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2018 Volume Issue 3
2018, (3): 321-322
doi: 10.11777/j.issn1000-3304.2018.18059
Abstract:
Prof.Chen and coworkers from Fudan University developed a graceful strategy to control the sugars' dispersion on particle surface, which can significantly influence their cellular uptake.
Prof.Chen and coworkers from Fudan University developed a graceful strategy to control the sugars' dispersion on particle surface, which can significantly influence their cellular uptake.
2018, (3): 323-335
doi: 10.11777/j.issn1000-3304.2017.17081
Abstract:
Surface modification of high-performance continuous fibers was carried out by inductively coupled plasma (ICP) and dielectric barrier discharge (DBD) cold plasma, respectively. The effects of treatment time, discharge power and pressure on the chemical composition, morphology and wetting ability of the fiber surface were investigated by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and dynamic contact angle analysis (DCA). The relationship between interface structure and interfacial adhesion, and the failure mechanism of the fibers reinforced bismaleimide (BMI) composites were discussed. The results indicated that the treatment of PBO fibers by O2, Ar and mixed O2/Ar ICP, respectively, would result in the decomposition of the phenyl rings and oxazole moieties on the fiber surface, along with the formation of some polar groups and active groups, such as ester bonds, amide bonds and free radicals. Sputtering and etching of plasma also brought about a rough morphology for fiber surface. The modification effect by Ar ICP was better than that by O2 ICP, and O2/Ar ICP presented the best activation effect on the chemical compositions of PBO surface due to the synergy effect. The optimum ratio of O2/Ar mixture was 40% -60% of O2 content. The interlaminar shear strength (ILSS) of PBO/BMI composite treated with O2/Ar ICP was 61.6 MPa, an increase by 38.1% compared with that of the untreated samples. The DBD plasma also improved the polarity, reactivity and the morphology of the PBO fiber surface. The effect of enhancement in ILSS values of PBO/BMI composites treated by O2DBD was better in comparison with that treated by air DBD. The ILSS value was increased to 57.1 MPa at 12 s when treated at 30 W/cm3by air DBD plasma, while that of PBO/BMI composites treated by oxy-DBD plasma under the same condition was 62 MPa. Scanning electron microscopy (SEM) micrographs demonstrated that the fracture failure mechanism of PBO/BMI composites treated by ICP or DBD plasma shifted from interface failure to matrix failure. Finally, the relationship between the aging behavior of the fiber surface and the interfacial property of the fiber reinforced BMI composites were also discussed. ILSS values of PBO/BMI composites decreased with storage time for the fibers treated by plasma.
Surface modification of high-performance continuous fibers was carried out by inductively coupled plasma (ICP) and dielectric barrier discharge (DBD) cold plasma, respectively. The effects of treatment time, discharge power and pressure on the chemical composition, morphology and wetting ability of the fiber surface were investigated by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and dynamic contact angle analysis (DCA). The relationship between interface structure and interfacial adhesion, and the failure mechanism of the fibers reinforced bismaleimide (BMI) composites were discussed. The results indicated that the treatment of PBO fibers by O2, Ar and mixed O2/Ar ICP, respectively, would result in the decomposition of the phenyl rings and oxazole moieties on the fiber surface, along with the formation of some polar groups and active groups, such as ester bonds, amide bonds and free radicals. Sputtering and etching of plasma also brought about a rough morphology for fiber surface. The modification effect by Ar ICP was better than that by O2 ICP, and O2/Ar ICP presented the best activation effect on the chemical compositions of PBO surface due to the synergy effect. The optimum ratio of O2/Ar mixture was 40% -60% of O2 content. The interlaminar shear strength (ILSS) of PBO/BMI composite treated with O2/Ar ICP was 61.6 MPa, an increase by 38.1% compared with that of the untreated samples. The DBD plasma also improved the polarity, reactivity and the morphology of the PBO fiber surface. The effect of enhancement in ILSS values of PBO/BMI composites treated by O2DBD was better in comparison with that treated by air DBD. The ILSS value was increased to 57.1 MPa at 12 s when treated at 30 W/cm3by air DBD plasma, while that of PBO/BMI composites treated by oxy-DBD plasma under the same condition was 62 MPa. Scanning electron microscopy (SEM) micrographs demonstrated that the fracture failure mechanism of PBO/BMI composites treated by ICP or DBD plasma shifted from interface failure to matrix failure. Finally, the relationship between the aging behavior of the fiber surface and the interfacial property of the fiber reinforced BMI composites were also discussed. ILSS values of PBO/BMI composites decreased with storage time for the fibers treated by plasma.
2018, 2018(3): 336-348
doi: 10.11777/j.issn1000-3304.2017.17152
Abstract:
Mineral nutrients from environment are required for plants growing, but the natural nutrients from soil can not completely meet the need. Therefore, use of fertilizers is the simple, effective and fast method to increase the yield and to improve the quality of the grains. However, only a small amount of the fertilizers used can be effectively absorbed by crops, and most of them are lost by volatilizing into the atmosphere or leaching into the ground, which leads to a serious waste of the fertilizers with severe environmental pollution (e.g. acidic rain, soil salinization and greenhouse gas release etc.). To solve these problems, polymer-based slow-release fertilizers were developed by functional modification to control the release of the nutrients and to prolong the effective use of the fertilizer. However, the release behavior of these slow-release fertilizers is always influenced by some factors such as temperature, humidity, pH and salinization of soil in practical applications. To address this issue, intelligent fertilizer, i.e. fertilizer with functional controlled-release, has been developed to regulate the release of various nutrients in accordance with the change of soil environment and the different stages of plant growth. Especially, polymer-based environment-responsive fertilizer, as an intelligent fertilizer, can change water absorbency, water-holding capacity and nutrient release behavior, by intelligently regulating water and nutrients in soil according to specific stimulus response signals of soil environment, such as temperature, humidity, pH value and ion concentration. This review briefly introduces the development stages of the fertilizer and their classification. On the basis of different stimulation signals from the environment and actual application, these environment-responsive fertilizers are classified as temperature-responsive, pH-responsive and salt-sensitive fertilizers. Their preparations, properties, stimulus-responsive behaviors and application are introduced in detail. Intelligentialization of the fertilizer is an important tendency in agriculture and horticulture field, and the polymer-based environment-responsive fertilizer has great potential in fertilizer development and application. With the development of agricultural modernization and polymer science, it can be expected that the preparation and application of the natural polymer-based responsive fertilizer, the multiple-responsive fertilizer and the biologically responsive fertilizer will be research trends in the fertilizer fields.
