Development of toughened bio‐based epoxy with epoxidized linseed oil as reactive diluent and cured with bio‐renewable crosslinker

In the current work, renewable resourced toughened epoxy blend has been developed using epoxidized linseed oil (ELO) and bio‐based crosslinker. Epoxidation of linseed oil was confirmed through FTIR and ¹H NMR spectra. The ELO bio‐resin was blended at different compositions (10, 20, and 30 phr) with a petroleum‐based epoxy (DGEBA) as reactive diluent to reduce the viscosity for better processibility and cured with cardanol‐derived phenalkamine to overcome the brittleness. The flow behavior of the neat epoxy and modified bio‐epoxy resin blend systems was analyzed by Cross model at low and high shear rates. The tensile and impact behavior studies revealed that the toughened bio‐epoxy blend with 20 to 30 phr of ELO showed moderate stiffness with much higher elongation at break 7% to 13%. Incorporation of higher amount of ELO (20 to 30 phr) increases enthalpy of curing without affecting peak temperature of curing. The thermal degradation behavior of the ELO based blends exhibits similar trend as neat epoxy. The higher intensity or broadened loss tangent curve of bio‐epoxy blends revealed higher damping ability. FE‐SEM analysis showed a rough and rippled surface of bio‐based epoxy blends ensuring effective toughening. Reduced viscosity of resin due to maximum possible incorporation of bio‐resin and use of phenalkamine as curing agent leads to an eco‐friendly toughened epoxy and can be useful for specific coating and structural application.     

Organic-inorganic hybrids from renewable plant oils and clay

This study deals with the preparation and properties of a new class of organic-inorganic hybrids from renewable resources. The hybrids were synthesized by an acid-catalyzed curing of epoxidized triglycerides in the presence of an organophilic montmorillonite (a modified clay). The mechanical properties were improved by the incorporation of clay in the oil-based polymer matrix. The reinforcement effect due to the addition of clay was confirmed by dynamic viscoelasticity analysis. The hybrids showed relatively high thermal stability. The co-curing of epoxidized soybean and linseed oils in the presence of clay produced hybrids with controlled mechanical and coating properties. The barrier property of the hybrid towards water vapor was superior to that of the oil polymer. The development of the present hybrids consisting of inexpensive renewable resources, triglyceride and clay is expected to contribute to global sustainability.     

Enzymatic epoxidation of soybean oil in the presence of perbutyric acid

Enzymatic epoxidation of vegetable oils using a long chain fatty acid as an active oxygen carrier could produce a desirable epoxy oxygen group content (EOC); however, the acid value (AV) of final epoxidized oil is too high. The present study was to investigate the effect of different fatty acids with varying length of carbon chain on EOC and AV of the final epoxidized soybean oil (ESO); finding butyric acid was the choice of active oxygen carrier when hydrogen peroxide was used as an oxygen donor in the presence of lipase Novozyme 435. And in situ IR was used to monitor the epoxidation process, which revealed that the formation of perbutyric acid was the key step in the whole reaction. The epoxidation process was optimized as follows: molar ratio of butyric acid/C=C bonds of 0.19:1, 8% of immobilized lipase Novozyme 435 load (relative to the weight of soybean oil) and molar ratio of H₂O₂/C=C bonds of 3.5:1, reaction time of 4 h and reaction temperature of 45 °C. Under these conditions, ESO with a high EOC (7.62 ± 0.20%) and a lower AV value (8.53 ± 0.18 mgKOH/g) was obtained. The oxriane conversion degree was up to 97.94%.     

Linseed oil‐based reactive diluents preparation to improve tetra‐functional epoxy resin properties

Two kinds of bio‐resourced reactive diluents have been synthesized from linseed oil. The prepared epoxidized linseed oil (ELO) and the cyclocarbonated linseed oil (CLO) were separately blended with a petroleum‐based tetra‐functional epoxy resin (TGDDM) to improve its processability and to overcome the brittleness of the thermoset network therefrom. The linseed oil modifications were spectrally established, and processability improvement of the resin blends was rheologically confirmed. The curing of samples was studied by differential scanning calorimetry, and their mechanical properties (ie, tensile, flexural, fracture toughness, and adhesion) were investigated as well. Scanning electron microscopy images were obtained to reconfirm the toughness improvement of the modified thermosets. In contrast of the epoxidized soybean oil (ie, the most conventionally studied bio‐based reactive diluent), ELO and CLO had no negative effects on the thermoset material characteristics. They improved properties such as tensile strength (up to 43.2 MPa), fracture toughness (1.1 MPa m^1/2), and peel‐adhesion strength (4.5 N/25 mm). It was concluded that ELO and CLO were efficient reactive diluents to be used in formulations of polymer composites, surface coatings, and structural adhesives based on epoxy resins.     

