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Reducing the flammability of kapok fiber (KF) is an important strategy to increase its applicability. In this work, the phosphorylation of KF with ammonium dihydrogen phosphate (ADP) was used to reduce its flammability, the conditions of phosphorylation reaction were studied in detail, and the chemical groups, crystalline structure, thermal stability, heat release capability, flammability and charring ability of phosphorylated KF were analyzed. KF showed significantly higher phosphorylation level than cotton, and its phosphorylation greatly depended on ADP and urea dosage, reaction temperature and time, and pH. Urea addition, pH 6, 150 ℃ and 1 h rendered high phosphorylation with acceptable whiteness. Phosphorylated KF exhibited good char-forming, low heat release and excellent flame retardant performances during thermal degradation and combustion as evidenced by thermogravimetric, microcalorimetric, vertical combustion and combustion residue morphology analyses. The residue rate of phosphorylated KF subjected to thermal degradation exceeded 50% in nitrogen, and 25% in air. This investigation demonstrates that phosphorylated KF is an intrinsically flame retardant material. [ABSTRACT FROM AUTHOR]

The nanostructure of materials plays a key role in interfacial solar vapor generation. Traditional approaches for optimizing interfacial evaporation rely on the external devices to enable floating on water. However, how to unlock the self-floating ability of absorbers for solar interfacial evaporation have not been taken into account. Here, we propose a self-floating absorber based on kapok fibers, which possess large hollow structure and hydrophobicity to enable this absorber float on water without assistance. Gold nanoparticles (AuNPs) were loaded on kapok fibres by in-situ synthesis and showed an extended adsorption (74.7%) wavelength ranging from 280 to 2500 nm. Both the hollow structure of kapok fibres and the thermal localization effect of AuNPs sustaintially enhance the solar interfere vapor generation effect (4 kW m−2, up to 89%). Also, Each cycle test was carried out under 1 h irradiation. The AuNPs/kapok membrane exhibited stable cycling performance, which maintained an evaporation rate of 6.98 kg m−2 h−1 over 10 times without performance decrease. These results provide new insights for design of advanced photothermal conversion materials with biomass as supporting material, We expect this as-prepared membrane can be used for a range of applications, such as solar interference steam generation, desalination and disinfection, to name a few. [ABSTRACT FROM AUTHOR]

To make full use of Chinese domestic kapok fiber, the microstructure and composition structure of kapok collected in Quanzhou, China, were investigated and compared with the popular Indonesia ceiba. FIB-SEM images showed the similar fine tube structures of both kapok fibers with the wall thickness and hollow ratios of 806.1 nm, 85.56% and 863.3 nm, 82.40% respectively. Mesopores with the average width of 48.247 and 38.758 Å were proved to be slit pores produced by the packing of porous lamellae. Quanzhou kapok was superior to Indonesia ceiba in terms of wall thickness, hollow ratio, specific surface area and pore size which would be better at oil adsorption. Both kapok fibers were primarily composed of cellulose, hemicellulose and lignin. Quanzhou kapok had better thermostability and higher degradation speed than those of Indonesia ceiba. Inside the fiber, cellulose skeletons were in the arrangement of helical ribbon, while amorphous lignin and hemicellulose made up the fibrillar interval and cemented the fiber together. The interstice between the different compositions should be the mesopores. In this paper, the experimental results were discussed and analyzed in detail aiming at microstructure and composition distribution of kapok fiber, providing reference values for the applications and product development process of Chinese domestic kapok fiber. [ABSTRACT FROM AUTHOR]

Properties of cellulose aerogels indicate their great potential in oil pollutant treatment, a domain that has received tremendous attention recently; however, there are only a small theoretical studies into their absorption mechanisms. Herein, we developed a dual-scale oil absorption model based on the Washburn capillary theory to investigate the oil absorption kinetics of aerogels. It was found that kapok/microfibrillated cellulose aerogels (KCAs) exhibit high oil absorption performance via a capillary wicking method that simulates oil removal by aerogels in polluted oceans. This theoretical model demonstrates that the oil absorption capacity is mainly derived from the continuous primary pores within the aerogel skeleton, while secondary pores introduced by chopped kapok could collect and conduct oil, leading to improved oil absorption rates of KCAs. The experimental results of the oil absorption coefficients confirm the accuracy of the developed dual-scale model. The study of this dual-scale model is significant in investigating the relationship between the pore structure and oil absorption of aerogels, which will provide valuable insights for the practical application of aerogels for oil removal in polluted oceans. [ABSTRACT FROM AUTHOR]

