Improved surface properties of CTMP fibers with enzymatic pretreatment of wood chips prior to refining

Surface properties of chemithermomechanical pulp (CTMP) fibers produced from enzymatically pretreated eucalyptus wood chips prior to refining were investigated by Field Emission Scanning Electron Microscope (FE-SEM), Transmission Electron Microscope (TEM) and X-ray Photoelectron Spectroscopy (XPS). The results showed that in a traditional CTMP refining process most fiber disruptions occur in the middle lamella (ML) leaving behind a significant amount of hydrophobic materials on the resulting fiber surface. However, in a Bio-CTMP refining process, fiber fractures preferentially take place in the primary (P) and secondary 1 (S1) layers or the S1 and secondary 2 (S2) layers, which results in more fibrillation being generated in the subsequent refining thus improving inter-fiber bonding strength and paper strength. XPS chemical composition analysis together with pulp physical strength property showed that the surfaces of Bio-CTMP fibers become enriched with a greater proportion of carbohydrates in comparison with CTMP fiber surface, which supports FE-SEM and TEM observations.     

Monitoring the polymerization process of polypyrrole films by thermogravimetric and X-ray analysis

Bio-composite fibers were developed from wood pulp and polypropylene (PP) by an extrusion process. The thermo-physical and mechanical properties of wood pulp-PP composite fibers, neat PP and wood pulp were studied using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The thermal stability of bio-composite fibers was found to be significantly higher than pure wood pulp. An understanding into the melting behaviour of the composite system was obtained which would assist in selecting a suitable temperature profile for the extruder during processing. The visco-elastic properties of bio-composite fibers were also revealed from the study. The generated bio-composite fibers were also characterized using Fourier transform infrared spectroscopy (FTIR) to understand the nature of chemical interaction between wood pulp reinforcement and PP matrix. The use of maleated polypropylene (MAPP) as a compatibilizer was investigated in relation to the fiber microstructure. Changes in absorption peaks were observed in FTIR spectra of bio-composite fibers as compared to the pure wood pulp which indicated possible chemical linkages between the fiber and polymer matrix.     

The potential in bioethanol production from waste fiber sludges in pulp mill-based biorefineries

Industrial production of bioethanol from fibers that are unusable for pulp production in pulp mills offers an approach to product diversification and more efficient exploitation of the raw material. In an attempt to utilize fibers flowing to the biological waste treatment, selected fiber sludges from three different pulp mills were collected, chemically analyzed, enzymatically hydrolyzed, and fermented for bioethanol production. Another aim was to produce solid residues with higher heat values than those of the original fiber sludges to gain a better fuel for combustion. The glucan content ranged between 32 and 66% of the dry matter. The lignin content varied considerably (1-25%), as did the content of wood extractives (0.2-5.8%). Hydrolysates obtained using enzymatic hydrolysis were found to be readily fermentable using Saccharomyces cerevisiae. Hydrolysis resulted in improved heat values compared with corresponding untreated fiber sludges. Oligomeric xylan fragments in the solid residue obtained after enzymatic hydrolysis were identified using matrix-assisted laser desorption ionization-time of flight and their potential as a new product of a pulp mill-based biorefinery is discussed.     

The improvement in interfacial shear strength of wood fiber/epoxy composite by sizing with epoxy sizing agent containing MWCNTs

This paper discloses a feasible and high efficient strategy for wood fiber treatment to introducing multi‐wall carbon nanotubes (MWCNTs) to the surface of wood fibers for the aim of improving the interfacial shear strength of wood fiber/epoxy composite. Briefly, a layer of MWCNT was deposited on wood fibers through sizing wood fibers with epoxy sizing agent containing amine‐treated MWCNTs (MWCNT‐PEI). The surface functional groups, morphology, wettability, and interphase properties of MWCNTs on the surface of wood fiber were studied. The remarkable enhancements were achieved in interfacial shear strength of reinforced composites by dipping wood fiber in MWCNTCOOH suspension and wood fiber sizing containing MWCNT‐PEI.     