A Comparison of the Syntheses of High Molar Mass Epoxy Resins on the Basis of two Groups of Modified Vegetable Oils

Application of epoxidized and hydroxylated natural oils as a new group of environmentally friendly and renewable raw materials for the synthesis of high molar mass epoxy resins is described. Selected vegetable oils were first oxidized and next reacted with mono and diethylene glycols. Obtained epoxidized soybean, rapeseed, linseed and sunflower oils were used together with Bisphenol A in the fusion process. Analogously, hydroxylated soybean and rapeseed oils were reacted with commercial grade Bisphenol A-based low molar mass epoxy resin. The fusion process was carried out in the presence of selected catalysts (i.e., lithium chloride, 2-methylimidazole, triphenylphosphine and triethanolamine) giving high molar mass epoxies. The relationship between type of modified oil used in the synthesis and reaction conditions and properties of synthesized resins (e.g., value and distribution of average molar mass, contents of epoxy groups and colour) is discussed.     

Thermal cure kinetics of epoxidized linseed oil with anhydride hardener

The thermal cure kinetics of an epoxidized linseed oil with methyl nadic anhydride as curing agent and 1-methyl imidazole as catalyst was studied by differential scanning calorimetry (DSC). The curing process was evaluated by non-isothermal DSC measurements; three iso-conversional methods for kinetic analysis of the original thermo-chemical data were applied to calculate the changes in apparent activation energy in dependence of conversion during the cross-linking reaction. All three iso-conversional methods provided consistent activation energy versus time profiles for the complex curing process. The accuracy and predictive power of the kinetic methods were evaluated by isothermal DSC measurements performed at temperatures above the glass transition temperature of the completely cured mixture (T _g∞ ). It was found that the predictions obtained from the iso-conversional method by Vyazovkin yielded the best agreement with the experimental values. The corresponding activation energy (E _a) regime showed an increase in E _a at the beginning of the curing which was followed by a continuous decrease as the cross-linking proceeded. This decrease in E _a is explained by a diffusion controlled reaction kinetics which is caused by two phenomena, gelation and vitrification. Gelation during curing of the epoxidized linseed/methyl nadic anhydride system was characterized by rheological measurements using a plate/plate rheometer and vitrification of the system was confirmed experimentally by detecting a significant decrease in complex heat capacity using alternating differential scanning calorimetry (ADSC) measurements.     

Castor oil modified by epoxidation,transesterification, and acrylation processes: Spectroscopic characteristics

In the present study, castor oil (CO) was modified by epoxidation, transesterification, and acrylation processes. In situ epoxidation method was used to prepare epoxidized castor oil (ECO) in acetic acid with hydrogen peroxide in the presence of Seralite SRC-120 catalyst. Transesterified epoxidized castor oil was synthesized from the reaction of methanol in the presence of sodium methoxide catalyst. The acrylated epoxidized castor oil was synthesized from the reaction of ECO with acrylic acid containing hydroquinone. Chemical structures of modified CO were analyzed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectra analysis.     

Structure and properties of partially epoxidized soybean oil

In the present study, the characteric-structure relationship of epoxidized soybean oils (ESO) with various degrees of epoxidation has been investigated. FTIR analysis was used to identify the relative extent of epoxidation of the samples during the epoxidation reaction. The viscosities of ESO were much higher than that of the raw oil, viscosity increased with degree of epoxidation. The viscous-flow activation energy of ESO was determined to be higher than that of the raw oil (20.72 to 77.93% higher). Thermogravimetry analysis (TG) of ESO was used to investigate the thermodynamic behavior of the samples. With increasing degree of epoxidation, the thermal stability of the samples initially decreased, then increased at the final reacting stage. Differential scanning calorimeter (DSC) indicated that the melting point of ESO was higher than that of soybean oil. Gel permeation chromatography (GPC) indicated the molecular mass of the samples increased initially, then decreased, with an increase in the extent of epoxidation.     

