Electrospinning with Condensed Tannins: Effects on Co-spinning with Zein

Abstract

Electrospinning can be applied to renewables creating new materials and applications. We have utilized electrospinning in an attempt to create nanofibers from condensed tannins as well as from binary conjugates formed between this tannin with zein protein. While attempts to directly electrospin pine bark tannin extract proved unsuccessful, combining zein with this tannin gave electrospun fiber from acetic acid and dimethyl formamide (DMF) solutions. To achieve nanofibers possessing significant tannin content, high solids content (≥35%) in DMF solution was required. Electrospun nanofibers (200–400 nm dia.) could be created from zein-tannin combinations with up to 80% tannin content and appropriate solution solids content. Nanofibers could be produced from pre-formed tannin-zein conjugates or via their direct combination as a mixture in the spinning solution. Analysis of thermal stability shows the zein-tannin conjugates have similar thermal properties and stability to zein, being stable up to 240°C.     

Synthesis,characterization, and thermal behaviors of tannin stearates prepared from quebracho and pine bark extracts

Reported is the preparation of various condensed tannin stearates and the associated chemical characterization and thermal properties of these products. Stearate esters of condensed tannins from both quebracho and pine bark extracts were prepared in generally high, isolated yields from reaction with stearic acid chloride. Tannin esterification was confirmed by both Fourier transform infrared and nuclear magnetic resonance (NMR), and the average degree of stearate substitution was calculated from ¹H‐NMR analysis. Product degree of substitution (DS) was observed to proportionately increase with higher stearic acid chloride ratio with maximum DS values of 4.0 and 5.1 achieved for quebracho and pine tannins, respectively. Thermal analysis revealed that tannin stearate products have increased thermal stability with a degradation onset at significantly higher temperature for those samples possessing relatively greater DS. Analysis using differential scanning calorimetry revealed isolated products to consist of multiple components which exhibit interesting melt behaviors, a likely result from their work up on isolation. However, multiple melt features of the individual components in products were lost on heating to give single, broad melt endotherms due to coalescence of sample components. Furthermore, tannin stearate samples with high DS show relatively greater endothermic melting at higher temperature than those samples with lower DS. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Modifying biodegradable plastics with additives based on condensed tannin esters

Condensed tannins derived from Pinus radiata bark have been esterified and added to biodegradable plastics as extrusion compounded functional plastic additives. The presence of longer alkyl chain hexanoate esters promoted tannin miscibility in the commercial polyesters Bionolle? and Biopol? whereas short chain acetate esters tended to remain as discrete domains, acting as fillers in the processed plastics. In the aliphatic polyester Bionolle the presence of tannin esters at typical plastic additive loadings did not alter plastic mechanical properties whereas at 5% content in Biopol the tannin‐additives reduced both flexural and tensile properties. Similarly tannin esters do not alter the melt or glass transition temperatures of the polyesters, but tannin hexanoate at 5% can influence the crystallization temperatures. Artificially aging plastics realized the functionality these plant extracts can impart to plastics in acting to reduce ultraviolet (UV)‐induced plastic degradation. Results indicate the tannin‐additives likely provide a stabilising role through inhibiting UV penetration into the plastic, with color analysis suggesting the tannin moiety itself was sacrificial and preferentially degrading. The imparted UV stability was linked to the dissolution of tannin esters in the plastic with longer chain esters providing greater protection against UV degradation. Tannin esters showed potential as functional additives for biodegradable polymers enhancing the UV stability of the plastic. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41626.     

Soy-based,tannin-modified plywood adhesives

In this research, two different types of commercial tannins, namely a hydrolysable tannin (chestnut) and a condensed flavonoid tannin (mimosa), were used to prepare two types of soy-based (soy flour (SF) and soy protein isolate) adhesives for making plywood. Thermogravimetric properties (TGA) and its derivative as function of temperature (DTG) of different soy-based adhesive were measured in the range 40°C–300°C. Thermomechanical analysis (TMA) from 25°C to 250°C was done for the different resin formulations. Duplicate three-ply laboratory plywood panels were prepared by adding 300 g/m² of the adhesives’ total resin solid content composed of SF or isolated soy protein (ISP), urea, chestnut, and mimosa tannin extracts with hexamine as hardener. Based on the results obtained, tannins can improve SF adhesion properties. The TMA showed that chestnut tannin extract appeared to react well with SF, while mimosa tannin extract appeared to react well with ISP. Matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry also showed that among other reactions, the soy protein amino acids reacted with the tannins. Furthermore, delamination and shear strength test results showed the good water resistance of plywood bonded with soy-based tannin modified adhesive.     

