Special Issue "Natural Compounds for Natural Polymers"

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Biomacromolecules, Biobased and Biodegradable Polymers".

Deadline for manuscript submissions: closed (31 August 2019).

Special Issue Editor

Prof. Dr. Nadka Tz. Dintcheva
Website
Guest Editor
Department of Engineering, University of Palermo, 90128 Palermo, Italy
Interests: structure/processing/properties relationships in polymers; biopolymers; micro- and nano- composites; polymers and biopolymers degradation and stabilization
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

In the continual quest for natural and renewable resource materials, fossil-based polymers have been gradually replaced by (bio)polymers. There is also a very important query related to the use of naturally occurring compounds that are able to improve and tune (bio)polymers’ performance and properties. This Special Issue is focused on our current understanding of the structure/processing/properties relationships in (bio)polymers containing naturally occurring compounds. Special attention is paid to (i) the two main (bio)polymer classes, i.e., starch-based biopolymers and biopolyesters, which offer suitable performance and properties for several industrial applications, such as the biomedical, agricultural, food packaging, and textile sectors; (ii) the supply and use of naturally occurring compounds, such as reinforcement fillers, antioxidant molecules, etc., which ensure the formulation of totally eco-friendly and sustainable materials; and (iii) the effect of processing conditions and additive concentrations on (bio)polymers’ performance, properties, durability, and biodegradation.

Prof. Nadka Tz. Dintcheva
Guest Editor / Editorial Board Member

Keywords

  • Natural resource materials
  • Renewable materials
  • Eco-friendly and sustainable materials
  • Starch-based biopolymers
  • Biopolyesters
  • Applications in biomedicine, agriculture, food packaging, and textiles
  • Biodegradation

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Published Papers (17 papers)

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Research

Open AccessArticle
Bioactive Edible Films Based on Arrowroot Starch Incorporated with Cranberry Powder: Microstructure, Thermal Properties, Ascorbic Acid Content and Sensory Analysis
Polymers 2019, 11(10), 1650; https://doi.org/10.3390/polym11101650 - 11 Oct 2019
Cited by 3
Abstract
The growing global awareness about environmental preservation has stimulated the search for alternatives to replace conventional plastics made from fossil sources. One of the advantages is using polymers from renewable sources, such as starch and gelatin, which, in addition to being biodegradable, may [...] Read more.
The growing global awareness about environmental preservation has stimulated the search for alternatives to replace conventional plastics made from fossil sources. One of the advantages is using polymers from renewable sources, such as starch and gelatin, which, in addition to being biodegradable, may also be edible. The incorporation of cranberry into a polymeric matrix can transfer bioactive composite films, colour and flavour to the film, which are characteristic of this fruit, expanding its application to fruit stripes or colourful coatings for specific foods. In this context, the aim of this work was to evaluate the influence of the incorporation of 0, 5, 15, 25, 35, 45 and 55% (solids mass/biopolymer mass) cranberry powder on the microstructure, thermal properties, ascorbic acid content and sensory analysis of gelatin and arrowroot starch films obtained by casting. Scanning electron microscopy (SEM) images showed that the incorporation of cranberry made the film surface rough and irregular. All films presented an X-ray diffraction pattern typical of a semicrystalline material. The glass transition temperature (Tg) decreased when increasing the concentration of cranberry in films. All films with cranberry presented high ascorbic acid content and were well accepted by the tasters when sensory analysis was performed. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Transparent Cellulose/Technical Lignin Composite Films for Advanced Packaging
Polymers 2019, 11(9), 1455; https://doi.org/10.3390/polym11091455 - 05 Sep 2019
Cited by 6
Abstract
Although recent work has shown natural lignin products are promising to fabricate various polymer based functional composites, high-value applications were challenged by their structural complexity and inhomogeneity. This work specially assessed the potential of four technical lignins for cellulose based functional films production. [...] Read more.
