Lignin-based Epoxy Research Articles

Performance of UV curable lignin based epoxy acrylate coatings

Abstract In this work, lignin based epoxy acrylate (LBEA) oligomer with various percentage of lignin was in situ synthesized with epoxy and acrylic acid. The first step was the etherification between lignin and epoxy to produce lignin based epoxy (LBE), and the second step was the esterification between LBE and acrylic acid to synthesize LBEA. Epoxy value and acid value were measured to determine the reaction conditions of the two steps, respectively. The structure of prepared LBEA was confirmed by Flourier infrared spectroscopy (FTIR) characterization. LBEA coatings were prepared through ultraviolet radiation curing method. The gel content, chemical resistance, mechanical properties and thermal properties of coatings were investigated. It was found that the mechanical properties and chemical resistance were much improved than those of epoxy acrylate (EA) resin with the addition of lignin. Thus, lignin was proved to be a new promising biomaterial which could be applied in biobased EA coatings.

Evaluation of Ligno Boost™ softwood kraft lignin epoxidation as an approach for its application in cured epoxy resins

In this study, modification of LignoBoost™ softwood kraft lignin with epichlorhydrin in water-organic solvents media was realized. Lignin-based epoxy resins were obtained by two ways: acetone extraction of glycidylated lignin or glycidylation of the acetone soluble lignin fraction. The effect of glycidylation regimes on the yields of acetone soluble fractions, their functional composition and physical-chemical characteristics was investigated using wet chemistry methods, FTIR spectroscopy, size exclusion chromatography (SEC) and differential scanning calorimetry (DSC). The positive effect of the biphasic phase transfer catalytic system – KOH/quaternary ammonium salt – on glycidylation of both phenolic and aliphatic hydroxyl groups was testified, exemplified using a lignin-like model compound – 4-hydroxy-3-methoxylbenzyl alcohol (vanillyl alcohol). The partial substitution (up to 10%) of commercial epoxy resin on the basis of bisphenol A (Araldite® LY1564) by lignin-based epoxy resin significantly increased the viscosity of resin. Therefore, the possible practical application of lignin-containing epoxies as adhesive, mastic or crack filler instead of binder for fiber reinforced composites was considered. A tendency towards increasing Young’s modulus of cured lignin-containing epoxies, compared with the case of the reference composition, was observed. The lignin chemically incorporated into the matrix of cured commercial epoxy resin acts as a charcoal formation promoter in high temperature treatment.

Synthesis of Renewable Thermoset Polymers through Successive Lignin Modification Using Lignin-Derived Phenols

An approach to lignin-based epoxy networks from both organosolv lignin and lignin-derived phenol (dihydroeugenol) are developed using multiple chemical modifications including demethylation, phenolation, and a phenol-formaldehyde reaction. Structures of lignin-incorporated novolac polyphenols and epoxy networks (LINENs) were characterized using proton nuclear magnetic resonance and infrared spectroscopy. Compared to a common synthesis route in which lignin was epoxidized prior to blend with comonomers, LINEN derivatives exhibited improved cross-link density, α-relaxation temperature and storage modulus in a glassy region as obtained from dynamic mechanical analysis, and increased thermal stability measured by thermogravimetric analysis. This study widens the routes of lignin modification. Renewable epoxy networks derived from both lignin and lignin derivatives are economically and ecologically attractive.

Synthesis and characterization of hydrolysis lignin-based epoxy resins

A novel bio-based epoxy resin was synthesized using de-polymerized hydrolysis lignin (DHL) as a feedstock under alkaline condition. The chemical functionality of DHL-based epoxy resin was studied using Fourier Transformation Infrared spectroscopy (FTIR).The curing behavior of DHL-based epoxy resin with a selective curing agent (4,4′-diaminodiphenyl methane; DDM) was also investigated using differential scanning calorimetry (DSC). The curing process was found to proceed via a ring opening reaction involving the epoxy and the amine groups followed by etherification reactions at the end. The thermal and mechanical behavior of the resulting DHL-based epoxy resin were investigated using a thermogravimetric analysis (TGA) and a universal testing machine (UTM), respectively. The cured DHL-based epoxy-DDM system demonstrated good thermal and mechanical performances, suggesting its potential of utilizing hydrolysis lignin—a byproduct/waste stream from cellulosic ethanol processes for the production of value-added bio-based materials.