Evolution of Extractive Composition During Thermal Treatment of Jack Pine

Abstract

The thermal treatment of wood has many benefits such as better dimensional stability and attractive dark color and does not use toxic chemicals. The resistance against biological decay can be improved when wood is not in contact with ground. On the other hand, after thermal transformation, wood becomes more fragile. The changes of the wood properties are related to the modification of the wood composition. During the thermal treatment, the evaporation of the moisture content is not the only event. Volatile extractives are evacuated from the wood, while new products and by-products of different chemical reactions appear. The comparison of the extracts obtained from untreated and treated wood can help to identify thermo-chemical reactions, taking place during the heat treatment. This article presents the analysis by Gas Chromatography–Mass Spectroscopy (GC-MS), High Performance Liquid Chromatography (HPLC), and Thin Layer Chromatography (TLC) of polar and non-polar extracts of untreated and heat-treated North American Jack pine (Pinus banksiana). The study of the impact of maximum heat treatment temperature on the composition of the Jack pine extracts showed that the major part of extractives leaves the wood under 200°C whereas most of the new products appear only above 200°C. While the extractives of the untreated Jack pine are dominated by non-polar components, the thermo-transformation seems to generate mainly polar compounds. However, presence of water vapor increases the portion of polar extractives in wood. Interestingly, an important decrease of concentration of phenolic compounds (such as pinosylvin, pinosylvin monomethyl ether, and pinobanksin) in Jack pine wood was observed between 160–200°C. On the other hand, 4-hydroxy-methylfurfural and vanillin have been identified as compounds generated by the heat treatment above 200°C. The identification of other by-products will be presented in a later paper.     

Synthesis and characterization of PLA nanocomposites containing nanosilica modified with different organosilanes II: Effect of the organosilanes on the properties of nanocomposites: Thermal characterization

Thermal behavior of polylactic acid (PLA)/nanosilica nanocomposites prepared via bulk ring opening polymerization from lactide was investigated by differential scanning calorimetry and thermogravimetric analysis (TGA). Both unmodified nanosilica and modified by surface treatments with different amounts of two distinct silanes were used. Samples containing pure silica show enhanced crystallization processes; with silane‐modified silica this effect is magnified, especially in the case of materials with high loadings of epoxy silane. Nonisothermal crystallization temperatures become higher and isothermal crystallization kinetics show a marked increase of Kinetic constant (K_c). TGA analyses show that, when pure nanosilica is present, nanocomposites have a thermal stability far greater than the one of standard PLA, starting their degradation at temperatures up to 70°C higher than the ones of pure PLA. When silanes are present, thermal stability lowers as silane content increases, but it is anyway higher than the one of the pure polymer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of Greek sage and summer savory extracts on vegetable oil thermal stability

The effect of ethanol and acetone extracts obtained from Greek sage (Salvia fruticosa) and summer savory (Satureja hortensis L.) on the thermal stability of vegetable oils heated at frying temperature (180 °C) was studied. Virgin olive oil (VOO), refined olive oil (ROO), sunflower oil (SO), and a commercial oil blend suitable for frying (BL), enriched with each extract obtained from the two plant materials at a concentration of 3 g/kg oil, were heated at 180 °C for 10 h. Changes during heating were assessed by quantification of total polar materials and determination of p‐anisidine values. The acetone extract obtained from Greek sage showed a better inhibitory effect against thermal oxidation of heated refined oils (BL, ROO, SO) than the respective ethanol extract, although the latter was found to have a relatively higher total phenol content. Both summer savory extracts effectively retarded the thermal oxidation reactions during oil heating, showing a more pronounced effect than the Greek sage acetone extract. The activity of the acetone extract obtained from summer savory was stronger (SO, BL) or similar (ROO, VOO) to that of the summer savory ethanol extract, although the latter was found to have a higher total phenol content.     

