Showing papers in "Journal of Polymers and The Environment in 2011"

Biodegradable Polymers- A Review on Recent Trends and Emerging Perspectives

Abstract: Recent trends in biodegradable polymers indicate significant developments in terms of novel design strategies and engineering to provide advanced polymers with comparably good performance. However, there are several inadequacies in terms of either technology or cost of production especially in the case of applications in environmental pollution. So, there is a need to have a fresh perspective on the design, properties and functions of these polymers with a view to developing strategies for future developments. The paper reviews the present state-of-art on biodegradable polymers and discusses the salient features of the design and properties of biodegradable polymers. Special emphasis is given to the problems and prospects of (1) approaches adopted to make non-biodegradable synthetic polymers such as polyethylene biodegradable and (2) biodegradable polymers and copolymers made from renewable resources especially poly(lactic acid) based polymers and copolymers which are emerging as the candidate biodegradable materials for the future.

Degradation of Cellulose Acetate-Based Materials: A Review

Abstract: Cellulose acetate polymer is used to make a variety of consumer products including textiles, plastic films, and cigarette filters. A review of degradation mechanisms, and the possible approaches to diminish the environmental persistence of these materials, will clarify the current and potential degradation rates of these products after disposal. Various studies have been conducted on the biodegradability of cellulose acetate, but no review has been compiled which includes biological, chemical, and photo chemical degradation mechanisms. Cellulose acetate is prepared by acetylating cellulose, the most abundant natural polymer. Cellulose is readily biodegraded by organisms that utilize cellulase enzymes, but due to the additional acetyl groups cellulose acetate requires the presence of esterases for the first step in biodegradation. Once partial deacetylation has been accomplished either by enzymes, or by partial chemical hydrolysis, the polymer’s cellulose backbone is readily biodegraded. Cellulose acetate is photo chemically degraded by UV wavelengths shorter than 280 nm, but has limited photo degradability in sunlight due to the lack of chromophores for absorbing ultraviolet light. Photo degradability can be significantly enhanced by the addition of titanium dioxide, which is used as a whitening agent in many consumer products. Photo degradation with TiO2 causes surface pitting, thus increasing a material’s surface area which enhances biodegradation. The combination of both photo and biodegradation allows a synergy that enhances the overall degradation rate. The physical design of a consumer product can also facilitate enhanced degradation rate, since rates are highly influenced by the exposure to environmental conditions. The patent literature contains an abundance of ideas for designing consumer products that are less persistent in the outdoors environment, and this review will include insights into enhanced degradability designs.

PLA Based Biopolymer Reinforced with Natural Fibre: A Review

Abstract: In recent years renewed interest on the development of biopolymers, based on constituents obtained from natural resources is gaining much attention. Natural fibres such as kenaf, hemp, flax, jute, bamboo, elephant grass and sisal based polymer with thermoplastic and thermoset matrices offer reductions in weight, cost and carbon dioxide emission, less reliance on foreign oil resources and recyclability. Reinforced biopolymer with natural fibres is the future of “green composites” addressing many sustainability issues. Among the available biopolymer, PLA (polylactide) is the only natural resource polymer produced at a large scale of over 140,000 tonnes per year. Natural fibre reinforced PLA based biocomposites are widely investigated by the polymer scientists in the last decade to compete with non renewable petroleum based products. The type of fibre used plays an important role in fibre/matrix adhesion and thereby affects the mechanical performance of the biocomposites. The aim of this review is to investigate the effects of processing methods, fibre length, fibre orientation, fibre-volume fraction, and fibre-surface treatment on the fibre/matrix adhesion and mechanical properties of natural-fibre-reinforced PLA composites. Although much work has been performed to engineer the design of such superior biocomposites, the information is scattered in nature. A comprehensive review on the major technical considerations undertaken to prepare such biocomposites over the last decade is investigated to address the feasibility of wide scale industrial acceptance to such biocomposites. A brief review on the available natural fibres and biopolymer is also given for a comparative study.