Although recent work has shown natural lignin products are promising to fabricate various polymer based functional composites, high-value applications were challenged by their structural complexity and inhomogeneity. This work specially assessed the potential of four technical lignins for cellulose based functional films production. These four technical lignins were obtained by emerging pretreatment systems, i.e., lactic acid-betaine deep eutectic solvent (DES), ethanol organosolv, soda/anthraquinone (Soda/AQ) and the sodium salicylate hydrotrope, and their phenolic substructures were comparatively identified by prevalent 31P NMR technique. The influence of lignin chemical structure on the antioxidant potential and UV-shielding performance of the prepared cellulose/technical lignin composite films were assessed. Results showed severe organosolv and soda/AQ pretreatment produced technical lignins with higher total phenolic hydroxyl groups (3.37 and 3.23 mmol g-1 respectively), which also exhibited higher antioxidant activities. The composite films could effectively block the ultraviolet lights especially for UVB region (ultraviolet B, 280–315 nm) at only 5 wt.% lignin content. The contribution of lignin phenolic substructures to both antioxidant activity and UV-shielding property from high to low was syringyl > guaiacyl > p-hydroxyphenyl phenolic hydroxyl groups. This work provided some useful information that could facilitate upstream lignin extraction or downstream value-added applications. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Optimization of the Curing and Post-Curing Conditions for the Manufacturing of Partially Bio-Based Epoxy Resins with Improved Toughness
Polymers 2019, 11(8), 1354; https://doi.org/10.3390/polym11081354 - 15 Aug 2019
Cited by 3
Abstract
This research deals with the influence of different curing and post-curing temperatures on the mechanical and thermomechanical properties as well as the gel time of an epoxy resin prepared by the reaction of diglycidyl ether of bisphenol A (DGEBA) with an amine hardener [...] Read more.
This research deals with the influence of different curing and post-curing temperatures on the mechanical and thermomechanical properties as well as the gel time of an epoxy resin prepared by the reaction of diglycidyl ether of bisphenol A (DGEBA) with an amine hardener and a reactive diluent derived from plants at 31 wt %. The highest performance was obtained for the resins cured at moderate-to-high temperatures, that is, 80 ° C and 90 ° C , which additionally showed a significant reduction in the gel time. This effect was ascribed to the formation of a stronger polymer network by an extended cross-linking process of the polymer chains during the resin manufacturing. Furthermore, post-curing at either 125 ° C   or 150 ° C yielded thermosets with higher mechanical strength and, more interestingly, improved toughness, particularly for the samples previously cured at moderate temperatures. In particular, the partially bio-based epoxy resin cured at 80 ° C and post-cured at 150 ° C for 1 h and 30 min, respectively, showed the most balanced performance due to the formation of a more homogeneous cross-linked structure. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
TiO2-Doped Chitosan Microspheres Supported on Cellulose Acetate Fibers for Adsorption and Photocatalytic Degradation of Methyl Orange
Polymers 2019, 11(8), 1293; https://doi.org/10.3390/polym11081293 - 02 Aug 2019
Cited by 2
Abstract
Chitosan/cellulose acetate (CS/CA) used as a biopolymer systema, with the addition of TiO2 as photocatalyst (C-T/CA) were fabricated by alternating electrospinning/electrospraying technology. The uniform dispersion of TiO2 and its recovery after the removal of methyl orange (MO) was achieved by incorporating [...] Read more.
Chitosan/cellulose acetate (CS/CA) used as a biopolymer systema, with the addition of TiO2 as photocatalyst (C-T/CA) were fabricated by alternating electrospinning/electrospraying technology. The uniform dispersion of TiO2 and its recovery after the removal of methyl orange (MO) was achieved by incorporating TiO2 in CS electrosprayed hemispheres. The effects of pH values, contact time, and the amount of TiO2 on adsorption and photocatalytic degradation for MO of the C-T/CA were investigated in detail. When TiO2 content was 3 wt %, the highest MO removal amount for fiber membranes (C-T-3/CA) reached 98% at pH value 4 and MO concentration of 40 mg/L. According to the data analysis, the pseudo-second-order kinetic and Freundlich isotherm model were well fitted to kinetic and equilibrium data of MO removal. Especially for C-T-3/CA, the fiber membrane exhibited multiple layers of adsorption. All these results indicated that adsorption caused by electrostatic interaction and photocatalytic degradation were involved in the MO removal process. This work provides a potential method for developing a novel photocatalyst with excellent catalytic activity, adsorbing capability and recycling use. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Assembly of Polyacrylamide-Sodium Alginate-Based Organic-Inorganic Hydrogel with Mechanical and Adsorption Properties
Polymers 2019, 11(8), 1239; https://doi.org/10.3390/polym11081239 - 26 Jul 2019
Cited by 11
Abstract
Hydrogels have been widely used in water purification. However, there is not much discussion and comparison about the effects of different nanofillers on the reinforcement and adsorption performances of hydrogels, which can be subjected to rapid water flow and possess strong adsorption ability. [...] Read more.
