Reactively Compatibilized Cellulosic Polylactide Microcomposites

Poly(lactic acid) (PLA) possesses a suite of favorable material properties that are enabling its penetration into diverse markets (e.g., as packaging material or textile fibers). In order to increase the range of applications for this material, it is necessary to modify its properties and for certain applications, reduce its cost. The introduction of fibers into a polymeric matrix is an established route towards property enhancement provided good dispersion and intimate interfacial adhesion can be achieved. In addition, cellulosic microfibers are obtainable at low to moderate cost. In this study, reactive compatibilization of cellulosic fibers with PLA is pursued. Hydroxyl groups available on the surface of cellulosic fibers are used to initiate lactide polymerization. Various processing strategies are investigated: (1) blending preformed PLA with the fiber material, (2) through a one-step process in which lactide is polymerized in the presence of the fibers alone, or (3) reactive compatibilization in the presence of preformed high molecular weight polymer. The results show that materials prepared by simultaneous introduction of lactide and preformed high molecular PLA at the beginning of the reaction possess superior mechanical properties compared to composites made by either purely mechanical mixing or solely polymerization of lactide in the presence of fibers. The modulus of materials containing 25% fibers which are prepared by reactive compatibilization of 30% preformed PLA and 70% lactide (30/70 P/L) improves by 53% compared to the homopolymer, whereas 36% reinforcement can be achieved upon purely mechanical mixing. A further increase to 35% fiber loading leads to a reduction in modulus due to an excess in initiating groups. The same trend was observed in systems containing 65% preformed PLA and 35% lactide (65/35 P/L) with an overall achievable reinforcement that was slightly lower.     

An Insight into Formation and Characterization of Nano-Cellulose Prepared From Industrial Cellulosic Wastes

Cellulose is naturally available most abundant biopolymer. Most of research has been focusing of extraction of cellulosic material from natural sources and waste sources. These waste sources are of two types: industrial waste and non-industrial wastes. However, industrial wastes are grabbing more interest as these could be available in enormous quantity, reduce environment pollution and also benefit commercially. To address this subject, in the present work, we have successfully converted the cellulosic wastes from viscose industry to high value materials such as Micro-crystalline cellulose (MCC) and Nanocrystalline cellulose (NCC). Furthermore, an important correlation between yield and crystallinity of produced NCC to molecular weight of cellulosic raw material was established. The above finding was characterized by different characterization techniques, such as Zeta sizer, Zeta potential and Scanning Electron Microscopy (SEM).

     

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.     

Thermogravimetric analysis and kinetic study on pyrolysis of representative medical waste composition

To obtain detailed information on the pyrolysis characteristics, a thermogravimetric study on the pyrolysis of 14 typical medical waste compositions was carried out in thermogravimetric analysis (TGA) equipment using dynamic techniques in a stream of N(2). An index representing pyrolysis reactivity of waste was presented. Kinetic parameters were obtained by Coats-Redfern method and used to model the TG curve. The results showed that: (a) Plastic, protein, cellulosic material, synthetic fibre, and rubber entered pyrolysis process in succession. (b) There was one decomposition stage in the pyrolysis of one-off medical glove, operating glove, cellulosic waste, absorbable catgut suture and adhesive plaster, while other components had two obvious weight loss stages. (c) The obtained apparent activation energy for second stage pyrolysis was comparably higher than that for first stage. (d) Each stage was controlled by only one kinetic mechanism, in which kinetic parameters were constant. (e) The degradation kinetics of medical waste may be affected by special physical and chemical treatment in the product manufacturing process. (f) Among 13 waste samples, the pyrolysis index of cellulosic matter was the highest, which indicated cellulosic matter had strong pyrolysis reactivity. (g) With increasing heating rate, TG curve and DTG peak shifted to high temperatures and main reaction interval of the sample became longer.     

Influence of the composition of the initial mixtures on the chemical composition,physicochemical properties and humic-like substances content of composts

The influence of the proportion of C- and N-rich raw materials (initial C/N ratio) and bulking agent on the chemical functional groups composition, humic-like substances (HS-like) content and physicochemical properties of composts was assessed. To achieve these goals, seven initial mixtures (BA1–6 and C1) of dog food (N-rich raw material) were composted with wheat flour (C-rich raw material). Composts were analyzed in terms of chemical functional groups, physicochemical, maturity and stability parameters.The C-rich raw material favored the formation of oxidized organic matter (OM) during the composting process, as suggested by the variation of the ratios of the peaks intensity of FT-IR spectra, corresponding to a decrease of the polysaccharides and an increase of aromatic and carboxyl-containing compounds. However, although with high proportion of C-rich raw material, mixtures with low initial C/N seems to have favored the accumulation of partially oxidized OM, which may have contributed to high electrical conductivity values in the final composts. Therefore, although favoring the partial transformation of OM into stabilized HS-like, initial mixtures with high proportion of C-rich raw material but with low initial C/N led to unstable composts.On the other hand, as long as a high percentage of bulking agent was used to promote the structure of biomass and consequently improve of the aeration conditions, low initial C/N was not a limiting factor of OM oxidation into extractable stabilized humic-like acids.     

