A Study on Benzoylation and Graft Copolymerization of Lignocellulosic Cannabis indica Fiber

Present work deals with the surface modification of Cannabis indica fiber through benzoylation and graft copolymerization of acrylonitrile (AN) onto C. indica fibers under the influence of microwave radiations. The Benzoylation of C. indica fiber was carried out by treating raw fiber with varying concentrations of benzoyl chloride solution. Different reaction parameters for graft copolymerization, such as reaction time, initiator concentration, nitric acid concentration, pH and monomer concentration were optimized to get the maximum percentage of grafting (25.54%). A suitable mechanism to explain benzoylation and graft copolymerization has been also proposed. Raw C. indica fiber, graft copolymerized and benzoylated fibers were subjected to evaluation of some of their properties like swelling behavior, moisture absorbance and resistance towards chemicals. Cannabis indica fibers treated with 5% benzoyl chloride solution and AN graft copolymerized fibers have been found to show more resistant towards moisture, water and chemicals when compared with that of untreated fibers. Morphological, structural changes, thermal stability and crystallanity of raw, graft copolymerized and benzoylated fibers have also been studied by SEM, FTIR, TGA and XRD techniques. It has been observed that the crystallinity of fiber decreases but thermal stability increases on surface modification.     

Effect of Fiber Surface Treatments on Thermo-Mechanical Behavior of Poly(Lactic Acid)/Phormium Tenax Composites

In the present study, Phormium Tenax fiber reinforced PLA composites were processed by injection molding and twin screw compounding with a fiber content ranging from 10 to 30 wt%. Three surface treatment methods have been used to improve the Phormium Tenax fiber-matrix interfacial bonding that are as follows: (1) aqueous alkaline solution, (2) silane coupling agent, and (3) a combination of alkaline and silane treatment. The mechanical, thermal and morphological properties of the resulting composites were investigated. The results have shown that the moduli of surface treated fiber reinforced composites are lower than the ones obtained for untreated composites (as a consequence of the decrease in fiber modulus caused by the chemical treatments) and no significant increase in strength was observed for any of the composites compared to neat PLA. SEM micrographs of composite fractured surfaces confirmed an improvement in the interfacial strength, which was insufficient nonetheless to significantly enhance the mechanical behavior of the resulting composites. Results from thermogravimetric analysis and differential scanning calorimetry suggest that surface treatment of Phormium affects the ability of PLA to cold crystallize, and the thermal stability of the composites at the different fiber contents was reduced with introduction of alkali and silane treated Phormium fibers.     

A Two-Step Chemical Process for the Extraction of Cellulose Fiber and Pectin from Mulberry Branch Bark Efficiently

In this work, a two-step method for the extraction of pectin and cellulose fiber from mulberry branch bark, a by-product of sericultural industry, was described. The method was based on the acid extraction of pectin and subsequently alkali treatment for obtaining cellulose fibers. The obtained pectin was high purity with the total galacturonic acid content of 85.46% ± 2.76% and the degree of esterification of 71.13% ± 1.67%. The chemical composition analysis, FTIR spectroscopy, XRD and TG analysis were used to characterize the cellulose fiber at different processing stages. After the two-step chemical process, the cellulose content was increased from 37.38% in original bark to 92.60% in cellulose fiber. The FTIR spectra revealed the removal of pectin, hemicelluloses and lignin from the bark by acid extraction and alkali treatment. The XRD and TG results indicated that the obtained cellulose fibers were with the increased crystallinity and thermal stability, whose crystallinity and degradation temperature were 86.36% ± 5.56% and 355 °C, respectively. This work may provide a new approach for high utilization of mulberry branch bark.     

Chemical Treatments of Natural Fiber for Use in Natural Fiber-Reinforced Composites: A Review

Studies on the use of natural fibers as replacement to man-made fiber in fiber-reinforced composites have increased and opened up further industrial possibilities. Natural fibers have the advantages of low density, low cost, and biodegradability. However, the main disadvantages of natural fibers in composites are the poor compatibility between fiber and matrix and the relative high moisture sorption. Therefore, chemical treatments are considered in modifying the fiber surface properties. In this paper, the different chemical modifications on natural fibers for use in natural fiber-reinforced composites are reviewed. Chemical treatments including alkali, silane, acetylation, benzoylation, acrylation, maleated coupling agents, isocyanates, permanganate and others are discussed. The chemical treatment of fiber aimed at improving the adhesion between the fiber surface and the polymer matrix may not only modify the fiber surface but also increase fiber strength. Water absorption of composites is reduced and their mechanical properties are improved.     