Hydrogels have been widely used in water purification. However, there is not much discussion and comparison about the effects of different nanofillers on the reinforcement and adsorption performances of hydrogels, which can be subjected to rapid water flow and possess strong adsorption ability. In this work, polyacrylamide (PAAM)-sodium alginate (SA) interpenetrating polymer network-structured hydrogels were prepared by in situ polymerization. PAAM formed the first flexible network and SA constructed the second rigid network. Three kinds of inorganic nanoparticles including carbon nanotubes (CNTs), nanoclays (NCs), and nanosilicas (NSs) were incorporated into a PAAM-SA matrix via hydrogen bond. The obtained hydrogels exhibited a macroporous structure with low density (≈1.4 g/cm3) and high water content (≈83%). Compared with neat PAAM-SA, the hydrogels with inorganic nanoparticles possessed excellent mechanical strengths and elasticities, and the compression strength of PAAM-SA-NS reached up to 1.3 MPa at ε = 60% by adding only 0.036 g NS in a 30 g polymer matrix. However, CNT was the best filler to improve the adsorption capacity owing to its multi-walled hollow nanostructure, and the adsorption capacity of PAAM-SA-CNT was 1.28 times higher than that of PAAM-SA. The prepared hydrogels can be potential candidates for use as absorbents to treat wastewater. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Adsorption, Antibacterial and Antioxidant Properties of Tannic Acid on Silk Fiber
Polymers 2019, 11(6), 970; https://doi.org/10.3390/polym11060970 - 03 Jun 2019
Cited by 5
Abstract
Natural bioactive compounds have received increasing attention in the functional modification of textiles. In this work, tannic acid was used to impart antibacterial and antioxidant functions to silk using an adsorption technique, and the adsorption properties of tannic acid on silk were studied. [...] Read more.
Natural bioactive compounds have received increasing attention in the functional modification of textiles. In this work, tannic acid was used to impart antibacterial and antioxidant functions to silk using an adsorption technique, and the adsorption properties of tannic acid on silk were studied. The adsorption quantity of tannic acid on silk increased with decreasing pH in the range of 3–7. The rates of the uptake of tannic acid by silk were well correlated to the pseudo-second-order kinetic model, and the calculated activation energy of adsorption was 93.49 kJ/mol. The equilibrium adsorption isotherms followed the Langmuir model. The adsorption rate and isotherm studies demonstrated that the chemical adsorption of tannic acid on silk occurred through the ion-ion interaction between tannic acid and silk. Tannic acid displayed good building-up properties on silk. The silk fabric treated with 0.5% tannic acid (relative to fabric weight) exhibited excellent and durable antibacterial properties. Moreover, the silk fabrics treated with 2% and 5% tannic acid had good and durable antioxidant properties. The treatment by tannic acid had less impact on the whiteness of the silk fabric. In summary, tannic acid can be used as a functional agent for preparing healthy and hygienic silk materials. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Synthetized Potato Starch—A New Eco Sizing Agent for Cotton Yarns
Polymers 2019, 11(5), 908; https://doi.org/10.3390/polym11050908 - 20 May 2019
Cited by 1
Abstract
The objective of this research was to verify the feasibility of the use of newly synthesized biopolymer materials for sizing cotton yarns based on the basic principles of chemical modification. Research included acid hydrolysis of potato starch up to controlled molar masses together [...] Read more.