Blends of Poly(ether imide) and Styrene Sulfonic Acid Based Polymer: Thermal,Mechanical and Ionic Conduction Behavior

Dense membranes based on poly(ether imide) (PEI) and poly(styrene sulfonic acid-co-maleic acid) (PSSAMA) was obtained by extrusion and compression molding. Blends with different PSSAMA content (1, 3, 5, and 10 wt%) were prepared. Their morphology was investigated by scanning electron microscopy (SEM) and their thermal properties by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic-mechanical analysis (DMA). Two glass transition temperatures (T_g) (100 and 216°C) appeared when high contents of PSSAMA were added to PEI, indicating that the polymers form an immiscible system. TGA curves showed that the first weight loss occurred above 400°C for all blends, indicating a good thermal stability. Water uptake measurements have shown that the membranes presented low swelling when compared with Nafion®. The proton conductivity of the membrane with 10 wt% of PSSAMA obtained bv impedance measurements was 0.006 × 10^?2 S·cm^?1.     

Hydrolytic and thermal stability of urea-formaldehyde resins based on tannin and betaine bio-fillers

In this work, betaine (trimethyl glycine) and tannin (complex biomolecules of polyphenolic nature) were used as bio-fillers. Urea-formaldehyde (UF) resin with a molar ratio of formaldehyde versus urea (FA/U) of 0.8 was synthesized in situ with tannin and betaine as bio-fillers, to obtain UF resin with reduced free FA content and increased hydrolytic and thermal stability by the principles of sustainability. The samples TUF (with tannin) and BUF (with betaine) were characterized by using X-ray diffraction analysis (XRD), non-isothermal thermogravimetric analysis (TGA), and differential thermal analysis (DTA), supported by data from Fourier Transform Infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The percentage of free FA in modified BUF resin is 0.1%, while the percentage of free FA in tannin-modified resin is 0.8%. The hydrolytic stability of the modified UF resins was determined by measuring the concentration of liberated FA in the modified UF resins, after acid hydrolysis. The modified BUF resin is hydrolytically more stable because the content of released FA is 3.6% compared to the modified TUF resin, where it was 7.4%. Based on the value for T_5%, the more thermally stable resin is the modified TUF resin (T_5% = 123.1°C), while the value of the T_5% for the BUF resin is 83.1°C. This work showed how UF bio-composite with reduced free FA content and increased hydrolytic and thermal stability can be obtained using tannin and betaine as bio-fillers.     

Rheological characteristics of proanthocyanidin polymers from Pinus radiata. II. Viscoelastic properties of sequential alkaline extracts based on phenolic acid fraction

Steady and dynamic oscillatory rheometry were used to characterize two members of the plant polyphenols from Pinus radiata bark, water-soluble proanthocyanidin polymers, and phenolic acids. The viscosity-controlling factor of the extracts could be revealed by examining the various extracts under different chemical and rheological environments. Water extracted (100°C) bark was successively extracted with aqueous NaOH solutions of increasing alkalinity at 100°C and the rheological characteristics of the each fraction were examined in detail. The significant viscoelasticity of the 100°C aqueous NaOH sequential extracts suggests that this fraction can have a critical impact on the flow characteristics of overall extracts and arises from a major contribution of colloidal interactions involving the carbohydrate component. © 1995 John Wiley & Sons, Inc.     

Thermal stability of electron beam-irradiated polytetrafluoroethylene

Polytetrafluoroethylene (PTFE) was subjected to 1 MeV electron beam irradiation in air. The thermal stability and the degradation fragments of the irradiated polymer were studied in dependence on the radiation dose up to 4 MGy by thermogravimetric analysis coupled with mass spectrometry. The TGA results confirm the known decrease in the thermal stability of irradiated PTFE with increasing radiation dose. At the thermal degradation, CO₂, HF, and fluorocarbon fragments are evolved from the irradiated samples. CO₂ and HF are formed by decomposition of peroxy radicals up to 250°C. In addition, low molecular weight fluorocarbons are desorbed from the irradiated PTFE. At temperatures above 300°C, CO₂ is formed by the decarboxylation of radiation-induced COOH groups inside the PTFE. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2287–2291, 1997     

