Enhanced thermal conductivity for PVDF composites with a hybrid functionalized graphene sheet-nanodiamond filler

A new thermal conductive poly(vinylidene fluoride) (PVDF) composite has been developed via a hybrid functionalized graphene sheets (FGS)-nanodiamonds (NDs) filler by a simple solution method. The PVDF composite showed different thermal conductivities at different proportion of hybrid filler. The thermal conductivity of the composite was up to 0.66 W/m·K for a mixture containing 45 wt% hybrid filler, which is about 2-fold increment in comparison to the PVDF martrix. The PVDF composites consisting of 20 wt% hybrid FGS/ND filler at the weight ratio of 1:3 shows the best thermal stability. The electrical conductivity of composites was increased from 5.1×10^?15 S cm^?1 (neat PVDF) to 7.1×10^?7 S cm^?1 of the PVDF composite with 10 wt% hybrid filler.     

Improvement of mechanical and electrical properties of poly(ethylene glycol) and cyanoresin based polymer electrolytes

Ionic conductivity and mechanical properties of a mixed polymer matrix consisting of poly(ethylene glycol) (PEG) and cyanoresin type M (CRM) with various lithium salts and plasticizer were examined. The CRM used was a copolymer of cyanoethyl pullulan and cyanoethyl poly(vinyl alcohol) with a molar ratio of 1:1, mixed plasticizer was ethylene carbonate (EC) and propylene carbonate (PC) at a volume ratio of 1:1. The conductive behavior of polymer electrolytes in the temperature range of 298∼338 K was investigated. The PEG/LiClO₄ complexes exhibited the highest ionic conductivity of ∼10⁻⁵ S/cm at 25°C with the salt concentration of 1.5 M. In addition, the plasticized PEG/LiClO₄ complexes exhibited improvement of ionic conductivity. However, their complexes showed decreased mechanical properties. The improvement of ionic conductivity and mechanical properties could be obtained from the polymer electrolytes by using CRM. The highest ionic conductivity of PEG/CRM/LiClO₄/(EC-PC) was 5.33×10⁻⁴ S/cm at 25°C.     

Electrospinning and microwave absorption of polyaniline/polyacrylonitrile/multiwalled carbon nanotubes nanocomposite fibers

Electrical conductive nanocomposite fibers were prepared with polyaniline (PANI), polyacrylonitrile (PAN) and multi-walled carbon nanotubes (MWCNTs) via electrospinning. The morphology and electrical conductivity of the PANI/PAN/MWCNTs nanocomposite fibers were characterized by scanning electron microscope (SEM) and Van De Pauw method. Electrical conductivity of nanocomposite fibers increased from 1.79 S·m^?1 to 7.97 S·m^?1 with increasing the MWCNTs content from 3.0 wt% to 7.0 wt%. Compared with PANI/PAN membranes, the mechanical property of PANI/PAN/MWCNTs nanocomposites fiber membranes decreased. The microwave absorption performance of composite films was analyzed using waveguide tube, which indicated that with the thickness increasing the value of R_L reduced from ?4.6 to ?5.9 dB.     

Preparation of the Multicomponent High Temperature Proton Exchange Membranes with Layer by Layer Self-assembly Technique

Layer by layer (LBL) self-assembly technique has been proved to be a feasible method that enables to accomplish the preparation of functional membranes with multilayered structure. In this research, the polymer of sulfonated polyetheretherketone (SPEEK) and thioglycolic acid capping of cadmium telluride (CdTe) nanocrystals as polyanion, the polymer of polyurethane (PU) as polycation have been used to prepare membrane electrolytes. These multilayered membranes showed good thermal stability and exhibited low liquid methanol permeability, which provided a possibility for the prepared membranes as proton exchange membranes (PEMs) to apply in direct methanol fuel cells (DMFCs). We have also demonstrated that the multicomponent (SPEEK/PU/CdTe/PU)₁₀₀ membranes favored to combine more phosphoric acid (PA) molecules and possessed a higher proton conductivity comparing to the bicomponent (SPEEK/PU)₂₁₀ membranes. So PA doped (SPEEK/PU/CdTe/PU)₁₀₀ membrane presented a maximum proton conductivity up to 8.6×10^-2 S/cm at 160 °C under anhydrous conditions. However, PA doped (SPEEK/PU)₂₁₀ membranes underwent a drop on proton conductivity while the temperature exceeded 120 °C.     

