Carbon fibres have been produced from hydroxypropyl-modified lignin(TcC)/bio-based polyamide 1010(PA1010)blended filaments.Two grades of PA1010,with different molecular weights and rheological properties,were used for...Carbon fibres have been produced from hydroxypropyl-modified lignin(TcC)/bio-based polyamide 1010(PA1010)blended filaments.Two grades of PA1010,with different molecular weights and rheological properties,were used for blending with TcC.An oxidative thermal stabilisation step was used prior to carbonisation in an inert atmosphere to prevent the fusion of the filaments during the latter step.Thermal stabilisation was not possible using a one-step stabilisation process reported in the literature for lignin and other lignin/synthetic polymer blends.As a consequence,a cyclic process involving an additional isothermal phase at a lower temperature than the precursor filaments’melting point,was introduced to increase the cross-linking reactions between the lignin and polyamide.Thermally stabilised filaments were characterised by DSC,TGA,TGA-FTIR,ATR,and SEM techniques.Polymer rheology and heating rate used during thermal stabilisation influenced the thermal stabilisation process and mechanical properties of the derived filaments.Thermally stabilised filaments using optimised conditions(heating in the air atmosphere at 0.25℃/min to 180℃;isothermal for 1 h,cooling back down to ambient at 5℃/min;heating to 250℃ at 0.25℃/min,isothermal for 2 h)could be successfully carbonised.Carbon fibres pro-duced had void-free morphologies and mechanical properties comparable to similarly thermally stabilised and carbonised polyacrylonitrile(PAN)filaments.展开更多
In this paper,polyamide(PA)woven fabric was used as the base fabric,and polyurethane(PU)solution containing silica nanoparticles(PU@SiO_(2)NPs)was used as the coating solution to prepare composite tent fabric(PA/PU@Si...In this paper,polyamide(PA)woven fabric was used as the base fabric,and polyurethane(PU)solution containing silica nanoparticles(PU@SiO_(2)NPs)was used as the coating solution to prepare composite tent fabric(PA/PU@SiO_(2)).The morphology,structure,and durability of the tent fabric under ultraviolet(UV)radiation,waterstained,or thermal conditions were investigated.The results show that compared with PA/PU fabric without SiO_(2)NPs,when the mass fraction of SiO_(2)NPs in PU coating is 5%,the air permeability of PA/PU@SiO_(2)fabric decreases from about 7.5 to 6.0 nm/s,while the reflectivity to UVvisible light is significantly improved.The surface wettability decreases,as indicated by the average water contact angle(WCA)on PA/PU@SiO_(2)remaining stable at 47°after 9 min.After thermal treatment,the PA/PU@SiO_(2)fabric shows superior mechanical stability.The degradation rate of the tensile strength is only 6.3%,approximately half that of the PA/PU fabric.Meanwhile,the elongation at break increases to 98.9%,compared to 61.8%for the PA/PU fabric.展开更多
Long-chain polyamides(LCPAs)are a class of bio-based polymers that can bridge conventional polyolefins and polycondensates.In this work,taking the advantage of the amphiphilic nature of polyamide 1012(PA1012),membrane...Long-chain polyamides(LCPAs)are a class of bio-based polymers that can bridge conventional polyolefins and polycondensates.In this work,taking the advantage of the amphiphilic nature of polyamide 1012(PA1012),membranes were prepared by using a non-conventional phase separation approach,namely,mixed‘non-solvents’evaporation induced phase separation(MNEIPS).PA1012 can be dissolved in a mixture of polar and non-polar solvents,both of which are non-solvents of PA1012.During the sequential evaporation of the two solvents,the phase separation of PA1012 occurred,inducing the formation of porous structures.We investigated the process of membrane formation in detail,with a specific focus on the liquid-liquid and liquid-solid phase transitions involved.Moreover,we studied the influence of critical factors,such as polymer concentration and mixed-solvent ratio,on the morphologies and properties of PA1012 membranes.This study provides new insights into the development of porous materials based on long-chain polycondensates.展开更多
Two master-batches,polyamide 66 (PA66)/organo-montmorillonite (OMMT) and polyamide 6 (PA6)/OMMT, prepared by melt compounding with methyl methacrylate (MMA) as co-intercalation agent,have been used to prepare nearly e...Two master-batches,polyamide 66 (PA66)/organo-montmorillonite (OMMT) and polyamide 6 (PA6)/OMMT, prepared by melt compounding with methyl methacrylate (MMA) as co-intercalation agent,have been used to prepare nearly exfoliated PA661montmorillonite (MMT) nanocomposites.The resulting nanocomposites are compared in view of their morphology and properties.Nano-scale dispersion of OMMT is realized in both types of nanocomposites,as revealed by XRD,TEM and Molau tests.PA66/MMT nanocomposites having superior mecha...展开更多
