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The focus of this study is to identify the best surface treatment to maximize the bonding between a commercially available Dyneema® fiber and a high-density polyethylene matrix. The effect of a new sol-gel derived organic-inorganic hybrid coating on interfacial shear strength (IFSS) was compared with that of oxygen plasma and chromic acid treatments identified by previous studies. The treated fiber surfaces were examined using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS) to support the analysis using IFSS. The fiber surface became rough after the treatments, which increased with treatment time. The XPS spectra revealed a similar change in surface chemistry of fibers for sol-gel treatment for 1 min and plasma treatment for 6 min, which resulted in a similar enhancement in IFSS when compared to untreated fiber. Chromic acid treatment for 1 min resulted in the largest change in the percentage of carbon- and oxygen-containing groups on the treated surface when compared to the untreated surface as well as maximum enhancement of the IFSS over untreated fiber. [ABSTRACT FROM AUTHOR]

Abstract: In this study, silk sericin nanofibers from sericin hope-silkworm, whose cocoons consist almost exclusively of sericin were successfully prepared by electrospinning method. Scanning electron microscopy (SEM) was used to observe the morphology of the fibers. The effect of spinning conditions, including the concentration of sericin cocoon solution, acceleration voltage, spinning distance and flow rate on the fiber morphologies and the size distribution of sericin nanofibers were examined. The structure and physical properties were also observed by Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The optimum conditions for producing finely thinner fibrous sericin nanofibers without beads were the concentration of sericin solution above 6–8wt%, acceleration voltage ranging from 25 to 32kV, spinning distance above 9cm, and flow rate above 0.06cmmin−1. The mean diameter of as spun sericin fibers varied from 114 to 430nm at the different spinning conditions. In the as-spun fibers, silk sericin was present in a random coil conformation, while after methanol treatment, the molecular structure of silk sericin was transformed into a β-sheet containing structure. Sericin hope nanofiber demonstrated thermal degradation at lower temperature than the sericin hope cocoon, which probably due to the randomly coiled rich structure of the sericin hope nanofiber. [Copyright &y& Elsevier]

Abstract: Silk fibers from Bombyx mori silkworm was degummed with different concentration of citric acid, and the physical properties and fine structure were investigated to elucidate the effects of citric acid treatment. The silk sericin removal percentage was almost 100% after degumming with 30% citric acid which resulted in a total weight loss of 25.4% in the silk fibers. The surface morphology of silk fiber degummed with citric acid was very smooth and fine, showed perfect degumming like traditional soap-alkali method. The tensile strength of silk fiber was increased after degumming with citric acid (507MPa), where as the traditional soap-alkali method causes to decrease the strength about half of the control silk fiber (250MPa). The molecular conformation estimated by Fourier transform infrared spectroscopy and the crystalline structure evaluated from X-ray diffraction curve stayed unchanged regardless of the degumming with citric acid and soap. The dye uptake percentage of silk fiber degummed with citric acid decreased slightly, about 4.2%. On the other hand, the dye uptake percentage of silk degummed with soap was higher which indicates the disordering of the molecular orientation of the laterally ordered structure, accompanied with the partial hydrolysis of silk fibroin molecules by the alkali action of soap. The thermal properties were greatly enhanced by soap and citric acid degumming agents. Dynamic mechanical thermal analysis showed silk degummed with citric acid is more stable in higher temperature than that of soap. With heating at above 300°C, the silk degummed with citric acid shows an increase in storage modulus and an onset of tan δ peaks at 325°C and the melt flow of the sample was inhibited. The degumming of silk fibers with citric acid is safe and the results obtained are quite promising as a basis for possible future industrial application. [Copyright &y& Elsevier]