Kapok fiber (KF) belongs to a type of seed fibers collected from the fruits of Ceiba pentandra tree. From sustainable biomass resource, KF is a naturally abundant cellulose fiber with good economic value, excellent biocompatibility and biodegradability. Especially, KF has inherent thin-walled large lumen and hydrophobic–oleophilic surface, which makes KF receive increasing attention in recent years as the starting material for fabrication of different types of functional materials. Among them, KF can be blended with, filled in, grafted by, coated with other components, or carbonized via pyrolysis or hydrothermal, and then is currently focused on by many researchers for adapting to different applications. In this review, we present the structural characteristics of KF, KF-based functional materials and their potential applications, especially in fields related to the environment and energy, such as oil sorbents, adsorbents for heavy metals and dyes, sound absorption materials, electrode materials of supercapacitors, photocatalysis and catalysis materials, and so forth. [ABSTRACT FROM AUTHOR]

Biomass-based composites are of immerse importance because they allow combining properties in ways that are not found in nature. This work reports facile routs to produce pressure sensor in large scale from biomass kapok fibers and natural rubber. Two different strategies were applied to introduce conductive elements into the pressure sensor and are systemically compared, which include carbonization of the tubular kapok fibers and coating the fibre with conductive polymer. When used as a pressure sensor, the kapok fiber and natural rubber-based composites can respond logarithmically to the loading in the compressive strain range of 0 ~ 15% with excellent recyclability. As a prototype of the concept for practical application, a weight scale was constructed using the kapok fiber and natural rubber-based composites and showed distinct weight-dependent resistance changes, being feasible for measuring weight within a certain weight range. Besides, the strategy based on conductive polymer enables the pressure sensor to be insulative at its original state and become conductive when pressed, hereby making the composite a potential pressure-sensing material and pressure-responsive circuit switch. This study provides a platform for developing biomass-based electronic pressure sensors. [ABSTRACT FROM AUTHOR]

A facile dipping strategy was performed for roughening the surface of two plant fibers (CGF, Calotropis gigantea fiber; KF, kapok fiber) via nano-sized MoS2 to obtain eco-friendly oil-absorbing materials, MoS2-CGF and MoS2-KF. The results indicated that in addition to the roughened surface topography, MoS2-CGF and MoS2-KF possessed also hydrophobic–oleophilic properties and highly hydrophobic stability to corrosive environments. For twelve selected model oils (including organic solvents), MoS2-roughened fibers had excellent absorption capacity, with the value of 25–100 g/g for MoS2-CGF and 65–135 g/g for MoS2-KF within a few seconds. Furthermore, MoS2-CGF and MoS2-KF exhibited outstanding oil–water selectivity by using trichloromethane and cyclohexane as the model oils. After ten absorption–desorption cycles, a limited reduction in the re-sorption percentage was observed, demonstrating that MoS2-CGF and MoS2-KF had good reusability. By combining the advantages of abundant resource, low cost, high efficiency and environmental friendliness, MoS2-roughened fibers may be promising as efficient oil sorbents for the removal of oil spills in water. [ABSTRACT FROM AUTHOR]

Abstract: Three-dimensional hollow microtubular nickel-cobalt layered double hydroxide composites were facilely fabricated by controlling the growth on the external and internal surface of natural kapok fibers. The incorporation of kapok fibers induced the confined growth of nickel-cobalt layered double hydroxide on the kapok fiber templates, and the tubular structure of the composite did not collapse with the extension of the hydrothermal time. The obtained unique structure was in favor of enhancing the electrochemical properties of nickel-cobalt hydroxide. The composites prepared after reaction for 8 h exhibited the maximum specific capacity of 1112.25 C g−1 at current density of 0.5 A g−1. Coupled with the active carbon negative electrode, the assembled hybrid supercapacitor device delivered a maximum energy density of 38.0 W h kg−1 with an operational voltage of 1.6 V.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Kapok is a natural fiber with an extremely high degree of hollowness. Numerous pores in its cell wall form the pathways for gas molecules. The delamination of the cell wall in scanning electron microscopy images and the hysteresis loop in nitrogen adsorption-desorption isotherms are interpreted to indicate that the kapok fiber has slit-shaped pores. Nitrogen adsorption method based on Brunauer-Emmett-Teller theory was used to analyze the mesopore. The specific surface area of kapok fiber is evaluated as 2.99 m2/g in the relative pressure range (0.05-0.35). The pore size of the fiber is distributed in 4-40 nm and mainly concentrated on 3-4 nm. The volume of the pores with diameters of 2-40 nm accounted for about 80% of the total pore volume, and those with diameters over 40 nm accounted for about 20%. By the Va ~ αs micropore evaluating method, it is found that the micropore volume of the fiber is about 7.0399×10−11 ml/g. [ABSTRACT FROM AUTHOR]

