Research Articles

Plantation poplar (Populus x euramericana cv. Pannonia) wood samples were steamed at 100 °C, 110 °C, and 120 °C and then irradiated by a strong UV emitter mercury lamp to test their colour stability. The colour change was evaluated and presented in a CIE Lab colour coordinate system. For the control, unsteamed poplar specimens were irradiated using the same mercury lamp. A considerable increase in colour saturation in the specimens was generated by steaming, and the saturation value further increased during the UV treatment. The lightness value of the unsteamed control specimens decreased continuously during the entire UV irradiation period. In contrast, the lightness value of the steamed samples decreased only during the first seven hours of the UV treatment and remained constant afterward. Steaming enhanced the redness stability of the poplar wood against UV irradiation. Modification of wood components during steaming at 120 °C stabilised the poplar wood redness against short-term photodegradation. Steaming slightly reduced the yellow colour sensitivity of the poplar to photodegradation.

Cassava bagasse (CB) was liquefied using polyethylene glycol to prepare polyol. The liquefied cassava bagasse (LCB) was reacted with polymeric diphenylmethane diisocyanate (PMDI) to produce novel bio-based polyurethane foams (PUF) via a one-pot process. The results showed that the density of the LCB-PUF was in the range of 0.027 to 0.039 g/cm3. When the LCB was used to instead of polyether polyol with a replacement ratio rising from 20% to 100%, the compressive strength of the LCB-PUF decreased from 0.171 to 0.057 MPa. The TGA results indicated that a higher replacement ratio (≥60%) of the LCB had a negative effect on the thermal stability of LCB-PUF, and the PUF with heterogeneous walls and irregular pore shapes was mainly caused by the high replacement ratio of the LCB. In addition, the mechanical properties of the LCB-PUF were improved through the adjustment of the [NCO]/[OH] ratio and the foam additive content.

The effects of nanoclay content were investigated vs. the mechanical, thermal, and morphological characteristics of a nanocomposite made from poplar wood flour and polypropylene. The wood flour, polypropylene, nanoclay, and the maleic anhydride grafted polypropylene (MAPP) were mixed in an extruder, and the test specimens were made via injection casting. Then, the mechanical and thermal properties were examined. The results showed that the tensile strength, flexural strength, and flexural modulus were improved when the wood flour content increased from 40% to 50%. Additionally, increasing the wood flour content from 40% to 60% enhanced the tensile modulus. The addition of nanoclay at dosages up to 2 wt% enhanced the tensile strength and the tensile modulus, whereas these properties were degraded with the addition of nanoclay at up to 4 wt%. The tensile strength and flexural modulus improved when the nanoclay content increased up to 4 wt%. The crystallinity enthalpy decreased when the wood flour content increased.

In order to find the suitable alkali recovery process for linter and reed pulping discharges, the physicochemical properties of the black liquor solids from linters pulping and black liquor solids from reed pulping were analyzed. The swelling volume index, calorific value, and pyrolysis characteristics of five samples of mixed black liquor solids were tested. The kinetics of the combustion process of the samples were further studied. The results showed that the calorific value and swelling index of the reed black liquor was higher and its inorganic content was lower. During the combustion period, the droplet undergoes four stages; drying, devolatilisation or pyrolysis, char burning, and smelt reaction. With the increase of reed pulping black liquor solids in the sample, the activation energy decreased, while the frequency factors increased. As a result, the combustion performance of the mixed solids was significantly improved.

The effects of bulk density on the structure and combustion characteristics of rice husk (RH) char were studied under isothermal conditions. The char from each reaction stage was obtained through pyrolysis of RH/Al2O3. Thermogravimetric-Fourier transform infrared analysis was used to study the release of gaseous products during the fine particle pyrolysis of RH/Al2O3. The results showed that the bulk density of the particles seriously affected the release rate and product distribution of gaseous products during pyrolysis, especially in the release phase of volatiles. In comparison, biomass pellets had a faster pyrolysis reaction rate at low bulk densities, which resulted in lower contents of O and H in the char obtained at this stage, and the aromatic structure content slowly increased. In the carbonization stage, the low bulk density promoted the increase in surface area and pore volume expansion of char. The degree of aromatization in char was higher, but the carbon content decreased. The addition of Al2O3 limited the growth of aromatic crystallites, while the char obtained at high bulk density tended to be graphitized. The char reactivity at the two bulk densities first decreased and then slightly increased, but the char obtained at high bulk density had better combustion reactivity.