The objective of this research was to verify the feasibility of the use of newly synthesized biopolymer materials for sizing cotton yarns based on the basic principles of chemical modification. Research included acid hydrolysis of potato starch up to controlled molar masses together with graft-polymerization and methacrylic acid onto hydrolyzed starch to improve hydrophilicity and solubility, to increase the capability of film forming, to increase adhesive potential and to avoid retrogradation phenomena. Research objectives were primarily focused on finding an appropriate, environmentally-friendly and productive sizing agent for cotton yarns via the analysis and systematization of a large number of synthesis methods in conjunction with the characterization and properties of graft-copolymers. The research results showed that potassium persulfate initiator was most efficient in grafting of methacrylic acid onto hydrolyzed starch, while azobisisobutyronitrile (AIBIN) initiator was most efficient in grafting of acrylic acid (AC). FTIR analysis confirmed that new and efficient products for sizing cotton yarns from synthetized potato starch were obtained. Research on rheological properties of copolymers shows a higher viscosity of grafted products indicating the good stability of potential starches. Ecological improvements have been established through high desizing degree as well as improvements in physical-mechanical properties of yarn, abrasion resistance and decrease in yarn surface hairiness were noticed. The use of new derivatives of potato starch, especially of hydrolyzed starch grafted with methacrylic acid (MAA), potassium persulfate (KPS) as initiator, was confirmed. Anova statistical analysis determined the influence of the entire sizing process on individual yarn parameters. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Lignin Transformation of One-Year-Old Plants During Anaerobic Digestion (AD)
Polymers 2019, 11(5), 835; https://doi.org/10.3390/polym11050835 - 08 May 2019
Cited by 4
Abstract
The aim of the research is to identify the changes which occur in lignin from miscanthus and sorghum, one of the main biomass components, as a result of an anaerobic digestion (AD) process. The percentage content and structure of lignin before and after [...] Read more.
The aim of the research is to identify the changes which occur in lignin from miscanthus and sorghum, one of the main biomass components, as a result of an anaerobic digestion (AD) process. The percentage content and structure of lignin before and after the fermentation process were analysed using biomass harvested in two growing periods—before and after vegetation. It was shown that plants at different developmental stages differ in lignin content. During plant growth, the lignin structure also changes—the syringyl-to-guaiacyl ratio (S/G) increases, whereas the aliphatic and aromatic structure ratio (Al/Ar) decreases. The AD process leads to an increase in percentage lignin content in cell walls, and the increase is higher for plants harvested during vegetation. It has been shown in studies that the methane fermentation of miscanthus and sorghum produces waste containing a large amount of lignin, the structure of which is altered relative to native lignin. The quantity and the new, simplified structure of lignin create new possibilities for using this aromatic polymer. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Preparation and Characterization of Whey Protein-Based Polymers Produced from Residual Dairy Streams
Polymers 2019, 11(4), 722; https://doi.org/10.3390/polym11040722 - 19 Apr 2019
Cited by 5
Abstract
The wide use of non-biodegradable, petroleum-based plastics raises important environmental concerns, which urges finding alternatives. In this study, an alternative way to produce polymers from a renewable source—milk proteins—was investigated with the aim of replacing polyethylene. Whey protein can be obtained from whey [...] Read more.
The wide use of non-biodegradable, petroleum-based plastics raises important environmental concerns, which urges finding alternatives. In this study, an alternative way to produce polymers from a renewable source—milk proteins—was investigated with the aim of replacing polyethylene. Whey protein can be obtained from whey residual, which is a by-product in the cheese-making process. Two different sources of whey protein were tested: Whey protein isolate (WPI) containing 91% protein concentration and whey protein concentrate (WPC) containing 77% protein concentration. These were methacrylated, followed by free radical polymerization with co-polymer poly(ethylene glycol) methyl ether methacrylate (PEGMA) to obtain polymer sheets. Different protein concentrations in water (11–14 w/v%), at two protein/PEGMA mass-ratios, 20:80 and 30:70, were tested. The polymers made from WPI and WPC at a higher protein/PEGMA ratio of 30:70 had significantly better tensile strength than the one with lower protein content, by about 1–2 MPa (the best 30:70 sample exhibited 3.8 ± 0.2 MPa and the best 20:80 sample exhibited 1.9 ± 0.4 MPa). This indicates that the ratio between the hard (protein) and soft (copolymer PEGMA) domains induce significant changes to the tensile strengths of the polymer sheets. Thermally, the WPI-based polymer samples are stable up to 277.8 ± 6.2 °C and the WPC-based samples are stable up to 273.0 ± 3.4 °C. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Acoustic Emission-Based Study to Characterize the Crack Initiation Point of Wood Fiber/HDPE Composites
Polymers 2019, 11(4), 701; https://doi.org/10.3390/polym11040701 - 17 Apr 2019
Cited by 2
Abstract
The crack initiation point can be regarded as a sign of composite failure and plays a vital role in the evaluation of fracture toughness. Wood-plastic composites (WPCs) are viscoelastic materials and the evaluation of fracture mechanism and toughness has a great significance in [...] Read more.