Fabrication and characterization of nano Al<Subscript>2</Subscript>O<Subscript>3</Subscript> filled PVA:NH<Subscript>4</Subscript>SCN electrolyte nanofibers by electrospinning

Present paper reports a method of preparing polymer composite electrolyte nanofiber mat using polyvinyl alcohol (PVA), ammonium thiocynate (NH₄SCN) salt, and aluminium oxide (Al₂O₃) nano particles based on electrospinning technique. Two-stage process of preparation of nanofibers, namely, preparation of nano particles filled PVA electrolyte gel solution followed by its electrospinning has been used. The so obtained nanofibers have been characterized by XRD, DSC, SEM, and Conductivity measurements. XRD patterns affirm the formation of nanocomposite while SEM pictures reveal formation of fibers on a nano scale format (300–800 nm). Fibers of the electrolytes are seen to be thermally stable. Ionic conductivity of electrolyte fiber is seen to improve in the presence of nano filler at room temperature with a maximum at 5.31×10⁻³ Scm⁻¹ for 4 wt% filler concentration, which is comparable to that for corresponding dried gel electrolyte films.     

Electrospun SiO<Subscript>2</Subscript>/PMIA nanofiber membranes with higher ionic conductivity for high temperature resistance lithium-ion batteries

The nanofiber membrane prepared by electrospinning has been widely applied in lithium-ion batteries. A powerful strategy for designing, fabricating and evaluating Poly-m-phenylene isophthalamide (PMIA) nanofiber membrane with SiO₂ nanoparticles was developed by electrospinning in this paper. The morphology, crystallinity, thermal shrinkage, porosity and electrolyte uptake, and electrochemical performance of the SiO₂/PMIA nanofiber membranes were investigated. It was demonstrated that the nanofiber membrane with 6 wt% SiO₂ possessed notable properties, such as better thermal stability, higher porosity and electrolyte uptake, resulting in higher ionic conductivity (3.23×10^-3 S·cm^-1) when compared with pure PMIA nanofiber membrane. Significantly, the SiO2/PMIA nanofiber membrane based Li/LiCoO₂ cell exhibited more excellent cycling stability with capacity retention of 95 % after 50 cycles. The results indicated that the SiO₂-doped PMIA nanofiber membranes had a potential application as separator in high temperature resistance lithium-ion batteries.     

Effects of soil water content and nitrogen supply on the productivity of Miscanthus × giganteus Greef et Deu. in a Mediterranean environment

Miscanthus × giganteus is one of the most promising biomass crops for non-food utilisation. Taking into account its area of origin (Far East), its temperature and rainfall requirements are not well satisfied in Mediterranean climate. For this purpose, a research was carried out with the aim of studying the adaptation of the species to the Mediterranean environment, and at analysing its ecophysiological and productive response to different soil water and nitrogen conditions. A split plot experimental design with three levels of irrigation (I₁, I₂ and I₃ at 25%, 50% and 100% of maximum evapotranspiration (ETm), respectively) and three levels of nitrogen fertilisation (0 kg ha⁻¹: N₀, 60 kg ha⁻¹: N₁ and 120 kg ha⁻¹: N₂ of nitrogen) were studied. The crop showed a high yield potential under well-watered conditions (up to 27 t ha⁻¹ of dry matter). M. × giganteus, in Mediterranean environment showed a high yield potential even in very limited water availability conditions (more than 14 t ha⁻¹ with a 25% ETm restoration). A responsiveness to nitrogen supply, with great yield increases when water was not limiting, was exhibited. Water use efficiency (WUE) achieved the highest values in limited soil water availability (between 4.51 and 4.83 g l⁻¹), whilst in non-limiting water conditions it decreased down to 2.56 and 3.49 g l⁻¹ (in the second and third year of experiment, respectively). Nitrogen use efficiency (NUE) decreased with the increase of water distributed (from 190.5 g g⁻¹ of I₀ to 173.2 g g⁻¹ of I₂); in relation to N fertilisation it did not change between the N fertilised treatments (N₁ and N₂), being much higher in the unfertilised control (177.1 g g⁻¹). Radiation use efficiency (NUE) progressively declined with the reduction of the N fertiliser level (1.05, 0.96 and 0.86 g d.m. MJ⁻¹, in 1994, and 0.92, 0.91 and 0.69 g d.m. MJ⁻¹, in 1995, for N₂, N₁ and N₀, respectively).     