Rheological Studies of Microfibrillar Cellulose Water Dispersions

Abstract: The rheological behaviour of microfibrillar cellulose (MFC) water dispersions has been investigated. For the first time a detailed study of shear dependent viscosity at low and high shear rate is presented. A peculiar time dependent behaviour measured in the area between 0 and 1000 s−1 was identified. The study shows a hysteresis loop in the shear rate–viscosity relationship at low shear rate. Additional time dependent shear rate measurements were performed, and a hypothesis for a mechanism of interaction and formation of a fibrils network was suggested. Higher temperature caused lower viscosity values, and this difference was increased at higher shear rate values. Oscillatory measurements showed how the closeness of the fibrils helps network creations. Data obtained from high shear measurements showed that 1% MFC water dispersions had a dilatant behaviour at ultra high shear rates with values increasing from 120 to 300 Pa s in the area between 180,000 and 330,000 s−1 .

Preparation of Cellulose Nanocrystals Using an Ionic Liquid

Abstract: In this paper cellulose nanocrystals were prepared by treating microcrystalline cellulose with 1-butyl-3-methylimidazolium hydrogen sulphate ionic liquid. Cellulose nanocrystals, after separation from ionic liquid, were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Field emission scanning electron microscopy (FESEM) Transmission Electron Microscope (TEM) and Thermogravimetric analysis. XRD results showed no changes in type of cellulose after the treatment with ionic liquid, however, high crystallinity index was observed in the ionic liquid treated sample. Cellulose nanocrystals, having length around 50–300 nm and diameter around 14–22 nm were observed in the ionic liquid treated sample under FESEM and TEM, and similar patterns of peaks as that of microcrystalline cellulose were observed for cellulose nanocrystals in the FTIR spectra. The thermal stability of the cellulose nanocrystals was measured low as compare to microcrystalline cellulose.

Analysis of the Structure-Properties Relationships of Different Multiphase Systems Based on Plasticized Poly(Lactic Acid)

Abstract: Poly(lactic acid) is one of the most promising biobased and biodegradable polymers for food packaging, an application which requires good mechanical and barrier properties. In order to improve the mechanical properties, in particular the flexibility, PLA plasticization is required. However, plasticization induces generally a decrease in the barrier properties. Acetyl tributyl citrate (ATBC) and poly(ethylene glycol) 300 (PEG), highly recommended as plasticizers for PLA, were added up to 17 wt% in P(D,L)LA. In the case of PEG, a phase separation was observed for plasticizer contents higher than 5 wt%. Contrary to PEG, the Tg decrease due to ATBC addition, modelled with Fox’s law, and the absence of phase separation, up to 17 wt% of plasticizer, confirm the miscibility of PLA and ATBC. Contents equal or higher than 13 wt% of ATBC yielded a substantial improvement of the elongation at break, becoming higher than 300%. The effect of PLA plasticization on the barrier properties was assessed by different molecules, with increasing interaction with the formulated material, such as helium, an inert gas, and oxygen and water vapour. In comparison to the neat sample, barrier properties against helium were maintained when PLA was plasticized with up to 17 wt% of ATBC. The oxygen permeability coefficient and the water vapour transmission rate doubled for mixtures with 17 wt% ATBC in PLA, but increased five-fold in the PEG plasticized samples. This result is most likely caused by increased solubility of oxygen and water in the PEG phase due to their mutual miscibility. To conclude, ATBC increases efficiently the elongation at break of PLA while maintaining the permeability coefficient of helium and keeping the barrier properties against oxygen and water vapour in the same order of magnitude.