Modified starch (MS) degraded composites were prepared via a molding method with starch as a substrate and a blending process with crumb rubber (CR) and added plasticizers such as glycerol, urea, and formamide. The mechanical properties and water absorbability of the MS degraded composites were measured. The functional group variations were confirmed by Fourier transform infrared spectroscopy (FT-IR), and the changes of the functional groups were investigated with a stereoscopic microscope to analyze the microstructure of the composites. The results indicated that the addition of CR substantially improved the performances of degradable composites. When the CR content was 50 wt% of the MS, the interfacial properties of the reinforced materials and the dispersing degree of the filler were improved. Compared with the composite without additive, the tensile strength and bending strength of the composites were increased by 107% and 49.5%, respectively. The minimum water absorption ratio was reduced by 78% compared with the composite without the additive.

Ultraviolet varnishes are widely used for production processes in the parquet industry. A large number of chemicals are used in this sector, and each one has different characteristics. In this study, the effects of accelerated aging of ultraviolet varnish (3 and 5 coats) when applied to lemonwood (Citrus limon (L.) Burm.) (grown in Mezitli, Mersin, Turkey) were investigated. The ultraviolet varnish coated samples were subjected to aging processes (144 h, 288 h, and 432 h) by using UV-A 340 nm lamps. Color (L*, a*, b*, and ΔE*) parameters, glossiness (perpendicular (⊥) and parallel (//) at 20°, 60°, and 85°), and surface adhesion strength via the pull-off method for ultraviolet varnish coated samples were quantified before and after weathering. According to the results, the varnish type, aging period, and interaction between all studied variables, i.e. L*, a*, b* color parameters, glossiness (perpendicular (⊥) and parallel (//) at 20°, 60°, and 85°), and adhesion strength were found to alter the surface properties. As a result, the lemon tree can be used in the production of an ultraviolet parquet system.

Starch has potential to be used in new, functional food packaging materials. The attractive factors of starch as a packaging material are its low price and degradable properties. However, brittleness hinders its function as a packaging film. In this study, chitosan nanofillers (CSN) were incorporated into sago starch (SS) formulations to improve the mechanical, physical, and chemical properties of the film. The synthesis of a new formulation from the optimization process resulted in increased mechanical properties; the tensile strength obtained for the sago starch/chitosan nanofillers (SS/CSN) film was 88 MPa compared with 46 MPa for the sago starch film (SSF). In terms of thermogravimetric analysis, the SS/CSN film sustained up to 390 °C with 60% weight loss, whereas SSF experienced a weight loss of 67% at 375 °C. The analyses summarize the concept of using biocomposites to improve the properties of film for the potential purpose in biodegradable packaging plastics.

The biomimetic application was studied for banana leaves (Musa acuminata Colla), which have been commonly used as a traditional cleaning technique for ironing plates. In this study, banana leaf surfaces were subjected to horizontal sliding forces of 5 N, 10 N, 15 N, and 30 N, using a heated plate at 100 °C, 200 °C, 300 °C, and 500 °C. The self-cleaning behavior of the banana leaves was determined by measuring the adhesion force, roughness, and contact angle, which were subsequently correlated with the surface morphology. Based on the results of this study, the adhesion force decreased from 6.39 nN ± 0.42 nN at 100 °C to 0.50 nN ± 0.50 nN at 500 °C with a load of 30 N, whereas the roughness increased from 0.79 µm ± 0.21 µm at 100 °C to 1.12 µm ± 0.30 µm at 500 °C. Furthermore, the contact angle decreased from 124.8° at 100 °C to 104.0° at 500 °C with a load of 30 N. This study established that the morphology of the banana leaves was altered with the temperature during sliding, which correlated with the surface characteristics.

New alternatives to plastic straws are being considered due to consumer demands for sustainability and recent changes in government policies and regulations, such as bans on single-use plastic products. There are concerns regarding paper straw quality and stability over time when in contact with beverages. This study evaluated the performance and properties of commercially available paper straws and their counterpart plastic straws in various intended applications. The physical, mechanical, and compositional characteristics, as well as the liquid interaction properties of the straws, were determined. The paper straws were composed mainly of hardwood fibers that were hard sized with a hydrophobic sizing agent to achieve a contact angle of 102° to 125°. The results indicated that all the evaluated paper straws lost 70% to 90% of their compressive strength after being in contact with the liquid for less than 30 min. Furthermore, the paper straws absorbed liquid at approximately 30% of the straw weight after liquid exposure for 30 min. Increased liquid temperatures caused lower compressive strengths and higher liquid uptake in the paper straws. This report provides directions and methods for testing paper straws and defines current property limitations of paper straws relative to plastic straws.