Spatial variability of soil saturated hydraulic conductivity in paddy field in accordance to subsurface percolation

Insufficient puddling with inappropriate implements or imprecise time/intensity may alter saturated water flow in paddy soil spatially or temporary due to change in aggregate size distribution, dry bulk density, saturated hydraulic conductivity, and percolation rate of the soil. In this study, spatial variability of saturated hydraulic conductivity (K _s), a key parameter of the saturated water flow, in Fuchu Honmachi paddy plot (100 m × 28 m) was characterized based on dielectric or ADR dry bulk density (ρ_b-ADR) with help of non-similar media concept (NSMC) and geostatistics model to meet its correlation to subsurface percolation. A 100 cc core and an ADR data were sampled from each sub-plot (7 m × 7.5 m), and then were used for measuring and predicting ρ_b and K _s. The predicted data agreed with the measured ones, in which they fitted well the x = y line with RMSE of 0.029 cm³ cm⁻³ (R ² = 0.68), 0.027 g cm⁻³ (R ² = 0.71) (ρ_b), and 0.098 cm d⁻¹ (R ² = 0.45) for θ, ρ_b, and K _s, respectively. The predicted ρ_b and K _s had similar trend in spatial variability to the measured ones particularly within the distance of 46.3–51.9 m and 26.2–27.9 m, respectively. The spatial variability of the predicted K _s coincided to that of the subsurface percolation rate, in which they had similar distance of dependence. The results indicated that the presenting method can be reasonably accepted.     

Structural and physical properties ofAntheraea pernyi silk fibroin fiber treated with I2-KI aqueous solution

Silk fibroin (SF) fiber from theAntheraea pernyi silkworm was treated with a 1.23 N iodine-potassium iodide (I₂-KI) aqueous solution, and the structure and physical properties were investigated to clarify the effects of the iodine treatment. The noticeably high weight gain value of SF fiber, about 25 wt% was attributed to the absorption of polyiodide ions in the form of I₃ ^? and I₅ ^?. Fourier transform infrared spectroscopy and X-ray diffraction measurements suggested that polyiodide ions mainly entered the amorphous region. In addition, a new sharp reflection on the meridional direction, corresponding to a period of 7.0 Å, was observed and indicated the possibility of the formation of mesophase structure ofβ-conformation chains. Dynamic viscoelastic measurements showed that the damping tanδ peak at 270°C gradually shifted to lower temperature in the iodinated SF fibers, suggesting an enhancement of the molecular motion of the fibroin chains induced by the presence of polyiodide ions. With heating above 254 °C, the iodine component introduced intermolecular cross-linking of SF, and the melt flow of the sample was inhibited. The thermal decomposition stability of fibroin molecules was greatly enhanced by iodine treatment.     

Morphology and properties of polyacrylonitrile/single wall carbon nanotube composite films

Composite films were prepared by casting the solution of polyacrylonitrile (PAN) and single wall nanotube (SWNT) in DMF subsequent to sonication. The SWNTs in the films are well dispersed as ropes with 20–30 nm thickness. Moreover, AFM surface image of the composite film displays an interwoven fibrous structure of nanotubes which may give rise to conductive passways and lead to high conductivity. The polarized Raman spectroscopy is an ideal characterization technique for identification and the orientation study of SWNT. The well-defined G-peak intensity at 1580 cm⁻¹ shows a dependency on the draw ratio under cross-Nicol. The degree of nanotube orientation in the drawn film was measurable from the sine curve obtained by rotating the drawn film on the plane of cross-Nicol of polarized Raman microscope. The threshold loading of SWNT for electrical conductivity in PAN is found to be lower than 1 wt% in the composite film. The electrical conductivity of the SWNT/PAN composite film decreased with increasing of draw ratio due to the collapse of the interwoven fibrous network of the nanotubes with uniaxial orientation.     