Bioplastic Wastes: The Best Final Disposition for Energy Saving

Abstract: The pressing need to reduce the consumption of non-renewable resources and the emission of greenhouse gases into the environment, in recent decades has led to the wide development of bio-based plastics that are produced from renewable sources, such as corn, wheat, oil seeds etc. Actually, the most important bio-based plastics on the market are the poly(lactic acid) (PLA) produced from Nature Works (USA) and the Mater-Bi, a starch based bioplastics, made from Novamont (Italy). The aim of this work is not only to assess the actual energy and greenhouse gases (GHGs) savings resulting from the production of bioplastics, compared with the production of conventional plastics, but also to analyze what might be the best final disposition of bioplastic wastes in order to maximize the energy saving. Therefore, by using the Life Cycle Assessment (LCA) methodology, LCAs cradle to gate and cradle to grave were carried out both for PLA and Mater-Bi, taking into consideration as final scenarios composting, incineration, anaerobic digestion and mechanical recycling processes. The work demonstrates how incineration, composting and anaerobic digestion processes are clearly under-performing, from an environmental point of view, with respect to the mechanical recycling process.

Comparative Biodegradation in Soil Behaviour of two Biodegradable Polymers Based on Renewable Resources

Abstract: This work presents the last phase of long-term experimental studies on the biodegradation in soil behaviour of polymers destined for agricultural applications. The paper focuses on comparative studies between the biodegradation in soil behaviour of two important biodegradable polymers based on renewable resources: poly(lactic acid) (PLA) versus polyhydroxyalkanoates (PHA). Full-scale experiments were carried out during the period June 2008–January 2009. Different methods of exposure were applied in the case of polyhydroxyalkanoates, simulating the agricultural biodegradable mulching films use and their fate in soil after the end of their useful lifetime. The field results were compared with the results of biodegradation under controlled laboratory conditions simulating biodegradation in soil, using soil from the experimental field. Further, the field results were compared against the results of biodegradation under farm composting conditions.

Hybrid Composites Made from Oil Palm Empty Fruit Bunches/Jute Fibres: Water Absorption, Thickness Swelling and Density Behaviours

Abstract: In this research, hybrid composite materials were prepared from combination of oil palm Empty fruit bunches (EFB) fibre and jute fibre as reinforcement, epoxy as polymer matrix This study intended to investigate the effect of jute fiber hybridization and different layering pattern on the physical properties of oil palm EFB-Epoxy composites Water absorption and thickness swelling test reveal that hybrid composite shows a moderate water absorption which is 1120% for hybrid EFB/Jute/EFB composite and 608% for hybrid Jute/EFB/Jute composite The thickness swelling and water absorption of the hybrid composites slightly increased as the layering pattern of hybrid composites changed Hybrid composites are more water resistance and dimensional stable compare to the pure EFB composites This is attributed to the more hydrophilic nature of EFB composites Hybridization of oil palm EFB composites with jute fibres can improve the dimensional stability and density of pure EFB and Jute fibre reinforced composites has higher density of 12 g/cm3 compared to all other composites

Natural Rubber-Based Pressure-Sensitive Adhesives: A Review

Abstract: The purpose of this review is to describe the various aspects of pressure-sensitive adhesives prepared from natural rubber. Pressure-sensitive adhesives (PSAs) adhere instantaneously to a variety of surfaces upon application of slight pressure and can be obtained using different technologies. PSAs are materials that develop tack for low pressures and short contact times. There are number of factors affecting the adhesion property of natural rubber based pressure-sensitive adhesives. In this review, factors affecting adhesion property such as tack, peel and shear are examined in light of their relevance to adhesion in addition to measurement methods of each of the three major adhesion properties. This review paper covers the work being carried out from the last 20 years in the field of natural rubber based pressure sensitive adhesives.

Eco-Synthesis of PVA/Chitosan Hydrogels for Biomedical Application

Abstract: A drug delivery system based on physically cross-linked poly vinyl alcohol (PVA)/chitosan blend hydrogels for the release of sparfloxacin antibiotic as a model for drugs was described. Eco-synthesis in current work is based on synthesizing a hydrogel without using chemical crosslinking agents like in the conventional method. In addition all materials are used are non- toxic, safe, non-carcinogenic and can be accepted by the human body without danger. The swelling behavior was tested to be dependent on pH as temperature as well as time and number of freezing thawing cycles. The physical properties of the hydrogels, such as swelling percent, dissolution percent, gel fraction and mechanical properties was assessed. The antimicrobial activity of hydrogels having different compositions was evaluated for both gram positive and gram negative bacteria. Furthermore, the release of antibiotic from hydrogels prepared using the freeze—thawed process was studied. Results obtained disclose that the swelling percent of the hydrogels is pH- dependent and increases by increasing the chitosan percent and decreases with increasing the time and number of freezing cycle. With respect to the antimicrobial activity of the prepared hydrogels, display a positive effect for both gram positive and gram negative bacteria. Freeze-thawed hydrogels could serve as drug delivery system to release sparfloxacin in acidic medium. Indeed, the release percent of sparfloxacin relies on both pH and temperature.

