Md. Iftekhar Shams

The transparent crab: preparation and nanostructural implications for bioinspired optically transparent nanocomposites

An optically transparent crab-shell with an intact original shape and substantial morphological detail is presented. Inorganic calcium carbonate particles, proteins, lipids and pigments are removed from a native crab-shell, and the remaining chitin nanofibrous structure is impregnated by a monomer and polymerized. The nanostructural implications for man-made nanocomposites are discussed. An important application of the finding is demonstrated as heterogeneous micro-scale crab shell chitin particles are successfully used to process transparent nanocomposites. The incorporation of nanostructured chitin macro-particles not only retains transparency of the matrix resin but also drastically reduces the coefficient of thermal expansion of the polymer. Moreover, the optical transmittance of the composite is stable over a large range of temperatures despite significant inhomogeneity at the mm scale and the large temperature changes in the refractive index of the resin in its isolated state. This class of materials is an interesting candidate for transparent substrates in next-generation electronic devices such as flexible displays and solar cells.

Compressive deformation of wood impregnated with low molecular weight phenol formaldehyde (PF) resin IV: Species dependency

Flat-sawn specimens of eight wood species, albizia (Paraserianthes falkata, 0.23 g/cm3), Japanese cedar (Cryptomeria japonica, 0.31 g/cm3), red lauan (Shorea sp., 0.36 g/cm3), European spruce (Picea abies, 0.44 g/cm3), Douglas fir (Pseudotsuga douglasii, 0.50 g/cm3), elm (Ulmus sp., 0.51 g/cm3), Japanese beech (Fagus crenata, 0.64 g/cm3), and Japanese birch (Betula maximowicziana, 0.71 g/cm3), were impregnated with low molecular weight phenol-formaldehyde (PF) resin and their compressive deformations were compared. The volume gain (VG) and weight gain due to 20% resin solution impregnation were different among species. Furthermore, the specific volume gain (VG/specific gravity), indicating the degree of swelling of the cell wall, also varied from 17.7% for European spruce to 26.4% for elm. Oven-dried specimens of each species were compressed using hot plates fixed to an Instron testing machine. The deformation behavior of resin-impregnated wood up to 10MPa was significantly different among the species. Stress development during cell wall collapse for low density wood was minimal. As a consequence, a significant increment of density occurred up to 2MPa for low density wood such as albizia and Japanese cedar. When PF resin-impregnated wood was compressed up to 2MPa and the pressure was kept constant for 30min, the density of Japanese cedar reached 1.18g/cm3, about 30% higher than the density of compressed Japanese birch, which possesses an original density that is 2.5 times higher than that of Japanese cedar. The mechanical properties of resin-impregnated wood, especially low density wood, increased with density. Hence, it is manifested that low density wood species have an advantage as raw materials for obtaining high-strength wood at low pressing pressure.

Doubly curved nanofiber-reinforced optically transparent composites

Doubly curved nanofiber-reinforced optically transparent composites with low thermal expansion of 15 ppm/k are prepared by hot pressing vacuum-filtered Pickering emulsions of hydrophobic acrylic resin monomer, hydrophilic chitin nanofibers and water. The coalescence of acrylic monomer droplets in the emulsion is prevented by the chitin nanofibers network. This transparent composite has 3D shape moldability, making it attractive for optical precision parts.

Compressive deformation of wood impregnated with low molecular weight phenol formaldehyde (PF) resin III: effects of sodium chlorite treatment

To obtain high-strength phenol–formaldehyde (PF) resin-impregnated compressed wood at low pressing pressure, we investigated the effects of sodium chlorite (NaClO2) treatment on wood prior to low molecular weight PF resin impregnation. Sawn veneers of Japanese cedar (Cryptomeria japonica) were treated with 2% aqueous NaClO2 solution at 45°C for 12 h to remove lignin, and the process was repeated up to four times, resulting in weight loss of 21%. NaClO2 treatment has shown considerable potential for high compression of PF resin-impregnated wood at low pressing pressure, especially after adding moisture to a content of 10%–11%. This deformation is further enhanced during pressure holding by creep deformation. The density, Young’s modulus, and bending strength of PF resin-impregnated veneer laminated composites that were treated with NaClO2 four times and compressed at 1 MPa, reached 1.15 g/cm3, 27 GPa, and 280 MPa, respectively. The values in untreated PF resin-impregnated wood reached 0.8 g/cm3, 16 GPa, and 165 MPa, respectively.

Flexible and transparent chitin/acrylic nanocomposite films with high mechanical strength

Chitin-nanofibers (CNFs) of <50 nm in width were successfully extracted from shrimp shell using ordinary household food blender by introducing electrostatic repulsion force, without altering the original chemical structure of chitin. The generated nanofibers were small enough and compatible with liquid acrylic to retain the transparency of acrylic resin films, even at nanofibers share of about 25 %. Young’s modulus of CNFs reinforced resin films has been increased 115-fold and the tensile strength 3-fold. The resulting nanocomposites had almost the same bending resistance of acrylic resin films. It is conceived that this finding is of a significant step in advancing the field of optoelectronic technology.

Introducing Areca catechu as a raw material of cement-bonded board through determining the properties of Areca catechu cement-bonded board

Abstract The study was conducted to assess the properties of cement bonded board made from Areca catechu (betel nut) stem. Fine, coarse and fine-coarse boards were prepared. The ratios of particles weight and cement were 1:2 and 1:3 for each type of board. The laboratory tests for characterization of physical and mechanical properties were carried out for each type of board. In case of physical properties, moisture content, density, water absorption, thickness swelling and linear expansion were evaluated. Modulus of elasticity (MOE) and Modulus of rapture (MOR) were evaluated for mechanical properties. From all the cement bonded boards, the board made with the ratio of 1:3 showed the best performance. Cement bonded particle board made from betel nut may be an alternative raw material for manufacturing cement bonded board.

Compressive deformation of wood impregnated with low molecular weight phenol formaldehyde (PF) resin V: effects of steam pretreatment

This study evaluated the potential of steam pre-treatment for making highly compressed phenol-formaldehyde (PF) resin-impregnated wood at a low pressing pressure. Sawn veneers of Japanese cedar (Cryptomeria japonica) were first subjected to saturated steam at different steaming temperatures (140°-200°C), followed by impregnation with a 20% low molecular weight PF resin aqueous solution resulting in a weight gain of around 50%-55%. Four oven-dried treated veneers were laminated and compressed up to a pressing pressure of 1 MPa at a pressing temperature of 150°C and pressing speed of 5 mm/min, and the pressure was held for 30 min. Steam treatment, causing partial hydrolysis of hemicellulose, accelerated the compressibility of Japanese cedar in the PF resin-swollen condition. As a consequence, a discernible increment in density was achieved at a pressing pressure of 1 MPa due to steam pretreatment between 140° and 200°C for 10 min. It was also found that even a short steaming time such as 2 min at 160°C is sufficient for obtaining appreciable compression of PF resin-impregnated wood. The density, Young’s modulus, and bending strength of steam-treated (200°C for 10 min) PF resin-impregnated wood composite reached 1.09 g/cm3, 20 GPa, and 207MPa, respectively. In contrast, the values of untreated PF resin-impregnated wood composite were 0.87 g/cm3, 13 GPa, and 170MPa, respectively.