(CE) involved in the composition of the hard segments of PCU. However, limited knowledge was discovered about how the chemical structure of CE affects the hydrogen bonding organization within PCUs and their mechanical properties.To investigate this problem, a group of PCUs were synthesized respectively by extending the polymer chain with 1,4-butanediol(BDO),aminoethanol(MEA), ethanediol(EO) as three kinds of chain extenders. Tiny differences in the CE chemical structure results in remarkable variations in phase separation, condensed morphologies, thermal and mechanical properties, which are characterized by Fourier transform infrared spectrometer, atomic force microscopy, small-angle X-ray scattering, differential scanning calorimetry, and tensile tests. The microstructural evolution during unilateral deformation and the different mechanism induced by the different CEs was probed and unveil by in situ wide-and small-angle X-ray diffraction. Symmetry of CE can improve the organization of the hydrogen bonding. The coherence strength of the urethane/urea group also plays a key role by comparing the two PCUs with ethanediol and aminoethanol.