Effect of Nucleating Agents on Physical Properties of Poly(lactic acid) and Its Blend with Natural Rubber

Abstract: Poly(lactic acid) (PLA) presents high strength and modulus, but very low toughness as well as slow crystallization. Natural rubber (NR) was blended to enhance the toughness and nucleating agent was added to improve the crystallization. Cyclodextrin (CD), considered as a green compound, as well as calcium carbonate (CaCO3) and talc were used as nucleating agents. Effects of these nucleating agents on crystallization, mechanical properties and morphology of neat PLA and PLA/NR blend were investigated. It was found that the addition of talc and CD decreased cold crystallization temperature (Tcc) of the PLA. Same result was obtained in PLA/NR blend containing talc. All nucleating agents increased the degree of crystallinity (ΧC) of PLA, whereas only talc and CaCO3 increased ΧC of PLA in PLA/NR blends. The enhanced toughness of PLA by the addition of nucleating agent was attributed to its increased crystallinity, as well as decreased spherulite size. For PLA/NR blends, the increase in toughness was mainly contributed by the presence of the rubber.

New Route for Devulcanization of Natural Rubber and the Properties of Devulcanized Rubber

Abstract: Devulcanization of natural rubber (NR) compound was carried out by means of benzoyl peroxide as a devulcanizing agent by two different techniques namely (a) chemical process and (b) mechano-chemical process. Furthermore, the effects of time and concentration of devulcanizing agent on the devulcanization process were investigated. The extent of devulcanization of natural rubber was studied by estimation of percent devulcanization, volume fraction of rubber after swelling, Mooney viscosity and crosslinked density. The devulcanized natural rubber obtained from mechano-chemical process was blended with virgin natural rubber in different proportions. The mechanical properties and morphology of the revulcanized blends were examined and found to be interesting. Thus, waste rubber could be reused successfully by this technique.

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

Abstract: 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. Tg 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.

Development of Proteinous Bioplastics Using Bloodmeal

Abstract: The aim of this work was to investigate the use of bloodmeal as a thermoplastic biopolymer. Processing required water and chemical additives to perform three main functions: breaking covalent cross-links using sodium sulfite (SS), sodium dodecyl sulfate and urea as processing aids, and evaporating some processing water to allow formation of new interactions to stabilize the final structure. Extrusion was only possible in the presence of SS and strongly influenced by water and urea content. It was found that once water had been removed, mechanical properties increased significantly, indicating the formation of new intermolecular forces. SDS was required for processing and consolidation, but, it may restrict formation of new intermolecular forces, if used in excessive quantities. Materials based on optimal additive levels had a tensile strength of 8 MPa, Young’s modulus of 320 MPa and toughness 1.6 MPa m½.

Dissolving Feather Keratin Using Sodium Sulfide for Bio-Polymer Applications

Abstract: Feather keratin has been widely studied for use as a bio-based material. In this paper, we dissolve feather keratin using industrial sodium sulfide to investigate the yield, dissolved keratin characteristics, and properties of regenerated products to assess the potential of using sodium sulfide as a means of converting waste feathers into a bio-polymer. Optimal conditions appeared to require short incubation times in order to give maximum strength in the regenerated product. This limits the yield to approximately 55%. Air-dried films and acid-precipitated samples are all readily re-crosslinked, suggesting the re-crosslinking process is robust. Minimizing exposure to the highly alkaline conditions appears favorable to final product strength through minimizing alkaline chain damage. The β-sheet structure of the parent keratin is largely maintained. The regenerated keratin was shown to have potentially attractive physical properties for use as a bio-polymer.