An improved method for preparing melamine cyanurate （MCA） based flame retardant polyamide 6 （FRPA6） materials has been proposed. This processing method, i.e., improved in situ polymerization, was used to synthesiz...An improved method for preparing melamine cyanurate （MCA） based flame retardant polyamide 6 （FRPA6） materials has been proposed. This processing method, i.e., improved in situ polymerization, was used to synthesize flame retardant PA6. In situ formed MCA nanoparticles were supposed to be linked to PA6 chains in the ε-caprolactam hydrolytic polymerization system to obtain startype polymers for the first time. Through TEM photographs, it can be found that the in situ formed MCA nanoparticles with diametric size of less than 50 nm, are nanoscaled, highly uniformly dispersed in the PA6 matrix. Synthesized flame retardant PA6 have good fire performance which can achieve UL-94 V-0 rating at 1.6 mm thickness with the presence of 7.34 wt.% MCA in the matrix.展开更多
Novel bio-based and biodegradable block copolymers were synthesized by "click" reaction between poly(L-lactide)(PLLA) and polyamide 4(PA4). Upon tuning the molar mass of PLLA block, the properties of copolym...Novel bio-based and biodegradable block copolymers were synthesized by "click" reaction between poly(L-lactide)(PLLA) and polyamide 4(PA4). Upon tuning the molar mass of PLLA block, the properties of copolymers and electrospun ultrafine fibers were investigated and compared with those of PLLA and PA4 blends. PLLA and PA4 were found incompatible and formed individual crystalline regions, along with reciprocal inhibition in crystallization. Electrospun fibers were highly hydrophobic, even if hydrophilic PA4 was the rich component. The crystallinity of either PLLA or PA4 decreased after electrospinning and PLLA-rich as-spun fibers were almost amorphous. Immersion tests proved that fibers of block copolymers were relatively homogeneous with micro-phase separation between PLLA and PA4. The fibrous structures of copolymers were different from those of the fibers electrospun from blends, for which sheath-core structure induced by macro-phase separation between homopolymers of PLLA and PA4 was confirmed by TEM, EDS, and XPS.展开更多
A diamine containing ether and ester units, as basic monomer for the preparation of polyamides, was prepared via three consecutive reactions. Nucleophilic substitution reaction of 1,4-dihydroxy benzene with 4-nitroben...A diamine containing ether and ester units, as basic monomer for the preparation of polyamides, was prepared via three consecutive reactions. Nucleophilic substitution reaction of 1,4-dihydroxy benzene with 4-nitrobenzoyl chloride produced 4-hydroxyphenyl 4-nitrobenzoate （HPNB）. Reduction of nitro groups to amino groups using Fe and HC1 resulted in preparation of 4-hydroxyphenyl 4-aminobenzoate （HPAB）. The diamine was synthesized through nucleophilic substitution reaction of HPAB with 2,6-dichloropyridine. The precursors and diamine were fully characterized by common methods, and the diamine was polycondensed with different diacid chlorides in the presence of an acid scavenger to prepare new polyamides. The polyamides were characterized, and their physical properties including thermal stability and behavior, inherent viscosity and solubility were studied.展开更多
Polyamide 6 underwent an efficient depolymerization in hydrophilic ionic liquids under microwave irradiation at 300C. The depolymerization completed within 60 min. Caprolactam was readily separated by simple extractio...Polyamide 6 underwent an efficient depolymerization in hydrophilic ionic liquids under microwave irradiation at 300C. The depolymerization completed within 60 min. Caprolactam was readily separated by simple extraction procedure and the ionic liquids were recovered and reused for several times. Addition of catalytic amounts of DMAP(N,N-dimethylaminopyridine) promoted the depolymerization effectively.The present improved procedure provides a method to avoid direct distillation procedure, which consumes energy for the separation of caprolactam from ionic liquids. Although some contamination of ionic liquids was observed, the present procedure provides a new possibility for the use of ionic liquids for plastic chemical recycling from the viewpoint of development of an energy-saving methodology. Use of solubility switchable ionic liquids is also examined to explore a possibility for better separation although depolymerization did not work well.展开更多
Liquid crystalline polymer-polyamide 66 (LCP/PA66) blends were compounded by using a Brabender mixing followed by compression moulding. The LCP employed was a semi-flexible liquid crystalline copolyesteramide based o...Liquid crystalline polymer-polyamide 66 (LCP/PA66) blends were compounded by using a Brabender mixing followed by compression moulding. The LCP employed was a semi-flexible liquid crystalline copolyesteramide based on 30% (molar fraction ) of p-amino benzoic acid (ABA ) and 70% (molar fraction) of poly (ethylene terephthalate) (PET). The LCP/PA66 blends were investigated in terms of the thermal and dynamic mechanical properties. It was found that PA66 and LCP components of the blends are miscible in the molten state, but are partially miscible in the solid state. The inclusion of the semi-flexible LCP into PA66 retards the crystallization rate of PA66. Furthermore, the melting temperature and the degree of crystallinity of PA66 are reduced considerably due to the LCP addition.展开更多