The crack initiation point can be regarded as a sign of composite failure and plays a vital role in the evaluation of fracture toughness. Wood-plastic composites (WPCs) are viscoelastic materials and the evaluation of fracture mechanism and toughness has a great significance in their applications. Therefore, we used the acoustic emission (AE) technique to measure the crack initiation point of the WPCs and evaluate their fracture toughness. The results show that the novel AE-based methods were more effective than the conventional standard methods for characterization of the crack initiation point. Using the relationship of cumulative AE events with time and load, the critical failure load was quickly determined, and then the critical stress intensity factor and fracture toughness were calculated. The fracture toughness of the WPCs increased with an increase in the wood fiber content. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Water/Alcohol Soluble Thickness-Insensitive Hyperbranched Perylene Diimide Electron Transport Layer Improving the Efficiency of Organic Solar Cells
Polymers 2019, 11(4), 655; https://doi.org/10.3390/polym11040655 - 10 Apr 2019
Cited by 1
Abstract
The electron transport layer (ETL) is very crucial for enhancing the device performance of polymer solar cells (PSCs). Meanwhile, thickness-insensitive and environment-friendly water/alcohol soluble processing are two essential requirements for large-scale roll-to-roll commercial application. Based on this, we designed and synthesized two new [...] Read more.
The electron transport layer (ETL) is very crucial for enhancing the device performance of polymer solar cells (PSCs). Meanwhile, thickness-insensitive and environment-friendly water/alcohol soluble processing are two essential requirements for large-scale roll-to-roll commercial application. Based on this, we designed and synthesized two new n-type ETLs with tetraethylene pentamine or butyl sulfonate sodium substituted tetraethylene pentamine as the branched side chains and high electron affinities perylene diimide (PDI) as the central core, named as PDIPN and PDIPNSO3Na. Encouragingly, both PDIPN and PDIPNSO3Na can effectively reduce the interfacial barrier and improve the interfacial contact. In addition, both of them can exhibit strong n-type self-doping effects, especially the PDIPN with higher density of negative charge. Consequently, compared to bare ITO, the PCE of the devices with ITO/PDIPN and ITO/PDIPNSO3Na ETLs has increased to 3–4 times. Our research results indicate that n-type self-doping PDI-based ETL PDIPN and PDIPNSO3Na could be promising candidates for ETL in environment-friendly water/alcohol soluble processing large-scale PSCs. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Green Preparation of Fluorescent Carbon Quantum Dots from Cyanobacteria for Biological Imaging
Polymers 2019, 11(4), 616; https://doi.org/10.3390/polym11040616 - 03 Apr 2019
Cited by 9
Abstract
Biomass-based carbon quantum dots (CQDs) have become a significant carbon materials by their virtues of being cost-effective, easy to fabricate and low in environmental impact. However, there are few reports regarding using cyanobacteria as a carbon source for the synthesis of fluorescent CQDs. [...] Read more.