Thermal characteristics and pyrolysis of methyl‐di(phenylethynyl)silane resin

Thermal stability of a recently synthesized polymeric methyl‐di(phenylethynyl)silane (MDPES) resin was studied using a number of thermal and spectrometric analytical techniques. The polymer exhibits extremely high thermal stability. Thermogravimetric analysis (TGA) shows that the temperature of 5% weight loss (T_d5) was 615°C and total weight loss at 800°C was 8.9%, in nitrogen atmosphere, while in air, T_d5 was found to be 562°C, and total weight loss at 800°C was found to be 55.8% of the initial weight. Differential thermal degradation (DTG) studies show that the thermal degradation of MDPES resin was single‐stage in air and two‐stage in nitrogen. The thermal degradation kinetics was studied using dynamic TGA, and the apparent activation energies were estimated to be 120.5 and 114.8 kJ/mol in air, respectively, by Kissinger and Coats–Redfern method. The white flaky pyrolysis residue was identified to be silicon dioxide by FTIR and EDS, indicating that the thermal stability of polymer may be enhanced by the formation of a thin silicon dioxide film on the material surface. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 103: 605–610, 2007     

Vacuum Pyrolysis of Bark From Pinus Ponderosa

Abstract

The inner and outer barks of ponderosa pine (P. ponderosa) have been pyrolysed at 350°C in vacuum and the tars analyzed by gas chromatography after tri-O-methylsilylation. The nine major peaks in the gas chromatogram have been identified and quantified and it is concluded that all (except pinitol) originate predominantly from polysaccharide components of the barks. They account for up to 53% of the total tar. Removal of most of the metal ions from the barks by ion exchange with dilute acid has a dramatic influence on the tar constituents, e.g. increasing the yield of levoglucanosan from inner bark from 0.8% to 13%. which represents 31% of the original glucan content of the bark. The polyphenol and lignin components of the bark are predominantly converted directly to char at 350°C.     

Evaluating the thermal stability of high performance fibers by TGA

The thermal degradation of eight types of high performance fibers (HPFs) was measured under nitrogen and air atmosphere. The degree of degradation, as measured by weight loss using thermogravimetric analysis (TGA), and the characteristic degradation temperatures were obtained. The kinetics of the thermal degradation has also been analyzed according to the Freeman–carroll method and the activation energies of the HPFs were estimated. The experimental results show that para‐aramids (Kevlar® 29, 49, 129, and Twaron®2000) have similar thermal stability, but their thermal degradation temperatures and activation energies in air are different from those in nitrogen, which means that the thermostability of the fiber depends not only on its intrinsic structure but also on the atmosphere and temperature of testing environment. Terlon® fiber shows higher degradation temperature as a copolymer of para‐aramid, and its initial degradation temperature is 476.4°C in air. It can also be found that the PBO (poly(p‐phenylene benzobisoxazole)) fiber has the highest thermal degradation temperature among the samples tested, but its activation energy is not the highest in both air and nitrogen atmosphere. And the UHMW‐PE (ultra high molecular weight polyethylene) fiber has the lowest thermal degradation temperature, and it begins to degrade when the temperature reaches 321.8°C under air atmosphere. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 937–944, 2006     

Enrichment of antibacterial compound from the stem bark of Stereospermum fimbriatum using supercritical carbon dioxide extraction

ABSTRACT

Supercritical carbon dioxide (sc-CO₂) extraction was carried out on Stereospermum fimbriatum’s stem bark in order to obtain an enriched extract containing the targeted active compound. The recovery of its active compound, C1, was compared with the most active Soxhlet’s extract of dichloromethane. A minimum inhibitory concentration (MIC) assay was done to examine the antibacterial activity of extracts against methicillin-resistant Staphylococcus aureus. The optimum condition for an enriched extract of sc-CO₂ to have a maximum recovery of C1 at MIC value of 400 µg/mL was suggested to be operated at 40°C and pressure at 30 MPa, with addition of 6% co-solvent.     