Crosslinking treatments for a commercially available aromatic polyamide reverse osmosis membrane were carried out to improve its chlorine resistance.The crosslinking agents including 1,6-hexanediol diglycidyl ether,ad...Crosslinking treatments for a commercially available aromatic polyamide reverse osmosis membrane were carried out to improve its chlorine resistance.The crosslinking agents including 1,6-hexanediol diglycidyl ether,adipoyl dichloride and hexamethylene diisocyanate ester with long flexible aliphatic chains and high reactivity with N-H groups were used in the experiments.Attenuated total reflective Fourier transform infrared spectra verified the successful preparation of highly crosslinked membranes by crosslinking treatments.It was suggested that the crosslinking agents were connected to membrane surface through the reactions with amine and amide Ⅱ groups,which is confirmed by surface charge measurements.Based on contact angle measurements,crosslinking treatments decreased membrane hydrophilicity by introducing methylene groups to membrane surface.With increasing amount of crosslinking agent molecules connected to membrane surface,the hydrolysis of unconnected functional groups of crosslinking agent produced polar groups and increased membrane hydrophilicity.The highly crosslinked membranes showed higher salt rejections and lower water fluxes as compared with the raw membrane.Since the active sites(N-H groups) vulnerable to free chlorine on membrane surface were eliminated by crosslinking treatments,the chlorine resistances of the highly crosslinked membranes were significantly improved by slighter changes in both water fluxes and salt rejections after chlorination.展开更多
Long chain semiaromatic polyamides with high molecular weight were synthesized by the reactions of undecanediamine with various aromatic diacids,and characterized by fourier transform infrared spectra（FT-IR） and nuc...Long chain semiaromatic polyamides with high molecular weight were synthesized by the reactions of undecanediamine with various aromatic diacids,and characterized by fourier transform infrared spectra（FT-IR） and nuclear magnetic resonance（1H-NMR）.The thermal behaviors were determined by differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA）.The solubility,dynamic mechanical,physical and mechanical properties of the polyamides were also investigated.The experimental results show that the polyamides with high molecular weights are obtained only the PH value of the polyamides salt are in the range of 7.2-7.4.The melting temperatures and the glass transition temperatures of the polyamides increase with the increase of the rigidity of aromatic diacids,and are near to those of poly（nonamethylenetere-phthalamide）（PA9T）.展开更多
In-situ composites based on dispersed poly (ethylene terephthalate) (PET) or polyamide (PA), and continuous polyethylene (PE) were prepared through a single screw extruder of Haake rheometer system with a rod-die rela...In-situ composites based on dispersed poly (ethylene terephthalate) (PET) or polyamide (PA), and continuous polyethylene (PE) were prepared through a single screw extruder of Haake rheometer system with a rod-die relatively small in diameter. The extrudate was drawn at a drawing ratio of 3.1, and then quickly cooled in cold water. The specimens were obtained by injection molding at processing temperatures less than 190℃, far below the melting temperature of PET (265℃) and PA (230℃), which can maintain the solid state of PET and PA microfiber phase in the composites. Morphological observation with scanning electron microscopy (SEM) indicated that PET and PA can more or less form in-situ microfibers at compositions studied (0~20 wt pct PET or PA), and especially, PET and PA were almost deformed into fibers at the concentration of 15 wt pct. Tensile strength and modulus of the blends reinforced by PET or PA microfibers showed to be increased from the tensile test results. The most noticeable improvement of the tensile properties occurred at 15 wt pct of PET in PET/PE system, corresponding to the highest microfiber content, where the tensile strength reached 32.5 MPa, whereas only 19.5 MPa for the pure PE.展开更多
Polyamide 11 (PA 11) is a widely used polyamide resin, but its application is limited since the impact properties, tensile strength, and thermal properties are not very satisfactory for industrial application. In orde...Polyamide 11 (PA 11) is a widely used polyamide resin, but its application is limited since the impact properties, tensile strength, and thermal properties are not very satisfactory for industrial application. In order to improve the mechanical properties of PA 11, in this paper, the preparation of polyamide 11/clay nanocomposites (PACN) via in-situ intercalated polymerization was reported. SEM, TEM and XRD were employed to investigate the dispersion of clay sheet in the matrix. The results indicate that clay layers were homogeneously dispersed in PA11 matrix on a nano-scale, and an exfoliated and intercalated structure co-existed in the composites. The mechanical and thermal properties of the obtained nanocomposites were improved to certain extent by the addition of clay.展开更多
A new hypocrellin B （HB） derivative bearing a bispyrrolecarboxamide-containing side chain was synthesized, which presents improved absorptivity in phototherapeufic window than HB and affinity feature towards dsDNA.
