Volume 11 Issue 4

Variation in microfibril angle (MFA) in the S2 of the tangent cell walls of resonance and non-resonance spruce wood (Picea abies [L.] Karst.) used in the manufacture of musical instruments was studied. MFA was measured directly after preliminary visualisation of microfibrils in the cell walls. In the tested samples the position of an annual ring in the samples had no significant influence on the MFA. In the resonance wood, MFA values were between two and three times smaller than in the non-resonance wood. In the resonance wood, the differences in the MFA between earlywood and latewood were smaller, and the MFA fluctuations were also smaller.

Processing was studied for air-laid nonwovens from natural hemp and flax fibres using SPIKE® air-laying technology (Formfiber Denmark ApS Company). The process of web-formation and the properties of the fibre-webs before needle-punching and reinforced fibre-mats were evaluated. The settings of the air-laying machine were found to influence the web-formation process and nonwoven properties. In order to monitor web-formation processes and evaluate the fibre-web or fibre-mat quality, several machine settings were defined that enhanced the productivity of the machine or favoured fabrication of nonwovens with high density or great tensile properties.

Pyrolysis processes of typical biomass, such as corn stalk and birch chips, were investigated by thermogravimetric analysis (TGA). The apparent activation energy and pre-exponential factor were calculated with the adoption of the improved Coats-Redfern integral method, 46 types of common mechanism functions, and the least square and iterative methods. By applying basic parameters of biomass pyrolysis, a reaction rate constant, activation entropy and activation enthalpy, activation Gibbs free energy, and the steric-hindrance factor were all calculated. Results showed that biomass pyrolysis can be divided into two primary reaction zones (Event 3 and Event 4). Event 3 is focused by cellulose and hemicellulose. Event 4 is oriented by lignin and cellulose. The thermogravimetric curves of the two biomass types under carbon dioxide and nitrogen atmospheres were roughly similar. The reaction mechanism function is 1 – alpha. It is possible to use activation entropy to represent the pre-exponential factor and to use the steric hindrance factor to predict the reaction rate.

To improve the mechanical properties of ultra-low density plant fiber composite (ULD_PFC), a suitable beating process to improve the fibrillation of cellulose fibers and maintain their length was investigated. The physical properties of cellulose fibers and papers, surface chemical bonds, and internal bond strength (IB) of ULD_PFCs were analyzed. The results showed that the beating degrees, degree of fibrillation, and fiber fines increased with the decreasing of beating gap, except for the fiber weight-average length, width, kink index, and curl index. The tensile index and burst index of paper showed an increasing trend with an increase in beating degree, while the tear index showed a decreasing trend. FTIR results showed that intermolecular and intramolecular hydrogen bonds in ULDF were broken. A suitable beating gap of 30 μm with a beating degree of 35 °SR was obtained. The corresponding IB was 50.9 kPa, which represented an increase of 73.1% over fibers with a beating degree of 13 °SR.

The removal of lignin from a high-temperature chemi-thermomechanical pulp (HT-CTMP) using a switchable ionic liquid prepared from an organic superbase (1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU)), monoethanol amine (MEA), and SO2 was investigated. The objective was to measure the fibre properties before and after removal of the lignin to analyse the contributions from lignin in the HT-CTMP fibre to the tensile properties. It was found that the fibre displacement at break – measured in zero span, which is related to fibre strain at break – was not influenced by the lignin removal in this ionic liquid system when tested dry. There was a small increase in displacement at break and a reduction in tensile strength at zero span when tested after rewetting. At short span, the displacement at break decreased slightly when lignin was removed, while tensile strength was almost unaffected when tested dry. Under rewetted conditions, the displacement at break increased and tensile strength decreased after lignin removal. Nevertheless, no dramatic differences in the pulp properties could be observed. Under the experimental conditions, treatment with the ionic liquid reduced the lignin content from 37.4 to 15.5 wt%.

The pyrolytic product vapor of Helianthus annuus stems was analyzed by Pyrolysis–gas chromatography–mass spectrometry (Py-GC/MS) using the internal standard (ISTD) method with different pyrolysis temperatures and times. 1,3,5-tri-tert-butylbenzene (TTBB) was found to be the best ISTD chemical in this study. Scanning electron microscopy (SEM) revealed that, for the solid-state product, the pores and mesh structure gradually increased along with the pyrolysis temperatures and time. Sintering and porous destruction were observed at a lower pyrolysis temperature (600 °C) with longer time (0.5 min). The pyrolysis vapors contained small gas molecules such as CO2 as well as complex organic compounds, mainly alcohols, esters, acids, aldehydes, ketones, aromatic compounds, etc. In these products, aldehyde, ketone, and aromatic compounds were the main biochemicals; the appropriate pyrolysis temperature to produce aldehydes and ketones was 700 °C, and 600 °C was suitable for aromatic compounds. The regularity of the distribution of products and pyrolytic conditions was explored through eight representative compounds. The relationship between the product contents and pyrolysis conditions were complex for Helianthus annuus stems, but partial least squares discriminant analysis (PLS-DA) methods were a powerful tool for screening biochemicals whose absolute contents were sensitive to the pyrolysis conditions.

Bionanocomposites from polylactic acid (PLA) filled with unmodified nanocrystalline cellulose from TEMPO-oxidized oil palm empty fruit bunch (OPEFB-NCC) at various loading levels were fabricated using the solvent casting technique. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), attenuated total reflectance Fourier transform infrared spectroscopy (ATF-FTIR), differential scanning calorimetry (DSC), and mechanical analyses were used to characterize the bionanocomposite films. FTIR suggested that the incorporation of the OPEFB-NCC was based on physical interaction. The melting temperature did not change markedly except at higher OPEFB-NCC additions, while the crystallization temperature shifted to lower temperatures and crystallinity increased with increasing OPEFB-NCC content.The SEM of cryo-fractured films indicated a rather weak compatibility between the OPEFB-NCC and PLA, resulting in the decrease of both the modulus and the tensile strength of the bionanocomposite.