Biomass-based carbon quantum dots (CQDs) have become a significant carbon materials by their virtues of being cost-effective, easy to fabricate and low in environmental impact. However, there are few reports regarding using cyanobacteria as a carbon source for the synthesis of fluorescent CQDs. In this study, the low-cost biomass of cyanobacteria was used as the sole carbon source to synthesize water-soluble CQDs by a simple hydrothermal method. The synthesized CQDs were mono-dispersed with an average diameter of 2.48 nm and exhibited excitation-dependent emission performance with a quantum yield of 9.24%. Furthermore, the cyanobacteria-derived CQDs had almost no photobleaching under long-time UV irradiation, and exhibited high photostability in the solutions with a wide range of pH and salinity. Since no chemical reagent was involved in the synthesis of CQDs, the as-prepared CQDs were confirmed to have low cytotoxicity for PC12 cells even at a high concentration. Additionally, the CQDs could be efficiently taken up by cells to illuminate the whole cell and create a clear distinction between cytoplasm and nucleus. The combined advantages of green synthesis, cost-effectiveness and low cytotoxicity make synthesized CQDs a significant carbon source and broaden the application of cyanobacteria and provide an economical route to fabricate CQDs on a large scale. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Removing Pb(II) Ions from Aqueous Solution by a Promising Absorbent of Tannin-Immobilized Cellulose Microspheres
Polymers 2019, 11(3), 548; https://doi.org/10.3390/polym11030548 - 22 Mar 2019
Cited by 2
Abstract
Tannin/cellulose microspheres (T/C) were successfully prepared via a facile homogeneous reaction in a water/oil (W/O) emulsion for removing Pb(II) ions from aqueous solution. The structure of the microspheres was characterized by scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, and a zeta potential [...] Read more.
Tannin/cellulose microspheres (T/C) were successfully prepared via a facile homogeneous reaction in a water/oil (W/O) emulsion for removing Pb(II) ions from aqueous solution. The structure of the microspheres was characterized by scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, and a zeta potential test. The effects of pH, adsorbent dosage, contact time, and temperature on adsorption ability were investigated. The results showed that T/C microspheres could combine Pb(II)ions via electrostatic attractions and physical adsorption. Adsorption kinetics could be better described by the pseudo-second-order kinetic model. The adsorption behaviors were in agreement with the Langmuir adsorption isotherm model with a fitting correlation coefficient of 0.9992. The maximum adsorption capacity was 23.75 mg/g from the Langmuir isotherm evaluation at 308K with an initial pH of 5. The results suggested that tannin/cellulose microspheres could be a low-cost and effective adsorbent for removing Pb(II) ions from aqueous solution. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Organic Acids of the Microbiological Post-Culture Medium as Substrates to be Used for Starch Modification
Polymers 2019, 11(3), 469; https://doi.org/10.3390/polym11030469 - 12 Mar 2019
Cited by 1
Abstract
This study aimed to identify the feasibility of producing highly-substituted starch esters via thermal modification of starch using a post-culture medium of Yarrowia lipolitica yeast. This manuscript describes a successful attempt at potato starch modification with a post-culture medium of Yarrowia lipolitica yeast [...] Read more.
This study aimed to identify the feasibility of producing highly-substituted starch esters via thermal modification of starch using a post-culture medium of Yarrowia lipolitica yeast. This manuscript describes a successful attempt at potato starch modification with a post-culture medium of Yarrowia lipolitica yeast with different concentrations of organic acids. Starch preparations produced by roasting (130 °C) and these produced by starch reaction with a synthetic acid mixture were compared in terms of the types and number of acid residues esterified with starch. The effectiveness of starch esterification was found to depend on medium composition and to be higher upon the use of a synthetic acid mixture. In addition, a higher reactivity with starch was demonstrated for citric acid than for α-ketoglutaric acid. The highly-substituted starch esters formed as a result of potato starch modification with post-culture medium were characterized by decreased values of thermal parameters of pasting characteristics, determined with a differential scanning calorimeter (DSC), and by compromised resistance to amylolysis. The intensity of these changes increased along with an increasing total percentage of starch ester substitution. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Mechanically and Thermally Induced Degradation and Modification of Cereal Biopolymers during Grinding
Polymers 2019, 11(3), 448; https://doi.org/10.3390/polym11030448 - 08 Mar 2019
Cited by 2
Abstract
It is presumed that structural and functional alterations of biopolymers, which occur during grinding, are caused by a mechanical modification of polymers. As a result, thermally induced changes of flours are neglected. In this study, the impact of thermo-mechanical stress (TMS), as occurring [...] Read more.