Na +-montmorillonite(Na +-MMT) was converted to organic montmorillonite(OMMT) using modifier which was synthesized at authors’ laboratory. PA6/OMMT nanocomposite was prepared via in situ intercalative polymerization....Na +-montmorillonite(Na +-MMT) was converted to organic montmorillonite(OMMT) using modifier which was synthesized at authors’ laboratory. PA6/OMMT nanocomposite was prepared via in situ intercalative polymerization. The limiting oxygen index (LOI), UL 94V flame retardancy and thermal stability of PA6/OMMT using thermal gravity analysis (TGA) were measured. The Fourier transform infrared (FTIR) technique was used to analyze the pyrolytic residuum and the cone calorimeter (CONE) was applied to determine a number of combustion parameters which were closely related to fire safety, including heat release rate, mass loss rate, effective combustion heat, total heat release, specific extinction area and the time of ignition. In addition, the elemental composition of the surface pyrolytic residuum and the corresponding X-ray photoelectron spectroscopy (XPS) data were obtained, and the morphology of the residuum from CONE measurement was examined by scanning electron microscope (SEM).展开更多
The objective of this study was to improve the toughness of bio based brittle poly(ethylene 2,5-furandicarboxylate)(PEF)by melt blending with bio based polyamide11(PA11)in the presence of a reactive multifunctional ep...The objective of this study was to improve the toughness of bio based brittle poly(ethylene 2,5-furandicarboxylate)(PEF)by melt blending with bio based polyamide11(PA11)in the presence of a reactive multifunctional epoxy compatibilizer(Joncryl ADR-4368).The morphological,thermal,rheological,and mechanical properties of PEF/PA11 blends were investigated.Compared with neat PEF,the toughness of PEF/PA11 blend was not improved in the absence of the reactive compatibilizer due to the poor compatibility between the two polymers.When Joncryl was incorporated into PEF/PA11 blends,the interfacial tension between PEF and PA11 was obviously reduced,reflecting in the fine average particle size and narrow distribution of PA11 dispersed phase as observed by scanning electron microscopy(SEM).The complex viscosities of PEF/PA11 blends with Joncryl were much higher than that of PEF/PA11 blend,which could be ascribed to the formation of graft copolymers through the epoxy groups of Joncryl reacting with the end groups of PEF and PA11 molecular chains.Thus,the compatibility and interfacial adhesion between PEF and PA11 were greatly improved in the presence of Joncryl.The compatibilized PEF/PA11 blend with 1.5 phr Joncryl exhibited significantly improved elongation at break and unnotch impact strength with values of 90.1%and 30.3kJ/m2,respectively,compared with those of 3.6%and 3.8 kJ/m2 for neat PEF,respectively.This work provides an effective approach to improve the toughness of PEF which may expand its widespread application in packaging.展开更多
The non-isothermal crystallization kinetics of polyamide 6/diamine-modified multi-walled carbon nanotube （PA6/D-MWNT） nanocomposite was investigated by differential scanning calorimetry （DSC）. The modified Avrami ...The non-isothermal crystallization kinetics of polyamide 6/diamine-modified multi-walled carbon nanotube （PA6/D-MWNT） nanocomposite was investigated by differential scanning calorimetry （DSC）. The modified Avrami equation, the Ozawa equation and the combined Avrami/Ozawa equation were employed to analyze the non-isothermal crystallization data. The crystallization activation energies were also evaluated by the Kissinger method. It was found that the combined Avrami/Ozawa equation could successfully describe the non-isothermal crystallization process. The results showed that D-MWNTs not only acted as effective heterogeneous nucleating agents for PA6 and noticeably increased the crystallization temperature of PA6, but also influenced the mechanism of nucleation and crystal growth of PA6 and then reduced the overall crystallization rate of the neat PA6 matrix. The crystallization activation energy for the nanocomposite sample was greater than that of the neat PA6, which indicated that the addition of D-MWNTs hindered the mobility of PA6 chain segments.展开更多
Five new optically active polyamides （PAs） 6a-6e were prepared by direct polycondensation reaction of 2-（1,3- isoindolinedione-2-yl）-glutaric acid 4 as a new chiral diacid with various aromatic diamines 5a-Se in a...Five new optically active polyamides （PAs） 6a-6e were prepared by direct polycondensation reaction of 2-（1,3- isoindolinedione-2-yl）-glutaric acid 4 as a new chiral diacid with various aromatic diamines 5a-Se in a medium consisting of triphenyl phosphite （TPP）, calcium chloride, pyridine （Py） and N-methyl-2-pyrrolidone （NMP）. The polycondensation reaction produced a series of polyamids 6a-6e in quantitative yields with inherent viscosities of 0.26-0.39 dL/g. The resulting polymers were fully characterized by means of ^1H-NMR, FT-1R spectroscopy, elemental analysis, inherent viscosity and specific rotation. Thermal properties of these polymers were investigated using thermal gravimetric analysis （TGA） and differential thermal gravimetry （DTG）. Phthalimide rings as a bulky pendent group in the polymer chains disturb the interchain and intrachain interactions and make these PAs readily soluble in polar, aprotic solvents such as N,N-dimethyl acetamide （DMAc）, N,N-dimethyl formamide （DMF）, dimethyl sulfoxide （DMSO）, N-methyl-2-pyrrolidone （NMP） and sulfuric acid.展开更多
This work is focused on simulating the rheological effects in polyamide. An experimental study is carried out in order to assess such features of polyamide as: the hysteretic behavior, the strain rate dependence, and ...This work is focused on simulating the rheological effects in polyamide. An experimental study is carried out in order to assess such features of polyamide as: the hysteretic behavior, the strain rate dependence, and the stress relaxation. The material response in tension is investigated. Digital images correlation method(DIC) is employed in order to measure the material compressibility. A newly developed constitutive model, which was previously used to simulate the mechanical response of polyethylene subjected to moderate strains and compressive loadings, is applied to capture the large strain, inelastic behavior of polyamide in tension. The gathered experimental data are utilized to determine the values of constitutive constants of viscoelasticity and plasticity, which describe the rheological properties of polyamide. The determined material parameters are included in the text. Different strategies for evaluating the material parameters are discussed. The proposed constitutive equation is implemented into the finite element(FE) system, ABAQUS, by taking advantage of the user subroutine UMAT, which allows to define custom material laws. Some exemplary FE simulations that were used to investigate the performance of the developed subroutine are described.展开更多