Synthesis and characterization of itaconic‐based epoxy resins

A trifunctional epoxy resin from itaconic acid (TEIA) was synthesized from a renewable resource‐based itaconic acid by allylation of itaconic acid to form diallyl itaconate by using m‐chloroperoxybenzoic acid as oxidizing agents followed by epoxidation of allylic C═C bond of diallyl itaconate methylhexahydropthalic anhydride as curing agent in the presence of 2‐methyl imidazole as a catalyst. The chemical structure of the synthesized resins was confirmed by Fourier transform infrared and nuclear magnetic resonance (¹H‐NMR and ¹³C‐NMR) spectroscopy analysis. The mechanical, thermal, and rheological performances of the TEIA were also investigated and compared with diglycidyl ether of bisphenol A and a plant‐based epoxidized soybean oil bioresin cured with the same curing agent. The higher epoxy value of 1.02, lower viscosity (0.96 Pa s at 25°C), higher mechanical, and higher curing reactivity toward methylhexahydropthalic anhydride of TEIA as compared with epoxidized soybean oil and comparable with diglycidyl ether of bisphenol A demonstrated significant evidence to design and develop a novel bio‐based epoxy resin with high performance to substitute the petroleum‐based epoxy resin.     

A fully biobased epoxy resin from vegetable oils: From the synthesis of the precursors by thiol‐ene reaction to the study of the final material

A novel vegetable oil‐based polyamine issued from grapeseed oil (GSO) was prepared using cysteamine chloride (CAHC) by thiol‐ene coupling (TEC). The structure of the polyamine oil (AGSO) was carefully examined using a large range of chemical analyses (FTIR, ¹H NMR and ¹³C NMR, LC‐MS…). The effects of the amination of GSO on the vegetable oil properties were also studied using viscosimetry. Then, AGSO was employed as a novel curing agent for bio‐based epoxy resin. The thermal crosslinking reaction between AGSO and epoxidized linseed oil (ELO) was studied by DSC and rheology. This study also dealt with the definition of the thermomechanical properties of the final material obtained by the mixing and curing of AGSO with ELO in stoichiometric proportions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and Properties of Renewable Environment‐Friendly Epoxy Resins for Surface Coatings

Sunflower, soybean, and linseed oils are renewable resources that can be readily epoxidized. Epoxidation of these oils has the potential for use as an environmentally friendly, reactive material in pigmented formulation, designed for use as functional coatings. This study concern the synthesis of phthalimide modified epoxy compounds through reacting N‐(2‐hydroxyethyl) phthalimide (HEP) with epoxidized sunflower, soybean and linseed oils. The resulting compounds possessed both oxirane ring and phthalimide group. Incorporation of phthalimide group into epoxy resins provided cyclic imide structure and high cross‐linking density to the stoved resins, to achieve good mechanical characteristics and high chemical resistance to these resins. The films of phthalimide sunflower, soybean and linseed‐based epoxy resins were found to be similar with respect to resistance to water, alkali, acids, and solvents as well as gloss%, adhesion, impact, hardness, bending, and flexibility.     

Development of completely bio‐based epoxy networks derived from epoxidized linseed and castor oil cured with citric acid

Bio‐based epoxy resins were synthesized from nonedible resources like linseed oil and castor oil. Both the oils were epoxidized through in situ method and characterized via Fourier transform infrared and ¹H‐NMR. These epoxidized oils were crosslinked with citric acid without using any catalyst and their properties compared with diglycidyl ether of bisphenol A‐epoxy. The tensile strength and modulus of epoxidized linseed oil (ELO) were found to be more than those of epoxidized castor oil (ECO)‐based network. However, elongation at break of ECO was significantly higher than that of both ELO and epoxy, which reveals its improved flexibility and toughened nature. Thermogravimetric analysis revealed that the thermal degradation of ELO‐based network is similar to that of petro‐based epoxy. Dynamic mechanical analysis revealed moderate storage modulus and broader loss tangent curve of bio‐based epoxies confirming superior damping properties. Bioepoxies exhibit nearly similar contact angle as epoxy and display good chemical resistant. The preparation method does not involve the use of any toxic catalyst and more hazardous solvents, thus being eco‐friendly.     

