Fast Preparation of Flexible Wet-Resistant and Biodegradable Films From a Stable Suspension of Xylan/Chitosan Polyelectrolyte Complexes

Journal of Polymers and the Environment - Novel hemicellulose-based films from polyelectrolyte complexes (PECs) of chitosan and xylan from sugar cane bagasse were prepared and characterized. PEC...     

Role of Hydrophilic and Hydrophobic Interactions in Structure Development of Zein Films

Zein has been studied for its potential as a biobased polymeric material. Due to the fact that films made exclusively from zein are brittle, composites of zein and oleic acid were prepared in our lab and formed into flexible films. Film properties were believed related to their structure. X-ray scattering measurements on zein films suggested the formation of layers along the plane of the film. Oleic acid seemed to play an important role in layer formation. However, X-ray measurements could not yield information on the nature of the interface between oleic acid and zein. Surface plasmon resonance (SPR) was used to further investigate interaction between zein and oleic acid. Dynamic adsorption of zein from alcoholic solutions onto hydrophilic and hydrophobic surfaces generated by self-assembled monolayers of 11-mercaptoundecanoic acid or 1-octanethiol was monitored by SPR. It was observed that zein had a greater affinity for hydrophilic than for hydrophobic surfaces under the prevalent experimental conditions. A mechanism for structure development of zein-oleate films was proposed based on these results and previous X-ray measurements. It is suggested that the structure development involves hydrophilic adsorption of fatty acids onto the zein surface followed by hydrophobic associations leading to a layered film structure organization.     

Preparation and Characterization of Xylan Derivatives and Their Blends

Although hemicellulose is found widely in nature, it is currently under-utilized as a raw material for commercial applications. It would be desirable to find new uses for hemicellulose in order to add value to this agro-based material. A common type of hemicellulose is xylan, which is found in a number of wood species and in cotton. In this work we prepared cationic and anionic xylan derivatives and characterized them by ¹³C NMR, FT-IR, size exclusion chromatography (SEC), thermal analysis, and rheology. In particular, the ¹³C NMR spectra of carboxymethyl xylan (CMX) and quaternary ammonium-adducted xylan (QAX) were fully assigned with the help of samples with different degrees of substitution. SEC indicated that the beechwood xylan showed a bimodal molecular weight distribution, but with derivatization the distribution tended to become unimodal. Thermal analysis and rheology studies did not uncover any surprises; the solution of xylan and its derivatives exhibited mostly Newtonian behavior. The blends of CMX and QAX produced a precipitate at almost all ratios, indicating the formation of a polyelectrolyte complex. When cationic and anionic xylan samples were added together to paper, the paper dry strength increased. Thus, the combination of cationic/anionic xylan may be of interest in selected applications.     

Oxygen and Water Barrier Properties of Coated Whey Protein and Chitosan Films

Films of whey protein and chitosan acetic acid salt have lower oxygen permeability than, for example, ethylene-co-vinylalcohol under dry conditions, but water and water vapor seriously impair the gas barrier properties. To reduce the oxygen permeability at 90% relative humidity and the water-vapor transmission rate at 100% relative humidity, the films were coated with an alkyd, a beeswax compound, or a nitrocellulose lacquer. Permeability and transmission rate measurements were performed in accordance with standard methods and showed that the beeswax compound and the nitrocellulose were appropriate as water-vapor barriers. Overall migration to water was measured after 10 days exposure time, with the coated surface exposed to the water, showing that the alkyd-coated and the nitrocellulose-coated films were both below the safety limit for food contact. Water absorbency tests, performed by the Cobb method, showed that the films coated with the beeswax compound or with nitrocellulose lacquer exhibit lower absorbency than the alkyd-coated films.     

Mechanical Properties, Water Vapor Permeability and Water Affinity of Feather Keratin Films Plasticized with Sorbitol

In poultry industry chicken feathers are normally hydrolyzed and used to prepare animal feed. In this work the use of this material to prepare films was investigated. Keratins were extracted from chicken feathers with 2-mercaptoethanol in concentrated urea solution using sodium dodecyl sulfate (SDS). The effect of varying the amount of sorbitol on properties of chicken feather keratin (CFK) was investigated. As the concentration of plasticizer increased, the moisture content (MC) of these films increase, the monolayer MC increased from 0.060 (without plasticizer) to 0.482 g water/g dry matter (0.30 g sorbitol/g keratin). The water vapor permeability (WVP) varied between 0.096 g/m s Pa and 8.098 g/m s Pa for films without sorbitol and with 0.30 g sorbitol/g keratin, respectively. Film strength decreased from 5.13 MPa to 0.45 MPa and the elongation at break achieved the maximum value of 52.75% for samples with 0.02 g sorbitol/g keratin. The dry matter density didn’t change significantly, varying between 0.86–0.89 g/cm³ for all samples. Films with potential applications in food packaging can be obtained from CFKs. However, further researches are necessary to decrease film solubility and increase mechanical resistance.     