Solid-state shear pulverization as effective treatment for dispersing lignocellulose nanofibers in polypropylene composites

Lignocellulose nanofibers (LCNFs) were prepared by the wet-disk milling of wood flour and were subsequently used as a reinforcing filler for a polypropylene (PP) polymer matrix. The specific surface area and the smallest fiber width of the LCNFs were found to be 106 m²/g and 20 nm, respectively. Solid-state shear pulverization (SSSP) using a batch-type kneader was performed at a temperature lower than the PP melting point in order to improve the dispersion of the LCNFs in the PP matrix, which also contained 5 wt% maleic anhydride-grafted PP. The SSSP treatment improved LCNF dispersion; this was determined through optical and scanning electron microscopy observations. The improvement in LCNF dispersion after the SSSP treatment increased the Young’s moduli, yield strengths, and toughnesses of the resulting composites. The composites showed higher Young’s moduli and yield strengths that those of the neat PP matrix; this was true in the case of both the tensile and the bending tests. However, the impact strengths of the composites were not significantly different from that of the neat matrix. Finally, the crystallization rate of the PP matrix also increased with the increase in LCNF dispersion.     

PP-g-(MAH/St)和PP-g-MAH对聚丙烯/木粉复合材料性能的影响

在转矩流变仪中用熔融接枝法制备马来酸酐(MAH)和苯乙烯(St)接枝聚丙烯（PP）-PP-g-(MAH/St)和PP-g-MAH,将其作为聚丙烯/木粉复合材料的相容剂。 FTIR证实MAH和St单体与PP发生接枝反应。 用SEM和DSC等手段考察两种相容剂对PP/木粉复合材料微观形貌和结晶性能的影响,探索了各种PP/木粉复合材料加工和力学性能不同的内在原因。 SEM显示,PP-g-(MAH/St)改性木粉比PP-g-MAH改性木粉在PP基体中分散性更佳,木粉与PP的界面更加模糊,相容性进一步改善。 DSC结果表明,PP-g-(MAH/St)改性体系可增强木粉对PP的异相成核作用,提高结晶温度和结晶度。 复合材料的加工和力学性能测试结果表明,PP-g-(MAH/St)改性效果明显优于PP-g-MAH。 复合材料的熔体质量流动速率随相容剂用量的增加而逐步下降,PP-g-(MAH/St)改性体系拉伸强度和弯曲强度却逐步上升,并在相容剂用量为4.8 g/100 g PP时达到极值。 此时其拉伸强度达40.62 MPa,分别是未改性体系和PP-g-MAH改性体系的1.29和1.17倍;其弯曲强度达45.72 MPa,分别是未改性体系和PP-g-MAH改性体系的1.23和1.59倍;而无缺口冲击强度却在相容剂用量为3.6 g/100 g PP时达到极值13.35 kJ/m2,分别是未改性体系和PP-g-MAH改性体系的1.62倍和1.42倍。     

硬脂酸/异氰酸酯摩尔比对聚丙烯/木粉复合材料性能的影响

用甲苯-2,4-二异氰酸酯（TDI）和硬脂酸（SA）复合改性木粉,在双螺杆挤出机中制备了聚丙烯（PP）基的木塑复合材料（WPC）,研究了SA/TDI摩尔比对木粉表面性能、复合材料力学性能和加工性能的影响。 结果表明,随着SA/TDI摩尔比的增大,改性木粉的表面张力逐渐减小,与PP的界面张力先减小后增大;与未改性的WPC相比,SA/TDI复合改性剂对WPC的拉伸强度、弯曲强度、缺口冲击强度影响不明显,但对无缺口冲击强度提升较大;当SA/TDI摩尔比为1.07时,复合材料的无缺口冲击强度和熔体质量流动速率分别达到9.74 kJ/m2和13.12 g/10 min,分别比未改性WPC提高了77%和22%。     

Surface properties of CTMP fibers modified with xylans

This study investigated the effect of modification with xylan on the surface properties of chemithermomechanical pulp (CTMP) from spruce. The surface modifications were carried out by controlled sorption of birch xylan from solution at high temperature and high pH. Several different analysis techniques were used to study the effects on fiber surface composition and morphology. The ESCA technique showed a reduction in the amount of carbons not bound to oxygen in the C(1s) resolved peak after treatment. Variations in surface topography between untreated samples and samples with xylan were studied with SEM and AFM in the tapping mode. Scanning electron micrographs show micrometersized xylan particle structures spread over the fiber surfaces. AFM images reveal differences in the fine structure of fibers. The modified fibers exhibit a nanometersized, bumplike morphology not seen on the untreated fibers. The wetting properties of single fibers were determined with the Wilhelmy plate technique and the water sorption of CTMP paper sheets was studied using a dynamic contactangle tester. The surface modification of CTMP with xylan significantly decreased the advancing contact angle of single fibers and also improved the water sorption of sheets.     