Effects of Alkali Treatment on the Properties of Short Flax Fiber–Poly(Lactic Acid) Eco-Composites

In this study, the influence of alkali (NaOH) treatment on the mechanical, thermal and morphological properties of eco-composites of short flax fiber/poly(lactic acid) (PLA) was investigated. SEM analysis conducted on alkali treated flax fibers showed that the packed structure of the fibrils was deformed by the removal non-cellulosic materials. The fibrils were separated from each other and the surface roughness of the alkali treated flax fibers was improved. The mechanical tests indicated that the modulus of the untreated fiber/PLA composites was higher than that of PLA; on the other hand the modulus of alkali treated flax fiber/PLA was lower than PLA. Thermal properties of the PLA in the treated flax fiber composites were also affected. T_g values of treated flax fiber composites were lowered by nearly 10 °C for 10% NaOH treatment and 15 °C for 30% NaOH treatment. A bimodal melting behavior was observed for treated fiber composites different than both of neat PLA and untreated fiber composites. Furthermore, wide angle X-ray diffraction analysis showed that the crystalline structure of cellulose of flax fibers changed from cellulose-I structure to cellulose-II.     

Characterization of Biodegradable Composite Films Prepared from Blends of Poly(Vinyl Alcohol), Cornstarch,and Lignocellulosic Fiber

Several composite blends of poly(vinyl alcohol) (PVA) and lignocellulosic fibers were prepared and characterized. Cohesive and flexible cast films were obtained by blending lignocellulosic fibers derived from orange waste and PVA with or without cornstarch. Films were evaluated for their thermal stability, water permeability and biodegradation properties. Thermogravimetric analysis (TGA) indicated the suitability of formulations for melt processing, and for application as mulch films in fields at much higher temperatures. Composite films were permeable to water, but at the same time able to maintain consistency and composition upon drying. Chemical crosslinking of starch, fiber and PVA, all hydroxyl functionalized polymers, by hexamethoxymethylmelamine (HMMM) improved water resistance in films. Films generally biodegraded within 30 days in soil, achieving between 50–80% mineralization. Both starch and lignocellulosic fiber degraded much more rapidly than PVA. Interestingly, addition of fiber to formulations enhanced the PVA degradation.     

Poly(lactic acid)/Cellulose Composites Obtained from Modified Cotton Fibers by Successive Acid Hydrolysis

This work is focused on the hydrolysis of cotton fibers from waste textiles to obtain micro and nanofibers to be used as reinforcements in polymer composites. To promote their compatibility with polymeric matrix, hydrolyzed cotton fibers were surface modified with various silane compounds. Thus, these fibers were mixed with commercial poly(lactic acid) (PLA) at 5% w/w loading by melt compounding. Acid treatments caused a decrease of the crystallinity index whereas the thermal stability was significantly improved, especially for cellulose fibers hydrolyzed in two steps. Morphological analysis revealed a reduction of the fibers diameter and a decrease of their length as a consequence of the hydrolysis. NMR analysis confirmed the silanization of the fibers by reaction with the silane agent. Tensile tests revealed that silanization treatments were able to increase the composite Young’s modulus and the stress at break with respect to the neat matrix, indicating that silanization improved the polymer/fiber compatibility interfacial adhesion. The overall results demonstrated that applying suitable surface modification strategies, waste cotton textiles can be effectively recycled as fillers in polymer based composites.     

Potential of <Emphasis Type="Italic">pinhão</Emphasis> Coat as Constituents of Starch Based Films Using Modification Techniques

The potential of lignocellulosic fibers obtained by dry grinding of pinhão coat as fillers in starch filmogenic solutions for packaging applications was evaluated in this work. To improve the incorporation of this waste into the starch solutions different physical and chemical treatments were conducted. Thereafter, morphology, chemical structure, crystallinity and water absorption of the pinhão coat powders were determined. The composites were also characterized regarding their morphology, chemical structure, crystallinity, mechanical properties, water vapor permeability and hydrophilicity. Poor fiber/matrix adhesion and high water absorption of the fibers were evidenced. Consequently, water vapor permeability of composites was increased by incorporating the fibers. Moreover, mechanical properties were improved and the morphological results were used to support the water absorption differences among the powders. Regarding the food packaging applications, starch/pinhão coat composites appeared as promising materials to reach the requirements of respiring food products.     

