Volume 11 Issue 3

The many uses of wood are greatly affected by its surface properties, which are significantly altered by heat treatment. Investigated here are the wettability and surface brittleness when treating poplar wood with heat at 160, 180, 200, and 220 °C for 2 h. Contact angles were measured by the sessile drop method, and surface free energy was calculated. Surface brittleness was expressed by hardness (HD value), roughness (Ra, Rq, Ry, and Rz values), and abrasive resistance (K value). Next, non-destructive Fourier transform near-infrared spectroscopic (FT-NIR) and X-ray photoelectron spectroscopic (XPS) measurements were employed to analyze the surface chemical changes. Scanning electron microscopy (SEM) revealed the post-heating microscopic structure. The results demonstrated that heat treatment reduces the surface wettability while increasing the surface brittleness, which becomes more apparent with increased temperature. Significant differences were determined (p < 0.05) between the surface parameters at four different temperatures. The degradation of cell wall components and the deterioration of microstructures was further expounded by FT-NIR, XPS, and SEM analyses. Furthermore, the abrasive resistance and hardness values decreased in line with the rate of weight loss (WL, %) and temperature. This indicates a strong correlation between the surface characteristics and the WL or temperature. The intensity of heat treatment appears to be predictable and easy to regulate.

The goal of this work was to evaluate the technical feasibility of walnut shell flour (WSF) as substitute for wood in walnut shell flour/thermoplastic starch (WSF/TPS) composites. The effects of walnut shell flour (WSF), thermoplastic starch (TPS), and nanoclay on the physical and mechanical properties of WSF/TPS composites were investigated. The composite samples were formed in a Colin extruder with four-chamber heat with temperatures. Then, test samples were made using injection molding. The addition of up to 40% WSF greatly improved the tensile strength, flexural strength, and elasticity modulus of the composite. Also, the composites made with higher WSF contents had increased thickness swelling and water absorption. The incorporation of nanoclay (0% to 5%), greatly improved the tensile properties. Soil burial degradation experiments showed that biodegradation was accelerated by the increase of starch in the composite mixtures. The study showed that WSF can be successfully utilized for the manufacture of composites with useful physical and mechanical properties.

In an attempt to find a more efficient technique for biodegradation of the recalcitrant Reactive Black 5 (RB-5) dye, a composite xylan-polyvinyl alcohol (xylan-PVOH) hydrogel was used to immobilize laccase from the white-rot fungusTrametes versicolor. Xylan was prepared from the black liquor of pulp and paper effluent, and it was esterified with citric acid prior to cross-linking with polyvinyl alcohol (PVOH). The optimum composition for the immobilized laccase bead formation consisted of 4% (w/v) modified xylan, 10% (w/v) PVOH, and 15 U.mL-1 crude laccase. The maximum decolorization of RB-5 (98.45 ± 1.96 %) was obtained within the first cycle (6 h) at 40 °C. In the eighth cycle, the reused beads were able to decolorize 55.35 ± 2.46 % of the RB-5. Moreover, the xylan-PVOH beads extended the optimum pH range of laccase activity from 6 to 10 and tolerated a temperature up to 10 °C higher than that of the free enzyme. These results suggest that the xylan-PVOH bead has great potential as the polymer matrix for enzyme immobilization, which has applications in wastewater treatment.

Wood plastic composites (WPCs) have recently gained increased market share as a result of their beneficial properties and use of sustainable material sources. Currently, however, WPC products are limited to extruded profiles. More complex product shapes and geometries will increase market potential, but they demand additional post-processing after extrusion. Post-processing machinery coupled online with an extruder necessitates material handling, which is commonly achieved using belt conveyors. This paper considers transport of WPC material through a post-extrusion process using a belt conveyor system. Special emphasis is placed on studying the friction and surface energy properties of the belt conveyor. Friction at the interface of the raw material and belt cover was tested using a standard incline-plane method, and adhesion and stickiness were evaluated by determining the surface free energies of the belt cover and WPC material at 23 and 100 °C. On the basis of these measurements, this paper investigates key aspects of belt cover material selection and proposes a conveyor belt configuration for a prototype post-extrusion process line that can be utilized in commercial mass production of WPC products.

The characterization of fibers extracted from leaflet, the empty fruit bunches, leaf sheath, and spath of palm tree was performed. The fibers were extracted using three different procedures through chemical and /or enzymatic methods. The raw fibers studied have xylose contents between 13-22% and glucose content between 30% and 45%. The microfibrillar angle (MFA) values are in the order: bunch > spath > leaf sheath >> leaflet. Spath and leaf sheath, which naturally occur in a woven form present poor mechanical strength but could be readily used to produce cheap composites. Leaflet fibers extracted from date palm tree exhibiting a low MFA (16°), a high cellulose content, and cellulose crystallinity present the highest ultimate tensile strengths (≈ 1250 N.mm-2).