Effects of Waste Paper Sludge on the Physico-Mechanical Properties of High Density Polyethylene/Wood Flour Composites

Abstract: The objective of this work was to determine some physical and mechanical properties of the high density polyethylene (HDPE) composites reinforced with various mixtures of the paper sludge and the wood flour, and to evaluate the coupling agent performance. The waste sludge materials originating from two different sources including paper making waste water treatment sludge (PS) and ink-eliminated sludge (IES) were characterized in terms of physico-chemical properties. In the experiment, four levels of paper sludge (20, 30, 40 and 60 wt%), three levels of wood flour (20, 40 and 60 wt%), and two levels of coupling agent (MAPE) content (2 and 3 wt%) were used. The flexural properties of the composites were positively affected by the addition of the sludge. Especially, tensile modulus improved with the increase of paper sludge content. With the addition of MAPE, flexural properties improved considerably compared with control specimens (without any coupling agent). The results showed that the water absorption (WA) and thickness swelling (TS) values of the samples decreased considerably with increasing sludge content in the composite, while they increased with increasing wood flour content. It is to be noted that with incorporation of MAPE in the composite formulation, the compatibility between the wood flour and HDPE was enhanced through esterification, which reduced the WA and TS and improved the mechanical properties. Composites made with IES exhibited superior physico-mechanical properties compared with the PS filled composites. Overall results suggest that the waste paper sludge materials were capable of serving as feasible reinforcing fillers for thermoplastic polymer composites.

Tensile, Flexural and Chemical Resistance Properties of Sisal Fibre Reinforced Polymer Composites: Effect of Fibre Surface Treatment

Abstract: In this study, effect of fibre surface treatment on tensile, flexural and chemical resistance properties were studied for sisal fibre reinforced composites Natural ligno cellulosic sisal fibre reinforced composites were prepared by different surface treatments by hand lay-up method Fibre surface treatments were carried out to produce good interface between the fibre and the matrix to improve the mechanical properties Fibre surface treatments were done by boiled the sisal fibres in different % of NaOH and treated the fibres in different % of NaOH, treated in acetic acid and methanol Unsaturated polyester resin was used as the matrix for preparing the composites For comparison, these properties for untreated sisal fibre reinforced composites were also studied From the results it was observed that 18% aqueous NaOH boiled sisal fibre reinforced composites have higher tensile, flexural properties than other composites Untreated sisal fibre composites show lower properties than treated composites Chemical resistance properties indicate that all sisal fibre reinforced composites are resistance to all chemicals except carbon tetra chloride The tests are carried out as per the ASTM standards

Ionic Liquids as Environmentally Friendly Solvents in Macromolecules Chemistry and Technology, Part II

Abstract: With the increasing emphasis on the environment and the need to find environmentally friendly solvent systems, ionic liquids (IL)s have been emerging as promising green solvents to replace conventional solvents in recent years. They possess unique properties such as nonvolatility, low toxicity, ease of handling, nonflammability and high ionic coductivity; thus they have received much attention as green media for various chemistry processes. This report provides an extensive overview of use of ILs in polymers chemistry and technology.

Effect of Cotton Fiber Contents and Lengths on Properties of Thermoplastic Starch Composites Prepared from Rice and Waxy Rice Starches

Abstract: Biodegradable polymer was prepared as thermoplastic starch (TPS) using rice and waxy rice starches. In order to increase mechanical properties and reduce water absorption of the TPS, cotton fiber was incorporated as the fiber reinforcement into the TPS matrix. The effect of cotton fiber contents and lengths on properties of the TPS was examined. Internal mixer and compression molding machine were used to mix and shape the samples. It was found that the thermoplastic rice starch (TPRS) showed higher stress at maximum load and Young’s modulus but lower strain at maximum load than the thermoplastic waxy rice starch (TPWRS). In addition, stress at maximum load and Young’s modulus of both TPRS and TPWRS increased significantly with the addition of the cotton fiber. Cotton fiber contents and lengths also affected mechanical properties of the TPRS and TPWRS composites. Moreover, water absorption of the TPRS and TPWRS composites decreased by the use of the cotton fibers. FT-IR and XRD techniques were used to study a change in functional group and crystallinity of the thermoplastic starch composites. Morphological, thermal and biodegradable properties of different thermoplastic starch composites were also investigated.

