Effects of chemical composition,mild alkaline pretreatment and particle size on mechanical,thermal, and structural properties of binderless lignocellulosic biopolymers prepared by hot-pressing raw microfibrillated Phoenix dactylifera and Cocos nucifera fibers and leaves

We developed value-added, high-strength lignocellulosic biopolymers by exploiting high-lignin biomass waste of palms. Lignocellulosic biopolymers were prepared by hot-pressing microfibrillated raw and alkaline pre-treated date and coconut fibers and leaves powders consisting of (≤53–≤106 μm) particles in the range 140–180 °C. The obtained biopolymers were subjected to three-point bending strength, water resistance, structural morphology (SEM), thermal stability (TGA/DTG), spectroscopy (FTIR), and crystallinity (XRD) analyses. Findings showed that raw fiber-based and alkaline-pretreated biopolymers exhibited bending strength, water resistance, and thermal stability (~200 °C) superior to those of leaf-based biopolymers. Furthermore, lignocellulosic biopolymers prepared from smaller particles showed enhanced bending and thermal properties, compared to those prepared from large particles. By mechanical and thermal properties, the optimum results were observed for biopolymers pre-treated with 1 wt% NaOH, except for coconut leaf-based biopolymers. Results were correlated to chemical composition and particle size of milled lignocellulosic biomass, allowing for efficient lignin condensation.     

Preparation and characterization of biodegradable sugarcane bagasse nano reinforcement for polymer composites using ball milling operation

The present work includes the processing and characterization of nano-based natural reinforcement for polymer composite materials. Sugarcane bagasse has been collected and the fibers were extracted using manual striping process. Undesirable materials present in the extracted fibers were removed by 1% NaOH-based chemical treatment. The macrofibers were reduced to nano scale by using high-energy ball milling process. Nanoparticles from bagasse fibers were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The degree of crystallinity of nano bagasse is 55.2% and it was reported by using XRD. A FTIR spectrum confirms the presence of cellulose functional groups in nano bagasse. The nano bagasse dimensions and morphology were investigated using SEM. The average length and diameter of the nano bagasse is 51.2 and 46.1 nm, respectively. Thermal stability of the nano bagasse was revealed by TGA analysis. The chemical composition of cellulose, lignin, and hemicellulose contents was also investigated.     

Extraction of cellulose and preparation of nanocellulose from sisal fibers

In this work a study on the feasibility of extracting cellulose from sisal fiber, by means of two different procedures was carried out. These processes included usual chemical procedures such as acid hydrolysis, chlorination, alkaline extraction, and bleaching. The final products were characterized by means of Thermogravimetric Analysis (TGA), Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and Scanning Electronic Microscopy (SEM). The extraction procedures that were used led to purified cellulose. Advantages and disadvantages of both procedures were also analyzed. Finally, nanocellulose was produced by the acid hydrolysis of obtained cellulose and characterized by Atomic Force Microscopy (AFM).     

Crystalline properties and decomposition kinetics of cellulose fibers in wood pulp obtained by two pulping processes

In this study two cellulose fibers, Eucalyptus grandis (CEG) and Pinus taeda (CPT), obtained through the kraft and sulfite pulping processes, respectively, were characterized. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were carried out. From the XRD analysis the interplanar distance, crystallite size and crystallinity index were calculated and the degradation kinetics parameters were determined by TGA at heating rates of 5, 10, 20 and 40 °C min⁻¹ using the Avrami, Flynn-Wall-Ozawa (FWO) and Criado methods. The results obtained by FTIR showed that the composition of the fibers is similar, while from the XRD analysis slight differences in the crystallinity were observed. The thermogravimetric analysis showed higher thermal stability for CPT than CEG while the values for the activation energy (E_a) were higher for CEG than CPT. The results obtained by Avrami and Criado methods showed that the degradation mechanism in the CEG samples involves a diffusion process while in the case of CPT the degradation process is a phase boundary controlled reaction. The degradation mechanisms demonstrated that the difference between thermal stability and E_a may be due to differences in the type of crystalline structure of the samples obtained through the two pulping processes.     

Optical and electromagnetic characteristics of clay�Ciron oxide nanocomposites

Fe-pillared bentonite clay-based nanoadsorbent was synthesized by the thermal aging technique. The characteristics of the nanocomposite were detected by X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), thermal gravimetric analysis (TGA), scanning electron microscope (SEM), electron dispersive X-ray spectrometer (EDX), reflectance spectrophotometer (RS), and electromagnetic transition instrument (ETI). The TGA result demonstrated that the Fe particles generated on the clay surface can significantly improve the thermal stability of clay particles. The SEM and EDX results showed the presence of chemical elements of Fe, Al, and Si on the surface of clay. In this research, the successful synthesis of Fe-pillared clay nanocomposite can be concluded from the FTIR spectra.     

