Polyethylene/poly (lactic acid)/chitosan films, with and without poly (ethylene-g-maleic anhydride) (PEgMA) as compatibilizer, were prepared by extrusion and the degradation behavior under different ...times of standard weathering conditions was analyzed. The materials were characterized by means of infrared spectroscopy, scanning electron microscopy, tensile strength, differential scanning calorimetry and thermogravimetric analysis. It was demonstrated that blends of synthetic and natural polymers have a higher susceptibility to degradation in comparison to neat polyethylene and poly (lactic acid) films. Additionally, it is found that the incorporation of PEgMA into the extruded films apparently favored the polymer degradation, as it deduced from the fall of the mechanical properties when the films are exposed to accelerated weathering simulation.
•Extruded polymeric blends of PE PLA Ch with and without compatibilizer were obtained.•The incorporation of PEgMA makes the films to have a larger degradation.•The accelerated degradation has a strong effect on the mechanical properties of the films.•Morphology of the films was greatly affected by accelerated weathering.•The compatibilizer has no significant effect on the thermic stability of the materials tested.
•Novel extruded films of polyethylene with a content of 20wt% chitosan were obtained.•Compatibilizer PEgMA and glycerol improved the processability of the mixtures.•The compatibilized films showed an ...improvement in the deformation at break.
Novel films of polyethylene and chitosan were obtained using extrusion. These polymers have interesting properties, and processing them with methods that are of high use in the industry, such as the extrusion method, can have a significant effect on the potential applications of these materials. The individual materials were thermally characterized; after this, extruded films of low density polyethylene and chitosan mixtures were prepared with the addition of polyethylene-graft-maleic anhydride as a compatibilizer for the blends, and glycerol, as a plasticizer for chitosan. The use of compatibilizer and plasticizer agents improved the processability and compatibility of the mixtures, as well as their mechanical properties, as revealed by mechanical property measurements and scanning electron microscopy. It was possible to prepare blends with a maximum chitosan content of 20wt%. The material stiffness increased with the increase of chitosan in the sample. FTIR studies revealed the existence of an interaction between the compatibilizer and chitosan.
In the present work, polylactic acid (PLA), elastin and gelatin fibers, containing clindamycin, were prepared to test their potential application as wound dressings. They underwent release studies to ...determine the mechanism of drug release through mathematical models. The fibers have a homogeneous morphology, without pores. The studies of FTIR and thermal analysis corroborate the presence of each of the components in the fibers; the results of the feasibility tests showed encouraging percentages with a viability of 82% after 7 days of direct contact of the HUVEC cells with the membranes. Similarly, cell adhesion assays show the presence of viable and stretched cells on the fibers, the tendency of the cells to position themselves on the fibers and follow this conformation was observed. On the other hand, studies of antimicrobial activity against
S. aureus
show us that in fibers loaded with clindamycin they have inhibition halos greater than 8 mm.
Optimal usage of urea-based fertilizers can increase their use efficiency and reduce pollution. A new alternative for prolonged-release (PR) urea based on wheat-gluten (WG) membranes obtained by ...electrospinning was studied. The effect of pH and temperature on the release rate of urea and its transport mechanisms were evaluated. At pH 4, 7, and 10, the equilibration times obtained were 1, 3, and 5 h, respectively. Additionally, at a higher temperature, a larger amount of urea was released into the medium. The Ritger–Peppas model suggests that with pH 4 and pH 10, at 25 °C, there is an anomalous diffusion mechanism. On the other hand, the remainder of the release conditions tested showed a release mechanism of urea by simple diffusion. According to the results, a potential application of these wheat-gluten membranes on the release system of urea for soils with pH 7 and soil temperatures between 25 and 40 °C is proposed.
Graphical Abstract
The optimal conditions for the fibers preparation of cellulose acetate (CA) and poly(vinyl pyrrolidone) (PVP) containing triclosan within the fiber were successfully found; the physicochemical ...characteristics of these fibrous membranes were corroborated by FTIR spectroscopy, thermal analysis, mechanical tests, SEM , and TEM analysis. The formation of composite fibers of CA and PVP containing triclosan at the core of the fiber was evidenced. A comparative study of the release properties of amoxicillin, epicatechin or triclosan embedded into fibers CA/PVP/CA was performed. As more interactions of the drug with CA or PVP occur, slower release of the drug into the release medium takes place. Regarding the drug delivery system design, it is important to consider the possible molecular interactions between the material components and predict how fast or slow the drug will be delivered into the corresponding medium.
Development of extruded films composed of biopolymers blended with synthetic polymers aims to minimize the environmental impact of plastic waste‐materials and lead to the sustainable plastic ...industry. To produce biodegradable polymeric blends, the weight content of biopolymers must be maximum without compromising the performance properties of the extruded films. Using a solvent‐free extrusion method, films composed of polypropylene, poly(lactic‐acid), and Chitosan, can be obtained with the use of polypropylene‐graft‐maleic anhydride and glycerol as compatibilizer and plasticizer, respectively. Extruded films with up to a 50 wt% content of biopolymers show acceptable thermal and mechanical properties, where the use of compatibilizer improves the processing characteristics and homogeneous distribution of chitosan throughout the films. Therefore, the extruded films can be considered as alternatives to conventional synthetic‐polymer films, due to their acceptable mechanical and thermal properties with direct potential applications in extrusion‐method mass production of biodegradable polymers.