Interactive Influence of Biofiber Composition and Elastomer on Physico-Mechanical Properties of PLA Green Composites

The objective of this work was to improve the impact and thermal properties of polylactic acid (PLA)-based biocomposite by appropriate application of cellulosic fiber and a bioelastomer. Biocomposites formulations with fiber contents of up to 20% in combination with a bioelastomer were extrusion-compounded in a twin-screw extruder followed by molding in an injection molding system. Fibers used in the formulations included three types of cellulosic fiber; namely, raw fiber from oat hull biomass (RF), hydrolysis byproduct (ATF) which was the solid fraction obtained from an acid-catalyzed hydrolysis of RF, and delignified fibers (AD30, AD65, AD100) which were the products of delignification of ATF. Formulated biocomposites were characterized for thermal (glass transition and melting temperatures, and enthalpy of melting) and physico-mechanical (tensile and bending strengths, stiffness, impact energy, and water absorption) properties. Among all types of biofibers, RF resulted in poor properties in the biocomposites due to the high hemicellulose content in the structure. On the other hand, the ratio of lignin to cellulose (in the absence of hemicellulose) in the modified fibers did not significantly affect the physico-mechanical and thermal properties of the biocomposites. The elastomer applied in the formulations improved the impact energy, thermal properties, and elongation at break of the composites. However, it adversely affected the strength and water resistance of biocomposites, especially in the presence of hemicellulose. The results indicated that, depending on the application, a wide range of PLA green composites with different physico-mechanical properties can be achieved.     

Processing and characterization of a new biodegradable composite made of a PHB/V matrix and regenerated cellulosic fibers

In this study, a biodegradable composite consisting of a degradable continuous cellulosic fiber and a degradable polymer matrix—poly(3-hydroxybutyrate)-co-poly(3-hydroxyvalerate (PHB/V with 19% HV)—was developed. The composite was processed by impregnating the cellulosic fibers on-line withPHB/V powder in a fluidization chamber. The impregnated roving was then filament wound on a plate and hot-pressed. The resulting unidirectional composite plates were mechanically tested and optically characterized by SEM. The fiber content was 9.9 ±0.9 vol% by volumetric determination. The fiber content predicted by the rule of mixture for unidirectional composites was 13.8 ±1.4 vol%. Optical characterization showed that the fiber distribution was homogeneous and a satisfactory wetting of the fibers by the matrix was achieved. Using a blower to remove excess matrix powder during processing increased the fiber content to 26.5 ±3.3 vol % (volumetric) or 30.0 ±0.4 vol% (rule of mixture). The tensile strength of the composite parallel to the fiber direction was 128 ±12 MPa (10 vol% fiber) up to 278 ±48 MPa (26.5 vol% fiber), compared to 20 MPa for the PHB/V matrix. The Young’s modulus was 5.8 ±0.5 GPa (10 vol% fiber) and reached 11.4 ±0.14 GPa (26.5 vol% fiber), versus 1 GPa for the matrix.     

煤气化细渣制备碳硅复合材料吸附去除水中Pb2+

以煤气化细渣为原料制备了高比表面积碳硅复合材料,并利用过硫酸铵对其进行表面改性,用于吸附100.0 mg/L PbCl₂溶液中Pb²⁺。表征结果显示：碳硅复合材料的比表面积为1 347 m²/g,改性后降为474 m²/g;改性后材料表面的羟基、羰基和羧基等含氧基团的含量显著增加。实验结果表明：溶液pH为5时,改性碳硅复合材料对Pb²⁺的平衡吸附量为124 mg/g,Pb²⁺去除率可达98.2%;吸附过程符合准二级动力学模型,以化学吸附为主,伴有物理吸附;吸附过程分为外扩散和内扩散两个阶段,受内扩散控制。     

Recycling of iron foundry sand and glass waste as raw material for production of whiteware.

The purpose of this study was to evaluate the production feasibility of triaxial whiteware using sand from cast iron moulds as a raw material instead of silica, and recycled glass in place of feldspar. Formulations were prepared using sand, glass waste, and white-firing clay such that only 50% of the composition was virgin material (clay). The ceramic bodies were formed by pressing and fired at different temperatures (between 1100 and 1300 degrees C). Specimens were characterized in terms of green density prior to firing; and their flexural strength, linear shrinkage, and water absorption were measured after firing. The microstructure was determined by scanning electron microscopy. Possible environmental impacts of this recycling process were also evaluated, through solubility and leaching tests, according to Brazilian standards. Gaseous emissions during the firing process were also analysed. The results showed that it is possible to produce triaxial ceramics by using such alternative raw materials.     