Cellulose nanocrystals (CNCs) grafted with fluorescent and thermo-responsive poly (N-isopropylacryalamide) (PNIPAM) brushes were prepared for encapsulation and the release of 5-fluorouracil (5-FU). The successful grafting was evidenced by Fourier transform infrared (FTIR) spectroscopy and solid-state 13C nuclear magnetic resonance (13C NMR). Differential scanning calorimetry measurements suggested that the lower critical solution temperature of PNIPAM-grafted CNCs is close 32 °C. During polymerization, tuned fluorescence signatures were obtained by varying the dye dosages. At room temperature, the release amount of the loaded 5-FU was about 42% at a pH of 2.1, while this value approached 60% at a pH of 7.4. Both the cumulative release amount and the release rate were greatly increased when the temperature was raised to 37 °C. The novel PNIPAM-grafted CNCs with both fluorescence and stimuli-sensitive properties possess potential for application in intelligent drug delivery systems.

The depletion of fossil resources and the environmental impact of petroleum-based plastic materials have driven a strong global interest in renewable biobased polymers and composites derived from natural resources. Since biodegradable polymers have their own drawbacks, it is often combined as a composite with other fillers. Polypropylene (PP)/Poly(3-hydroxybutyrate) (PHB) composite films and lignocresol (LC)/PP/PHB composite films were cast by blending methods. This study investigated the effects of the amounts of added PP fiber and LC on the mechanical and thermal properties in the corresponding composite films. The overall properties of LC/PP/PHB composite films were best with 8 wt.% PP fiber content and 3 wt.% LC content. The tensile strength (13.00 MPa) was up to 1.25 times that of the original PHB film (10.44 MPa), and the thermal properties of the composite films were improved by adding 3 wt.% LC. Thermogravimetry (TG) analysis indicated that the onset temperature (382.0 °C) rose by 50.7 °C compared with PP/PHB film (331.3 °C), and the residual mass was close to 0%.

Galactomannan in industrial Gleditsia microphylla and guar gum was successfully fractionated by gradual precipitation in an aqueous solution with increasing ethanol concentrations. The molecular properties of each fraction were characterized, and the galactomannans were added to photopolymerized hydrogels to test their effects on mechanical properties and swelling capacity. In the series fractions of guar gum, the sample precipitated from 20% EtOH solution had the highest yield, mannose to galactose ratio, and viscosity, and it had a slightly lower molecular weight than that precipitated by 30% EtOH. Correspondingly, the best tensile property of its photopolymerized hydrogel was finally detected. In terms of G. microphylla gum, the precipitation in 30% EtOH solution achieved the highest yield, M/G ratio, and molecular weight value, and it exhibited the best rheological property of all the samples. The hydrogel with the addition of this sample also had the best mechanical properties despite its lower hydroscopicity than the blank hydrogel. The unique properties of each fraction could probably lead to their use as biodegradable alternatives in different applications.

Soda black liquors from the Specel® process, which used wheat straw as the raw material, were subjected to an acid precipitation process to recover the lignin. Lignin was isolated by acid precipitation using three different inorganics acids (H3PO4, H2SO4, and HCl) at three concentration levels, and at pH values of 2 and 4. Even though the highest lignin yield was achieved using phosphoric acid, the most economical inorganic acid was sulphuric acid. Physico-chemical characterizations of the precipitated lignin samples were performed using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) (for thermal properties), Fourier transform infrared spectroscopy (FT-IR), and heteronuclear single quantum correlation spectroscopy (HSQC) (for chemical structures). No significant differences were found in the thermal properties and chemical structures of the isolated lignins, except for the lignin obtained with phosphoric acid to lower the black liquor from pH 10.72 to pH 2. Apart from the lignin fraction collected, the soda pulp obtained by the Specel® process using wheat straw could represent a good alternative for packaging industries.

Biomorphic charcoal/TiO2 composites (C/TiO2) from moso bamboo templates were produced for absorbing microwave. Subsequently, the characteristics of the C/TiO2 were investigated by scanning electron microscopy, thermogravimetric analysis, and vector network analysis. The results showed that the biomorphic microstructure of the moso bamboo charcoal was duplicated in the C/TiO2. Thus, the density of the C/TiO2 sintered at 1200 °C was lower and approximately 0.916 ± 0.003 g/cm3. Moreover, the ignition, the maximum combustion, and the burnout temperatures of the C/TiO2 sintered at 600 °C were ~320 °C, ~530 °C, and ~585 °C, respectively. Additionally, with the rising of the temperature sintering C/TiO2, the microwave absorbency of the C/TiO2 was improved over high frequency zones. Furthermore, the average imaginary-part values of the permittivity of the C/TiO2 sintered at 600 °C and 1200 °C notably increased by 11.16-fold. In addition, the peak of microwave reflection loss of the samples (2.0 mm thickness) from the C/TiO2 powder (wt. 20%) sintered at 1200 °C and the paraffin wax (wt. 80%) was observed as -18.0 dB at 17.4 GHz. Therefore, the C/TiO2 sintered at higher temperatures exhibited lower geometrical density, better thermostability, and favorable microwave absorptive properties.