Mineral nutrients from environment are required for plants growing, but the natural nutrients from soil can not completely meet the need. Therefore, use of fertilizers is the simple, effective and fast method to increase the yield and to improve the quality of the grains. However, only a small amount of the fertilizers used can be effectively absorbed by crops, and most of them are lost by volatilizing into the atmosphere or leaching into the ground, which leads to a serious waste of the fertilizers with severe environmental pollution (e.g. acidic rain, soil salinization and greenhouse gas release etc.). To solve these problems, polymer-based slow-release fertilizers were developed by functional modification to control the release of the nutrients and to prolong the effective use of the fertilizer. However, the release behavior of these slow-release fertilizers is always influenced by some factors such as temperature, humidity, pH and salinization of soil in practical applications. To address this issue, intelligent fertilizer, i.e. fertilizer with functional controlled-release, has been developed to regulate the release of various nutrients in accordance with the change of soil environment and the different stages of plant growth. Especially, polymer-based environment-responsive fertilizer, as an intelligent fertilizer, can change water absorbency, water-holding capacity and nutrient release behavior, by intelligently regulating water and nutrients in soil according to specific stimulus response signals of soil environment, such as temperature, humidity, pH value and ion concentration. This review briefly introduces the development stages of the fertilizer and their classification. On the basis of different stimulation signals from the environment and actual application, these environment-responsive fertilizers are classified as temperature-responsive, pH-responsive and salt-sensitive fertilizers. Their preparations, properties, stimulus-responsive behaviors and application are introduced in detail. Intelligentialization of the fertilizer is an important tendency in agriculture and horticulture field, and the polymer-based environment-responsive fertilizer has great potential in fertilizer development and application. With the development of agricultural modernization and polymer science, it can be expected that the preparation and application of the natural polymer-based responsive fertilizer, the multiple-responsive fertilizer and the biologically responsive fertilizer will be research trends in the fertilizer fields.
2018, (3): 349-355
doi: 10.11777/j.issn1000-3304.2017.17210
Abstract:
Poly(ionic liquid)s have been used as electrolytes in lithium-ion battery due to their good electrochemical properties and thermal stability.In this work, we firstly synthesized organic poly(ionic liquid) gel, PCnvimPF6, by γ-ray radiation inducing polymerization of 1-alkyl-3-vinylimidazolium hexafluorophosphate ([Cnvim]PF6) (n=6, 12), with 1, 1'-(1, 6-ethylidene)-bis(3-vinylimidazolium) hexafluorophosphate as crosslinking agent in a mixed carbonate ester solution.The gel fraction of the resultant gel increased along with the radiation absorbed dose, while the degree of equilibrium swelling (EDS) of the gel decreased, and the changes of the gel fraction and EDS were no longer obvious with the radiation absorbed dose above 20 kGy.FTIR results showed that the characteristic vibration absorption peaks of C=C for[Cnvim]PF6 from 1654 cm-1 to 1656 cm-1 disappeared after radiation, indicating the successful synthesis of PCnvimPF6gel.TGA experiment indicated that PCnvimPF6gel was of good thermal stability.Based on this PCnvimPF6gel, a novel gel polymer electrolyte (GPE), PCnvimPF6-Li GPE, was prepared by adding 1 mol/L LiPF6 into monomer solution using one-step radiation synthesis.Effects of the alkyl chain length of the monomer, the contents of the monomer and the crosslinking agent on the property of PCnvimPF6-Li GPE were investigated.The obtained PCnvimPF6-Li GPE exhibited good mechanical property and high ionic conductivity.The ionic conductivity of the GPE increased with the decrease of monomer concentration and alkyl chain length, and changed slightly with the content of crosslinking agent.As the monomer concentration increased, the compressive strength (σm) of the GPE increased, and the compressive strain (εm) decreased.The σm of the GPE ranged from 40 kPa to 1685 kPa, and its ionic conductivity from 1.5 mS/cm to 7.18 mS/cm.The highest ionic conductivity (7.18 mS/cm) was obtained for a sample prepared using 0.4 mol/L C6vimPF6 monomer solution containing 8 mol% of crosslinker and 1 mol/L LiPF6.It is expected that the resultant PCnvimPF6-Li GPE is a promising candidate for lithium-ion battery electrolytes.
Poly(ionic liquid)s have been used as electrolytes in lithium-ion battery due to their good electrochemical properties and thermal stability.In this work, we firstly synthesized organic poly(ionic liquid) gel, PCnvimPF6, by γ-ray radiation inducing polymerization of 1-alkyl-3-vinylimidazolium hexafluorophosphate ([Cnvim]PF6) (n=6, 12), with 1, 1'-(1, 6-ethylidene)-bis(3-vinylimidazolium) hexafluorophosphate as crosslinking agent in a mixed carbonate ester solution.The gel fraction of the resultant gel increased along with the radiation absorbed dose, while the degree of equilibrium swelling (EDS) of the gel decreased, and the changes of the gel fraction and EDS were no longer obvious with the radiation absorbed dose above 20 kGy.FTIR results showed that the characteristic vibration absorption peaks of C=C for[Cnvim]PF6 from 1654 cm-1 to 1656 cm-1 disappeared after radiation, indicating the successful synthesis of PCnvimPF6gel.TGA experiment indicated that PCnvimPF6gel was of good thermal stability.Based on this PCnvimPF6gel, a novel gel polymer electrolyte (GPE), PCnvimPF6-Li GPE, was prepared by adding 1 mol/L LiPF6 into monomer solution using one-step radiation synthesis.Effects of the alkyl chain length of the monomer, the contents of the monomer and the crosslinking agent on the property of PCnvimPF6-Li GPE were investigated.The obtained PCnvimPF6-Li GPE exhibited good mechanical property and high ionic conductivity.The ionic conductivity of the GPE increased with the decrease of monomer concentration and alkyl chain length, and changed slightly with the content of crosslinking agent.As the monomer concentration increased, the compressive strength (σm) of the GPE increased, and the compressive strain (εm) decreased.The σm of the GPE ranged from 40 kPa to 1685 kPa, and its ionic conductivity from 1.5 mS/cm to 7.18 mS/cm.The highest ionic conductivity (7.18 mS/cm) was obtained for a sample prepared using 0.4 mol/L C6vimPF6 monomer solution containing 8 mol% of crosslinker and 1 mol/L LiPF6.It is expected that the resultant PCnvimPF6-Li GPE is a promising candidate for lithium-ion battery electrolytes.