The various morphologies of polyaniline are grown on carbon fibers derived from natural hollow cellulose by in situ polymerization of aniline. The morphologies of nanofibers, pyramid-like, nanorods and nanowires can be facilely controlled by the doping of hydrochloric acid, sulfuric acid, perchloric acid, phosphoric acid and p-toluenesulfonic acid, respectively. The perchloric acid doped composite shown the maximum specific capacitance of 580 F g at 1.0 A g. Remarkably, the all solid-state supercapacitors based on this sample deliver a maximum energy density of 13.3 Wh kg. The excellent performance is attributed to the unique morphology and hollow structure of the conductive substrate, which can drastically facilitate the ion diffusion and improve the utilization of the electroactive. [ABSTRACT FROM AUTHOR]

A hydrophobic layer was formed on smooth surfaces of Calotropis gigantea fiber (CGF) and kapok fiber (KF) by adsorption of octadecyltrichlorosilane (OTS) from a toluene solution and then a comparative study was carried out on the basis of various characterizations and oil-absorbing performances for the two natural plant fibers. The resulting OTS-CGF and OTS-KF exhibit outstanding hydrophobic-oleophilic property and an enhancement in the oil-absorbing capacity for engine oil, soybean oil and kerosene. Moreover, the fibers can be utilized for rapid and selective removal of oil spills on the water surface. Compared to KF, CGF seems to be acid-resistant during the hydrolysis process of OTS, with the result that the oil-absorbing capacity exhibits no significant decrease after ten cycles. Eventually, CGF-based material can be further developed for oil-water separation, demonstrating its potential as a promising alternative for treatment of oil-containing wastewaters. [ABSTRACT FROM AUTHOR]

A facile approach was developed for the preparation of iodine-doped polyaniline/kapok fiber (PAn/KF) composites via a semidry method using iodine vapor as dopant and oxidant. The as-prepared PAn/KF composites with a uniform PAn coating exhibited good hydrophilicity and excellent adsorption performance toward a low concentration of dyes and precious metal ions. The adsorption rate of PAn/KF composites could reach 94.5 % with 50 mg/l of methylene blue. The adsorbed Au(III) was reduced in situ into elemental gold to obtain PAn/KF-supported Au composites because of the good redox activities of the coated PAn, which exhibited excellent catalytic activity in the catalytic reduction of 4-NP and MB in the presence of NaBH. [ABSTRACT FROM AUTHOR]

Kapok fiber, a natural hollow fiber with thin shell and large cavity, has rarely been used as adsorbent for heavy metal ions. In this paper, kapok fibers were modified with diethylenetriamine pentaacetic acid (DTPA) after hydrophilicity treatment. The adsorption behavior of the resultant kapok-DTPA influenced by pH, adsorption time and initial concentration of metal ion was investigated. The results demonstrate that adsorption equilibrium was reached within 2 min for Pb and Cd. Adsorption kinetics showed that the adsorption rate was well fitted by pseudo-second-order rate model. The adsorption isotherms were studied, and the best fit was obtained in the Langmuir model. The maximum adsorption capacities of kapok-DTPA were 310.6 mg g for Pb, 163.7 mg g for Cd, 101.0 mg g for Cu, respectively. After eight desorption and re-adsorption loops, the lost adsorption capacities for Pb and Cu were less than 10 %. Because of the large specific area derived from the hollow fiber structure, kapok-DTPA exhibited much better adsorption capacity compared with many other reported adsorbents based on natural materials. [ABSTRACT FROM AUTHOR]