Preparation and properties of polarizing films for liquid crystal display prepared using iodine vapor

The properties of polarizing films prepared using iodine vapor and using I₂/KI solution are compared to investigate the possibility of using vapor phase iodine adsorption in preparing polarizing film. The structure of PVA films drawn to different draw ratios and the amount of iodine adsorbed in drawn PVA films using iodine vapor were investigated. Increases in the degree of crystallinity, crystalline orientation index and birefringence with increase in draw ratio of PVA film, were observed by WAXD and polarizing microscope analysis. The amounts of iodine adsorbed by PVA film were 2–4 wt% for 20 min. UV-visible analysis suggests that I₃ ^? and I₅ ^? structures of iodine exist in the polarizing film after drawing in boric acid solution. Single transmittance and degree of polarization of polarizing films prepared using iodine vapor were about 30–50 % and over 99 %, respectively, at total draw ratios of over 3. The possibility of employing vapor phase adsorption of iodine instead of solution adsorption to prepare commercial polarizing film is suggested.     

In-situ preparation of multi-walled carbon nanotube (MWNT)/cellulose nanocomposites and their physical properties

The multi-walled carbon nanotube (MWNT)/cellulose nanocomposites were prepared by using monohydrated Nmethylmorpholine-N-oxide (NMMO) as a solvent for dispersing the acid-treated MWNTs (A-MWNTs) as well as for dissolving the cellulose. The A-MWNTs were well dispersed in both monohydrated NMMO and the nanocomposite films. The nanocomposite films were prepared by a film-casting method onto a glass plate. The tensile strain at break, Young’s modulus, and toughness of nanocomposite films increased by ～5, ～2 and ～12 times, respectively at ? (A-MWNT content in the nanocomposite)=0.8 wt%, as compared to those of the pure cellulose film. The thermal degradation temperature of the nanocomposite films also increased from 329 to 339 oC by incorporation of 1 wt% A-MENTs. The electric conductivities of the A-MWNT/cellulose nanocomposites at ? =1 and 10 wt% were 2.09×10^?5 and 3.68×10^?3 S/cm, respectively. The transmittances were 86, 69 and 55 % at 550 nm for 0.4, 0.8 and 1 wt% nanocomposite films, respectively. Thus, these nanocomposites are promising materials in terms of all the properties studied in this paper and can be used for many applications, such as toughened cellulose fibers, transparent electrodes, etc.     

Effect of Phosphorus and Irrigation Levels on Yield,Water Productivity,Phosphorus Use Efficiency and Income of Lowland Rice in Northwest Pakistan

With decreasing availability of water for agriculture and increasing demand for rice production, an optimum use of irrigation water and phosphorus may guarantee sustainable rice production. Field experiments were conducted in 2003 and 2004 to investigate the effect of phosphorus and irrigation levels on yield, water productivity (WP), phosphorus use efficiency (PUE) and income of low land rice. The experiment was laid out in randomized complete block design with split plot arrangements replicated four times. Main plot consisted of five phosphorus levels, viz. 0 (P0), 50 (P50), 100 (P100), 150 (P150), and 200 (P200) kg/hm2, while subplots contained of irrigation times, i.e. 8 (I8), 10 (I10), 12 (I12), and 14 (I14) irrigation levels, each with a water depth of 7.5 cm. Mean values revealed that P150 in combination with I10 produced the highest paddy yield (9.8 t/hm2) and net benefit (1 231.8 US$/hm2) among all the treatments. Phosphorus enhanced WP when applied in appropriate combination with irrigation level. The highest mean WP [13.3 kg/(hm2?mm)] could be achieved at P150 with I8 and decreased with increase in irrigation level, while the highest mean PUE (20.1 kg/kg) could be achieved at P100 with I10 and diminished with higher P levels. The overall results indicate that P150 along with I10 was the best combination for sustainable rice cultivation in silty clay soil.     