Cardanol Based Matrix for Jute Reinforced Pipes

The aim of this work is the development of composite pipes using renewable resources. The pipes, manufactured by filament winding technology, were obtained using an epoxy resin crosslinked with a cardanol based novolac as matrix and jute fibres as reinforcement. Cardanol is a natural oil extracted from the shell of the cashew (Anacardium occidentale L.) nut. An amount of natural materials higher than 50% by weight was achieved in the final composites. Tensile and parallel plate compression tests were carried out on the composite pipes.     

Synthesis and Characterization of Polymeric Materials from Vegetable Oils

Although the petrochemical polymers have revolutionized the technological development, the intensive use of these materials have contributed to the global pollution. In this context, researches involving ecofriendliness materials are growing up, as well as, a current interest in developing materials from inexpensive and renewable resources, such as vegetable oils. In this work, is described the synthesis of polymeric materials by thermal polymerization from linseed oil (Linum usitatissimum L.) and passion fruit oil (Passiflora edulis) and their characterization by gas chromatographic (GC), Fourier transform infrared (FTIR) spectroscopy, solubility in organic solvents, thermogravimetry (TG), differential scanning calorimetry (DSC) and Raman spectroscopy. The TG curve shows that those polymeric materials present two stages of decomposition. DSC plots of the vegetable oils showed some endothermic and exothermic transitions which are not present in the DSC curves corresponding to oil-based polymers. The Raman spectra of the polymers indicate declining of absorbance in the region of CC stretching (∼1600 cm⁻¹). This absorption was used to estimate the degree of polymerization (79% and 67.5% for linseed and passion fruit oils, respectively).     

Synthesis and Photoinitiated Cationic Polymerization of Epoxidized Castor Oil and Its Derivatives

ABSTRACT

In this communication we describe the synthesis of epoxidized castor oil (ECO) as an interesting and inexpensive biorenewable monomer by an efficient and low cost epoxidation process. Also described are studies of the photoinitiated cationic polymerization of ECO using diaryliodonium salt photoinitiators. The influence of the structure and the concentration of the photoinitiator on the polymerization are reported. The ability of photosensitizers to accelerate the photopolymerization was also studied. Studies comparing the photopolymerization behavior of ECO with other commercially available epoxidized linseed and soybean oils and with other types of synthetic epoxy monomers were conducted. The excellent reactivity of ECO can be ascribed to the presence of both epoxy and hydroxyl groups in the molecule which permits this material to polymerize mainly by an activated monomer mechanism.

     

Properties of HTPB based polyurethane membrane prepared by epoxidation method

Hydroxyl-terminated polybutadiene (HTPB) based polyurethane (PU) was synthesized by solution polymerization. The PU was then cast into membrane. The epoxidation of HTPB based PU membrane by an in situ generated peracid method is discussed. The chemical composition of the epoxidized PU membrane was studied by infrared spectroscopy. The absorption peak at 970 cm⁻¹ for the CC double bond decreased with epoxidation time whereas the absorption peak at 1183 cm⁻¹ for oxirane group increased. The absorption peak at about 1700–1740 cm⁻¹ for the CO group and –OH group at about 3200–3700 cm⁻¹ increased with epoxidation time that indicated the side reaction of epoxidation took place. The oxirane weight content was determined by titration method. The density, tensile strength, elongations, and decomposition temperature of the epoxidized PU membranes were measured. The molecular weight between crosslinking points PU membrane was calculated. Contact angle and protein absorption of fibrinogen and albumin experiments were also determined. It was found that the density and the tensile strength of epoxidized PU membrane increased with increasing epoxidation time whereas the molecular weight between crosslinking points, elongation and the amount of protein adsorption on the epoxidized PU membrane decreased. By using Kaelble’s equation and the contact angle data, the surface tension of epoxidized PU membrane was determined. It was found that the surface tension of epoxidized PU membrane increased whereas the contact angle decreased with epoxidation time. The property changes reduced the permeability of gas through epoxidized PU membrane, but increased the gas selectivity between oxygen and nitrogen. The activation energies (E_p) for gas diffusing through various epoxidized PU membranes were obtained by the Arrhenius law; it is evident that E_p increased with the extent of epoxidation.     