有机蒙脱土改性松香乳液增强废纸纤维的结构与性能

采用逆转法制备了有机蒙脱土(OMMT)改性松香乳液,利用X-射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、热分析(TGA)、差示扫描量热(DSC)和扫描电镜(SEM)等分别对有机改性蒙脱土(OMMT)及松香乳液的结构进行了表征,同时研究了OMMT改性松香乳液对废纸纤维施胶后的耐水性能和力学性能的影响。结果表明,OMMT在试验中对松香乳液的玻璃化温度(Tg)没有产生明显的影响,但显著地提高了施胶后的废纸纤维的耐水性和力学性能。     

Thermal behavior and the compensation effect of vegetal fibers

The thermal degradation behavior and the Arrhenius parameter of curaua, kenaf, and jute vegetal fibers were studied using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and thermogravimetry analysis. XRD showed that the crystallite sizes in the (200) plane were in the order: curaua < jute < kenaf, and similar results were obtained for basal spacing. FTIR spectroscopy corroborated the XRD results. The thermal behavior of the fibers was analyzed by identifying the cellulose and hemicellulose content using independent parallel first-order models. The results were not very consistent with the kinetic degradation models of Kissinger, Friedman, and Flynn–Wall–Ozawa (taking into account the standard errors), which were used to determine the apparent activation energy of the fibers. In addition, the frequency factor (pre-exponential parameter) was observed to be independent of the heating rate. The fibers exhibited a compensation effect; i.e., higher apparent activation energies led to higher frequency factors. Finally, the solid-state degradation mechanism of all fibers was found to comprise diffusion and random nucleation followed by instantaneous growth of nuclei.     

Cellulose nanocrystals obtained from microcrystalline cellulose by p-toluene sulfonic acid hydrolysis,NaOH and ethylenediamine treatment

Cellulose nanocrystals (CNCs) were first isolated from microcrystalline cellulose (MCC) by p-toluene sulfonic acid (p-TsOH) hydrolysis. Cellulose II nanocrystal (CNC II) and cellulose III nanocrystal (CNC III) were then formed by swelling the obtained cellulose I nanocrystal (CNC I) in concentrated sodium hydroxide solutions and ethylenediamine (EDA) respectively. The properties of CNC I, CNC II and CNC III were subjected to comprehensive characterization by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The results indicated that CNC I, CNC II and CNC III obtained in this research had high crystallinity index and good thermal stability. The degradation temperatures of the resulted CNC I, CNC II and CNC III were 300 °C, 275 °C and 242 °C, respectively. No ester bonds were found in the resulting CNCs. CNCs prepared in this research also had large aspect ratio and high negative zeta potential.

     

共溶剂存在下N-烯丙基吡啶氯盐离子液体对纤维素的溶解性能研究

采用一步法合成N-烯丙基吡啶氯盐离子液体([APy]Cl),考察其对纤维素的溶解性能.结果发现,在120℃下对棉浆粕(聚合度(DP)=556)的溶解度可高达19.71%,但再生后聚合度为223,热降解严重.通过添加不同种类共溶剂的方法克服此缺点.结果表明,有机溶液(DMSO,DMAc,DMF或吡啶)作为[APy]Cl的共溶剂时,[APy]Cl/DMAc复合溶剂对棉浆粕的溶解效果最佳,100℃下溶解度为15.03%,再生后聚合度为403.此外降低了溶剂成本.但70℃下,溶解度仅为1.36%,溶解能力较弱.继续探讨了[AMIM]Cl作为[APy]Cl的共溶剂时对纤维素的溶解性能,结果表明,70℃下,[APy]Cl/[AMIM]Cl复合溶剂对棉浆粕的溶解度为8.78%,再生后聚合度为516.可知添加上述2种共溶剂均使[APy]Cl在低于自身熔点下形成液体并能够溶解一定量纤维素,拓宽了溶解温度区间及应用平台.对FTIR,XRD和TGA谱图分析,结果表明上述为纤维素的直接溶剂,可将其晶型由Ⅰ型转变成Ⅱ型,再生后热稳定性稍有降低.通过照片和SEM表明再生膜无色透明,结构致密.     

Effect of pyrolysis conditions on the properties of carbonaceous nanofibers obtained from freeze-dried cellulose nanofibers

Carbonaceous nanofibers (CsNFs) were produced by pyrolysis of cellulose nanofibers synthesised from wood pulp using a top-down approach. The effects of heat treatment conditions on the thermal, morphological, crystal and chemical properties of the CsNFs were investigated using TGA, SEM, XRD and FT-IR, respectively. The results showed that heat treatment conditions around the thermal decomposition temperature of cellulose greatly influence the morphology of resulting materials. Slow heating rates (1 °C/min) between 240 and 400 °C as well as prolonged isothermal heat treatment (17 h) at 240 °C were necessary to avoid destruction of the original fibrous morphology in carbonized nanofibers. On the other hand, such heat treatment had little effect on micron sized fibers. The optimized heat treatment conditions led to the release of oxygen and hydrogen from cellulose before thermal breakdown of glycosidic rings, which in turn prevented depolymerization and tar formation, resulting in the preservation of the fibrous morphology.     