Surface Modification of Sisal Fibers (Agave sisalana) Using Bacterial Cellulase and Methyl Methacrylate

The hydrophilic nature of cellulose fibers often results in poor compatibility with hydrophobic polymer matrices. Therefore, it becomes necessary to modify the surface of natural fiber for better binding between fiber and matrix. Chemicals are commonly used for the modification of cellulosic materials but large amount of solvents are usually involved. Microwave radiation induced grafting is one of the promising methods for the surface modification of natural fibers. In the present paper, we have reported the microwave radiations induced grafting onto sisal fibers (Agave sisalana) using methyl methacrylate monomer, which has been compared to the surface modification of sisal fibers using bacterial cellulase. The effects of these treatments on the properties of sisal fibers are discussed in the present paper. The modified fibers were characterized by scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis/differential thermal analysis techniques to determine their morphology, crystallinity and thermal stability.     

Chemically Modified Banana Fiber: Structure,Dielectrical Properties and Biodegradability

Banana fibers, as well as other lignocellulosic fibers, are constituted of cellulose, hemicellulose, lignin, pectin, wax and water soluble components. The abundance of this fiber combined with the ease of its processing is an attractive feature, which makes it a valuable substitute for synthetic fibers that are potentially toxic. In this work, the structure characterization of the banana fiber modified by alkaline treatment was studied. Some important properties of this fiber changed due to some chemical treatments, such as the crystalline fraction, dielectric behavior, metal removal (governed by solution pH) and biodegradation. Our results showed that treated banana fiber is a low cost alternative for metal removal in aqueous industry effluents. Thus, for regions with low resources, the biosorbents are an alternative to diminish the impact of pollution caused by local industries, besides being a biodegradable product.     

Effect of Coconut, Sisal and Jute Fibers on the Properties of Starch/Gluten/Glycerol Matrix

Coconut, sisal and jute fibers were added as reinforcement materials in a biodegradable polymer matrix comprised of starch/gluten/glycerol. The content of fibers used in the composites varied from 5% to 30% by weight of the total polymers (starch and gluten). Materials were processed in a Haake torque rheometer (120 °C, 50 rpm) for 6 min. The mixtures obtained were molded by heat compression and further characterized. Addition of lignocellulosic fibers in the matrix decreased the water absorption at equilibrium. The diffusion coefficient decreased sharply around 5% fiber concentration, and further fiber additions caused only small variations. The thermogravimetric (TG) analysis revealed improved thermal stability of matrix upon addition of fibers. The Young’s modulus and ultimate tensile strength increased with fiber content in the matrix. The storage modulus increased with increasing fiber content, whereas tanδ curves decreased, confirming the reinforcing effect of the fibers. Morphology of the composites analyzed under the scanning electron microscope (SEM) exhibited good interfacial adhesion between the matrix and the added fibers. Matrix degraded rapidly in compost, and addition of increased amounts of coconut fiber in the matrix caused a slowdown the biodegradability of the matrix. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may be suitable.     

Fungal-modification of Natural Fibers: A Novel Method of Treating Natural Fibers for Composite Reinforcement

Growing interest in green products has provided fresh impetus to the research in the field of renewable materials. Plant fibers are not only renewable but also light in weight and low in cost. Polymer composites manufactured using them find applications in diverse fields such as automobiles, housing, and furniture. However, their hydrophilic nature and inadequate adhesion with matrix limits their use in high performance applications. In this study, a novel method for improving adhesion characteristics of natural fibers has been developed. This method is carried out by treating hemp fibers with a fungus: Ophiostoma ulmi, obtained from elm tree infected with Dutch elm disease. Treated fibers showed improved acid–base characteristics and resistance to moisture. Improved acid–base interactions between fiber and resin are expected to improve the interfacial adhesion, whereas improved moisture resistance would benefit the durability of the composites. Finally, composites were prepared using untreated/treated fibers and unsaturated polyester resin. Composites with treated fibers showed slightly better mechanical properties, which is most probably due to improved interfacial adhesion.     

