Preparation and physical characterization of strongly swellable oligo(oxyethylene) lignin hydrogels

Holzforschung ◽  
2011 ◽  
Vol 65 (3) ◽  
Author(s):  
Lars Passauer ◽  
Klaus Fischer ◽  
Falk Liebner
Keyword(s):  
Dynamic Viscosity ◽  
Loss Modulus ◽  
Gelation Time ◽  
Rheological Behaviour ◽  
Diglycidyl Ether ◽  
Cross Linking ◽  
Available Water Content ◽  
The Cross ◽  
Poly Ethylene ◽  
Tan Δ

Abstract Highly swellable, mechanically stable hydrogels were obtained by cross-linking different technical lignins with poly(ethylene) glycol diglycidyl ether (PEGDGE). The gelation time and the properties of the products can be controlled by the extent of pre-oxidation and the cross-linking conditions, namely the dynamic viscosity η*, storage and loss modulus (G′; G″), and loss factor tan δ. The highest free swelling capacities (FSC) of up to 50 g water per g xerogel were obtained from pre-oxidized pine kraft lignin Indulin® AT and spruce organosolv lignin. Dynamic rheological measurements confirmed the typical rheological behaviour of gel structures, i.e. a linear decrease of dynamic viscosity about three orders of magnitude within a frequency range of 0.08 and 20 s-1. The results furthermore revealed a good mechanical sturdiness of the cross-linked lignin hydrogels. Sandy soils supplemented with small quantities of the hydrogels were found to feature a significantly increased plant-available water content. Based on the observed effects, oligo(oxyethylene) lignins are promising materials with respect to a prolonged water retention in soils.

scholarly journals Fabrication and Properties of High-Content Keratin/Poly (Ethylene Oxide) Blend Nanofibers Using Two-Step Cross-Linking Process

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Yong Liu ◽  
Xia Yu ◽  
Jia Li ◽  
Jie Fan ◽  
Meng Wang ◽  
...  
Keyword(s):  
Ethylene Oxide ◽  
Average Diameter ◽  
Diglycidyl Ether ◽  
Cross Linking ◽  
Electrospun Fibers ◽  
Hydrophobic Property ◽  
Poly Ethylene Oxide ◽  
Cross Linker ◽  
Poly Ethylene ◽  
Nanofiber Mats

High-content keratin/poly (ethylene oxide) (PEO) (90/10) blend nanofibers were prepared by electrospinning combined with a two-step cross-linking process. The keratin/PEO aqueous solution was firstly mixed with ethylene glycol diglycidyl ether (EGDE) as cross-linker and then electrospun into nanofibers. The resulting nanofibrous mats were cross-linked with EGDE vapor to decrease the solubility of nanofibers in water. The morphologies and properties of electrospun fibers were investigated by SEM, FTIR, TG, XRD, and contact angle testing, respectively. The results showed that the morphologies of nanofibers were uniform at the fiber average diameter of 300 nm with negligible bead defects by adding EGDE to keratin/PEO solutions. The cross-linking results showed that EGDE vapor could improve the hydrophobic property of blended nanofibers. The crystallinity of the keratin/PEO blend nanofiber mat increased from 13.14% for the uncross-linked sample to 21.54% and 35.15% for the first cross-linked and second cross-linked samples, respectively. Free defect nanofiber mats with high keratin content producing from this two-step cross-linking process are particularly promising for tissue engineering and cell-seeded scaffold.

scholarly journals Hyaluronic Acid Based Hydrogels for Regenerative Medicine Applications

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Assunta Borzacchiello ◽  
Luisa Russo ◽  
Birgitte M. Malle ◽  
Khadija Schwach-Abdellaoui ◽  
Luigi Ambrosio
Keyword(s):  
Hyaluronic Acid ◽  
Viscoelastic Properties ◽  
Structural Parameters ◽  
Weight Ratio ◽  
Rheological Behaviour ◽  
Biological Properties ◽  
Cross Linking ◽  
In Vitro Tests ◽  
The Cross