2018, (3): 356-365
doi: 10.11777/j.issn1000-3304.2017.17087
Abstract:
The synthesis of epoxidized star-shaped polymers by incorporation of living anionic polymerization with polyhedral oligomericsilsesquioxane (POSS) is seldom reported.In this study, the living (polyisopryl)lithium (PI-Li) is first synthesized in cyclohexane via high-vacuum living anionic polymerization using sec-butyllithium as the initiator and isoprene as the monomer.Subsequently, PI-Li is used to react with octavinyl polyhedral oligomericsilsesquioxane (OVPOSS) in cyclohexane to prepare an eight-arm star-shaped polyisoprene (8PI-POSS) in one pot.Purified 8PI-POSS is obtained after fractionation precipitation using cyclohexane/ethanol as solvent/nonsolvent, and characterized by nuclear magnetic resonance (1H-and 13C-NMR), gel permeation chromatography (GPC), matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectroscopy and Fourier transform infrared spectroscopy (FTIR), respectively.Star-shaped polyisoprenes with different arm lengths are synthesized by changing the feed ratio of the monomer to the initiator.The compositions of the polymers are determined by comparison of integrals of characteristic signals from 1H-NMR spectra.GPC tests demonstrate that the eluent curves of the crude star-shaped polyisoprenes show an apparent shift to higher molecular weight compared with that of the base PI.The purified star-shaped polyisoprene (8PI-POSS) by fractionation precipitation possesses symmetric peaks with relatively narrow polydispersity.MALDI-TOF MS analysis indicates that the observed molecular weight of base PI is in good agreement with the calculated value.In addition, there are two minor peaks with an interval of 16 Da in the MALDI-TOF MS spectrum, which may be attributed to the possible oxidation reaction during storage or MALDI-TOF MS test.Unfortunately, the MALDI-TOF MS spectra of 8PI-POSS are not obtained probably due to their high molecular weights.Finally, the epoxidized star-shaped polyisoprene (8EPI-POSS) is obtained by oxidation of 8PI-POSS catalyzed by HCOOH/H2O2.The 8EPI-POSS polymer is also characterized by 1H-and 13C-NMR, GPC and FTIR analyses, respectively.The characteristic signals found in 1H-and 13C-NMR spectra, as well as in FTIR spectra confirm the formation of epoxy group in the 8EPI-POSS.By changing the temperature and time of oxidation reaction, the star-shaped 8EPI-POSS with different percentages of epoxidation (PE) are prepared.It is also found that the GPC eluent curve of 8EPI-POSS change a little after the oxidation reaction.TGA tests show that the thermal decomposition temperature of 8PI-POSS and 8EPI-POSS are higher than that of the base PI.Moreover, it is also found that about 3% residue is left at about 800 ℃, which maybe because of the incorporation of POSS segment in the star-shaped polymers.The epoxidized star-shaped polyisoprenes reported here may serve as an important intermediate in the preparation of highly branched polymers and as the novel tougheners for epoxy resins.
The synthesis of epoxidized star-shaped polymers by incorporation of living anionic polymerization with polyhedral oligomericsilsesquioxane (POSS) is seldom reported.In this study, the living (polyisopryl)lithium (PI-Li) is first synthesized in cyclohexane via high-vacuum living anionic polymerization using sec-butyllithium as the initiator and isoprene as the monomer.Subsequently, PI-Li is used to react with octavinyl polyhedral oligomericsilsesquioxane (OVPOSS) in cyclohexane to prepare an eight-arm star-shaped polyisoprene (8PI-POSS) in one pot.Purified 8PI-POSS is obtained after fractionation precipitation using cyclohexane/ethanol as solvent/nonsolvent, and characterized by nuclear magnetic resonance (1H-and 13C-NMR), gel permeation chromatography (GPC), matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectroscopy and Fourier transform infrared spectroscopy (FTIR), respectively.Star-shaped polyisoprenes with different arm lengths are synthesized by changing the feed ratio of the monomer to the initiator.The compositions of the polymers are determined by comparison of integrals of characteristic signals from 1H-NMR spectra.GPC tests demonstrate that the eluent curves of the crude star-shaped polyisoprenes show an apparent shift to higher molecular weight compared with that of the base PI.The purified star-shaped polyisoprene (8PI-POSS) by fractionation precipitation possesses symmetric peaks with relatively narrow polydispersity.MALDI-TOF MS analysis indicates that the observed molecular weight of base PI is in good agreement with the calculated value.In addition, there are two minor peaks with an interval of 16 Da in the MALDI-TOF MS spectrum, which may be attributed to the possible oxidation reaction during storage or MALDI-TOF MS test.Unfortunately, the MALDI-TOF MS spectra of 8PI-POSS are not obtained probably due to their high molecular weights.Finally, the epoxidized star-shaped polyisoprene (8EPI-POSS) is obtained by oxidation of 8PI-POSS catalyzed by HCOOH/H2O2.The 8EPI-POSS polymer is also characterized by 1H-and 13C-NMR, GPC and FTIR analyses, respectively.The characteristic signals found in 1H-and 13C-NMR spectra, as well as in FTIR spectra confirm the formation of epoxy group in the 8EPI-POSS.By changing the temperature and time of oxidation reaction, the star-shaped 8EPI-POSS with different percentages of epoxidation (PE) are prepared.It is also found that the GPC eluent curve of 8EPI-POSS change a little after the oxidation reaction.TGA tests show that the thermal decomposition temperature of 8PI-POSS and 8EPI-POSS are higher than that of the base PI.Moreover, it is also found that about 3% residue is left at about 800 ℃, which maybe because of the incorporation of POSS segment in the star-shaped polymers.The epoxidized star-shaped polyisoprenes reported here may serve as an important intermediate in the preparation of highly branched polymers and as the novel tougheners for epoxy resins.