Isolation and Characterization of Cellulose Micro/Nanofibrils from Douglas Fir

Cellulose micro/nanofibrils were successfully extracted from softwood Douglas fir in three distinct stages. Initially raw Douglas fir wood chips were subjected to a hot water extraction (HWE) treatment. Then HWE treated cellulosic fibers underwent a bleaching process followed by a mild ultrasonication. Chemical composition analysis according to ASTM standards confirmed that most of hemicelluloses and nearly all lignin were removed during the first two stages, respectively. Microscopy studies showed formation of nanofibrils during the ultrasonication process, and increasing ultrasonication time led to generation of greater percentage of nanofibrils. With the removal of the matrix materials, the crystallinity of the cellulosic fibers was increased, whereas thermal stability was maintained. HWE opened up the cell wall structure, thereby facilitating the subsequent fractionation into micro/nanofibrils. The obtained cellulose micro/nanofibrils could serve as reinforcing material in composite products or raw material for other applications, such as filtration membrane.     

Polylactic Acid Composites Utilising Sequential Surface Treatments of Lignocellulose: Chemistry,Morphology and Properties

Polylactic acid (PLA)—maple fibre composites have been synthesised using a series of sequentially modified cellulose fibres (namely alkylation followed by either acetylation or silanation). Confirmations of the sequential modifications were made using Fourier Transform Infrared Spectroscopy and Inductively Coupled Plasma—Atomic Emission Spectroscopy and the new surface morphologies analysed using Scanning Electron Microscopy. The key advantage of the use of sequential treatments (with initial alkali treatment) was the allowance for direct grafting of suitable chemical groups onto the cellulose in the fibre due to the removal of lignin, hemicellulose and other surface impurities. However, a balance was found to exist between alkali exposure time, concentration and resulting fibre integrity. The conditions used resulted in a loss in fibre weight, fibre moisture content and tensile strength. Sequential treatments with acetylation or silane resulted in a 15–21% strength recovery from that of the alkali treated composite. Factors that influenced this recovery in strength were the improved fibre-polymer interface, namely the hydrophilic balancing of the fibres and this further affected the thermal-hydrolysis of the PLA during composite fabrication.     

Soda-Treated Sisal/Polypropylene Composites

Treated sisal fibers were used as reinforcement of polypropylene (PP) composites, with maleic anhydride-grafted PP (MAPP) as coupling agent. The composites were made by melting processing of PP with the fiber in a heated roller followed by multiple extrusions in a single-screw extruder. Injection molded specimens were produced for the characterization of the material. In order to improve the adhesion between fiber and matrix and to eliminate odorous substances, sisal fibers were treated with boiling water and with NaOH solutions at 3 and 10 wt.%. The mechanical properties of the composites were assessed by tensile, bend and impact tests. Additionally, the morphology of the composites and the adhesion at he fiber–matrix interface were analyzed by SEM. The fiber treatment led to very light and odorless materials, with yields of 95, 74 and 62 wt.% for treatments with hot water, 3 and 10 wt.% soda solution respectively. Fiber treatment caused an appreciable change in fiber characteristics, yet the mechanical properties under tensile and flexural tests were not influenced by that treatment. Only the impact strength increased in the composites with alkali-treated sisal fibers.     

酰基化反应废水的综合利用

以含AlCl3的酰基化反应工业废水为原料,采用聚芳醚砜酮中空纤维超滤膜为反应介质制备聚合氯化铝（PAC）。通过正交实验考察了碱浓度、碱化度、碱类型和加碱速率对PAC絮凝性能的影响。经优化后的试制参数用于PAC的放大实验,并将试制产品应用于染料废水的处理,考察了PAC对一定浓度的染料废水（达旦黄、活性红、甲基橙和食品黄）的脱色效果。实验结果表明,在NaOH溶液浓度0．5mol／L、渗透压0．2MPa、碱化度2．0时制备的PAC对4种染料的脱色率均大于96％。     

Extraction and Characterization of Nanocrystalline Cellulose from Doum (<Emphasis Type="Italic">Chamaerops humilis</Emphasis>) Leaves: A Potential Reinforcing Biomaterial

The aim of this investigation was to extract nanocrystalline cellulose (NCC) from Moroccan Doum fibers (Chamaerops humilis) by chemical treatment to examine their potential for use as reinforcement fibers in bionanocomposite applications. The chemical composition, morphological and structural properties of the Doum fibers was determined at different stages of chemical treatment. Morphological (transmission electron microscopy and scanning electron microscopy), structural characterization (X-ray diffraction, Fourier transformed infrared), thermal characterization (thermogravimetric analysis). The suspension electrostatic stabilization (zeta potential) of NCCs was also carried out. The results of these characterization analysis found that average size of the NCC is 220 nm in length and 11 nm in diameter, with high crystallinity index (93 %), a thermal stability comparable to that of untreated Doum fibers (degradation temperature 340 °C), which is reasonably promising for the use of these nanofibers in reinforced-polymer manufacturing, and a good stability in water suspension that it allows their utilization such as reinforcement of the water-soluble polymers to prepare the bio-nanocomposite.     