•Rare eddy covariance flux measurements of CO2 and CH4 in a palm swamp peatland in the Peruvian Amazon.•The peatland was a large CO2 sink and a CH4 source.•Photosynthetic activity was inhibited and ...respiration enhanced during warm-dry conditions.•Carbon cycling in Amazonian palm swamp forests are sensitive to hydrometeorological forcings.•Longer-term measurements are needed to assess their potential vulnerability to climate change.
Tropical peatlands are a major, but understudied, biophysical feedback factor on the atmospheric greenhouse effect. The largest expanses of tropical peatlands are located in lowland areas of Southeast Asia and the Amazon basin. The Loreto Region of Amazonian Peru contains ~63,000 km2 of peatlands. However, little is known about the biogeochemistry of these peatlands, and in particular, the cycling of carbon dioxide (CO2) and methane (CH4), and their responses to hydrometeorological forcings. To address these knowledge gaps, we established an eddy covariance (EC) flux tower in a natural palm (Mauritia flexuosa L.f.) swamp peatland near Iquitos, Peru. Here, we report ecosystem-scale CO2 and CH4 flux observations for this Amazonian palm swamp peatland over a two-year period in relation to hydrometeorological forcings. Seasonal and short-term variations in hydrometeorological forcing had a strong effect on CO2 and CH4 fluxes. High air temperature and vapor pressure deficit (VPD) exerted an important limitation on photosynthesis during the dry season, while latent heat flux appeared to be insensitive to these climate drivers. Evidence from light-response analyses and flux partitioning support that photosynthetic activity was downregulated during dry conditions, while ecosystem respiration (RE) was either inhibited or enhanced depending on water table position. The cumulative net ecosystem CO2 exchange indicated that the peatland was a significant CO2 sink ranging from −465 (−279 to −651) g C m−2 y−1 in 2018 to −462 (−277 to −647) g C m−2 y−1 in 2019. The forest was a CH4 source of 22 (20 to 24) g C m−2 y−1, similar in magnitude to other tropical peatlands and larger than boreal and arctic peatlands. Thus, the annual carbon budget of this Amazonian palm swamp peatland appears to be a major carbon sink under current hydrometeorological conditions.
Chemical hydrogel based on poly(γ-glutamic acid) obtained from
Bacillus licheniformis (
ATCC-9945a) and using urea as a crosslinking agent was synthesized. The hydrogel was characterized by infrared ...spectroscopy, scanning electron microscopy, thermal analysis and swelling capacity. The crosslinking of the biopolymer was evidenced by changes in the intensities of signals in the infrared spectrum corresponding to amide groups, with respect to the spectrum of the pure biopolymer. Moreover, a porous structure, characteristic of hydrogels, with average pore size of 80 ± 31 μm was confirmed. The hydrogel showed a glass transition temperature of 144.5 °C and a decomposition temperature of 219 °C. The swelling ratio of the hydrogel increased with the increase of contact time with the swelling medium and pH, presenting values at equilibrium of 6.6, 13.4 and 15.3 at pH 3.6, 7.4 and 10, respectively; meanwhile, little influence of temperature on the swelling of the material was observed. Moreover, through the use of mathematical models, it is deduced that the swelling of the hydrogel in the buffer solutions occurs through lower Fickian and Fickian type mechanisms, and in deionized water an anomalous mechanism predominates.
Graphical abstract
A novel semi-interpenetrating polymer network (s-IPN) based on the entrapment of a thermosensitive polymer, the poly(vinyl methyl ether) (PVME), within a crosslinked 3D structure of poly(vinyl ...alcohol) (PVA) and poly(vinyl methyl ether-
alt
-maleic acid) (COP) was synthesized by an autoclaving process. The preparation method avoids the use of toxic crosslinkers and allows the simultaneous sterilization of material. The PVA/COP/PVME hydrogel were characterized by Fourier transform infrared spectroscopy, thermal techniques, swelling kinetic measurements, scanning electron microscopy, and rheological analysis. The entrapment of PVME within the hydrated polymer framework significantly modified its transition temperature at pH 7.4 and pH 3 conditions. The swelling kinetics of the s-IPN were dependent on pH (7.4, 3 and 1), and temperature (25 and 37 °C). The interpenetrated polymer chains reduced the internal pore sizes of crosslinked network without altering its elastic, solid-like behavior. The loading and
in vitro
release of 5-fluorouracil, a chemotherapeutic agent, from hydrogel systems were studied at different temperature and pH values. The hydrogels showed a sustained drug release up to 5 h at 37 °C, in different pH media. The s-IPN exhibited a promising performance for a range of biomedical applications, in particular, for the controlled drug delivery in response to the pH and temperature conditions.
PDF