2018, 49(3): 366-373
doi: 10.11777/j.issn1000-3304.2017.17091
Abstract:
Snowman-like Janus particles of PVDF/P4VP were prepared via a soap-free seeded emulsion polymerization using poly(vinylidene fluoride) (PVDF) latex particles as seeds and 4-vinyl pyridine (4VP) as functional monomer. All seeded emulsion polymerization was carried out in a four-necked round-bottom flask of 100 mL capacity. First, dialyzed PVDF latex (4.0 g) with a solid content of 12.5 wt% was dispersed in deionized water (40.0 g), and the dispersion was further ultrasonicated for 40 min to avoid any particle agglomeration. The flask was placed in a water bath preset at 30 ℃ and nitrogen-purged for 15 min to remove O2 before additions of ammonia solution (1.0 g) and 4VP (0.5 g). Nitrogen-purge was maintained during the entire reaction process. The mixture was stirred at 250 r/min for 1 h to allow the monomers to swell the PVDF seed particles, followed by heating to 60 ℃. Subsequently, 1.5 mg of K2S2O8 were added to trigger the polymerization, and the reaction lasted for 4 h. The average particle diameter and particle size distribution (PDI) of the composite particles were determined by dynamic light scattering. The micromorphology of the composite particles was characterized by scanning electron microscopy. The chemical composition of the composite particles was confirmed by Fourier transform infrared spectroscopy. The confined crystallization of PVDF in the composite particles was studied by differential scanning calorimetry. In this study, the introduction of an appropriate amount of ammonia solution into the polymerization system played a vital role in maitaining the stability of the reaction system and the uniformity of the composite particles, possibly due to the prevention of P4VP nucleation in the aqueous phase. One side of the compsite particles obtained was PVDF and the other side was P4VP with pyridine groups, which could be used for further modification and assembly.
Snowman-like Janus particles of PVDF/P4VP were prepared via a soap-free seeded emulsion polymerization using poly(vinylidene fluoride) (PVDF) latex particles as seeds and 4-vinyl pyridine (4VP) as functional monomer. All seeded emulsion polymerization was carried out in a four-necked round-bottom flask of 100 mL capacity. First, dialyzed PVDF latex (4.0 g) with a solid content of 12.5 wt% was dispersed in deionized water (40.0 g), and the dispersion was further ultrasonicated for 40 min to avoid any particle agglomeration. The flask was placed in a water bath preset at 30 ℃ and nitrogen-purged for 15 min to remove O2 before additions of ammonia solution (1.0 g) and 4VP (0.5 g). Nitrogen-purge was maintained during the entire reaction process. The mixture was stirred at 250 r/min for 1 h to allow the monomers to swell the PVDF seed particles, followed by heating to 60 ℃. Subsequently, 1.5 mg of K2S2O8 were added to trigger the polymerization, and the reaction lasted for 4 h. The average particle diameter and particle size distribution (PDI) of the composite particles were determined by dynamic light scattering. The micromorphology of the composite particles was characterized by scanning electron microscopy. The chemical composition of the composite particles was confirmed by Fourier transform infrared spectroscopy. The confined crystallization of PVDF in the composite particles was studied by differential scanning calorimetry. In this study, the introduction of an appropriate amount of ammonia solution into the polymerization system played a vital role in maitaining the stability of the reaction system and the uniformity of the composite particles, possibly due to the prevention of P4VP nucleation in the aqueous phase. One side of the compsite particles obtained was PVDF and the other side was P4VP with pyridine groups, which could be used for further modification and assembly.
2018, (3): 374-379
doi: 10.11777/j.issn1000-3304.2017.17097
Abstract:
A pump-probe setup consisting of two mid-infrared quantum cascade lasers (QCLs) is designed to engrave polymer spherulites via selective melting induced by infrared resonance absorption. When the wavelength of QCL is tuned to the infrared absorbance peak of specific molecular group and the vibration direction of the group is the same as the direction of light polarization, infrared resonance absorption results in strong thermal effect. Combing with the high polarization property of QCL, selective melting can be realized. The molecular chains in polymer spherulites are aligned in all directions and the corresponding orientation direction is fixed, suitable for verifying the feasibility of the spherulites engraving by pumping different parts of the spherulites. The wavelength of the pump beam is set to a strong absorption peak in the infrared spectrum, inducing crystal melting by resonant heating, while the wavelength of the probe beam is turned to the conformation absorption peak of specific groups to trace the structure change. There are mainly three highlights of this method:(1) the melting process and the melting degree are studied in situ based on the change of the transmission intensity; (2) both pump and probe beams can reflect the structure information; (3) selectively melting of designated position in spherulites can be realized. Results of isotactic polybutene-1 (iPB-1) show that, when the energy of the pump stays constant, the melting effect is different at distinct positions of the spherulites. Melting degree of the sample decreases with the increase of the angle between the vibration direction of the groups and polarization direction of the pump beam, which proves feasible to use QCL to perform engraving on spherulite scale. Selective melting induced by infrared resonance absorption provides a new way for in situ study of rapid melting process and a guideline for controlling crystal form transition and aggregation morphology at specific position.