Recycled PP/EPDM/talc reinforced with bamboo fiber: Assessment of fiber and compatibilizer content on properties using factorial design

Thermoplastic composites reinforced with natural fibers have attracted the attention of many researchers, not only for environmental concerns, but also for economic reasons, recyclability, ease of processing, etc. One promising application is in the automotive industry due to their low cost and weight. This industry is increasingly pressured to produce vehicles that consume less fuel and are less polluting. Therefore, plastics reinforced with fibers are required to produce lighter parts to replace the much more abrasive glass fiber and mineral filled composites. One of the most widely used polymers in the automotive sector for manufacturing interior and exterior vehicle components is talc filled EPDM (ethylene-propylene-diene monomer) toughened polypropylene (PP). In this context, the aim of this study was to assess mechanical and thermal properties of bamboo fiber reinforced recycled talc filled PP/EPDM composites compatibilized with maleic anhydride grafted polypropylene (PP-g-MAH). Composites were prepared, according to a 2² factorial design with center point, in a Haake twin screw extruder with subsequent injection molding. Injected specimens were subjected to tensile, flexural, impact and fatigue testing. Morphological analyses were performed by scanning electron microscopy (SEM), and thermal analyses by thermogravimetry (TGA) and differential scanning calorimetry (DSC). Addition of bamboo fiber significantly increased tensile and bending strength, modulus and fatigue life, and decreased elongation at break and impact strength. On the other hand, addition of the compatibilizer had a positive effect only on tensile and flexural strength, and fatigue life whereas the effect was negative on elongation at break and impact strength. The addition of fiber and compatibilizer did not appreciably affect the matrix melting temperature, but slightly increased crystallization temperature and in some cases the degree of crystallinity.     

Effect of long fiber thermoplastic extrusion process on fiber dispersion and mechanical properties of viscose fiber/polypropylene composites

Viscose fiber reinforced polypropylene (PP/VF) composites were manufactured using long fiber thermoplastic (LFT) extrusion techniques with two different methods namely LFT‐l and LFT‐2. The compatibilizer [maleated polypropylene (MAPP)] and dispersing agent [stearic acid (SA)] were added to the PP/VF in order to improve the fiber dispersion and interfacial adhesion. The PP/VF composites manufactured using LFT‐2 showed better fiber dispersion with higher tensile and flexural properties compared to the composites manufactured using LFT‐1 method. Similarly, the impact strength and toughness of the LET‐2 composites showed an improvement of 36 and 20% than LFT‐1 whereas the average fiber length of composites was decreased from 6.9 mm to 4.4 mm because of the increase in shear energy as a result of residence time. Further, the addition of SA and MAPP to LFT‐2 process has significantly improved the fiber dispersion and mechanical performance. The fiber dispersion and fracture behavior of the LFT‐1 and LFT‐2 composites were studied using scanning electron microscopy analysis. The Fourier transformation infrared spectra were also studied to ascertain the existence of type of interfacial bonds. Copyright © 2015 John Wiley & Sons, Ltd.     

Qualitative evaluation of microfibrillated cellulose using the crill method and some aspects of microscopy

It has been a challenge to develop rapid online characterisation techniques for nanocellulose given the fibrillar structure of the nanoparticles. The crill optical analyser uses optical response signals in the infrared (IR) and ultraviolet (UV) wavelength ranges to evaluate the particle size properties of micro/nanofibrillar cellulosic materials. In this work, the crill analyser was used to measure the projected areas of UV and IR light sources by measuring the light blocked by nanocellulosic particles. This work uses the crill methodology as a new, simplified technique to characterise the particle size distribution of nanocellulosic material based on chemi-thermomechanical pulp (CTMP), thermomechanical pulp (TMP), and sulphite pulp (SP). In the first part, hydrogen peroxide pretreatment of CTMP and TMP in a wing mill refiner followed by high-pressure homogenisation to produce microfibrillated cellulose (MFC) was evaluated using the crill method. In the second part, TEMPO oxidation of CTMP and SP combined with high-shear homogenisation to produce MFC was studied using the crill method. With 4 % hydrogen peroxide pretreatment, the crill values of the unhomogenised samples were 218 and 214 for the TMP and CTMP, respectively, improving to 234 and 229 after 18 homogenisation passes. The results of the TEMPO method indicated that, for the 5 mmol NaClO SP-MFC, the crill value was 108 units at 0 min and 355 units after 90 min of treatment, a 228 % improvement. The CTMP and TMP fibres and the MFC were freeze dried and fibrillar structure of the fibres and microfibrils was visualised using scanning electron and transmission electron microscopy.     