Polyamide(PA)thin-film composite(TFC)na nofiltration(NF)membrane has extremely broad application prospects in separation of monovalent/diva lent inorganic salts mixed solutio n.However,membrane fouling is the main obs...Polyamide(PA)thin-film composite(TFC)na nofiltration(NF)membrane has extremely broad application prospects in separation of monovalent/diva lent inorganic salts mixed solutio n.However,membrane fouling is the main obstacle to the application of PA,TFC and NF membrane.Streptomycin(SM)is a hydrophilic antibiotic containing a large number of hydroxyl and amino groups.In this work,the NF membrane was prepared via interfacial polymerization(IP)between trimesoyl chloride(TMC)in the organic phase and SM/piperazine(PIP)mixture in the aqueous phase.The NF membrane structure and performance were characterized in detail.The results showed that SM successfully participated in the IP.The negative charge and hydrophilicity of membrane surface were improved.The prepared membrane exhibited good anti-adhesion and anti-bacterial performance,Additionally,when the SM concentration was 2%,the prepared membrane exhibited the optimal permselectivity.The water permeance was 89.4L·m^(-2)·h^(-1)·MPa^(-1).The rejection of NaCl and Na_(2)SO_(4) were 17,17%and 97.84%,respectively.The NaCl/Na_(3)SO_(4) separation factor of the SM2-PIP/TMC membrane in 1000 mg·L^(-1) NaCl and 1000 mg·L^(-1)Na_(2)SO_(4) mixed solution was 40,which was 3.3 times that of PIP/TMC membrane.It indicated that SM2-PIP/TMC demonstrated excellent monovalent/divalent salts separation performance.This work provided an easy and effective approach to preparing anti-fouling NF membrane while possessing superior monovalent/divalent salts separation performance.展开更多
文摘Carbon fibres have been produced from hydroxypropyl-modified lignin(TcC)/bio-based polyamide 1010(PA1010)blended filaments.Two grades of PA1010,with different molecular weights and rheological properties,were used for blending with TcC.An oxidative thermal stabilisation step was used prior to carbonisation in an inert atmosphere to prevent the fusion of the filaments during the latter step.Thermal stabilisation was not possible using a one-step stabilisation process reported in the literature for lignin and other lignin/synthetic polymer blends.As a consequence,a cyclic process involving an additional isothermal phase at a lower temperature than the precursor filaments’melting point,was introduced to increase the cross-linking reactions between the lignin and polyamide.Thermally stabilised filaments were characterised by DSC,TGA,TGA-FTIR,ATR,and SEM techniques.Polymer rheology and heating rate used during thermal stabilisation influenced the thermal stabilisation process and mechanical properties of the derived filaments.Thermally stabilised filaments using optimised conditions(heating in the air atmosphere at 0.25℃/min to 180℃;isothermal for 1 h,cooling back down to ambient at 5℃/min;heating to 250℃ at 0.25℃/min,isothermal for 2 h)could be successfully carbonised.Carbon fibres pro-duced had void-free morphologies and mechanical properties comparable to similarly thermally stabilised and carbonised polyacrylonitrile(PAN)filaments.
文摘In this paper,polyamide(PA)woven fabric was used as the base fabric,and polyurethane(PU)solution containing silica nanoparticles(PU@SiO_(2)NPs)was used as the coating solution to prepare composite tent fabric(PA/PU@SiO_(2)).The morphology,structure,and durability of the tent fabric under ultraviolet(UV)radiation,waterstained,or thermal conditions were investigated.The results show that compared with PA/PU fabric without SiO_(2)NPs,when the mass fraction of SiO_(2)NPs in PU coating is 5%,the air permeability of PA/PU@SiO_(2)fabric decreases from about 7.5 to 6.0 nm/s,while the reflectivity to UVvisible light is significantly improved.The surface wettability decreases,as indicated by the average water contact angle(WCA)on PA/PU@SiO_(2)remaining stable at 47°after 9 min.After thermal treatment,the PA/PU@SiO_(2)fabric shows superior mechanical stability.The degradation rate of the tensile strength is only 6.3%,approximately half that of the PA/PU fabric.Meanwhile,the elongation at break increases to 98.9%,compared to 61.8%for the PA/PU fabric.
基金supported by the Fundamental Research Funds for the Central Universities(No.2023ZYGXZR107)the TCL Science and Technology Innovation Fund。
文摘Long-chain polyamides(LCPAs)are a class of bio-based polymers that can bridge conventional polyolefins and polycondensates.In this work,taking the advantage of the amphiphilic nature of polyamide 1012(PA1012),membranes were prepared by using a non-conventional phase separation approach,namely,mixed‘non-solvents’evaporation induced phase separation(MNEIPS).PA1012 can be dissolved in a mixture of polar and non-polar solvents,both of which are non-solvents of PA1012.During the sequential evaporation of the two solvents,the phase separation of PA1012 occurred,inducing the formation of porous structures.We investigated the process of membrane formation in detail,with a specific focus on the liquid-liquid and liquid-solid phase transitions involved.Moreover,we studied the influence of critical factors,such as polymer concentration and mixed-solvent ratio,on the morphologies and properties of PA1012 membranes.This study provides new insights into the development of porous materials based on long-chain polycondensates.
文摘Two master-batches,polyamide 66 (PA66)/organo-montmorillonite (OMMT) and polyamide 6 (PA6)/OMMT, prepared by melt compounding with methyl methacrylate (MMA) as co-intercalation agent,have been used to prepare nearly exfoliated PA661montmorillonite (MMT) nanocomposites.The resulting nanocomposites are compared in view of their morphology and properties.Nano-scale dispersion of OMMT is realized in both types of nanocomposites,as revealed by XRD,TEM and Molau tests.PA66/MMT nanocomposites having superior mecha...