Interactions between Sediment and Water: Perspectives on the 10th International Association for Sediment Water Science Symposium

The 10^th International Symposium on Interactions Between Sediment and Water was held in Lake Bled, Slovenia from August 28 to September 3, 2005. Approximately 155 delegates, attended the symposium where talks and posters addressed five themes incorporating the physical, chemical, biological, and/or management aspects of lacustrine, reverine, estuarine, and/or marine sediment were presented. A review of the symposium themes and plenary talks was provided. As well, this symposiums’ focus is put into context with respect to historical changes noted over the 29 years that the International Association for Sediment Water Science (IASWS) has been meeting.     

Water Vapour Transport in Biopolymeric Materials: Effects of Thickness and Water Vapour Pressure Gradient on Yeast Biomass-Based Films

Journal of Polymers and the Environment - Biopolymer-based films are hydrophilic biodegradable matrices that exhibit poor water vapour barrier. Ideally, water vapour permeability does not depend on...     

Tailor Made Thin Film Composite Membranes: Potentiality Towards Removal of Hydroquinone from Water

The study investigated the use of thin film composite membrane (TFC) as a potential candidate for hydroquinone removal from water. Thin film composite membranes were prepared by polyamide coating on Polysulfone asymmetric membrane. FTIR study was performed to verify the Polysulfone as well as polyamide functionality. TFC membrane was characterized by contact angle, zeta potential, scanning electron microscopy studies. The salt rejection trend was seen from 500 to 1000 mg/L. The membrane is marked by permeability co-efficient B based on solution diffusion studies. The value is 0.98 × 10^?6 m/s for NaCl solution at 1.4 MPa. The separation performance was 88.87% for 5 mg/L hydroquinone at 1.4 MPa. The separation was little bit lowered in acid medium because of the nature of the membrane and feed solute chemistry. The ‘pore swelling’ and ‘salting out’ influenced hydroquinone separation in the presence of NaCl. The hydroquinone separation was 80.63% in 1000 mg/L NaCl solution. In acidic pH, NaCl separation was influenced much more compared to hydroquinone. The separation is influenced by field water matrix.     

Effect of Casting Process Conditions on Mechanical Properties and Water Solubility of Films Made from Wolf Fruit and Its Optimization

Journal of Polymers and the Environment - Biodegradable films based on wolf fruit flour were prepared by the casting process using glycerol as a plasticizing agent. The influence that the process...     

Sediment–Water Interactions in an Eroded and Heavy Metal Contaminated Peatland Catchment,Southern Pennines,UK

Atmospherically deposited lead in the upper layer of the heavily eroded peatlands of the Peak District, southern Pennines, UK, reaches concentrations in excess of 1,000 mg kg⁻¹. Erosion of the upper peat layer in this region is releasing lead, associated with eroded peat particles, into the fluvial system. Understanding the process mechanisms that control dissolved lead concentrations in contaminated peatland streams is vital for understanding lead cycling and transport in peatland streams. Many headwater streams of the southern Pennines recharge drinking water reservoirs. Measurements in the Upper North Grain (UNG) study catchment show that mean sediment-associated and dissolved lead concentrations are 102 ± 39.4 mg kg⁻¹ and 5.73 ± 2.16 μg l⁻¹, respectively. Experimental evidence demonstrates that lead can desorb from suspended sediments, composed of contaminated peat, into stream waters. In-stream processing could therefore account for the elevated dissolved lead concentrations in the fluvial system of UNG.     

Comparative Study of Xylan Extracted by Sodium and Potassium Hydroxides (NaOH and KOH) from Bagasse Pulp: Characterization and Morphological Properties

Xylan is the second most abundant polysaccharide and the predominant hemicellulose component of soda bagasse pulp. The present endeavor focuses on increasing the value addition to underutilized agro-industrial residue such as bagasse. For this purpose, xylan was isolated by two conventional alkali extraction methods i.e. NaOH and KOH. The recovery rate and sugar composition of different reaction times and alkali consumptions were monitored with advanced method such as High Performance Liquid Chromatography (HPLC). The Fourier Transform Infrared Spectroscopy (FTIR) and Wide Angle X-ray spectroscopy (WAXS) were respectively employed to characterize the functional groups and Crystallinity Index (CrI) changes during the extraction process. It was explored that highest xylan recovery rates were obtained with 6% of NaOH at 120 min and 6% KOH at 45 min. The xylan morphology via WAXS was found that its structure to be amorphous. HPLC results also showed KOH had higher effectiveness than NaOH in terms of extracted xylan purity. Highest XGRs (Xylose to Glucose Ratios) were also achieved by KOH processes. Hence, this study contributes to the adequate utilization of agricultural residues, with promising potential for applications in the production of certain novel materials and chemical conversion industries.     