Influence of homogenization and drying on the thermal stability of microfibrillated cellulose

Homogenization has been used to release microfibrils from cellulose fibres to produce microfibrillated cellulose (MFC). Oven drying, atomization or freeze-drying were used to dry MFC. Morphological differences were observed linked to the compaction of the system and the formation of microfibril agglomerates. Thermal stability of the dried MFC, checked by TGA, decreased after homogenization and drying. Char level at the end of the pyrolysis was higher than for cellulose fibres. Derivative TGA (dTGA) showed a shoulder around 250 °C for the dried MFC. Volatile degradation product detection by FTIR spectroscopy (FTIR) coupled to TGA and DSC showed that the shoulder corresponds to expected dehydration reactions of the cellulose. Increasing the contacts between microfibril(s) (bundles) and agglomerates of the freeze-dried MFC by compression promoted dehydration reactions. Homogenization and drying modified the thermal properties of the MFC. No significant influence of freeze-drying kinetics on the thermal behaviour of the MFC was observed.     

Thermal degradation of a reactive flame retardant based on cyclotriphosphazene and its blend with DGEBA epoxy resin

Hexaglycidyl cyclotriphosphazene (HGCP) was synthesized, and characterized by FTIR, ³¹P, ¹H, and ¹³C-NMR. This compound was used as a reactive flame retardant to blend with commercial epoxy resin DGEBA (Diglycidyl ether of bisphenol A). Its effect on the DGEBA decomposition pathways was characterized by studying both gas and solid phases produced during thermogravimetric analysis (TGA). The gases evolved during TGA in air were studied by means of thermogravimetry coupled with Fourier transform infrared spectroscopy (TG–FTIR), while the solid residues were analysed by FTIR and scanning electron microscopy (SEM). The results showed that HGCP presents a good dispersion in DGEBA, and the blend thermoset with 4,4′-methylene-dianiline (MDA) curing agent leads to a significant improvement of the thermal stability at elevated temperature with higher char yields compared with pure DGEBA thermoset with the same curing agent. Improvement has also been observed in the fire behaviour of blend sample.     

Extraction and Characterization of Cellulose Nanowhiskers from Balsa Wood

Summary: In this study cellulose nanowhiskers were obtained from balsa wood. For this purpose, fibers of balsa wood were exposed to hydrolysis reactions for lignin and hemicellulose digestion and acquisition of nano-scale cellulose. Transmission electron microscopy (TEM) results demonstrated that the obtained cellulose nanocrystals had average length and thickness of 176 (±68 nm) and 7.5 (±2.9 nm), respectively. Infrared spectroscopy (FTIR) and wide angle x-ray diffraction (WAXD) showed that the process for extracting the nanowhiskers digested nearly all the lignin and hemicellulose from the balsa fiber and still preserved the aspect ratio and crystallinity satisfactory enough for future application as nanofillers in polymer nanocomposites. The thermogravimetric analysis (TGA) showed that the onset temperature of thermal degradation of the cellulose nanocrystals (226 °C) was higher than the onset temperature of the balsa fiber (215 °C), allowing its use in molding processes with polymers melts.     

Comparison of different methods for determining the imidization degree of polyimide fibers

In this study, polyimide fibers at different stages of imidization were characterized by TGA, DSC, and FTIR. The imidization degree(ID) calculated by TGA was based on the weight loss of each sample, which was caused by the imidization of residual amic acid groups. The results of TGA showed good regularity with the thermal treatment temperature of the PI fibers. For DSC, the ID was calculated based on the area of endothermal peak of each sample. Compared with TGA, DSC showed a relatively higher value because the endothermal peak was reduced by the exothermic re-formation of polyamic acid which may be partially degraded during thermal treatment. The IDs obtained by the FTIR spectra generally showed poorer regularities than those obtained by both TGA and DSC, especially for the results calculated using the 730 cm-1 band. Based on the 1350 cm-1 band, the obtained IDs showed better agreement with the TGA or DSC results. The results obtained by these three methods were compared and analyzed. The ID obtained by TGA showed much more reliability among these three methods.     