文摘An improved method for preparing melamine cyanurate （MCA） based flame retardant polyamide 6 （FRPA6） materials has been proposed. This processing method, i.e., improved in situ polymerization, was used to synthesize flame retardant PA6. In situ formed MCA nanoparticles were supposed to be linked to PA6 chains in the ε-caprolactam hydrolytic polymerization system to obtain startype polymers for the first time. Through TEM photographs, it can be found that the in situ formed MCA nanoparticles with diametric size of less than 50 nm, are nanoscaled, highly uniformly dispersed in the PA6 matrix. Synthesized flame retardant PA6 have good fire performance which can achieve UL-94 V-0 rating at 1.6 mm thickness with the presence of 7.34 wt.% MCA in the matrix.
基金financially supported by the National Key Research and Development Program of China (Nos. 2017YFB0309301 and 2017YFB0309302)the Natural Science Foundation of Shanghai, China (No. 17ZR1407200)
文摘Novel bio-based and biodegradable block copolymers were synthesized by "click" reaction between poly(L-lactide)(PLLA) and polyamide 4(PA4). Upon tuning the molar mass of PLLA block, the properties of copolymers and electrospun ultrafine fibers were investigated and compared with those of PLLA and PA4 blends. PLLA and PA4 were found incompatible and formed individual crystalline regions, along with reciprocal inhibition in crystallization. Electrospun fibers were highly hydrophobic, even if hydrophilic PA4 was the rich component. The crystallinity of either PLLA or PA4 decreased after electrospinning and PLLA-rich as-spun fibers were almost amorphous. Immersion tests proved that fibers of block copolymers were relatively homogeneous with micro-phase separation between PLLA and PA4. The fibrous structures of copolymers were different from those of the fibers electrospun from blends, for which sheath-core structure induced by macro-phase separation between homopolymers of PLLA and PA4 was confirmed by TEM, EDS, and XPS.
文摘A diamine containing ether and ester units, as basic monomer for the preparation of polyamides, was prepared via three consecutive reactions. Nucleophilic substitution reaction of 1,4-dihydroxy benzene with 4-nitrobenzoyl chloride produced 4-hydroxyphenyl 4-nitrobenzoate （HPNB）. Reduction of nitro groups to amino groups using Fe and HC1 resulted in preparation of 4-hydroxyphenyl 4-aminobenzoate （HPAB）. The diamine was synthesized through nucleophilic substitution reaction of HPAB with 2,6-dichloropyridine. The precursors and diamine were fully characterized by common methods, and the diamine was polycondensed with different diacid chlorides in the presence of an acid scavenger to prepare new polyamides. The polyamides were characterized, and their physical properties including thermal stability and behavior, inherent viscosity and solubility were studied.
基金partially supported by the Grant-inAid for Scientific Research A(24241023)Grant-in-Aid for Challenging Exploratory Research(17K19139)from the Japan Society for the Promotion of Science
文摘Polyamide 6 underwent an efficient depolymerization in hydrophilic ionic liquids under microwave irradiation at 300C. The depolymerization completed within 60 min. Caprolactam was readily separated by simple extraction procedure and the ionic liquids were recovered and reused for several times. Addition of catalytic amounts of DMAP(N,N-dimethylaminopyridine) promoted the depolymerization effectively.The present improved procedure provides a method to avoid direct distillation procedure, which consumes energy for the separation of caprolactam from ionic liquids. Although some contamination of ionic liquids was observed, the present procedure provides a new possibility for the use of ionic liquids for plastic chemical recycling from the viewpoint of development of an energy-saving methodology. Use of solubility switchable ionic liquids is also examined to explore a possibility for better separation although depolymerization did not work well.
基金Supported by the National Natural Science Foundation of China.
文摘Liquid crystalline polymer-polyamide 66 (LCP/PA66) blends were compounded by using a Brabender mixing followed by compression moulding. The LCP employed was a semi-flexible liquid crystalline copolyesteramide based on 30% (molar fraction ) of p-amino benzoic acid (ABA ) and 70% (molar fraction) of poly (ethylene terephthalate) (PET). The LCP/PA66 blends were investigated in terms of the thermal and dynamic mechanical properties. It was found that PA66 and LCP components of the blends are miscible in the molten state, but are partially miscible in the solid state. The inclusion of the semi-flexible LCP into PA66 retards the crystallization rate of PA66. Furthermore, the melting temperature and the degree of crystallinity of PA66 are reduced considerably due to the LCP addition.
基金Supported by the National Natural Science Foundation of China （20676095）the Program of Introducing Talents of Discipline to Universities （B06006）
文摘Crosslinking treatments for a commercially available aromatic polyamide reverse osmosis membrane were carried out to improve its chlorine resistance.The crosslinking agents including 1,6-hexanediol diglycidyl ether,adipoyl dichloride and hexamethylene diisocyanate ester with long flexible aliphatic chains and high reactivity with N-H groups were used in the experiments.Attenuated total reflective Fourier transform infrared spectra verified the successful preparation of highly crosslinked membranes by crosslinking treatments.It was suggested that the crosslinking agents were connected to membrane surface through the reactions with amine and amide Ⅱ groups,which is confirmed by surface charge measurements.Based on contact angle measurements,crosslinking treatments decreased membrane hydrophilicity by introducing methylene groups to membrane surface.With increasing amount of crosslinking agent molecules connected to membrane surface,the hydrolysis of unconnected functional groups of crosslinking agent produced polar groups and increased membrane hydrophilicity.The highly crosslinked membranes showed higher salt rejections and lower water fluxes as compared with the raw membrane.Since the active sites(N-H groups) vulnerable to free chlorine on membrane surface were eliminated by crosslinking treatments,the chlorine resistances of the highly crosslinked membranes were significantly improved by slighter changes in both water fluxes and salt rejections after chlorination.