Curing kinetics and mechanical properties of bio-based epoxy composites comprising lignin-based epoxy resins

Lignin-based epoxy resins derived from de-polymerized Kraft/organosolv lignins were blended with a conventional bisphenol A (BPA)-based epoxy resin at various percentages to prepare bio-based epoxy systems as polymer matrices for manufacturing of fiber-reinforced plastics (FRPs) and coatings. The curing process of epoxy composites was studied using DSC and the activation energy was calculated by isoconversional methods. Epoxy composites comprising a low percentage (25wt%) of lignin-based epoxy resin can be cured faster than the pure BPA-based epoxy resin used in particular at the early stage of curing. However, blending a large amount (>50wt%) of lignin-based epoxy resin with the BPA-based epoxy resin retarded the curing process particularly at the late stage of curing. Tensile and flexural strengths of the prepared FRPs using bio-based epoxy composites were found to be superior or comparable to those of the FRP with the pure BPA-based epoxy resin when the lignin-based epoxy resin blending ratio is less than 50–75wt%. Furthermore, the bio-based epoxy films comprising up to 50wt% of DOL-based epoxy resin were exhibited high adhesion strength on a metal substrate.

에폭시 강화 리그닌 기반 나노탄소섬유 복합재료의 특성

본 연구에서는 리그닌 기반 폴리아크릴로나이트릴(polyacrylonitrile, PAN) 공중합체를 전기방사하여 나노탄소섬유매트를 제조한 다음, 에폭시 수지를 보강하여 제조한 복합재료의 열적 특성 및 기계적 강도를 조사하였다. 나노탄소섬유 매트/에폭시 복합재는 에폭시 수지와 유사한 열분해 거동을 보이고 있는 반면에 유리전이온도는 106.9℃로 순수에폭시 수지의 유리전이온도(Tg) 90.7℃보다 다소 높은 경향으로 나타나 열적 안정성이 향상된 결과로 사료된다. 리그닌 기반 공중합체 및 순수 PAN으로 만든 나노탄소섬유 매트의 인장강도는 각각 7.2 및 9.4 MPa로 나타났으며, 리그닌 기반 나노탄소섬유 매트/에폭시 복합재료의 인장강도는 43.0 MPa로 나타났다. 이는 나노탄소섬유 매트/에폭시 복합재료에서 에폭시 수지 매트릭스(matrix) 내에서 나노탄소섬유가 강화제(reinforcing filler)로 작용한 효과로 약 6배의 인장강도 향상을 보였다. 인장강도 측정 후 시편의 절단면에서 나노탄소섬유 자체의 높은 인장강도(478.8 MPa) 및 에폭시 수지와의 약한 계면접착성에 기인하는 나노섬유의 뽑힘현상이 관찰되었다.

Green Epoxy Resin System Based on Lignin and Tung Oil and Its Application in Epoxy Asphalt

In this work, lignin-based epoxy was synthesized by reacting epichlorohydrin (ECH) and partially depolymerized lignin (PDL) and then used for modification of asphalt. The Diels–Alder adduct of methyl esters of eleostearic acid and maleic anhydride (ME-MA) was synthesized and used as a biobased curing agent. The structure of PDL-epoxy was characterized by FTIR and 31P NMR. Nonisothermal curing kinetics and thermal properties of the cured epoxy resins were studied by differential scanning analysis, dynamic mechanical analysis, and thermogravimetric analysis, respectively. Curing behaviors of PDL-epoxy and a commercial epoxy DER332 were compared. Effects of epoxy content on rheological properties of the modified asphalt binder were studied using a parallel plate rheometer. Results show that the elastic behavior of asphalt binder at elevated temperatures was improved with increase in epoxy content.

Thermal performance and thermal decomposition kinetics of lignin-based epoxy resins

Lignin-based epoxy resins derived from depolymerized Kraft/organosolv lignins were blended with a commercial bisphenol A (BPA)-type epoxy resin at various percentages to prepare bio-based epoxy composites. The thermal stability and thermal decomposition kinetics of lignin-based epoxy composites were investigated using thermogravimetric analysis coupled with Fourier transformation infrared spectroscopy (TGA-FTIR) and compared with the conventional BPA-based epoxy resin. The activation energy of the decomposition process of the cured lignin-based epoxy composites was calculated by Kissinger, Kissinger-Akahira-Sunoe (KAS), and Flynn-Wall-Ozawa (FWO) methods. The presence of lignin-based epoxy resin demonstrated a significant effect on the activation energy of the decomposition process in particular at the early and the final stages of decomposition. The increase in the percentage of lignin-based epoxy resins in the composites reduced the initial activation energy of the system. Carbon oxides, methane, carbonyl compounds, amines and aromatic compounds were identified as the principal components during the thermal decomposition of the bio-based epoxy composites.