Thermogravimetric analysis of rice husk flour filled thermoplastic polymer composites

The thermal degradation and thermal stability of rice husk flour (RHF) filled polypropylene (PP) and high-density polyethylene (HDPE) composites in a nitrogen atmosphere were studied using thermogravimetric analysis. The thermal stability of pure PP and HDPE was found to be higher than that of wood flour (WF) and RHF. As the content of RHF increased, the thermal stability of the composites decreased and the ash content increased. The activation energy of the RHF filled PP composites increased slowly in the initial stage until α=0.3 (30% of thermal degradation region) and thereafter remained almost constant, whereas that of the RHF filled HDPE composites decreased at between 30 and 40 mass% of RHF content. The activation energy of the composites was found to depend on the dispersion and interfacial adhesion of RHF in the PP and HDPE matrix polymers. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of wood flour content on surface properties of 3D printed materials produced from wood flour/PLA filament

Amount of wood flour was gradually increased from 0 to 50?wt% in the production of polylactic acid (PLA) based filaments with 1.75?mm diameter using twin screw extruder. Surface roughness and wettability were measured of the specimens. Surface roughness of the specimens significantly increased with incorporation of wood flour into PLA filament. Wettability of the specimens significantly decreased with increasing wood flour content. This was mainly attributed to the higher surface free energy of PLA than the beech wood. Contact angle values of the 3D printed wood/PLA specimens having wood flour content up to 30?wt% were less than 90°.     

Surface properties of lignocellulosic fibers bearing carboxylic groups

Fibers with various amounts of carboxylic acid functionalities as determined with FTIR and conductometric titration were prepared by chemical modification of high bleached kraft pulp (CP) and chemical thermomechanical pulp (CTMP) with succinic anhydride. The degree of the modification was dependent on reaction time and the type of fiber used. The modification levelled off after 15h of reaction, and this effect was similar for both fiber substrates. The amount of carboxylic acid attached to CTMP, determined by weight gain, was however less than half of the amount of carboxylic moieties introduced to CP fibers at any reaction time. ESCA characterization of the succinylated fibers indicates that the carboxylic acid functionalities are predominantly introduced at the fiber surface. The wettability in water, measured as contact angle, of the succinylated CTMP fibers was significantly improved by the modification, whereas the wettability of CP fibers was slightly decreased. The differences in wettability are caused by the dispersive and polar characteristics of succinic acid attached to the fiber surface and its interaction with the fiber surface. The character of the linkage group in the anhydride used for modification as well as the composition of the cellulose fiber surface are suggested to play a crucial role in the surface energy of the modified fibers and hence their wetting properties.     

Swelling of compressed cellulose fiber webs in organic liquids

Maximum liquid-holding capacities of various compressed fibers in water and in a series of various organic liquids have been investigated. The maximum liquid-holding capacity versus bulk density relationships gave polynomial curves, generally with a peak. Good relative correlations for cellulose, compressed fiber pellets and wood were found for the series of liquids tested. In general, liquids that swelled wood to a low to medium range (up to 6%) did not swell appreciably -cellulose and sulfite pulp, while good to excellent wood-swelling agents swelled all the fibers very significantly. It was also found that the hydrogen-bonding parameter of the swelling liquid was the most important factor. The swelling rate of various compressed fiber systems in organic liquids was dramatically increased by raising the temperature. Activation energies and molar volume of the swelling liquid were linearly correlated.     

The influence of surface treatment on the tensile and tribological properties of wood fiber‐reinforced polyimide composite

In this paper, the effect of coupling agent surface treatment of wood fiber on tensile and tribological property of wood fiber‐reinforced thermoplastic polyimide (PI) composites was experimentally investigated. Experimental results revealed that coupling agent surface treatment could effectively improve the interfacial adhesion between wood fiber and PI matrix. Compared with the untreated wood fiber/PI composite, the coupling agent‐treated composite had better interfacial adhesion. The fracture surfaces and worn surface of samples were investigated by scanning electronic microscopy to analyze the effects of surface treatment methods.     