Hyaluronic acid (HA) hydrogels, obtained by cross-linking HA molecules with divinyl sulfone (DVS) based on a simple, reproducible, and safe process that does not employ any organic solvents, were developed. Owing to an innovative preparation method the resulting homogeneous hydrogels do not contain any detectable residual cross-linking agent and are easier to inject through a fine needle. HA hydrogels were characterized in terms of degradation and biological properties, viscoelasticity, injectability, and network structural parameters. They exhibit a rheological behaviour typical of strong gels and show improved viscoelastic properties by increasing HA concentration and decreasing HA/DVS weight ratio. Furthermore, it was demonstrated that processes such as sterilization and extrusion through clinical needles do not imply significant alteration of viscoelastic properties. Both SANS and rheological tests indicated that the cross-links appear to compact the network, resulting in a reduction of the mesh size by increasing the cross-linker amount. In vitro degradation tests of the HA hydrogels demonstrated that these new hydrogels show a good stability against enzymatic degradation, which increases by increasing HA concentration and decreasing HA/DVS weight ratio. Finally, the hydrogels show a good biocompatibility confirmed by in vitro tests.

scholarly journals Influence on the cross-linking and plasticization degree of poly(ethylene-co-vinyl acetate) and evaluation of expansion capacity to the production of foams with supercritical CO2

2018 ◽  
Vol 35 (1) ◽  
pp. 23-40
Author(s):  
Matheus VG Zimmermann ◽  
Marcos Aurélio Colombo ◽  
Diego Pizza ◽  
Ademir J Zattera
Keyword(s):  
Vinyl Acetate ◽  
Polymer Matrix ◽  
Polymer Melt ◽  
Thermoplastic Elastomer ◽  
Cross Linking ◽  
Melt Temperature ◽  
Foaming Capacity ◽  
The Cross ◽  
Poly Ethylene ◽  
Foaming Temperature

The modification of a thermoplastic elastomer by cross-linking or plasticizing allows the manipulation of material properties for different applications. Cross-linking additives promote the increase of mechanical, thermal, and rheological properties, while the use of plasticizers has the opposite effect, giving the material soft properties. Such characteristics affect the development of polymeric foams directly, where the polymer matrix properties have large influence on the foaming capacity and morphology of the cells. This study investigated the use of cross-linking and plasticizer additives in ethylene-co-vinyl acetate copolymer, as well as its influence on the foaming capacity. The increasing content of cross-linking additive impacts on formation of preferentially closed cells, with high cell density and smaller size, while using plasticizers a higher occurrence of cell deformation and open cells was verified. The low formation of cells due to the decreasing of the polymer matrix thermal stability allows gases to escape during the processing and favors the cell coalescence effect. The foaming temperature is directly related to the polymer melt temperature, so, for the plasticizer-added samples, lower temperatures were required during the foaming than the samples with the cross-linking agent.

Investigation of the Interaction between Epoxides and Collagen in Epoxy Tanning based on BDDGE Cross-linked Collagen Solution

2020 ◽  
Vol 115 (8) ◽  
pp. 279-287
Author(s):  
Yuanzhi Zhang ◽  
Guoying Li
Keyword(s):  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Decomposition Temperature ◽  
Diglycidyl Ether ◽  
Cross Linking ◽  
Force Microscopy ◽  
Atomic Force ◽  
Alkaline Conditions ◽  
The Cross ◽  
Dynamic Frequency