Construction of the di(trimethylolpropane) cross linkage and the phenylnaphthalene structure coupled with selective β-O-4 bond cleavage for synthesizing lignin-based epoxy resins with a controlled glass transition temperature

Lignin-based epoxy resins with controlled thermodynamic properties were synthesized.

Sustainable lignin-based epoxy resins cured with aromatic and aliphatic amine curing agents: Curing kinetics and thermal properties

Lignin-based epoxy resins were synthesized by reacting de-polymerized organosolv lignin (DOL) or de-polymerized Kraft lignin (DKL) with epichlorohydrin under an alkaline condition in the presence of a phase transfer catalyst. The synthesized lignin-based epoxy resins were cured with 4,4′-diaminodiphenyl methane (DDM, an aromatic amine) and diethylenetriamine (DETA, an aliphatic amine) to generate a 3-dimentional cross-linked structure. The effects of curing agents on the curing process were investigated by non-isothermal differential scanning calorimetry (DSC). The dependency of activation energy of the curing reaction on the extent of curing (conversion) was determined in this study by model-free kinetics based on the DSC results. In addition, it was found that the thermal stability of the cured lignin-based epoxy resins was also influenced by the type of curing agents and the types of lignin used in the synthesis of the bio-based epoxy resins.

Synthesis of Lignin-Based Epoxy Resin in Ionic Liquid [BMIm]Cl

Industrial alkali lignin (LG) was used as raw material and ionic liquid 1-butyl 3-methylimidazolium chloride ([BMIm]Cl) was used as solvent. Alkali lignin was dissolved into the [BMIm]Cl and modified as propyl ether lignin(HLG). Then the HLG modified lignin was used to synthesizing the lignin-based epoxy resin (LGEP) with epoxy chloropropane. The structure of LG, HLG and LGEP were characterized with FT-IR, the results indicated that the propyl group was introduced to the LG and the reaction activity was improved. The expoxy value analysis results showed that the optimum synthesis temperature was 80°C and the epoxy value was 0.218.

Synthesis of lignin-based epoxy resins: optimization of reaction parameters using response surface methodology

Synthesis of lignin-based epoxy resin of a high yield and epoxy content was realized and the synthesis conditions were optimized using Central Composite Design (CCD).

The Study on Curing Kinetics of Lignin Based Epoxy Resin System Using Non-Isothermal DSC Method

The synthesis of Lignin Base Epoxy Resin was based on industrial alkali lignin, and lignin-based epoxy resin curing characteristics were analyzed using the thermal weight loss technology under the oxygen atmosphere conditions. In light of the infra-red analysis of raw materials, the curing reaction kinetic parameters of lignin-based epoxy resin system were calculated using the Kissinger-Crane and Flynn-Wall-Ozawa method, and the curing reaction kinetics model of lignin-based epoxy resin system was established. The results showed that the kinetic parameters obtained using two methods were approximate, which validated that the curing reaction was consistent with the principle of the first-order reaction model. Initial curing temperature Ti0=454.88 K, curing temperature Tp0=507.55 K, and terminal temperature Tf0=598.77 K of lignin-based epoxy resin system were obtained when the extrapolation method was applied.

The Relative Performance Study of Foam Concrete Straw-Based

The experiment is to extract lignin from straw as the basic material, then to develop cheap resin. By mechanical foaming, we are to research lignin-based epoxy compounds with commercial foaming agent or sodium lauryl sulfate and the foam stabilizing effect under the experimental condition that adding or not coagulant. The study shows that the actual amount of foam can change the strength and weight of foam concrete to some extent. The results of experimental show that the lignin-based epoxy resins prepared by inexpensive straw can be applied YX-M-8-type foaming agent and the modification of sodium dodecyl sulfate in order to improve the utilization of straw, with great social and economic benefits. CLC:TU522 Document Code:A