Variations in fiber length within a first-thinning Scots pine (Pinus sylvestris) stem

Variations in average fiber length and fiber length distribution both in the longitudinal and horizontal directions of a first-thinning Scots pine (Pinus sylvestris) stem and between six stems of similar age (26–30 years) and height (10.7–12.8 m) were studied. As a general trend, fiber length increased from the pith (0.8–1.3 mm) to the outer part of the stem (1.9–2.9 mm) maximizing at the relative stem height of 20–40%. Variations in fiber length between stems were smaller than those within a stem. The average fiber length of different stems of the same age (28 years) or diameter at breast height (11 cm) depended typically on wood growth rate. Finally, kraft cooking experiments on different parts of the stem (i.e., butt and top as well as inner and outer parts of the stem) indicated clear differences in their pulp properties. It was concluded that due to the acceptable properties of these pulps, first-thinning wood material as such or after the suitable fractionation may offer a potential source of fiber for a variety of different purposes.     

NMR cryoporometry to study the fiber wall structure and the effect of drying

NMR cryoporometry has been used for investigating the porosity changes of bleached wood pulp upon drying. This NMR method follows the same principles as thermoporosimetry, which has been used for the same purpose during the last decade and makes it possible to investigate porous material in the water-swollen state. In this study bleached softwood kraft pulp was exposed to a series of drying procedures where the decrease in porosity within the fiber cell wall could be characterized for pore radii below 100 nm. This decrease in porosity is called hornification, which is an irreversible collapse of the fiber wall structure during drying and results in decreased uptake of water and reduced swelling of the fiber upon rewetting. Our results have been compared to the traditionally used water retention value (WRV) and correlates well with these. Furthermore, this NMR method could show the reduction of hornification when adsorbing the hemicellulose glucuronoxylan to the fiber.     

The manufacture of three types of organic butternut squash flour and their impact on the development of some oat gluten-free products

Butternut squash is common fruit world-wide, considered as a rich source of nutrients and bioactive compound and has promising food industrial application. Local organic butternut squash is pyriform in shape, with a semi-grooved shell, copper skin, and yellowish-orange flesh. The fruits weigh an average of 884.11 g and have a pulp yield of 82.98% and a peel yield of 12.36%.This study aims to manufacture three types of organic butternut squash flour (peel, unpeeled pulp, and peeled pulp) and utilize them as a substitute for oat flour at various ratios (5, 10, and 15%) to prepare gluten-free muffins, cookies, and waffles. A sensory evaluation of prepared products was carried out. The nutritional value, color, mineral content, phytochemicals, microstructure, functional, and physicochemical properties of butternut squash flours and top rated oatmeal products were determined. According to the findings, organic butternut squash flours were low-calorie flours with high protein, fiber, minerals, beta-carotene, and antioxidant content. For all sensory assessment parameters, muffins with a replacement ratio of 15%, cookies with 10%, and waffles with 5% pulp flour were considered the most acceptable. The protein, fiber, beta-carotene, and mineral contents of optimised gluten-free products increased significantly compared with control samples. The current study will help flour suppliers and food scientists better understand and promote the use of butternut squash flour. Gluten-free prepared products can meet the nutritional needs of celiac disease patients.     

Interfacial studies on the ozone and air‐oxidation‐modified carbon fiber reinforced PEEK composites

In this work, ozone modification method and air‐oxidationwere used for the surface treatment of polyacrylonitrile(PAN)‐based carbon fiber. The surface characteristics of carbon fibers were characterized by XPS. The interfacial properties of carbon fiber‐reinforced (polyetheretherketone) PEEK (CF/PEEK) composites were investigated by means of the single fiber pull‐out tests. As a result, it was found that IFSS (interfacial shear strength) values of the composites with ozone‐treated carbon fiber are increased by 60% compared to that without treatment. XPS results show that ozone treatment increases the amount of carboxyl groups on carbon fiber surface, thus the interfacial adhesion between carbon fiber and PEEK matrix is effectively promoted. The effect of surface treatment of carbon fibers on the tribological properties of CF/PEEKcomposites was comparativelyinvestigated. Experimental results revealed that surface treatment can effectively improve the interfacial adhesion between carbon fiber and PEEK matrix. Thus the wear resistance was significantly improved. Copyright © 2009 John Wiley & Sons, Ltd.