Preparation and Characterization of Electrospun Polyimide Microfibrous Mats with High Whiteness and High Thermal Stability from Organo-soluble Polyimides Containing Rigid-rod Moieties

A series of flexible and tough polyimide (PI) microfibrous mats (PI-1~PI-4) have been prepared via the one-step electrospinning procedure with the organo-soluble PI resins as the starting materials. For this purpose, four PI resins were first synthesized by the chemical imidization reaction from 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and four aromatic diamines containing rigid-rod moieties in their molecular skeletons, respectively. The PI resins derived from 6FDA and aromatic diamines, including PI-1 from 2-(4-aminophenyl)-5-aminobenzimidazole (APBI), PI-2 from 2-(4-aminophenyl)-5-aminobenzoxazole (APBO), PI-3 from 4,4′-diaminobenzanilide (DABA), and PI-4 from 2-chloro-4,4-diaminobenzanilide (Cl-DABA) exhibited good solubility in polar aprotic solvents, such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc). Flexible and tough microfibrous mats were successfully prepared by a one-step electrospinning procedure from the PI/DMAc solution (solid content: 15–20 wt%; absolute viscosity: 8000–10000 mPa·s). The derived PI mats exhibited good whiteness according to the CIE Lab measurements with W (whiteness) values as high as 94.31, L (lightness) values higher than 94.00, b* (yellowness) values as low as 2.98 and yellow indices (YI) as low as 4.87. In addition, the prepared PI mats exhibited excellent thermal and dimensional stability with the glass transition temperatures (T_g) higher than 345 °C and linear coefficients of thermal expansion (CTE) as low as 27.8×10^-6 /K.     

Einige physikochemische Eigenschaften des Kartoffel-virus M

Zusammenfassung Die Sedimentationskonstante S _20.w ^° des Kartoffelvirus M (KVM) betr?gt 167±1 S. Die Konzentrationsabh?ngigkeit ergibt sich aus der Beziehung s _20.w ^c =(167−33×c) S. Die Schwebedichte des KVM in C?siumchlorid (⌕ _C5C1 ²⁵ ) betr?gt 1,321 bis 1,322 g/ml. Mit Hilfe der SDS-Polyacrylamid-Gelektrophorese fanden wir zwei Proteine mit Molekülmassen von 35 700 und 33 000 Dalton. Die Nukleins?ure des KVM ist eine einstr?ngige RNS mit einer Molekülmasse von 2,38×10⁶ Dalton (nicht denaturierende Bedingungen) bzw. 2,14×10⁶ Dalton (nach Formaldehydbehandlung). Damit ist das KVM ein typischer Vertreter der Carlavirus-Gruppe.

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Summary Particles of potato virus M (PVM) were purified by the method of Proll & Richter (1979). After sugar density gradient centrifugation, preparations had a high level of purity and were homogeneous when examined under the electron microscope and in the analytical ultra-centrifuge. The sedimentation constant of particles (s°) is 167±1 S and the concentration relation s _20.w ^c =(167−33×c)S, where c is in mg/ml. The density of the PVM particles in caesium chloride (⌕ _C5C1 ²⁵ ) is 1.321 to 1.322 g/ml, with tobacco mosaic virus particles (density=1.325 g/ml) as a standard. In SDS-polyacrylamide gel electrophoresis, PVM protein sub-units migrated as two compounds with apparent sizes of 35 700 and 33 000 daltons, respectively. PVM nucleic acid is single stranded RNA, as shown by its positive orcinol and negative diphenylamine reactions, its degradation by RNase and its temperature melting curve. The RNA comprised 5.4% of the particle weight and its estimated molecule size was 2.38×10⁶ daltons (undenatured) and 2.14×10⁶ daltons (treated with formaldehyde). Physicochemical data on PVM are summarized in Table 1. The cryptogram of PVM is R/1: 2.4/5.4: E/E: S/Ap, carlavirus group.

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Résumé é virus M de la pomme de terre (PVM) a été urifié selon la méthode Proll & Richter 979). Après deux centrifugations selon la chnique du gradient de sucrose, nous avons btenu des préparations purifiées qui se sont firmées très homogènes au microscope ectronique, ainsi qu’avec l’ultracentrifugeuse analytique. Nous avons observé un effet de concentration de la valeur S et avons éterminé la constante de sédimentation (s^O) à aide de distribution de S dans une zone de concentration de 0,5 à 0,1 mg de virus/ml à 57±1 S. L’effet de concentration peut être obtenu ar la relation s _20.w ^c =(167−33×c)S, dont c at à utiliser en mg/ml. La densité spécifiquedu PVM dans le aloride de césium (⌕ _C5C1 ²⁵ ) est de 1,321 à 322 g/ml avec le virus de la mosa?que du abac comme marqueur, dont la densité est de 1,325 g/ml. Les masses moléculaires des capsomers ont été déterminées à l’aide de la SDS-polyacrylamide-gel-electrophorèse. Nous avons observé deux zones de protéines dont la masse moléculaire calculée fut de 35 700 et 33 000 dalton. L’acide nucléique du PVM comprend une spirale ARN; ceci a été obtenu avec la réaction positive d’orcine, des essais de catabolisme avec la RNase et de la courbe de fusion. Le poids représente 5,4 % de celui de la particule. La masse moléculaire est de 2,38×10⁶ dalton (conditions non dénaturantes) 2,38×10⁶ (après traitement au formaldéhyde). Dans le tableau 1 sont résumées les données physicochimiques du PVM selon Proll & Richter (1979). Le cryptogramme suivant a été obtenu: R/1: 2,4/5,4: E/E: S/Ap, ce qui permet de classer ce virus dans le groupe Carla.