Evaluation of epoxy resins synthesized from steam-exploded bamboo lignin

Lignin extracted from steam-exploded bamboo has been used as resource material for the production of cured epoxy resins. In this study, 3 types of cured epoxy resin were prepared. The bamboo lignin extracted with methanol from steam-exploded bamboo (steam pressure 35atm; steaming time 5min) was epoxidized with epichlorohydrin and then cured with the general curing agent 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole (2E4MZ-CN) and bamboo lignin. General epoxy resin, cured with diglycidyl ether bisphenol A (DGEBA) and 2E4MZ-CN, was simultaneously synthesized as a petroleum-derived epoxy resin control. The mechanical and thermal properties of lignin-based epoxy resins were compared with petroleum epoxy resins. As indicated by their thermal decomposition properties (Td5), the lignin-based epoxy resins exceeded the dip-solder resistance (250–280°C). Furthermore, lignin-based epoxy resin showed 70% of the flexural strength of the petroleum-based epoxy resin.

Preparation and characterization of acetic acid lignin-based epoxy blends

Lignin-based epoxy resin (LER) was prepared from phenolated lignin (PL) and epichlorohydrin (ECH) in the presence of sodium hydroxide. The eucalyptus acetic acid lignin (AAL) was first reacted with phenol in the presence of sulfuric acid to obtain PL. Then, PL was reacted with ECH in aqueous sodium hydroxide to obtain LER. LER was mixed with diglycidyl ether of bisphenol A (E-44) and then cured with triethylenetetramine (TETA). The initial thermal degradation temperature (Td) of the cured epoxy blends decreased with the increase in LER content. The residue ratio at 500 °C of the cured epoxy blends (R500), however, increased with the LER content. The maximum adhesive shear strength of the cured epoxy blends was obtained at 20 wt% of LER. The water absorption of epoxy blends increased with increasing the content of LER. SEM photos showed that increasing the content of LER increased inhomogeneity and porosity of epoxy blends.

Curing Kinetics of Lignin-based Epoxy Resins

Curing Kinetics of Lignin-based Epoxy Resins

Characterization of alkaline lignins for use in phenol-formaldehyde and epoxy resins

Besides polyurethanes and polyesters, phenolic and epoxy resins are the most prominent applications for technical lignins in thermosetting materials. To evaluate the potential application of lignin raw materials in phenol formaldehyde and epoxy resins, three types of alkaline lignins were characterized in terms of their structures and thermal properties. The lignin samples analyzed were kraft lignin (LIG-1), soda–rice straw lignin (LIG-2), and soda-wheat straw lignin (LIG-3). FTIR and 1H-NMR methods were used to determine their structure. Gel permeation chromatography (GPC) was used to determine the molecular weight distribution (MWD). Differential scanning calorimetry (DSC) was used to measure the glass transition temperature (Tg), and thermogravimetric analysis (TGA) to determine the thermal stability of lignin samples. Results showed that kraft lignin (LIG-1) has moderate hydroxyl-group content, is rich in G-type units, and has good thermal stability. These properties make it more suitable for direct use in phenol formaldehyde resins, and it is therefore a good raw material for this purpose. The alkaline soda-rice straw lignin (LIG-2) with a high hydroxyl-group content and excellent thermal stability is most suited to preparing lignin-based epoxy resins.

Synthesis and characterization of kraft lignin-based epoxy resins

Epoxidization is an interesting way to develop a new application of lignin and therefore to improve its application potential. In this work, kraft lignin-based epoxy resins were obtained by the epoxidization reaction, using the kraft lignin recovered directly from pulping liquor and modified by a methylolation reaction. The methylolated lignins were obtained by the reaction of original kraft lignin with formaldehyde and glyoxal, which is a less volatile and less toxic aldehyde. 1H-NMR spectroscopy showed that methylolated kraft lignin has more hydroxymethyl groups than glyoxalated kraft lignin. For the epoxidization reaction we studied the influence of the lignin:NaOH (w/w) ratio, temperature, and time of the reaction on the properties of the prepared epoxidized lignins. The structures of lignin-based epoxy resins were followed by epoxy index test and FTIR spectroscopy. Optimal conditions were obtained for lignin-based epoxy resin produced at lignin/NaOH = 1/3 at 70 ºC for 3h. Thermogravimetry analysis (TGA) revealed that the epoxidization enhances the thermal stability of lignins and may allow a wider temperature range for applications with lignin epoxy-PF blends.