Research Articles

The convertibility of paperboard in a press-forming process was studied using a novel type of tool set that allows forming of small substrates such as laboratory handsheets (i.e. experimental materials) to investigate the role of mold design on substrate-press-tool interaction. The tool set makes it possible to prepare rectangular trays in both sliding and fixed blank modes in a pilot-scale press-forming machine. The tests showed that the fixed-blank mode makes it possible to estimate the elongation of the substrate in the forming process by determining the maximum forming depth for rupture-free samples. A more detailed inspection with an optical microscope of grid-patterned materials revealed that elongation took place mostly on the rim area in addition to the tray wall, and that the outer dimensions of the blank remained practically unchanged. The behavior of the material in press forming process was evaluated in addition to the novel tool set in a bigger, production-scale mold, and results showed good agreement between the small tool set and the standard mold, in spite of the dimensional differences. The smaller size of the mold did not require a compromise in any aspect of the press-forming process.

The physical and degradation properties of polylactic (PLA)/thermoplastic starch (TPS) blends after TPS modification with citric acid (CA) were investigated. The interfacial adhesion between the PLA and TPS was expected to improve, thus enhancing the physical properties of the PLA/TPS blends. The tensile strength and Young’s modulus for PLA/TPS blends at (60/40) and (40/60) blends ratio were found to increase after modification with CA. On the other hand, the elongation at break of the (60/40) blend decreased, while elongation at break of the (40/60) blend increased. Meanwhile, an additional peak at 1721 cm-1 was detected by the FTIR spectroscopic analysis, which indicated that the TPS had chemically interacted with the CA. The biodegradability properties of PLA/TPS blends were also improved after treatment with CA. The deterioration of PLA/TPS blends was attributed to the incorporation of CA; O2 from the soil was attracted to the PLA/TPS blends, thus speeding up the degradation process of the blends.

Hydrothermal and acid pretreatments using different acid charges (1.5%, 3.0%, and 4.5% H2SO4) were proposed for eucalyptus, sugarcane bagasse, and sugarcane straw prior to their bioconversion into ethanol using the semi-simultaneous saccharification and fermentation (SSSF) process. The hydrothermal and acid pretreatments were efficient for hemicelluloses removal from eucalyptus (63 to 96%), bagasse (25 to 98%), and straw (23 to 95%) and to remove a substantial amount of lignin from eucalyptus (10 to 34%) and bagasse (10 to 27%). During pretreatments, pseudo-extractives and pseudo-lignin were generated from biomasses. The SSSF was performed in pretreated biomasses using 24 h presaccharification followed by an additional 10 h of simultaneous saccharification and fermentation (SSF). With hydrothermal pretreatment, the eucalyptus presented the highest ethanol production, but only low values for SSSF parameters were obtained, as follows: ethanol yield (0.017 g ethanol/g biomass), volumetric productivity of ethanol (0.16 g L-1 h-1), and ethanol concentration (1.6 g L-1). On the other hand, using acid pretreatment, the straw (pretreated using 4.5% H2SO4) presented the highest ethanol production among the biomasses, assessed based on ethanol yield (0.056 g ethanol/g biomass), volumetric productivity of ethanol (0.51 g L-1 h-1), and ethanol concentration (5.1 g L-1).

Changes in the physical structure and nutrients contents of apple branches were explored after decomposition, and the soil quality of an orchard was evaluated after returning apple branches in situ. Scanning electron microscopy, X-ray diffractometry, and Fourier transform infrared spectroscopy were used to analyse the structural changes of the experimental material. The results showed that the structure of this material is obviously destroyed in the transverse sections and longitudinal sections. Collapsed cell walls had a negative effect on complete branches, which presented sharp decreases in cellulose contents and the partial removal of lignin and carbohydrate contents by the third year. In a final analysis of the nutrients in the branches, there was an obvious decline in macroelements (e.g., phosphorus and potassium), whereas manganese, which is a limiting factor, increased by 4-fold compared with the control. The results indicated that the addition of mulch from branches can be used to maintain a high soil quality in the third year of decomposition.

Fast growing and low-density species can be modified by various thermo-hydro-mechanical (THM) treatments. Wood densification is one of the promising techniques for broadening the application of these species. This study focuses on the use of a high-capacity continuous pressing technique that considerably increases the density in the region beneath the surface of poplar wood. Prior to densification at 185 °C, a softening stage was implemented, with water spraying followed by heating at a temperature of 205 °C to 235 °C. The density profile, set-recovery, and morphology of the densified surface were investigated. Densitometry revealed that an M-shaped density profile was created through the thickness, with a peak density of approximately 700 kg/m3 close to the surfaces. The set-recovery after three wetting-drying cycles was 44%, which revealed that partial stress relaxation occurred during the densification. Scanning electron microscopy (SEM) confirmed that both sides of the wood were successfully densified and that after the wetting-drying cycles, the deformed cells did not completely recover.

Corrugating medium was made from the solid waste of bamboo paper sludge and old corrugated container (OCC) pulp. The medium also incorporated additions of anion polyacrylamide as a retention agent and cationic starch as a strengthening agent. The estimated molecular mass of anion polyacrylamide, the addition level of anionic polyacrylamide, and the addition level of cationic starch were optimally designed using single-factor analysis. On this premise, the optimum addition level of the solid waste of bamboo paper sludge was found. The best process conditions for the corrugating medium included a base weight of 120 g/m-2, 10 wt.% bamboo paper sludge solid waste, 0.3 wt.% APAM (Estimated molecular mass of 600 × 104 Daltons), and 1.5 wt.% cationic starch. The apparent density, breaking length, and ring crush index were 0.53 g/cm-3, 2.51 km, and 7.48 N/mg-1, respectively, under the best process conditions. This finding could help satisfy the demand for materials used for making the corrugating medium and could support the full utilization of the solid waste of bamboo paper sludge to achieve higher value.

The main compositional characteristics of rapeseed hulls (RH) and sunflower shells (SS) were examined in terms of non-cellulosic components. The non-sugar fractions were analyzed by solid nuclear magnetic resonance (NMR) and pyrolysis-gas-chromatography/mass spectrometry (Pyr-GC-MS). Unlike SS, RH is a non-lignified biomass. The presence of large amounts of catechol and cresol suggested the presence of phytomelanin in both materials. Sugars accounted for 60% of RH and 45% of SS. Pectic compounds were extracted from the holocellulose of RH with ammonium oxalate or with citric acid, with 17% and 31% yield, respectively. A glucuronoxylan was isolated from the holocellulose of SS in basic conditions with 16% yield.