Morphology and thermal properties of polyhedral oligomeric silsesquioxane/polybutadiene nanocomposites prepared by anionic polymerization

The morphology and thermal properties of Allylisobutyl Polyhedral Oligomeric Silsesquioxane (POSS)/Polybutadiene (PB) nanocomposites prepared through anionic polymerization technique were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results of XRD, SEM and TEM showed that the aggregation of POSS in PB matrix occurred obviously, forming crystalline domains and the size of POSS particles increased with increasing POSS content. The DSC and TGA results indicated that the glass transition temperature (T _g) of the nanocomposites was significantly increased and the maximum degradation temperature (T _dmax) of nanocomposites was slightly increased compared with pure PB, implying an increase in thermal stability.     

Synthesis and characterization of hydroxypropyl cellulose from bacterial cellulose

Bacterial cellulose produced by Acetobacter xylinum has been reacted with propyleneoxide to synthesize hydroxypropyl cellulose(HPC) under different reaction conditions while diluted by toluene. The effects of mass ratio of bacterial cellulose to propyleneoxide, dilutability of toluene, reaction temperature(T) and time(t) were investigated by series of experiments. The degree of substitution(DS), hydroxypropyl content(A) and yield(η) were compared. The optimized product exhibited cold-water solubility and hot-water gelatinization in aqueous medium. Further study was carried out with FTIR, TGA, XRD, SEM and 13C-NMR for characterization. The water/air contact angle measurement reveals that it is a good hydrophobic material with good mechanical properties.     

Untreated and alkali treated fibers from Alfa stem: effect of alkali treatment on structural,morphological and thermal features

Alfa stems are rich in cellulose and they are an inexpensive, easily renewable source of natural fibers with the potential for polymer reinforcement. However, large amounts of non-cellulosic materials, surface impurities and low degradation temperature make natural fibers less attractive for reinforcement of polymeric materials, unless they can be modified in a proper way. In this paper, Alfa stems were treated with NaOH solution with two different concentrations (1 and 5 wt%). Raw and treated stems were crushed to obtain fibers. Stems and fibers were characterized by scanning electron microscopy (SEM) and optical microscopy, respectively. Their crystallinity index was determined by X-ray diffraction, thermal stability by thermogravimetry and structural change by FT-IR and ¹³C NMR spectroscopy. Comparison and analysis of results confirmed some thermal, structural and morphological changes of the fibers after treatment due to removal of some non-crystalline constituents from the plant. SEM showed rougher surfaces after alkalization. FT-IR and ¹³C NMR showed a gradual improvement in cellulose level by alkali treatment with increasing NaOH concentration. The crystallinity index and thermal stability of treated Alfa fibers were also found to be improved.     

Preparation and Characteration of UV-cured EA/MMT Nanocomposites Via In-Situ Polymerization

A long-chain surfactant, enzoylbenzyl-N,N-dimethyl-N-octadecylammonium bromide (BDOB) with a benzophenone group, was synthesized to modify the montmorillonites (MMT) for the preparation of nanocomposites via photo-induced polymerization. The BDOB-modified MMT was characterized by the fourier transform infrared spectrometer (FTIR), thermal gravimetric analyzer (TGA) and X-ray diffraction (XRD), and the results of XRD indicated that the intercalated structures of BDOB-modified MMT was obtained. The conversion of the bisphenol A epoxy diacrylate (EA) was quantified by the FTIR, and the results indicated that conversion increased with an increase in the amount of BDOB-modified MMT. The morphologies of the UV-cured EA/MMT nanocomposites prepared from this organically modified MMT were studied by means of XRD and TEM, and the results showed that all the samples contained an intercalated structure with partial exfoliated structure. The results of TGA and mechanical properties also indicated that the thermal and mechanical properties of UV-cured nanocomposites were significantly enhanced due to the presence of the long chain surfactant organically modified MMT.     

细菌纤维素/聚丙烯酰胺水凝胶的制备及性能表征

通过自由基聚合在细菌纤维素(BC)网络中引入聚丙烯酰胺(PAM),制备了细菌纤维素/聚丙烯酰胺(BC/PAM)复合水凝胶,并采用扫描电子显微镜(SEM)、红外光谱(IR)、热失重分析(TGA)、X射线衍射(XRD)和力学测试等手段对复合凝胶的结构和性能进行了研究.研究结果显示在复合水凝胶中,虽然PAM自身没有交联,但由...     

β-环糊精功能化石墨烯的制备及热稳定性的增强

采用2种有机合成路线制备了结构不同的环糊精共价修饰的功能化石墨烯纳米材料,并利用FTIR,XRD,TEM,SEM和TG分析等技术对产物的结构和性能进行了表征.结果表明,2种石墨烯基纳米材料由于合成策略的不同导致溶剂分散性能存在一定的差别,但它们均可均匀分散于N,N-二甲基甲酰胺(DMF)、二甲基亚砜(DMSO)和乙二醇中.同时,环糊精的引入使其热学稳定性显著提高.该材料在阻燃型复合材料等领域中具有一定的潜在应用价值.