From Aminolysis Product of PET Waste to Novel Biodegradable Polyurethanes

Abstract: Chemical recycling of PET has been developed by various methods. Aminolysis is one of chemical recycling methods of PET has been developed recently. The obtained product using aminolysis, Bis (2-hydroxy ethylene) terephthalamide (BHETA), has the potential for further reactions to obtain useful products. There are few reports on usage of recycled BHETA from PET waste to synthesis of polyurethanes. On the other hand, various biodegradable polyurethanes have been synthesized using polycaprolactone diol. Therefore, caprolactone is a new potential in synthesis of biodegradable polyurethanes from PET waste. In this work, novel biodegradable polyurethanes have been synthesized using BHETA. In this order, at first polyols with different molecular weights have been synthesized through ring opening polymerization of caprolactone by BHETA, then urethane linkages were formed using HDI (Hexamethylene Diisocyanate) without chain extender. Chemical, thermal, mechanical and dynamic mechanical properties, biodegradability, morphology and UV resistance of synthesized polyurethanes have been investigated.

Adhesive Performance of Sorghum Protein Extracted from Sorghum DDGS and Flour

Abstract: Distillers dried grains with solubles (DDGS) is the main co-product from grain-based ethanol production. The objective of this research was to compare the adhesive performance of three types of sorghum proteins: acetic acid-extracted sorghum protein from DDGS (PI), aqueous ethanol-extracted sorghum protein from DDGS (PII) and acetic acid-extracted sorghum protein from sorghum flour (PF). Physicochemical properties including amino acid composition, and rheological, thermal and morphological properties also were characterized. Results showed that PI had the best adhesion performance in terms of dry, wet and soak adhesion strength, followed by PF and PII. The wet strength of PI at a concentration of 12% protein assembled at 150 °C was 3.15 MPa, compared to 2.17 MPa and 2.59 MPa for PII and PF, respectively. DSC thermograms indicated that the PF protein isolates contained higher levels of carbohydrates than PI and PII; such non-protein contaminants in the PF isolate could be the reason for its lower adhesion strength than PI. In addition, PI might have more hydrophobic amino acids aligned at the protein-wood interface than PII, which could explain the better water resistance of PI. The optimum sorghum protein concentration and pressing temperature for maximum adhesion strength was 12% and 150 °C. PI had a significantly higher wet strength (3.15 MPa) than unmodified soy protein (1.63 MPa for soy protein). The high percentage of hydrophobic amino acids in PI (57%) was likely a key factor in the increased water resistance of PI compared with soy protein (36% hydrophobic amino acids). These results indicated that sorghum protein has huge potential as an alternative to petroleum-based adhesives.

Natural Weathering of Kenaf Bast Fibre-Filled Poly(Butylene Succinate) Composites: Effect of Fibre Loading and Compatibiliser Addition

Abstract: Natural weathering was performed on poly(butylene succinate) (PBS) and its kenaf bast fibre (KBF) filled composites by exposing the specimens to a tropical climate for a period of 6 months (max–min temperature: 31.5–23.9 °C; relative humidity: 78.9%). The aim of this study was to investigate the effects of KBF loading and the addition of maleated PBS compatibiliser (PBSgMA) on the performance of the composites under natural weathering. As expected, the flexural properties of both the uncompatibilised and compatibilised composites dropped with increasing exposure time. The weathered specimens were also assessed by colour change analysis, FTIR spectroscopy analysis and SEM examination. The total colour change, ΔE ab , of both the uncompatibilised and compatibilised composites increased with weathering time. FTIR spectroscopy analysis confirmed the presence of oxidation products such as hydroxyl, carbonyl and vinyl species in the weathered uncompatibilised and compatibilised composites. SEM examination revealed the presence of surface defects such as cracking, tiny holes and degraded fibre, which explain the poor performance of the composites upon weathering.