A pump-probe setup consisting of two mid-infrared quantum cascade lasers (QCLs) is designed to engrave polymer spherulites via selective melting induced by infrared resonance absorption. When the wavelength of QCL is tuned to the infrared absorbance peak of specific molecular group and the vibration direction of the group is the same as the direction of light polarization, infrared resonance absorption results in strong thermal effect. Combing with the high polarization property of QCL, selective melting can be realized. The molecular chains in polymer spherulites are aligned in all directions and the corresponding orientation direction is fixed, suitable for verifying the feasibility of the spherulites engraving by pumping different parts of the spherulites. The wavelength of the pump beam is set to a strong absorption peak in the infrared spectrum, inducing crystal melting by resonant heating, while the wavelength of the probe beam is turned to the conformation absorption peak of specific groups to trace the structure change. There are mainly three highlights of this method:(1) the melting process and the melting degree are studied in situ based on the change of the transmission intensity; (2) both pump and probe beams can reflect the structure information; (3) selectively melting of designated position in spherulites can be realized. Results of isotactic polybutene-1 (iPB-1) show that, when the energy of the pump stays constant, the melting effect is different at distinct positions of the spherulites. Melting degree of the sample decreases with the increase of the angle between the vibration direction of the groups and polarization direction of the pump beam, which proves feasible to use QCL to perform engraving on spherulite scale. Selective melting induced by infrared resonance absorption provides a new way for in situ study of rapid melting process and a guideline for controlling crystal form transition and aggregation morphology at specific position.
2018, (3): 380-388
doi: 10.11777/j.issn1000-3304.2017.17102
Abstract:
The differences between the microstructure and composition of high-strength high-modulus carbon fibers and those of high-modulus carbon fibers, both domestic products, are presented by laser micro-Raman scattering (Raman), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), elemental analysis (EA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). The results show that the graphite crystallites in high-strength high-modulus carbon fibers are fine (La = 0.543 nm, Lc = 0.301 nm). There are many defects in the plane and at the edge of the graphite sheets. On one hand, the small graphite crystallites are linked to each other by sp3 amorphous carbons, which are shown as the wave-like and winkled ribbons in TEM images. The defects in the micro-crystallites, mainly composed of non-conjugated carbon atoms and oxygenated/nitrous carbon, cause a relative larger space between graphite layers (d002 = 0.343 nm) with a lower degree of graphitization (R = 1.15). The fine crystallites and defect structures have a larger orientation angle (Z = 10.33°) of (002) crystal face of the graphite crystallites in the high-strength high-modulus carbon fibers. In addition, the microvoids in the high-strength high-modulus carbon fibers are smaller in size (L = 74.7 nm) and larger in orientation angle (Beq = 9.97º) than those in high-modulus carbon fibers, which attributes to the mergence and development of the microvoids at the interface of graphite crystallites resulted from exhausting of the non-carbon elements during the heat treatment. The high-modulus carbon fibers have a higher degree of graphitization (R = 0.29), and the graphite crystallites are bulky and stacked orderly (La = 0.687 nm, Lc = 0.484 nm, d002 = 0.337 nm, Z = 9.77º). Moreover, the cracks and microvoids in high-modulus carbon fibers are larger in sizes (L = 102.4 nm) and smaller in orientation angle (Beq = 8.11º) than those in the high-strength high-modulus carbon fibers. The hierarchical structure in the high-strength high-modulus carbon fibers, including the microcrystalline structure, the microvoids and the nitrogen/oxygen doped graphite sheets, offers various paths to dispersing the stress during the stretching process of the carbon fibers, which leads to large elongation and high tensile strength for the carbon fibers.
The differences between the microstructure and composition of high-strength high-modulus carbon fibers and those of high-modulus carbon fibers, both domestic products, are presented by laser micro-Raman scattering (Raman), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), elemental analysis (EA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). The results show that the graphite crystallites in high-strength high-modulus carbon fibers are fine (La = 0.543 nm, Lc = 0.301 nm). There are many defects in the plane and at the edge of the graphite sheets. On one hand, the small graphite crystallites are linked to each other by sp3 amorphous carbons, which are shown as the wave-like and winkled ribbons in TEM images. The defects in the micro-crystallites, mainly composed of non-conjugated carbon atoms and oxygenated/nitrous carbon, cause a relative larger space between graphite layers (d002 = 0.343 nm) with a lower degree of graphitization (R = 1.15). The fine crystallites and defect structures have a larger orientation angle (Z = 10.33°) of (002) crystal face of the graphite crystallites in the high-strength high-modulus carbon fibers. In addition, the microvoids in the high-strength high-modulus carbon fibers are smaller in size (L = 74.7 nm) and larger in orientation angle (Beq = 9.97º) than those in high-modulus carbon fibers, which attributes to the mergence and development of the microvoids at the interface of graphite crystallites resulted from exhausting of the non-carbon elements during the heat treatment. The high-modulus carbon fibers have a higher degree of graphitization (R = 0.29), and the graphite crystallites are bulky and stacked orderly (La = 0.687 nm, Lc = 0.484 nm, d002 = 0.337 nm, Z = 9.77º). Moreover, the cracks and microvoids in high-modulus carbon fibers are larger in sizes (L = 102.4 nm) and smaller in orientation angle (Beq = 8.11º) than those in the high-strength high-modulus carbon fibers. The hierarchical structure in the high-strength high-modulus carbon fibers, including the microcrystalline structure, the microvoids and the nitrogen/oxygen doped graphite sheets, offers various paths to dispersing the stress during the stretching process of the carbon fibers, which leads to large elongation and high tensile strength for the carbon fibers.
2018, (3): 389-394
doi: 10.11777/j.issn1000-3304.2017.17113
Abstract:
Mono-disperse polystyrene (PS) microspheres with different particle sizes were synthesized by soap-free emulsion polymerization, and deposited for the first time by electrophoretic deposition on the surface of the self-made graphene fibers prepared by wet spinning, and photonic crystal fibers with different structural colors were finally obtained, and characterized by SEM, optical microscopy, UV reflection spectra and colorimetric analysis. The results showed that the three PS microspheres, with diameters of 198, 233 and 287 nm, respectively, were of smooth surface and uniform particle size with monodispersion coefficient less than 5%. After electrophoretic deposition, they were orderly aligned on the surface of graphene fibers as hexagonal close packing with a core-shell structure, forming photonic crystal fibers with different colors including blue, green and purplish red. Moreover, the photonic bandgaps of the three photonic crystal fibers were located at 471, 547, 670 and 398 nm, respectively, consistent with their colors. Calculated with Bragg's law, the reflection peaks of the photonic crystal fibers made from PS microspheres with 198 and 233 nm located at 474 and 558 nm, respectively, which are close to their experimental results. While the reflection peak of the photonic crystal fiber made from PS microspheres of 287 nm size was found at 687 nm, close to the longer wave peak of the experimental results. The CIE xyY color space was used to identify the color of the photonic crystal fibers. It was found that the brightness factors of blue, green, and purplish red photonic crystal fibers were 15.96, 29.72 and 3.85, respectively, which corresponded to 44%, 63% and 32% of pure blue, green and purple lightness, indicating that they all were of high brightness. Furthermore, the calculated saturation values of the blue, green, purplish red photonic crystal fibers were 63%, 59% and 60%, respectively, showing that they all had a high degree of saturation. The photonic crystal fibers do not need dyeing and their colors never fade, which meet the requirements of green and environmental protection, presenting broad prospect for their applications.