To investigate further the interaction between epoxides and collagen in epoxy tanning, collagen solutions (3 mg/ml) cross-linked with various concentrations (0.5–4-wt%) of 1,4-butanediol diglycidyl ether (BDDGE) at low temperature (4ºC), alkaline conditions (pH = 10) were prepared. The sodium dodecyl sulfate–polyacrylamide gel electrophoresis and Fourier transform infrared spectroscopy confirmed the intact triple-helix structure of the cross-linked collagen. With the increasing concentration of BDDGE, the denaturation temperature measured using VP-DSC increased from 42.56 ºC to 44.25ºC and thermogravimetric analysis showed that the decomposition temperature increased from 333.0ºC to 351.8ºC. In addition, the rheology properties such as G¢, G² and ?* were measured with a rotary rheometer using dynamic frequency scanning. The trinitrobenzensulfonic acid method and atomic force microscopy were used to investigate the interaction between collagen and BDDGE. The results indicated that the changes in cross-linked collagen performance were attributed to the transition of collagen aggregation caused by cross-linking. In addition, the transition point of 2-wt% BDDGE was the key node for the formation of a mature cross-linked network and the cross-linking barely increased above that. It is hoped that these findings deepen the understanding of epoxy tanning and provide guidance for the practical use of epoxides in tanning and biomaterials.

Activation of pine kraft lignin by Fenton-type oxidation for cross-linking with oligo(oxyethylene) diglycidyl ether

Holzforschung ◽  
2011 ◽  
Vol 65 (3) ◽  
Author(s):  
Lars Passauer ◽  
Klaus Fischer ◽  
Falk Liebner
Keyword(s):  
Ethylene Glycol ◽  
Water Sorption ◽  
Structural Changes ◽  
Kraft Lignin ◽  
Diglycidyl Ether ◽  
Fenton Oxidation ◽  
Cross Linking ◽  
Ferrous Chloride ◽  
Poly Ethylene Glycol ◽  
Poly Ethylene

Abstract Mechanically stable hydrogels featuring water absorption capacities of up to 75 gH2O ggel -1 can be obtained by cross-linking of activated technical lignins with poly(ethylene) glycol diglycidyl ether under strong alkaline conditions. Fenton oxidation prior to cross-linking by hydrogen peroxide and catalytic amounts of ferrous chloride has been found to be superior to an alkaline H2O2 pre-treatment with respect to gel formation, water sorption, and rheological properties of the resulting oligo(oxyethylene) lignin gels. Purified pine kraft lignin undergoes in the course of Fenton oxidation hydroxylation of both aliphatic and aromatic moieties. This is the main reason for the enhanced cross-linking density obtained after treatment with poly(ethylene) glycol diglycidyl ether. The oxidative changes have been demonstrated by principal component analysis of Curie point pyrograms, wet chemical methods, FT-IR, and 31P NMR spectroscopy. Cleavage of side-chains, radical 5,5′-coupling of phenylpropane units, formation of carbonyl and carboxyl groups, and cleavage of aromatic rings were observed. These structural changes may increase or decrease the water sorption capability of the cross-linked products.

scholarly journals The Use of the ATD Technique to Measure the Gelation Time of Epoxy Resins

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6022
Author(s):  
Jakub Smoleń ◽  
Piotr Olesik ◽  
Paweł Gradoń ◽  
Mateusz Chudy ◽  
Bogusław Mendala ◽  
...  
Keyword(s):  
Carbon Fibers ◽  
Epoxy Resins ◽  
Gelation Time ◽  
Graphite Powder ◽  
Cross Linking ◽  
Gel Point ◽  
Curing Process ◽  
Carbon Particles ◽  
The Cross ◽  
The Stability

In this paper, we investigated the thermodynamics of the resin curing process, when it was a part of composition with graphite powder and cut carbon fibers, to precisely determine the time and temperature of gelation. The material for the research is a set of commercial epoxy resins with a gelation time not exceeding 100 min. The curing process was characterized for the neat resins and for resins with 10% by weight of flake graphite and cut carbon fibers. The results recorded in the analysis of temperature derivative (ATD) method unequivocally showed that the largest first derivative registered during the test is the gel point of the resin. The innovative approach to measuring the gelation time of resins facilitates the measurements while ensuring the stability of the curing process compared to the normative tests that introduce mechanical interaction. In addition, it was found during the research that the introduction of 10% by weight of carbon particles in the form of graphite and cut carbon fibers rather shortens the gelation time and lowers the temperature peak due to the effective absorption and storage of heat from the cross-linking system. The inhibiting (or accelerating) action of fillers is probably dependent on chemical activity of the cross-linking system.

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