Enhancement and Characterization of Chitosan Extraction from the Wastes of Shrimp Packaging Plants

Abstract: Chitin is the second most abundant carbohydrate polymer in nature next to cellulose. The main source of chitin is crustacean shells. Chitosan, derived from chitin by alkaline deacetylation, characteristically plays an important role in applications. Several parameters determine the chitosan specifications, namely, chitosan sources, incubation time, pretreatment conditions, temperature and acid and alkaline treatment. Chitosan extraction has been achieved by microwave heating and compared with that of conducting the deacetylation in an autoclave. High molecular weight chitosan (as determined by viscosity measurements of chitosan in dilute acetic acid solution), white color, high water binding capacity (WBC) and fat binding capacity (FBC) has been obtained by microwave treatment. In addition, microwave treatment saves a large amount of energy (due to the shorter time of heating) which is a very important factor for commercial productions. The data extracted from X-ray diffraction, nuclear magnetic resonance and Fourier transforms infrared spectroscopy have shown more crystalline and higher DDA of chitosan produced in microwave than the one in autoclave. Moreover, the antibacterial activity of chitosan prepared by microwaves was higher than that produced using the autoclave.

Aging of Toughened Polylactic Acid Nanocomposites: Water Absorption, Hygrothermal Degradation and Soil Burial Analysis

Abstract: The environmental aging behaviour of montmorillonite (MMT) filled polylactic acid (PLA) nanocomposites (PLA/MMT) and linear low density polyethylene (LLDPE)-toughened PLA (PLA/LLDPE ratio = 90/10) nanocomposites (PLA/LLDPE/MMT) were investigated in this study The nanocomposites were subjected to water absorption, hygrothermal degradation and soil burial analysis Both PLA/MMT and PLA/LLDPE/MMT nanocomposites were immersed in distilled water at three different temperatures (room temperature, 60, and 90 °C) and the weight difference before and after immersion was calculated The kinetics of water absorption for both nanocomposites followed the Fick’s second law of diffusion, where a linear relationship exists between the initial moisture absorption at any time t and t 1/2 (the square root of time), followed by a horizontal plateau (saturation) The equilibrium moisture content (M m ) and diffusion coefficient (D) of PLA nanocomposites increased with the addition of MMT (2 phr) and LLDPE However, the D values of both nanocomposites decreased by increasing MMT (4 phr) The M m for PLA/MMT and PLA/LLDPE/MMT nanocomposites increased by increasing immersion temperature (60 °C) and prolonged immersion resulted in hygrothermal degradation of both nanocomposites The hygrothermal degradation studies showed that PLA degrades much faster at 90 °C as compared to 60 °C in both the nanocomposites The addition of MMT and LLDPE improved the hygrothermal stability of PLA in both nanocomposites Soil burial test revealed deterioration of impact strength in all samples while the rate of biodegradation was retarded in the presence of MMT and LLDPE

Self-Bonding Boards From Plantain Fiber Bundles After Enzymatic Treatment: Adhesion Improvement of Lignocellulosic Products by Enzymatic Pre-Treatment

Abstract: Self-bonding boards were manufactured with treated fibers at different concentrations of a laccase enzyme. This enzyme induced the generation of phenoxy radicals in the fiber lignin which can generate covalent bonds and cross-linked by radical–radical coupling. The effect of laccase concentration on the properties of obtained fiberboards was evaluated. The formation of free radicals and changes in the lignin macromolecule was measured using scavenging activity test, infrared spectroscopy, electron paramagnetic resonance and scanning electron microscopy. Thermal and mechanical properties of the resulting fiberboards were determined by differential scanning calorimetry, thermo gravimetric analysis and flexion tests. Increased thermal stability, modulus of elasticity and modulus of rupture and also, a reduction in thickness swelling and water absorption, were observed at higher concentrations of laccase. These results are ascribed to the effect of the free radicals that were generated during the enzymatic treatment.