It is presumed that structural and functional alterations of biopolymers, which occur during grinding, are caused by a mechanical modification of polymers. As a result, thermally induced changes of flours are neglected. In this study, the impact of thermo-mechanical stress (TMS), as occurring during general grinding procedures, was further differentiated into thermal stress (TS) and mechanical stress (MS). For TS, native wheat flour, as well as the purified polymers of wheat—starch and gluten—were heated without water addition up to 110 C. Isolated MS was applied in a temperature-controlled ultra-centrifugal grinder (UCG), whereby thermal and mechanical treatment (TMS) was simultaneously performed in a non-cooled UCG. TS starch (110 C) and reference starch did not show differences in starch modification degree (2.53 ± 0.24 g/100 g and 2.73 ± 0.15 g/100 g, AACC 76-31), gelatinization onset (52.44 ± 0.14 C and 52.73 ± 0.27 C, differential scanning calorimetry (DSC)) and hydration properties (68.9 ± 0.8% dm and 75.8 ± 3.0%, AACC 56-11), respectively. However, TS led to an elevated gelatinization onset and a rise of water absorption of flours (Z-kneader) affecting the processing of cereal-based dough. No differences were visible between MS and TMS up to 18,000 rpm regarding hydration properties (65.0 ± 2.0% dm and 66.5 ± 0.3% dm, respectively). Consequently, mechanical forces are the main factor controlling the structural modification and functional properties of flours during grinding. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Facile Fabrication of Magnetic, Durable and Superhydrophobic Cotton for Efficient Oil/Water Separation
Polymers 2019, 11(3), 442; https://doi.org/10.3390/polym11030442 - 07 Mar 2019
Cited by 4
Abstract
In this paper, we present a facile and efficient strategy for the fabrication of magnetic, durable, and superhydrophobic cotton for oil/water separation. The superhydrophobic cotton functionalized with Fe3O4 magnetic nanoparticles was prepared via the in situ coprecipitation of Fe2+ [...] Read more.
In this paper, we present a facile and efficient strategy for the fabrication of magnetic, durable, and superhydrophobic cotton for oil/water separation. The superhydrophobic cotton functionalized with Fe3O4 magnetic nanoparticles was prepared via the in situ coprecipitation of Fe2+/Fe3+ ions under ammonia solution on cotton fabrics using polyvinylpyrrolidone (PVP) as a coupling agent and hydrophobic treatment with tridecafluorooctyl triethoxysilane (FAS) in sequence. The as-prepared cotton demonstrated excellent superhydrophobicity with a water contact angle of 155.6° ± 1.2° and good magnetic responsiveness. Under the control of the external magnetic field, the cotton fabrics could be easily controlled to absorb the oil from water as oil absorbents, showing high oil/water separation efficiency, even in hot water. Moreover, the cotton demonstrated remarkable mechanical durable properties, being strongly friction-resistant against sandpaper and finger wipe, while maintaining its water repellency. This study developed a novel and efficient strategy for the construction of magnetic, durable, and superhydrophobic biomass-based adsorbent for oil/water separation, which can be easily scaled up for practical oil absorption. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Maleinized Linseed Oil as Epoxy Resin Hardener for Composites with High Bio Content Obtained from Linen Byproducts
Polymers 2019, 11(2), 301; https://doi.org/10.3390/polym11020301 - 11 Feb 2019
Cited by 5
Abstract
Green composites, with more than 78 wt.% of products obtained from linen linum usitatissimum, were developed in this research work. Epoxidized linseed oil (ELO) was used as bio-based resin, a mix of nadic methyl anhydride (MNA) and maleinized linseed oil (MLO) [...] Read more.
Green composites, with more than 78 wt.% of products obtained from linen linum usitatissimum, were developed in this research work. Epoxidized linseed oil (ELO) was used as bio-based resin, a mix of nadic methyl anhydride (MNA) and maleinized linseed oil (MLO) were used as cross-linkers and finally, flax fabrics were used to obtain composite laminates by resin transfer molding (RTM). The flax fibers were modified using amino-silane, glycidyl-silane and maleic anhydride treatment in order to increase the compatibility between lignocellulosic fibers and the polymeric matrix. Mechanical and thermal properties were studied by flexural, tensile and impact test, as well as dynamic mechanical analyses (DMA) to study the viscoelastic behavior. Contrary to what could be expected, when fibers are previously treated in presence of MLO, a reduction of anchorage points is obtained causing a substantial increase in the ductile properties compared with composites without previous fiber treatment or without MLO. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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