Preparation and Biodegradation of Starch/Polycaprolactone Films

Starch granules were modified with trisodium trimetaphosphate (TSTP) and characterized by P³¹-NMR, FTIR and DSC. Seventy-micron films were prepared from modified starch and polycaprolactone blends by solvent casting technique. Three different types of films—PCL (100% polycaprolactone), MOD-ST/PCL (50% modified starch and 50% polycaprolactone blend) and NONMOD-ST/PCL (50% nonmodified starch and 50% polycaprolactone blends)—were prepared, and their thermal, mechanical, and morphologic properties were investigated to show the increased performance of PCL with the addition of starch and also the effect of modification. It was observed that with the addition of starch the Young's modulus of polycaprolactone was increased and became less ductile, whereas tensile strength and elongation at break values decreased. Biodegradation of these films was inspected under different aerobic environments with the presence of Pseudomonas putida, activated sludge, and compost. It was observed that whereas P. putida had almost no effect on degradation during 90 days, with the presence of activated sludge, considerable deformation of films was observed even in the first 7 days of degradation. In a compost environment, degradation was even faster, and all polymer films were broken into pieces within first 7 days of degradation and no film remained after 15 days.     

Mechanical Performance and Design Criteria of Biodegradable Low-tunnel Films

The overall mechanical behaviour of a series of experimental Mater-Bi made thin low-tunnel films is analysed with respect to the effect of two major factors: the film processing optimisation during manufacturing and the design of the low-tunnels structural system. The analysis of the mechanical behaviour of the biodegradable low-tunnel films, based on the results of extensive full-scale and small-scale experiments, combined with laboratory testing of the mechanical properties of the film, proves that a rather good mechanical behaviour is possible for these films, comparable to the behaviour of conventional agricultural films in terms of strength, provided that two criteria are met: (a) the low tunnel structural design is based on the initial stress at yield value of the film, which represents the asymptotic value of the tensile strength of the film, following its evolution with the time of exposure to real field conditions; (b) the processing of the film is optimised for the particular biodegradable material and film thickness under consideration. It is also confirmed that the stabilisation schemes used with conventional polyethylene films are not suitable for the biodegradable films.

Biodegradation and Ecotoxicity of Polyethylene Films Containing Pro-Oxidant Additive

The worldwide accumulation of non-degradable plastic materials, such as plastic bags, is one of the most important environmental concerns nowadays. The use of degradable materials is an option to mitigate the environmental impact generated by the consumption of plastics. One of the technologies used for the manufacture and use of degradable plastics is the use of pro-degradant additives that are incorporated in conventional plastics to promote their degradation under certain conditions. The aim of this study is to evaluate the process of oxidation, biodegradation and potential ecotoxicity of polyethylene films containing an oxo-degradable additive, according to the standard ASTM D-6954. This method establishes a procedure in which the samples are subjected to consecutive steps of accelerated oxidation, biodegradation by composting and ecotoxicity assessment. Furthermore, the effect of the presence of printing ink in the polyethylene samples with oxo-degradable additive was evaluated, and the results were compared with those obtained for samples of conventional polyethylene and polylactic acid. After 180 days of laboratory controlled composting, the samples reached the following percentages of biodegradation: polylactic acid, 41 %; printed oxo-degradable polyethylene, 32.24 %; oxo-degradable polyethylene, 25.84 %; printed polyethylene, 18.23 % and polyethylene, 13.48 %. The cellulose sample used as a control was mineralized in 58.45 %. Ecotoxicity assessment showed that the products of biodegradation of the samples tested, did not generate a negative effect on germination or development of the vegetal species studied. Under proper waste management conditions, these plastics can be used as an option to decrease the environmental impact of plastic films.     

Agricultural Application and Environmental Degradation of Photo-Biodegradable Polyethylene Mulching Films

Photo-biodegradable polyethylene (PBD-PE) films containing starch have been developed and used in agriculture. They are better able to raise temperature, preserve moisture, and raise yield than common polyethylene films, and they can be degraded environmentally after finishing these functions. The photo-biodegradation induction periods of four kinds PBD-PE films range from 46 to 64 days, which basically satisfies the needs of agricultural cultivation. All PBD-PE films can be degraded to Stage V, in which almost no film exists on the surface of the ridges 2–3 months or so after the induction periods. The PBD-PE films buried in soil have also good degradability.     