Mono-disperse polystyrene (PS) microspheres with different particle sizes were synthesized by soap-free emulsion polymerization, and deposited for the first time by electrophoretic deposition on the surface of the self-made graphene fibers prepared by wet spinning, and photonic crystal fibers with different structural colors were finally obtained, and characterized by SEM, optical microscopy, UV reflection spectra and colorimetric analysis. The results showed that the three PS microspheres, with diameters of 198, 233 and 287 nm, respectively, were of smooth surface and uniform particle size with monodispersion coefficient less than 5%. After electrophoretic deposition, they were orderly aligned on the surface of graphene fibers as hexagonal close packing with a core-shell structure, forming photonic crystal fibers with different colors including blue, green and purplish red. Moreover, the photonic bandgaps of the three photonic crystal fibers were located at 471, 547, 670 and 398 nm, respectively, consistent with their colors. Calculated with Bragg's law, the reflection peaks of the photonic crystal fibers made from PS microspheres with 198 and 233 nm located at 474 and 558 nm, respectively, which are close to their experimental results. While the reflection peak of the photonic crystal fiber made from PS microspheres of 287 nm size was found at 687 nm, close to the longer wave peak of the experimental results. The CIE xyY color space was used to identify the color of the photonic crystal fibers. It was found that the brightness factors of blue, green, and purplish red photonic crystal fibers were 15.96, 29.72 and 3.85, respectively, which corresponded to 44%, 63% and 32% of pure blue, green and purple lightness, indicating that they all were of high brightness. Furthermore, the calculated saturation values of the blue, green, purplish red photonic crystal fibers were 63%, 59% and 60%, respectively, showing that they all had a high degree of saturation. The photonic crystal fibers do not need dyeing and their colors never fade, which meet the requirements of green and environmental protection, presenting broad prospect for their applications.
2018, (3): 395-401
doi: 10.11777/j.issn1000-3304.2017.17083
Abstract:
Cracks may appear in epoxy resins once suffered the external impact and pressure. If cracks can be remended by material itself, then the service life of the materials can be extended and severe incident can be avoided. Herein, an epoxy monomer containing diene is synthesized via the reaction between epichlorohydrin and furfuryl alcohol. A self-healing epoxy resin based on thermo-reversible Diels-Alder reaction (EP-DA) is prepared by the reaction between the resultant epoxy monomer and bismaleimide. The chemical structure, thermal property, and thermal reversibility of the prepared EP-DA are characterized by FTIR, DSC, and gel-sol transition. Results show that thermo-reversible DA bonds are introduced into the epoxy resin successfully. Consequently, EP-DA is endowed with excellent thermal reversibility and reprocessing performance. The self-healing behavior is examined by investigating both the crack evolution and the recovery of mechanical property. Based on the study about the effect of heat treatment on the crack repair in depth, the optimal heat treatment parameters are determined as 122 ℃/45 min and 67 ℃/36 h. By simulating the impact failure situation in actual state, the self-healing performance of the epoxy resin is investigated by a combination of qualitative observation and quantitative measurement of flexural load restoring. Results reveal that the crack narrows down and flexural strength enhances gradually with extended heat treatment. It is shown that the epoxy resins exhibit excellent self-healing performance, and the healing efficiency can achieve 77.1%. Meanwhile, cracks can be caused and repaired for more than three times. The healing efficiency can still reach 53.9% when the same sample has been impacted and repaired for three cycles. These manifest that the epoxy resins also show outstanding multiple self-healing performance. Additionally, the EP-DA exhibits excellent reprocessing performance, and PU-DA fragments can recombine together as a whole upon heating treatment at 122 ℃/2 h and 67 ℃/36 h. The result makes it possible for recycling the waste epoxy resins.
Cracks may appear in epoxy resins once suffered the external impact and pressure. If cracks can be remended by material itself, then the service life of the materials can be extended and severe incident can be avoided. Herein, an epoxy monomer containing diene is synthesized via the reaction between epichlorohydrin and furfuryl alcohol. A self-healing epoxy resin based on thermo-reversible Diels-Alder reaction (EP-DA) is prepared by the reaction between the resultant epoxy monomer and bismaleimide. The chemical structure, thermal property, and thermal reversibility of the prepared EP-DA are characterized by FTIR, DSC, and gel-sol transition. Results show that thermo-reversible DA bonds are introduced into the epoxy resin successfully. Consequently, EP-DA is endowed with excellent thermal reversibility and reprocessing performance. The self-healing behavior is examined by investigating both the crack evolution and the recovery of mechanical property. Based on the study about the effect of heat treatment on the crack repair in depth, the optimal heat treatment parameters are determined as 122 ℃/45 min and 67 ℃/36 h. By simulating the impact failure situation in actual state, the self-healing performance of the epoxy resin is investigated by a combination of qualitative observation and quantitative measurement of flexural load restoring. Results reveal that the crack narrows down and flexural strength enhances gradually with extended heat treatment. It is shown that the epoxy resins exhibit excellent self-healing performance, and the healing efficiency can achieve 77.1%. Meanwhile, cracks can be caused and repaired for more than three times. The healing efficiency can still reach 53.9% when the same sample has been impacted and repaired for three cycles. These manifest that the epoxy resins also show outstanding multiple self-healing performance. Additionally, the EP-DA exhibits excellent reprocessing performance, and PU-DA fragments can recombine together as a whole upon heating treatment at 122 ℃/2 h and 67 ℃/36 h. The result makes it possible for recycling the waste epoxy resins.