Abstract: Compressive behaviour of hemp (Cannabis Sativ L.) stems is important for the design of hemp handling and processing machines. Experiments were carried out to measure the compressive properties of stems from two hemp varieties: Alyssa (grown for fibre only) and Petera (grown for both fibre and seed), produced in Manitoba, Canada. The physical properties of the hemp specimens were measured. For each variety, an air-dried hemp stem was divided into three height sections along the stem: upper, middle and lower. For each section, the hemp stem was further cut into 25.4 mm long specimens. Individual specimens were compressed in the axial and lateral directions using a universal testing machine. The load-displacement curves were recorded, and compressive properties were derived from the load-displacement curves. The outer diameter of the hollow hemp specimens varied from 6 to 17 mm; the linear density varied from 10 to 37 g m−1. Diameter and linear density were greater for Petera than Alyssa, and at the lower height section than the higher section for both varieties. The compression tests showed that the maximum compressive load varied from 58 to 1425 N, and the energy requirement varied from 23 to 1809 mJ, depending on the variety, height section and diameter of stem, and compression direction. In general, the maximum compressive load and the energy requirement were greater in the lower section and for larger diameters; higher loads and energy were observed for Petera than for Alyssa and for the axial compression direction than for the lateral direction. [Copyright &y& Elsevier]

Abstract: To study the properties and structure of aquatic silk, nest-spinning hydropsychid caddisfly (Stenopsyche marmorata) larva were collected from a Japanese river and the silk glands were removed from the larva by dissecting and dried on the glass plate at room temperature. The silk fibers were obtained by removing fibrous materials, which the aquatic insects spun at the bottom of glass container and the microstructure and physical properties of aquatic silk protein fibres and their solid silk protein gland were evaluated. Silk fiber produced by the caddisfly larvae is composed of two filament embedded in a layer of glue. The results of Fourier transform infrared spectroscopy and X-ray diffraction measurements suggested the existence of binary structure containing random coil conformation and additional minor β-molecular structure. Differential scanning calorimetry results are characterized by two broad endothermic transitions, at 230°C and 320°C, which corresponds to the decomposition of silk glue and silk fiber from caddis fly, respectively. The storage modulus (E′) remained almost unchanged and nearly constant at above 60°C until about 214°C, where it began to show a sharp drop. A prominent relaxation peak appeared in the imaginary part of the modulus (loss peak at 230°C), in response to the strong motional transitions exhibited by the silk fiber at this temperature. There was significant difference of tensile strength of single solid silk protein gland in dry and wet state. The results obtained are quite promising as a basis for possible future biotechnological and adhesive applications of aquatic silk. [Copyright &y& Elsevier]

Abstract: To study the spinning condition of natural biopolymer silk, the silk fibers were directly acquired from Bombyx mori silkworm, N140×C140 by a simple artificial forcibly silking method at the speed of 60, 120, 180 and 240cmmin−1, respectively and its microstructure and physical properties were evaluated. The fine silk fibers (about 8μm) were obtained at faster spinning speed, 240cmmin−1. The tensile properties of silk fibers were remarkably increased with raising the forcibly spinning speeds. The β-sheet structure contents of silk fibers obtained at higher speed were considerably increased. The fibers obtained by different spinning speeds exhibited a fairly similar X-ray crystallinity, while the degree of molecular orientation increased with decreasing the fiber diameter. The fine silk fibers obtained at higher speed (240cmmin−1) exhibited a slightly higher thermal stability, as shown by the upward shift of differential scanning calorimetry (DSC) decomposition temperature. [Copyright &y& Elsevier]

Abstract: Carbon fibers were prepared from silk fibers after an iodine treatment and the carbon yield, fiber morphology, structure and mechanical properties were investigated. A single or multi-step carbonization process was used for the preparation. In the single step process, silk fibroin (SF) fibers were heated from 25 to 800°C with a heating rate of 5°Cmin−1 under Ar atmosphere. However, the carbon fiber obtained was partially melted and was too fragile to handle. For better performance, SF fibers were treated with iodine vapor at 100°C for 12h and untreated and iodinated SF fibers were heated from 25 to 800°C by a multi-step carbonization process, which was defined based on the optimum thermal degradation rate of silk. In this multi-step process, the carbon fibers obtained from iodinated SF were structurally intact and stable in appearance, and the carbon yield achieved was ca. 36wt.%, much higher than the value for untreated SF. X-ray diffraction, Raman spectroscopy and transmission electron microscopic observation revealed that the obtained carbon fibers from both untreated and iodinated SFs had a basically amorphous structure. The strength of carbon fibers prepared from iodinated SF using the multi-step carbonization was considerably increased compared to that of untreated SF. According to viscoelastic measurement, by heating above 280°C the iodine introduced intermolecular cross-linking of the SF, and its melt flow was inhibited which produced a higher yield and better performance of the carbon fiber. [Copyright &y& Elsevier]