Application of Modified Natural Oils as Reactive Diluents for Epoxy Resins

Bisphenol A based low-molecular-weight epoxy resin was modified with epoxidized soybean oil, which exhibit viscosity reducing ability comparable to commercial grade active diluents. The studied compositions showed a non-Newtonian rheological behavior, typical for Bingham liquids. The values of the flow index (n) and the consistency index (k) for the compositions tested in the temperature range 25–65 °C were calculated from the Ostwald-de Waele rheological model and were used to calculate the flow-activation energy (E_a) using the Arhenius equation. Studies of co-crosslinking of mixed oil-resin compositions using isophorone diamine showed essential decrease of the reaction heat and peak maximum temperature. Mechanical properties, thermal stability, water absorption and chemical resistance of the epoxy resin modified with natural oil, were also investigated. Compositions of epoxy resin Ruetapox 0162, modified with the oil diluent, preserved very good mechanical properties of the epoxy resins and demonstrated relatively low water absorption as well as high chemical resistance. The compositions displayed even higher impact strength than pure epoxy resin due to plasticizing effect of the built-in oil. Compositions with the high contents (up to 60 weight %) of the oil were flexible materials with fast elastic recovery.     

摩阻材料用亚麻油改性酚醛树脂的制备及耐热性研究

利用亚麻油改性酚醛树脂,得到高性能的摩阻材料用树脂基体.推导了改性机理和结构特征,并进行了耐热试验和分析.结果表明,亚麻油参与了反应并成为聚合物的一部分,亚麻油改性酚醛树脂固化后的结构特征是互穿聚合物网络(IPN),与普通酚醛树脂相比,亚麻油改性酚醛树脂的耐热性能显著提高,可望用作耐高温磨阻材料树脂基体.     

Thermal analysis of polyesters containing oxirane groups

The preliminary studies of the thermal behaviour of polyester obtained in polycondensation process of cyclohex-4-ene-1,2-dicarboxylic anhydride and ethylene glycol and its new epoxidized form have been performed. The thermal characterization of initial polyester and its completely oxidized form was done by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The non-isothermal DSC was applied to determine the influence of time and the temperature on the chemical modification of initial polyester using 38-40% solution of peracetic acid. On the basis of DSC profiles it has been found that the endothermic transition, due to the degradation process of initial polyester was characteristic feature under controlled heating program. The two characteristic transitions for the new epoxidized polyester, the exothermic peak corresponded to the thermal crosslinking of epoxidized polyester (322.8–336.4°C) and the endothermic decomposition peak of the cured material (363.8–388.9°C) were observed. The peak maximum temperatures (Tmax) and the heat of cross-linking reaction (ΔH_c) for epoxypolyester prepared at 20–60°C under 1–4 h were evaluated. The Tmax1 were almost independent from epoxidation conditions, while, the values of ΔH_c were dependent from conditions of synthesis. The ΔH_c values of this process decreased when time of oxidation increased. The highest values of ΔH_c at 40°C were obtained. Additionally, TG experiments confirmed two separated degradation steps of the new epoxidized polyester indicating the ester (370–380°C) and ether (450–460°C) bond breakdown.     

Calorimetric analysis of the cross-linking reaction of epoxidized polybutadienes

Liquid polybutadienes were epoxidized with hydrogen peroxide-acetic acid confirming the influence of the microstructure on the epoxy content. Thermal cross-linking of the epoxidized products was studied by DSC and a different behaviour due to epoxy content as well as to microstructure was found. A correlation between enthalpy/epoxy ratio and vinyl content was also observed. The addition of a radical initiator as dicumyl peroxide (DCP) yielded exothermal effects of cross-linking in the original polybutadienes, confirming the higher reactivity of the vinyl groups. In the epoxidized products, the introduction of DCP gave a peak split, which was explained by the overlap of two cross-linking mechanisms, due to residual double bonds and epoxy groups. From the DSC data, the isothermal curves of cross-linking conversion were calculated as a function of time, for a better comparison of the performances and properties of the epoxidized polybutadienes.