Environmental assessment of sewage sludge as secondary raw material in cement production--a case study in China

A life cycle assessment was carried out to estimate the environmental impact of sewage sludge as secondary raw material in cement production. To confirm and add credibility to the study, uncertainty analysis was conducted. Results showed the impact generated from respiratory inorganics, terrestrial ecotoxicity, global warming, and non-renewable energy categories had an important contribution to overall environmental impact, due to energy, clinker, and limestone production stages. Also, uncertainty analysis results showed the technology of sewage sludge as secondary raw material in cement production had little or no effect on changing the overall environmental potential impact generated from general cement production. Accordingly, using the technology of sewage sludge as secondary raw material in cement production is a good choice for reducing the pressure on the environment from dramatically increased sludge disposal. In addition, increasing electricity recovery rate, choosing natural gas fired electricity generation technology, and optimizing the raw material consumption in clinker production are highly recommended to reduce the adverse effects on the environment.     

Feasibility of incorporating treated lignins in fiberboards made from agricultural waste

This paper studies the feasibility of incorporating treated lignins in fiberboards made from Vitis vinifera as an agricultural waste. The treated lignins are the purified Kraft lignin and the alkaline hydrolyzed Kraft lignin. V. vinifera raw material and its fibers were characterized in terms of chemical composition and the results were compared to other biomass species. The chemical composition of treated lignins shows that they have high purity compared to the lignin raw material. The lignin-V. vinifera fibreboards were produced on laboratory scale by adding powdered treated lignins to the material that had previously been steam exploded. Some of the important properties of fibreboards prepared using the treated lignins as natural adhesives were evaluated. These properties were density, thickness swelling, water absorption, modulus of elasticity, modulus of rupture, internal bond strength. The explored levels of treated lignins vary from 5% to 20%. The results showed that binderless fibreboards, fibreboards made from V. vinifera fibers and alkaline hydrolyzed Kraft lignin have weaker mechanical properties. However, the fibreboards obtained using purified Kraft lignin have good mechanical and water resistance properties which satisfy the requirements of the relevant standards specifications.     

Predicting the degradation pattern of organic materials in the composting of a fed-batch operation as inferred from the results of a batch operation

The degradation pattern of organic materials was confirmed by continuously measuring the quantity of CO₂ evolved during the composting process in both batch and fed-batch operations. It was possible to predict the degradation pattern for organic material during a fed-batch operation from that observed during a batch operation after corrections made on the basis of two suppositions. First, it was assumed that the degradation of dog food (which degrades easily) occurred prior to the degradation of the bulking agent and seeding material that were contained in the raw compost mixture; second, it was assumed that the dog food thrown into the fed-batch operation, where the microorganisms were already proliferating, began to be actively degraded with only a short lag time. Received: June 16, 1998 / Accepted: August 7, 1999     

Influence of the recycled material percentage on the rheological behaviour of HDPE for injection moulding process

The amount of polymer material wasted during thermoplastic injection moulding is very high. It comes from both the feed system of the part, and parts necessary to set up the mould, as well as the scrap generated along the process due to quality problems. The residues are managed through polymer recycling that allows reuse of the materials in the manufacturing injection process. Recycling mills convert the parts into small pieces that are used as feed material for injection, by mixing the recycled feedstock in different percentages with raw material. This mixture of both raw and recycled material modifies material properties according to the percentage of recycled material introduced. Some of the properties affected by this modification are those related to rheologic behaviour, which strongly conditions the future injection moulding process. This paper analyzes the rheologic behaviour of material with different percentages of recycled material by means of a capillary rheometer, and evaluates the influence of the corresponding viscosity curves obtained on the injection moulding process, where small variations of parameters related to rheological behaviour, such as pressure or clamping force, can be critical to the viability and cost of the parts manufactured by injection moulding.     

Extraction and Characterization of Fiber Treatment Inula viscosa Fibers as Potential Polymer Composite Reinforcement

Journal of Polymers and the Environment - This research aims to characterize and analysis of newly cellulosic fiber extracted from Inula viscosa bark. The obtained Inula viscosa fibers were also...     

Application of Cellulose Microfibrils in Polymer Nanocomposites

Cellulose microfibrils obtained by the acid hydrolysis of cellulose fibers were added at low concentrations (2–10% w/w) to polymer gels and films as reinforcing agents. Significant changes in mechanical properties, especially maximum load and tensile strength, were obtained for fibrils derived from several cellulosic sources, including cotton, softwood, and bacterial cellulose. For extruded starch plastics, the addition of cotton-derived microfibrils at 10.3% (w/w) concentration increased Young’s modulus by 5-fold relative to a control sample with no cellulose reinforcement. Preliminary data suggests that shear alignment significantly improves tensile strength. Addition of microfibrils does not always change mechanical properties in a predictable direction. Whereas tensile strength and modulus were shown to increase during addition of microfibrils to an extruded starch thermoplastic and a cast latex film, these parameters decreased when microfibrils were added to a starch–pectin blend, implying that complex interactions are involved in the application of these reinforcing agents.     