     

Synthesis of hydrophilic copolyesters and the characterization of their moisture-related cooling properties

A series of copolyesters (Co-PETs) containing poly(ethylene glycol) (PEG), 5-sodiumsulfodimethyl isophthalate (DMS), and dimethyl isophthalate (DMI) were synthesized via the conventional two-step melt-polycondensation method. The synthesized Co-PETs were characterized by ¹H-NMR spectroscopy, FT-IR spectroscopy, differential scanning calorimeter (DSC), and thermogravimetric analyzer (TGA). The DSC results showed that the melting temperature (T _m) and the heats of fusion (ΔH _m) of Co-PETs decreased with increasing the DMS content in Co-PET, while the inclusion of PEG did not affect their thermal properties significantly. The water absorption and the water contact angle of the Co-PET films were found to be significantly affected by the DMS content rather than PEG content. The moisture-related cooling properties of the fabric samples made of Co-PET 5 as well as PET were evaluated by using liquid moisture management tester (MMT) and Q _max measurements. The MMT and Q _max results indicated that Co-PET 5 fabric containing DMS 1.0 mol% and PEG 10.0 wt% in Co-PET seemed to be a good candidate for the fabric having durable cooling effects.     

Long-term effect of tillage systems on soil microbiological,chemical and physical parameters and the incidence of charcoal rot by Macrophomina phaseolina (Tassi) Goid in soybean

A 20-year field experiment was employed with the aim of evaluating the effect of tillage systems on biological, chemical and physical aspects of the soil, and to establish whether there was a correlation of these parameters with the incidence of charcoal rot (Macrophomina phaseolina) of soybean and crop yield. The tillage systems evaluated were direct seeding (DS), DS + scarifier (DS + S), minimum tillage (MT) and conventional tillage (CT). DS presented higher values than CT in culturable total fungi (26.33 × 10⁵ vs. 2.33 × 10⁵ CFU g⁻¹ dry soil), total bacteria (182 × 10⁷ vs. 64 × 10⁷ CFU g⁻¹ dry soil), microbial respiration (0.77 mg CO₂ g⁻¹ week⁻¹ vs. 0.45 mg CO₂ g⁻¹ week⁻¹) and fluorescein diacetate (FDA) hydrolysis (4.17 ug fluorescein g⁻¹ h⁻¹ vs. 1.70 ug fluorescein g⁻¹ h⁻¹ in CT. Fungal and bacterial community fingerprints, by terminal restriction fragment length polymorphism (T-RFLP) analysis, of Intergenic spacer regions of rRNA and 16S rRNA genes, respectively, were influenced by the tillage system. Also FAME (fatty acid methyl ester) profiles showed that microbial community structure in DS and CT was clearly different. DS samples contained significantly higher total microbial biomass than the other tillage treatments, but there were no significant differences in fungal biomass or any consistent trend with respect to stress index. Our results showed that microbial communities were more abundant and active in DS than in CT in response to high nutrient content in soil. Indeed, DS systems presented higher soil OM, total N, K and Ca than CT. Electrical conductivity and aggregate stability (AS) were also improved by DS. Soybean grown in high-quality soil was not affected by charcoal rot, however, under CT, disease incidence in soybean was 54%. These differences were correlated to the higher microbial abundance and activity under DS, the biological component being a key factor determining soil capacity to suppress the soilborne pathogen.     