Development of wood-products adhesives from mangrove bark

Mangrove bark was extracted using either water, ethanol, acetone, or various binary mixtures of these, as solvent. With plywood panels as substrates, joints prepared with adhesives derived from these extracts were tested for strength properties. In terms of the quantity of extracts from mangrove bark, water was the most effective solvent, followed sequentially by ethanol and acetone. However, in terms of the tannin content of these extracts, the order of extraction effectiveness of these solvents was reversed. The use of solvent mixtures in tannin extraction did not produce an observable synergistic effect. The quantity of extract and its tannin content were dictated primarily by the predominant solvent in the binary mixture. The reactivity of mangrove bark extracts is influenced significantly by formaldehyde concentration, cure temperature, type, and pH of the adhesive medium. Adhesive joints of significant bond strength were obtained from mangrove tannin adhesives. Prolonged cure periods, particularly at elevated temperatures, have deleterious effects on the strength properties of these adhesive joints.     

Degradation of lignin with monomethylamine

Wood chips were treated with gaseous mixtures of monomethylamine and water vapour at temperatures between 160 and 120°C and pressurs ranging between 1.5 and 7.0 MPa. The degradation products were subsequently extracted with different solvents at ambient pressure. First, The degradation products of lignin were extracted with highly selective organic solvents such as diethyl ether or 2-butanone. Then, the remaining decomposition products were extracted with water or an aqueous solution of monomethylamine. The latter extract contains the degradation products of the hemicelluloses in a relatively high concentration. After a three hour digestion, the residue obtained from spruce had a lignin content of 3.1 wt-% (pine: 3.7 wt-%; birch 0.3 wt-%). The total yield of unbleached cellulose was approximately 60 wt-%.     

One-pot synthesis of soluble wholly aromatic liquid crystalline copoly(ester amide)s with high thermal and dimensional stability

Abstract

Thermotropic liquid crystalline polymers (LCPs) have been of great interest for electronic packaging. Herein, we introduce a series of wholly aromatic, thermotropic LCPs from copoly(ester amide)s of 6-hydroxy-2-naphthalic acid, isophthalic acid, terephthalic acid, and 4-aminophenol, prepared by a convenient one-pot melt polycondensation. Almost synthesized copoly(ester amide)s exhibited good solubility in common organic solvents at room temperature. Furthermore, they possessed high thermal stability with 2% degradation temperatures (T_id) of 359–368?°C and the char yields (at 600?°C) of 50.3–55.6%. The synthesized copoly(ester amide)s had relatively low coefficient of thermal expansion (CTE) values, which were 35.85–41.21?ppm °C^?1 in the temperature range of 50–200?°C. Furthermore, an annealing process could be employed to improve the thermomechanical properties of synthesized polymers. For instance, the CTE of sample LCP3 in range temperature of 275–315?°C was reduced by more than 90% after annealing at 320?°C for 1?h, implying the feasibility for electronic packaging.     

Characterization of Almond Cultivars by the Use of Thermal Analysis Techniques. Application to Cultivar Authenticity

Almonds are subjected to thermal processes in the production of processed food and this can affect their thermal stability and lead to oxidation processes. In this work, almond samples from three different cultivars (Spanish Guara and Marcona, and American Butte) were characterized by using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) at different heating rates. Crystallization and melting parameters were determined by DSC; whereas thermal stability was studied by TGA, showing no apparent degradation for all samples up to around 290 °C. Butte samples showed the lowest DSC values and TGA initial degradation temperature. These results were linked with differences in fatty acid profiles between Butte and Spanish almond cultivars, Butte presenting higher linoleic acid content. Successful discrimination was obtained for samples analyzed at 2 and 10 °C min⁻¹ heating rates for DSC and TGA, respectively, by applying multivariate stepwise linear discriminant analysis (LDA). The results obtained proved the suitability of thermal analysis techniques combined with LDA for an easy and fast discrimination among different almond cultivars to control eventual adulteration in food processing.     

桉树皮单宁分析

对广西高峰林场桃源分厂4年生的大叶桉和尾叶桉树皮的单宁含量进行了分析,并分别进行了栲胶的试制。分析结果表明:大叶桉和尾叶桉树皮单宁属于缩合类单宁,树皮单宁含量分别为7.6%和7.8%,纯度分别为67.9%和70.3%;大叶桉树皮栲胶单宁含量为65.4%,尾叶桉树皮栲胶单宁含量为63.3%。桉树皮可作为新品种栲胶原料,其栲胶值得推广应用。