Biodegradation of Poly(vinyl alcohol) and Bacterial Cellulose Composites by Aspergillus niger

Abstract: The ability of fungal strains to attack a composite material obtained from poly(vinyl alcohol) (PVA) and bacterial cellulose (BC) is investigated. The fungal strain tested was Aspergillus niger. This fungal strain was able to change not only the polymer surface from smoother to rougher, but also to disrupt the polymer. The degradation results were confirmed by visual observations, scanning electron microscopy (SEM) analyses, X-ray diffraction analyses and FTIR spectra of the film samples. SEM micrographs confirmed the growth of fungi on the composite film surface. The degree of microbial degradation depends on culture medium and on composition of polymeric materials, especially on PVA content. The biodegradation process is accelerated by the presence of glucose in the culture medium as an easily available carbon source.

Processing and Characterization of Glycerol-Plasticized Soy Protein Plastics Reinforced with Citric Acid-Modified Starch Nanoparticles

Abstract: Citric acid-modified starch nanoparticles with an average size of 82 nm were prepared through precipitation from gelatinized starch solution by ethanol and further modification with citric acid. When being incorporated in glycerol-plasticized soy protein plastics, citric acid-modified starch nanoparticles displayed dramatic reinforcing effect. The resulted nanocomposite plastics exhibited improvement in mechanical performance. Also, the water uptake decreased, indicating an increase of water resistance. The modified starch nanoparticles had a good compatibility with soy protein matrix. Possessing a relative hydrophobic surface, the filler would prefer to interact with protein-rich domains in glycerol-plasticized soy protein. The work provided a green approach of biodegradable materials based on naturally occurring biopolymers.

Effect of Compatibilizing Agent on the Properties of Highly Crystalline Composites Based on Poly(lactic acid) and Wood Flour and/or Mica

Abstract: This article contains a concept of the mechanical properties improvement of the highly crystalline poly(lactic acid) (PLA) and filled composites. PLA as a semi-crystalline thermoplastic polymer was plasticized with poly(ethylene glycol) and filled with 30 vol% of organic and/or inorganic filler. The degree of crytallinity was intentionally increased by annealing. The filler/polymer matrix interphase was modified with the addition of 4, 4′-Methylenediphenyl diisocyanate (MDI). The effect of compatibilizing as well as plasticizing agent on the thermal and mechanical properties, the water-absorption behaviour and crystallization characteristics were studied. The results indicated that high content of filler and crystallites have a strong influence on the composite′s mechanical properties despite of the plasticizer content, showing a high Young modulus. The MDI seems to react in preference easy with plasticizing agent and then alternatively with filler due to the low functionality of commercial PLA grade.

Preformed Amide-containing biopolymer for Improving the Environmental Performance of Synthesized Urea-formaldehyde in Agro-fiber Composites

Abstract: Investigations have continued for production high performance agro-based composites using environmentally acceptable approaches. This study examines the role of adding amide-containing biopolymers during synthesis of urea–formaldehyde (UF) on properties of adhesive produced, especially its adhesion potential. The environmental performance of UF-resin synthesized in the presence of modified amide-containing biopolymer was evaluated by evaluating the free-HCHO of both adhesive (during processing) and of the eventual engineered composite product. Also, the benefits of this synthesis-modified adhesive in enhancing the bondability of sugar-cane fibers used in engineered composite panels was evaluated and compared to using UF-resin. The results obtained show that, static bending of the produced composites varied from 27.7 to 33.13 N/mm2 of modulus of rupture (MOR) and from 2860 to 3374 N/mm2 of Modulus of Elasticity (MOE); while for internal bond (IB) it’s varied from 0.64 to 0.866 N/mm2. Based on the ANSI and EN Standards modified UF-based agro composites produced meet the performance requirements for high grade particleboards with respect to static bending strength. These agro-based composite also tested out as having free-HCHO values of ~13 mg/100 g board.