2018, (3): 402-409
doi: 10.11777/j.issn1000-3304.2017.17085
Abstract:
Temperature responsive shape memory polymers (SMPs) find important applications in automotive, military, biomedical and other fields. In particular, SMPs responsive to human body temperature are highly desired for biomedical applications. Polynorbornene (PNB) has a Tg around human body temperature, exhibiting excellent shape memory properties, whereas poly(lactic acid) (PLA) has attracted great interest in biomedical fields due to its nontoxic and bioresorbable characteristics. Therefore, it is of great significance to explore the possibility of combining advantages of PNB and PLA. In this work, a simple blending strategy was adopted at varying weight ratios, and the shape memory, thermal and mechanical properties of the resultant blends were studied. The results showed that PLA promoted blend yield, and crystallization of PNB favored shape fixation and shape recovery. For PNB/PLA=80/20 blend, the shape fixation rate was 99.88% and the shape recovery rate was 81.04% with the average shape recovery rate of 1.2%/min in the double shape memory. The total shape fixation rate and shape recovery rate were 98.83% and 94.26%, respectively, in the triple shape memory. In PNB/PLA blends, there was a certain interaction between the molecules, which limited, to a certain extent, the movement of the two polymer chains and reduced the crystallization of PLA. When the temperature was over 100 ℃, cold crystallization of PLA appeared in the blends, and this cold crystallization degree increased with decreased PNB. With increased PNB content, PNB/PLA blend became more ductile, the elongation at break increased from a few percent to more than 200%, and the forced elastic deformation occurred, which were favorable for the shape fixation. In the blends, the super-macromolecular chains of PNB were intertwined, resulting in a large number of entanglement points, namely, physical cross-linking points in the materials, which could make the polymer chain movement seriously blocked and their wide range of slippage hampered, so as to provide the driving force for the shape recovery and to improve the shape recovery performance of the blends.
Temperature responsive shape memory polymers (SMPs) find important applications in automotive, military, biomedical and other fields. In particular, SMPs responsive to human body temperature are highly desired for biomedical applications. Polynorbornene (PNB) has a Tg around human body temperature, exhibiting excellent shape memory properties, whereas poly(lactic acid) (PLA) has attracted great interest in biomedical fields due to its nontoxic and bioresorbable characteristics. Therefore, it is of great significance to explore the possibility of combining advantages of PNB and PLA. In this work, a simple blending strategy was adopted at varying weight ratios, and the shape memory, thermal and mechanical properties of the resultant blends were studied. The results showed that PLA promoted blend yield, and crystallization of PNB favored shape fixation and shape recovery. For PNB/PLA=80/20 blend, the shape fixation rate was 99.88% and the shape recovery rate was 81.04% with the average shape recovery rate of 1.2%/min in the double shape memory. The total shape fixation rate and shape recovery rate were 98.83% and 94.26%, respectively, in the triple shape memory. In PNB/PLA blends, there was a certain interaction between the molecules, which limited, to a certain extent, the movement of the two polymer chains and reduced the crystallization of PLA. When the temperature was over 100 ℃, cold crystallization of PLA appeared in the blends, and this cold crystallization degree increased with decreased PNB. With increased PNB content, PNB/PLA blend became more ductile, the elongation at break increased from a few percent to more than 200%, and the forced elastic deformation occurred, which were favorable for the shape fixation. In the blends, the super-macromolecular chains of PNB were intertwined, resulting in a large number of entanglement points, namely, physical cross-linking points in the materials, which could make the polymer chain movement seriously blocked and their wide range of slippage hampered, so as to provide the driving force for the shape recovery and to improve the shape recovery performance of the blends.
2018, (3): 410-418
doi: 10.11777/j.issn1000-3304.2017.17099
Abstract:
Bisphenol-A based cyanate ester (BACDy) and propargyloxy-containing benzoxazine (P-appe) were used to improve the mechanical properties of poly(silylene-acetylenearyleneacetylene) (PSA). PSA/P-appe/BADCy (PPB) terpolymers were prepared by blending in solution and concentrating with evaporation. The thermal cure reaction of the terpolymers were studied by differential scanning calorimetry (DSC) and in situ Fourier-transition infrared (FTIR) monitoring. The thermal properties, dynamic mechanical properties, flexural property and impact strength of the cured terpolymers were further investigated. The results show that the cure peak temperature of BADCy decreased from 325 ℃ to 247 ℃ when P-appe and PSA were added. In the blends, the ring opening of the P-appe firstly occurs with increasing cure temperature. Then the formation of the triazine ring arises. P-appe and phenolic hydroxyl groups on the ring-opened benzonxazine can catalyze the cyclotrimerization of the cyanate ester, making the cure temperature of the cyanate ester decrease effectively. Meanwhile, the self-polymerization of the terminal acetylene of PSA, P-appe and BADCy occurs simultaneously. The PPB terpolymer can polymerize at 130 ℃ within 2 h or at 170 ℃ within 30 min. The copolymerization of BACDy and P-appe arises from the coreaction of triazine ring cyclotrimeized by BADCy with oxazine of P-appe, by which the compatibility of PPB terpolymer is favorable. In comparison with cured PSA resin, the 5% mass loss temperature (Td5) of the cured PPB terpolymer in nitrogen is above 510 ℃, and the residual yield at 800 ℃ and the glass transition temperature of the cured terpolymer are above 84% and 450 ℃, respectively. For PSA blended with 15% mass fraction of P-appe and 15% mass fraction of BADCy, the flexural strength and impact strength of the cured PSA resin can increase by 115% and 104%, respectively. The fracture surface of the cured terpolymer is rough and displays obvious ductile feature.