Interactions of Natural Colloidal Material and Phenanthrene in the Aquatic Environment

Resuspension of contaminated aquatic sediments by natural and anthropogenic activities (i.e., dredging, boat activities, fish, wildlife, storms, runoff) increases the flux of natural colloidal material and colloidally bound contaminants into the overlying water column. Colloidal material extracted from lower Fox River sediments was analyzed for various physical and chemical characteristics and subjected to batch aggregation studies under controlled conditions of pH (～3–8) and colloid concentrations (5 and 9 mg L^?1 as TOC equivalents) in the presence of dissolved phenanthrene in solution. Under water chemistry conditions where pH and K⁺ concentration are typical of most natural waters (10^?2 M K⁺ and pH～8), the presence of phenanthrene in solution (average [phen] = 0.2–0.4 mg/L) prevents particle aggregation and decreases the settling rate of these particles. Ultimately, this increases the total concentration of colloidally bound contaminants in the water column. Dredging is the most popular remediation technique for removing contaminated sediments from the aquatic environment. However, this laboratory study suggests that for typical waters, dredging may potentially elevate the concentrations of contaminants found in the water column. © 2001 John Wiley & Sons, Inc.     

Biodegradation by Composting of Surface Modified Starch and PVA Blended Films

Several starch/PVA/glycerol polymer blends were prepared by a solution casting technique and examined for biodegradation by composting over 45 days. Within this time frame, the starch and glycerol components were fully degraded, leaving the PVA component essentially intact. The lowest PVA content film (20%) was selected as a polymer with enough PVA to impart important physical characteristics, but also enough starch to be considered biodegradable. The film characteristics were further improved by surface modification with chitosan. This modification did not interfere with the biodegradation of the starch component. Furthermore, there was slight evidence that PVA biodegradation had been initiated in composted, surface modified starch/PVA blends.     

Biodegradability of Banana and Plantain Cellulose Microfibrils Films in Anaerobic Conditions

Currently, cellulose microfibrils are being investigated as nanofillers for polymers to increase their biodegradability. However, until now there has been no report on their degradability by microorganisms. In this work the anaerobic degradation of cellulose microfibril films extracted from banana and plantain plant rachis residues has been studied. Samples were exposed to burial tests in nature compost during 14?days. Changes due to the degradation process were investigated by techniques as optical microscopy, tensile tests, viscosity measurements, ATR-FTIR spectroscopy, X-ray diffraction and thermogravimetric analysis. Biodegradability was higher for cellulose microfibril films extracted from banana (BCMF) than plantain films (PCMF). Growth of microorganism colonies on BCMF films and just yellowing on PCMF films was observed by microscopic analysis. New bands characteristic of aldehyde functional groups due to the breaking of ??-(1,4)-glycosidic bonds were observed in infrared spectra. This breakage was also responsible for the fall-down of mechanical properties and polymerization degree. X-ray diffraction and thermogravimetric analysis showed that BCMF films were at the first stage of degradation for the used burial test times because the microorganisms only attacked the amorphous cellulose leading to a slight increase in crystallinity. In the case of PCMF films this variation remained practically invariant.     

Mechanical,Barrier and Antioxidant Properties of Chitosan Films Incorporating Cinnamaldehyde

Chitosan films (CF) [1 and 2% w/v] alone and with cinnamaldehyde (CNE) [0.25, 0.5 and 1% v/v] were prepared using an emulsion method, and the obtained films were characterized in terms of water vapor permeability (WVP), water solubility and optical, mechanical and antioxidant properties. The incorporation of CNE at 1% (v/v) significantly decreased the water solubility of the film by approximately 4% for the 1 and 2% CF films, whereas the WVP increased (2.5–3.5 times). The incorporation of CNE (0.25 and 0.5%) into 2% CF significantly increased the tensile strength (TS) (62 and 34%, respectively) and the percent elongation (%E) values, 26, 30 and 52% for CF that contained 0.25, 0.5 and 1% CNE, respectively. The largest value of the elasticity modulus (EM) was observed for 2% CF with 0.25% CNE. All films exhibited a yellow appearance (b*), but the CNE content had a marked impact on the coloration of the films. The CNE recoveries of the CF films (1 and 2%) with 1% of CNE were high (43 and 67%). The antioxidant activities indicated that the incorporation of 1% CNE into CF films (1 and 2%) increased the antioxidant activity. The protective effects of the films with and without CNE on erythrocytes were very strong (36–72% hemolysis inhibition). These results suggest there are potential applications for CF-CNE films as active packaging for the preservation of food products.