Dispersing Bacterial Cellulose Nanowhiskers in Polylactides via Electrohydrodynamic Processing

In the present study, hybrid electrospun polylactide (PLA) fibers reinforced with highly dispersed crystalline bacterial cellulose nanowhiskers (BCNW) in solution concentrations up to 15 wt% were developed and characterized. The overall aim was to encapsulate dispersed BCNW in fibers to be later re-dispersed in virgin PLA by melt compounding. Initially, the suitability of three different solvents [1,1,1,3,3,3-hexafluoro-2-propanol (HFP), acetone–chloroform and chloroform/polyethylene glycol (PEG)] for fiber production was evaluated and solutions containing 5 wt% BCNW were used to generate electrospun hybrid PLA fibers. These fibers presented a homogeneous morphology, as assessed by scanning electron microscopy, and transmission electron microscopy images demonstrated that BCNW were well distributed along the fibers. Differential scanning calorimetry analyses showed that the incorporation of PEG into the fibers resulted in a T_g drop due to a plasticization effect and decreased thermal stability as a result of low interactions between the matrix and the BCNW. Subsequently, fibers were produced from the selected solutions (HFP and acetone–chloroform) containing up to 15 wt% BCNW. As a result of the great increase in the viscosity of the solutions, lower solids contents were required, leading to a better dispersion and incorporation degree of BCNW within the fibers. HFP was found to be a more suitable solvent, since higher incorporation levels were estimated by X-ray diffraction and improved matrix–filler interactions were suggested by a slight increase in the T_g of the fibers.     

Mechanical, Thermal and Water Absorption Properties of Kenaf-Fiber-Based Polypropylene and Poly(Butylene Succinate) Composites

The use of composites made from non-biodegradable conventional plastic materials (e.g., polypropylene, PP) is creating global environmental concern. Biodegradable plastics such as poly(butylene succinate) (PBS) are sought after to reduce plastic waste accumulation. Unfortunately, these types of plastics are very costly; therefore, natural lignocellulosic fibers are incorporated to reduce the cost. Kenaf fibers are also incorporated into PP and PBS for reinforcing purposes and they have low densities, high specific properties and renewable sourcing. However without good compatibilization, the interfacial adhesion between the matrix and the fibers is poor due to differences in polarity between the two materials. Maleic anhydride-grafted compatibilizers may be introduced into the system to improve the matrix-fiber interactions. The overall mechanical, thermal and water absorption properties of PP and PBS composites prepared with 30 vol.% short kenaf fibers (KFs) using a twin-screw extruder were being investigated in this study. The flexural properties for both types of composites were enhanced by the addition of compatibilizer, with improvements of 56 and 16 % in flexural strength for the PP/KF and PBS/KF composites, respectively. Good matrix-fiber adhesion was also observed by scanning electron microscopy. However, the thermal stability of the PBS/KF composites was lower than that of the PP/KF composites. This result was confirmed by both DSC and TGA thermal analysis tests. The water absorption at equilibrium of a PBS composite filled with KFs is inherently lower than of a PP/KF composite because the water molecules more readily penetrate the PP composites through existing voids between the fibers and the matrix. Based on this research, it can be concluded that PBS/KF composites are good candidates for replacing PP/KF composites in applications whereby biodegradability is essential and no extreme thermal and moisture exposures are required.     

Biopolymers Based Green Composites: Mechanical, Thermal and Physico-chemical Characterization

Natural cellulosic fibers are one of the smartest materials for use as reinforcement in polymers possessing a number of applications. Keeping in mind the immense advantages of the natural fibers, in present work synthesis of natural cellulosic fibers reinforced polymer composites through compression molding technique have been reported. Scanning Electron microscopy (SEM), Thermo gravimetric/Differential thermal/Derivative Thermogravimetry (TGA/DTA/DTG), absorption in different solvents, moisture absorbance, water uptake and chemical resistance measurements were used as characterization techniques for evaluating the different behaviour of cellulosic natural fibers reinforced polymer composites. Effect of fiber loading on mechanical properties like tensile strength, flexural strength, compressive strength and wear resistances has also been determined. Reinforcing of the polymer matrix with natural fibers was done in the form of short fiber. Present work indicates that green composites can be successfully fabricated with useful mechanical properties. These composites may be used in secondary structural applications in automotive, housing etc.