Bisphenol-A based cyanate ester (BACDy) and propargyloxy-containing benzoxazine (P-appe) were used to improve the mechanical properties of poly(silylene-acetylenearyleneacetylene) (PSA). PSA/P-appe/BADCy (PPB) terpolymers were prepared by blending in solution and concentrating with evaporation. The thermal cure reaction of the terpolymers were studied by differential scanning calorimetry (DSC) and in situ Fourier-transition infrared (FTIR) monitoring. The thermal properties, dynamic mechanical properties, flexural property and impact strength of the cured terpolymers were further investigated. The results show that the cure peak temperature of BADCy decreased from 325 ℃ to 247 ℃ when P-appe and PSA were added. In the blends, the ring opening of the P-appe firstly occurs with increasing cure temperature. Then the formation of the triazine ring arises. P-appe and phenolic hydroxyl groups on the ring-opened benzonxazine can catalyze the cyclotrimerization of the cyanate ester, making the cure temperature of the cyanate ester decrease effectively. Meanwhile, the self-polymerization of the terminal acetylene of PSA, P-appe and BADCy occurs simultaneously. The PPB terpolymer can polymerize at 130 ℃ within 2 h or at 170 ℃ within 30 min. The copolymerization of BACDy and P-appe arises from the coreaction of triazine ring cyclotrimeized by BADCy with oxazine of P-appe, by which the compatibility of PPB terpolymer is favorable. In comparison with cured PSA resin, the 5% mass loss temperature (Td5) of the cured PPB terpolymer in nitrogen is above 510 ℃, and the residual yield at 800 ℃ and the glass transition temperature of the cured terpolymer are above 84% and 450 ℃, respectively. For PSA blended with 15% mass fraction of P-appe and 15% mass fraction of BADCy, the flexural strength and impact strength of the cured PSA resin can increase by 115% and 104%, respectively. The fracture surface of the cured terpolymer is rough and displays obvious ductile feature.
2018, (3): 419-428
doi: 10.11777/j.issn1000-3304.2017.17101
Abstract:
As a novel generation synthetic rubber, trans-1, 4-poly(butadiene-co-isoprene) copolymer rubber (TBIR) was used in high performance passenger car radical (PCR) tire tread stock, the structures and properties of solution polymerized styrene butadiene rubber (SSBR)/cis-1, 4-poly-butadienere rubber (BR)/TBIR blends were studied. Compared with amorphous SSBR and BR, TBIR raw rubber showed greatly improved green strength, modulus and toughness due to its crystallizability. However, the enthalpy of the crystallization (ΔH), the melting temperature (Tm) and the glass transition temperature (Tg) of TBIR were significantly lower than those of trans-1, 4-polyisoprene (TPI) because of the decreased structure regularity of the polymer chains from the copolymerization of isoprene with butadiene. Blended with 30 phr carbon black and 45 phr silica, SSBR/BR/TBIR compounds with 10 -20 phr TBIR showed improved green strength, modulus at 100%, and hardness due to the crystallizability of TBIR. Blending TBIR with SSBR/BR, the scorch time (tc10) and the optimum curing time (tc90) of the compounds changed little. After vulcanization at 150 ℃, the obtained SSBR/BR/TBIR vulcanizates showed excellent physical, mechanical and dynamic properties, including greatly improved tensile fatigue resistance (4.6 to 6.3 times higher), increased compressive strength (21.4% to 23.1% higher), wear resistance (10.8% to 15.1% higher), wet skid resistance (13.6% to 40.4% higher) and relatively unchanged rolling resistance. Both transmission electron microscopy (TEM) and carbon black dispersity test showed that the filler dispersion level in SSBR/BR/TBIR blends increased by 7.3% to 10.9%, and the mean filler aggregate size reduced by 1.4 -2.7 mm. The crystalline TBIR, with relatively high green strength and modulus of TBIR compared with the other general rubber materials like SSBR and BR, endowed the SSBR/BR/TBIR vulcanizates with good filler dispersion, and finally contributed to the greatly improved tensile fatigue resistance, increased wear resistance, wet skid resistance, compressive strength, modulus etc. So TBIR as a novel synthetic rubber is expected to be used in PCR tire tread stock for high performance.
As a novel generation synthetic rubber, trans-1, 4-poly(butadiene-co-isoprene) copolymer rubber (TBIR) was used in high performance passenger car radical (PCR) tire tread stock, the structures and properties of solution polymerized styrene butadiene rubber (SSBR)/cis-1, 4-poly-butadienere rubber (BR)/TBIR blends were studied. Compared with amorphous SSBR and BR, TBIR raw rubber showed greatly improved green strength, modulus and toughness due to its crystallizability. However, the enthalpy of the crystallization (ΔH), the melting temperature (Tm) and the glass transition temperature (Tg) of TBIR were significantly lower than those of trans-1, 4-polyisoprene (TPI) because of the decreased structure regularity of the polymer chains from the copolymerization of isoprene with butadiene. Blended with 30 phr carbon black and 45 phr silica, SSBR/BR/TBIR compounds with 10 -20 phr TBIR showed improved green strength, modulus at 100%, and hardness due to the crystallizability of TBIR. Blending TBIR with SSBR/BR, the scorch time (tc10) and the optimum curing time (tc90) of the compounds changed little. After vulcanization at 150 ℃, the obtained SSBR/BR/TBIR vulcanizates showed excellent physical, mechanical and dynamic properties, including greatly improved tensile fatigue resistance (4.6 to 6.3 times higher), increased compressive strength (21.4% to 23.1% higher), wear resistance (10.8% to 15.1% higher), wet skid resistance (13.6% to 40.4% higher) and relatively unchanged rolling resistance. Both transmission electron microscopy (TEM) and carbon black dispersity test showed that the filler dispersion level in SSBR/BR/TBIR blends increased by 7.3% to 10.9%, and the mean filler aggregate size reduced by 1.4 -2.7 mm. The crystalline TBIR, with relatively high green strength and modulus of TBIR compared with the other general rubber materials like SSBR and BR, endowed the SSBR/BR/TBIR vulcanizates with good filler dispersion, and finally contributed to the greatly improved tensile fatigue resistance, increased wear resistance, wet skid resistance, compressive strength, modulus etc. So TBIR as a novel synthetic rubber is expected to be used in PCR tire tread stock for high performance.