Preparation and characterization of intumescent flame retardant biodegradable poly(lactic acid) nanocomposites based on sulfamic acid intercalated layered double hydroxides

A novel sulfamic acid intercalated MgAl-LDH (SA-LDH) was prepared by intercalating NH₃SO₃^? into MgAl-layered double hydroxides (LDH), and it was then introduced into poly(lactic acid) (PLA) resin in association with intumescent flame retardant (IFR) by melt blending to prepare a flame-retardant biodegradable PLA composite. The effects of SA-LDH on the flame retardancy of PLA composites were characterized by limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter test (CONE). The results showed that the composite sample containing 19.0 wt% IFR and 1.0 wt% SA-LDH achieved the maximal LOI value of 48.7 %, passed the UL-94 V-0 rating, and significantly decreased the peak heat release rate from 306.3 kW/m² of neat PLA to 58.1 kW/m². Thermogravimetric analysis showed that both the thermal stability and the char formation were enhanced. The char morphology observation revealed that SA-LDH was beneficial to form dense and compact char layers. It was demonstrated that there existed a synergistic effect between IFR and SA-LDH in promoting the char formation and enhancing the fire resistance. The mechanical and crystallization properties were also tested and discussed.     

Preparation and Characterization of A Semi-interpenetrating Network Alkaline Anion Exchange Membrane

A series of semi-interpenetrating network (semi-IPN) anion exchange membranes (QCS/St-G_8-2-8, Quaternized chitosan/styrene-[maleic alkylene group diethyl bis (octyl dimethyl chloro/bromide), abbreviated as G_8-2-8] were prepared via in-situ polymerization by Styrene (St) and G_8-2-8 in QCS casting solution. During the process of in-situ polymerization, linear block polymers (St-G_8-2-8) of Styrene and G_8-2-8 was constructed, then was mixed with QCS casting solution, followed crosslinking the QCS by glutaraldehyde (GA). With the increasing content of linear block polymer, water uptake and swelling ratio of the composite membrane decreased; This kind of linear structure makes an order arrangement of quaternary ammonium groups which improves the OH? migration efficiency. At 70 °C, the M-30 composite membrane performs a high OH? conductivity of 8.20×10^-2 S·cm^-1, the methanol permeability is 3.23×10^-6 cm^-2·s^-1 which is still lower than Nafion 115 of 2.42×10^-6 cm^-2·s^-1, but M-30 shows a higher selectivity of 25.3 than Nafion 115 of 11.6. Furthermore, the membranes exhibited excellent thermal stability (≥150 °C), the tensile strength of the composite membrane is in the range of 14-25 MPa and elongation at break is in the range of 16-37 % at room temperature, as well as superior chemical stability in 1.0 M KOH solution for 250 h.     

An improved water-use efficiency for winter wheat grown under reduced irrigation

Single irrigation, compared to the conventional four or five irrigations, has been practised in northern China on winter wheat on a relatively large scale since 1991. In a field study, irrigation was reduced from normally four times (I₄, 4×75 mm) to one (I₁, 75 mm at the end of the second internode elongation) in an area with an annual rainfall of about 600 mm. A control without irrigation (I₀) was also included. Late sowing and early soil drying at seedling stage resulted in a relatively deep root system. Leaf area index, the size of upper leaves and the length of base internodes were also significantly reduced under I₁, but kernel number per panicle was not reduced, suggesting that the development of inflorescence was not disrupted. During the active grain-filling stage, it was found that leaf water potential under I₁ was maintained similar to that of I₄, while daytime stomatal conductance was substantially reduced. Leaf temperature was increased, indicating an inhibited leaf transpiration. Early senescence was induced in I₁ and I₀ crops and resulted in a substantially lower kernel weight. Although the grain yield of I₁ was reduced by about 15% from I₄, the water-use efficiency (WUE) for total water consumption was increased by 24–30%. Single irrigation can potentially make wheat cropping sustainable in this area in terms of water usage and prevent further depletion of the underground water resource. Explanations for the small or zero reduction in yield are: (1) the encouraging development of a deep root system that enabled the plants to use more water at depth (below 1 m), which is recharged annually by the relatively high summer rainfall. (2) A large portion of root system in the drying soil and its induced shoot physiological changes, that is, reduced leaf expansion and stomatal conductance, which helped the plants to establish a better canopy structure with a much reduced water consumption. (3) An improved harvest index.