文摘Long chain semiaromatic polyamides with high molecular weight were synthesized by the reactions of undecanediamine with various aromatic diacids,and characterized by fourier transform infrared spectra（FT-IR） and nuclear magnetic resonance（1H-NMR）.The thermal behaviors were determined by differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA）.The solubility,dynamic mechanical,physical and mechanical properties of the polyamides were also investigated.The experimental results show that the polyamides with high molecular weights are obtained only the PH value of the polyamides salt are in the range of 7.2-7.4.The melting temperatures and the glass transition temperatures of the polyamides increase with the increase of the rigidity of aromatic diacids,and are near to those of poly（nonamethylenetere-phthalamide）（PA9T）.
基金Thanks are kindly given to the Scientific and Technological Committee of Sichuan for financial supportWe are also grate-ful for project subsidizing by the Special Funds for Major Basic Research (Contract No. G1999064805) the National Natural Science
文摘In-situ composites based on dispersed poly (ethylene terephthalate) (PET) or polyamide (PA), and continuous polyethylene (PE) were prepared through a single screw extruder of Haake rheometer system with a rod-die relatively small in diameter. The extrudate was drawn at a drawing ratio of 3.1, and then quickly cooled in cold water. The specimens were obtained by injection molding at processing temperatures less than 190℃, far below the melting temperature of PET (265℃) and PA (230℃), which can maintain the solid state of PET and PA microfiber phase in the composites. Morphological observation with scanning electron microscopy (SEM) indicated that PET and PA can more or less form in-situ microfibers at compositions studied (0~20 wt pct PET or PA), and especially, PET and PA were almost deformed into fibers at the concentration of 15 wt pct. Tensile strength and modulus of the blends reinforced by PET or PA microfibers showed to be increased from the tensile test results. The most noticeable improvement of the tensile properties occurred at 15 wt pct of PET in PET/PE system, corresponding to the highest microfiber content, where the tensile strength reached 32.5 MPa, whereas only 19.5 MPa for the pure PE.
基金We would like to express our heartfelt thanks to the China National Distinguished Young Investigator Fund(No. 29925413) and the National Natural Science Foundation of China (No. 20274028) for Financial Support.
文摘Polyamide 11 (PA 11) is a widely used polyamide resin, but its application is limited since the impact properties, tensile strength, and thermal properties are not very satisfactory for industrial application. In order to improve the mechanical properties of PA 11, in this paper, the preparation of polyamide 11/clay nanocomposites (PACN) via in-situ intercalated polymerization was reported. SEM, TEM and XRD were employed to investigate the dispersion of clay sheet in the matrix. The results indicate that clay layers were homogeneously dispersed in PA11 matrix on a nano-scale, and an exfoliated and intercalated structure co-existed in the composites. The mechanical and thermal properties of the obtained nanocomposites were improved to certain extent by the addition of clay.
文摘A new hypocrellin B （HB） derivative bearing a bispyrrolecarboxamide-containing side chain was synthesized, which presents improved absorptivity in phototherapeufic window than HB and affinity feature towards dsDNA.
文摘Na +-montmorillonite(Na +-MMT) was converted to organic montmorillonite(OMMT) using modifier which was synthesized at authors’ laboratory. PA6/OMMT nanocomposite was prepared via in situ intercalative polymerization. The limiting oxygen index (LOI), UL 94V flame retardancy and thermal stability of PA6/OMMT using thermal gravity analysis (TGA) were measured. The Fourier transform infrared (FTIR) technique was used to analyze the pyrolytic residuum and the cone calorimeter (CONE) was applied to determine a number of combustion parameters which were closely related to fire safety, including heat release rate, mass loss rate, effective combustion heat, total heat release, specific extinction area and the time of ignition. In addition, the elemental composition of the surface pyrolytic residuum and the corresponding X-ray photoelectron spectroscopy (XPS) data were obtained, and the morphology of the residuum from CONE measurement was examined by scanning electron microscope (SEM).
基金This work was financially supported by the National Natural Science Foundation of China(No.51803224).
文摘The objective of this study was to improve the toughness of bio based brittle poly(ethylene 2,5-furandicarboxylate)(PEF)by melt blending with bio based polyamide11(PA11)in the presence of a reactive multifunctional epoxy compatibilizer(Joncryl ADR-4368).The morphological,thermal,rheological,and mechanical properties of PEF/PA11 blends were investigated.Compared with neat PEF,the toughness of PEF/PA11 blend was not improved in the absence of the reactive compatibilizer due to the poor compatibility between the two polymers.When Joncryl was incorporated into PEF/PA11 blends,the interfacial tension between PEF and PA11 was obviously reduced,reflecting in the fine average particle size and narrow distribution of PA11 dispersed phase as observed by scanning electron microscopy(SEM).The complex viscosities of PEF/PA11 blends with Joncryl were much higher than that of PEF/PA11 blend,which could be ascribed to the formation of graft copolymers through the epoxy groups of Joncryl reacting with the end groups of PEF and PA11 molecular chains.Thus,the compatibility and interfacial adhesion between PEF and PA11 were greatly improved in the presence of Joncryl.The compatibilized PEF/PA11 blend with 1.5 phr Joncryl exhibited significantly improved elongation at break and unnotch impact strength with values of 90.1%and 30.3kJ/m2,respectively,compared with those of 3.6%and 3.8 kJ/m2 for neat PEF,respectively.This work provides an effective approach to improve the toughness of PEF which may expand its widespread application in packaging.