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.     

Effect of carbon dioxide injection on production of wood cement composites from waste medium density fiberboard (MDF)

The possibility of recycling waste medium density fiberboard (MDF) into wood-cement composites was evaluated. Both new fibers and recycled steam exploded MDF fibers had poor compatibility with cement if no treatment was applied, due to interference of the hydration process by the water soluble components of the fiber. However, this issue was resolved when a rapid hardening process with carbon dioxide injection was adopted. It appears that the rapid carbonation allowed the board to develop considerable strength before the adverse effects of the wood extractives could take effect. After 3-5 min of carbon dioxide injection, the composites reached 22-27% of total carbonation and developed 50-70% of their final (28-day) strength. Composites containing recycled MDF fibers had slightly lower splitting tensile strength and lower tensile toughness properties than those containing new fibers especially at a high fiber/cement ratio. Composites containing recycled MDF fibers also showed lower values of water absorption. Unlike composites cured conventionally, composites cured under CO(2) injection developed higher strength and toughness with increased fiber content. Incorporation of recycled MDF fibers into wood cement composites with CO(2) injection during the production stage presents a viable option for recycling of this difficult to manage waste material.     

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.     

Morphological characteristics of waste polyethylene/polypropylene plastics during pyrolysis and representative morphological signal characterizing pyrolysis stages

In this work, the morphological characteristics of waste polyethylene (PE)/polypropylene (PP) plastics during their pyrolysis process were investigated, and based on their basic image changing patterns representative morphological signals describing the pyrolysis stages were obtained. PE and PP granules and films were used as typical plastics for testing, and influence of impurities was also investigated. During pyrolysis experiments, photographs of the testing samples were taken sequentially with a high-speed infrared camera, and the quantitative parameters that describe the morphological characteristics of these photographs were explored using the “Image Pro Plus (v6.3)” digital image processing software. The experimental results showed that plastics pyrolysis involved four stages: melting, two stages of decomposition which are characterized with bubble formation caused by volatile evaporating, and ash deposition; and each stage was characterized with its own phase changing behaviors and morphological features. Two stages of decomposition are the key step of pyrolysis since they took up half or more of the reaction time; melting step consumed another half of reaction time in experiments when raw materials were heated up from ambient temperatures; and coke-like deposition appeared as a result of decomposition completion. Two morphological signals defined from digital image processing, namely, pixel area of the interested reaction region and bubble ratio (BR) caused by volatile evaporating were found to change regularly with pyrolysis stages. In particular, for all experimental scenarios with plastics films and granules, the BR curves always exhibited a slowly drop as melting started and then a sharp increase followed by a deep decrease corresponding to the first stage of intense decomposition, afterwards a second increase – drop section corresponding to the second stage of decomposition appeared. As ash deposition happened, the BR dropped to zero or very low values. When impurities were involved, the shape of BR curves showed that intense decomposition started earlier but morphological characteristics remained the same. In addition, compared to parameters such as pressure, the BR reflects reaction stages better and its change with pyrolysis process of PE/PP plastics with or without impurities was more intrinsically process correlated; therefore it can be adopted as a signal for pyrolysis process characterization, as well as offering guide to process improvement and reactor design.     

Pyrolysis behavior of different type of materials contained in the rejects of packaging waste sorting plants

In this paper rejected streams coming from a waste packaging material recovery facility have been characterized and separated into families of products of similar nature in order to determine the influence of different types of ingredients in the products obtained in the pyrolysis process. The pyrolysis experiments have been carried out in a non-stirred batch 3.5 dm³ reactor, swept with 1 L min^?1 N₂, at 500 °C for 30 min. Pyrolysis liquids are composed of an organic phase and an aqueous phase. The aqueous phase is greater as higher is the cellulosic material content in the sample. The organic phase contains valuable chemicals as styrene, ethylbenzene and toluene, and has high heating value (HHV) (33–40 MJ kg^?1). Therefore they could be used as alternative fuels for heat and power generation and as a source of valuable chemicals. Pyrolysis gases are mainly composed of hydrocarbons but contain high amounts of CO and CO₂; their HHV is in the range of 18–46 MJ kg^?1. The amount of COCO₂ increases, and consequently HHV decreases as higher is the cellulosic content of the waste. Pyrolysis solids are mainly composed of inorganics and char formed in the process. The cellulosic materials lower the quality of the pyrolysis liquids and gases, and increase the production of char.