基金Guoxin Sui would like to acknowledge the financial supports of the Hundreds’ Talents Program of Chinese Academy of Sciences.
文摘The non-isothermal crystallization kinetics of polyamide 6/diamine-modified multi-walled carbon nanotube （PA6/D-MWNT） nanocomposite was investigated by differential scanning calorimetry （DSC）. The modified Avrami equation, the Ozawa equation and the combined Avrami/Ozawa equation were employed to analyze the non-isothermal crystallization data. The crystallization activation energies were also evaluated by the Kissinger method. It was found that the combined Avrami/Ozawa equation could successfully describe the non-isothermal crystallization process. The results showed that D-MWNTs not only acted as effective heterogeneous nucleating agents for PA6 and noticeably increased the crystallization temperature of PA6, but also influenced the mechanism of nucleation and crystal growth of PA6 and then reduced the overall crystallization rate of the neat PA6 matrix. The crystallization activation energy for the nanocomposite sample was greater than that of the neat PA6, which indicated that the addition of D-MWNTs hindered the mobility of PA6 chain segments.
文摘Five new optically active polyamides （PAs） 6a-6e were prepared by direct polycondensation reaction of 2-（1,3- isoindolinedione-2-yl）-glutaric acid 4 as a new chiral diacid with various aromatic diamines 5a-Se in a medium consisting of triphenyl phosphite （TPP）, calcium chloride, pyridine （Py） and N-methyl-2-pyrrolidone （NMP）. The polycondensation reaction produced a series of polyamids 6a-6e in quantitative yields with inherent viscosities of 0.26-0.39 dL/g. The resulting polymers were fully characterized by means of ^1H-NMR, FT-1R spectroscopy, elemental analysis, inherent viscosity and specific rotation. Thermal properties of these polymers were investigated using thermal gravimetric analysis （TGA） and differential thermal gravimetry （DTG）. Phthalimide rings as a bulky pendent group in the polymer chains disturb the interchain and intrachain interactions and make these PAs readily soluble in polar, aprotic solvents such as N,N-dimethyl acetamide （DMAc）, N,N-dimethyl formamide （DMF）, dimethyl sulfoxide （DMSO）, N-methyl-2-pyrrolidone （NMP） and sulfuric acid.
文摘This work is focused on simulating the rheological effects in polyamide. An experimental study is carried out in order to assess such features of polyamide as: the hysteretic behavior, the strain rate dependence, and the stress relaxation. The material response in tension is investigated. Digital images correlation method(DIC) is employed in order to measure the material compressibility. A newly developed constitutive model, which was previously used to simulate the mechanical response of polyethylene subjected to moderate strains and compressive loadings, is applied to capture the large strain, inelastic behavior of polyamide in tension. The gathered experimental data are utilized to determine the values of constitutive constants of viscoelasticity and plasticity, which describe the rheological properties of polyamide. The determined material parameters are included in the text. Different strategies for evaluating the material parameters are discussed. The proposed constitutive equation is implemented into the finite element(FE) system, ABAQUS, by taking advantage of the user subroutine UMAT, which allows to define custom material laws. Some exemplary FE simulations that were used to investigate the performance of the developed subroutine are described.
基金supported by the Joint Funds of the National Natural Science Foundation of China(U2006220)。
文摘Polyamide(PA)thin-film composite(TFC)na nofiltration(NF)membrane has extremely broad application prospects in separation of monovalent/diva lent inorganic salts mixed solutio n.However,membrane fouling is the main obstacle to the application of PA,TFC and NF membrane.Streptomycin(SM)is a hydrophilic antibiotic containing a large number of hydroxyl and amino groups.In this work,the NF membrane was prepared via interfacial polymerization(IP)between trimesoyl chloride(TMC)in the organic phase and SM/piperazine(PIP)mixture in the aqueous phase.The NF membrane structure and performance were characterized in detail.The results showed that SM successfully participated in the IP.The negative charge and hydrophilicity of membrane surface were improved.The prepared membrane exhibited good anti-adhesion and anti-bacterial performance,Additionally,when the SM concentration was 2%,the prepared membrane exhibited the optimal permselectivity.The water permeance was 89.4L·m^(-2)·h^(-1)·MPa^(-1).The rejection of NaCl and Na_(2)SO_(4) were 17,17%and 97.84%,respectively.The NaCl/Na_(3)SO_(4) separation factor of the SM2-PIP/TMC membrane in 1000 mg·L^(-1) NaCl and 1000 mg·L^(-1)Na_(2)SO_(4) mixed solution was 40,which was 3.3 times that of PIP/TMC membrane.It indicated that SM2-PIP/TMC demonstrated excellent monovalent/divalent salts separation performance.This work provided an easy and effective approach to preparing anti-fouling NF membrane while possessing superior monovalent/divalent salts separation performance.
