Epoxidized soybean oil = ESBO = ESO = Soybean oil, epoxidized
EC / List no.: 232-391-0
CAS no.: 8013-07-8
Mol. formula: C3H5O3
Epoxidized soybean oil (ESO) is the oxidation product of soybean oil with hydrogen peroxide and either acetic or formic acid obtained by converting the double bonds into epoxy groups, which is non-toxic and of higher chemical reactivity.
Epoxidized soybean oil is mainly used as a green plasticizer for polyvinyl chloride, while the reactive epoxy groups imply its great potential in both the monomer synthesis and the polymer preparation fields.
Functional polymers are obtained by different kinds of reactions of the ESO with co-monomers and/or initiators shown in this chapter.
The emphasis is on Epoxidized soybean oil based epoxy cross-linked polymers which recently gained strong interest and allowed new developments especially from both an academic point of view and an industrial point of view.
It is believed that new ring-opening reagents may facilitate the synthesis of good structural Epoxidized soybean oil based materials.
Epoxidized soybean oil is a collection of organic compounds obtained from the epoxidation of soybean oil.
Epoxidized soybean oil is used as a plasticizer and stabilizer in polyvinyl chloride (PVC) plastics. ESBO is a yellowish viscous liquid.
Epoxidized Soybean Oil is a non-toxic, clear to yellow liquid that is used as a plasticizer and stabilizer in plastic materials, especially PVC and its copolymers.
Epoxidized Soybean Oil is also used as a pigment dispersing agent and acid/mercaptan scavenging agent as well as an epoxy reactive diluent.
Epoxidized Soybean oil is the most readily available and one of the lowest-cost vegetable oils in the world. Epoxidized soybean oil is the result of the oxidation of soybean oil with hydrogen peroxide and either acetic or formic acid.
Due to its low cost and biodegradability over traditional phthalate plasticizers, epoxidized soybean oil is replacing dioctyl phthalate (DOP) in some applications.
ATAMAN KIMYA’s epoxidized soybean oil is a cost efficient choice for a variety of applications that also includes functional fluids, flavor and fragrances, sealants, coatings, and special inks.
Epoxidized soybean oil can be converted by different kinds of reactions with co-monomers and/or initiators.
Permanent network that comes from the directing cross-linking of Epoxidized soybean oil and hardeners endows Epoxidized soybean oil with great stability, superior mechanical properties and satisfying chemical resistance, which make the products competitive among a variety of materials.
In addition, the chemical modification of Epoxidized soybean oil has gained more and more attention in recent years.
Introducing hydroxyl groups to make polyols for polyurethanes synthesis is one of the most important chemical modification methods.
Acrylated epoxidized soybean oil (AESO) obtained by ring opening esterification between acrylic acid and ESO is of high reactivity for thermal and UV initiated polymerization
This chapter reviews the applications of ESO and its derivatives for the preparation of a series of bio-based polymeric materials.
Epoxidized Soybean Oil is a non-toxic, clear to yellow liquid that is used as a plasticizer and stabilizer in plastic materials, especially PVC and its copolymers.
KEYWORDS:
Epoxidized soybean oil, ESBO, ESO, Soybean oil epoxidized, 232-391-0, 8013-07-8, Epoxol D65, Epoxol D65S, Ergoplast ES, ESOPOL, ESOPOL LA
Epoxidized soybean oil is also used as a pigment dispersing agent and acid/mercaptan scavenging agent as well as an epoxy reactive diluent.
Epoxidized soybean oil and other epoxide substances are used as raw materials for various applications that include functional fluids, fuel additives, polyol replacements, agricultural and pharmaceutical molecules, flavor and fragrances, reactive diluents and UV cure applications, surfactants, adhesives, sealants, coatings, and special inks.
Epoxidized soybean oil is used as a co-plasticizer, as an acid scavenger in soft PVC process for hydrochloric acid liberated from PVC when PVC undergoes heat treatment and acts as a mercaptan/acid scavenger in many other applications, as well as a secondary heat and light stabilizer.
Due to low cost non-toxic and environmentally friendly properties, as well as biodegradability over traditional plasticizers partially replacing DOP (DI OCTYL PHTHALATE) in PVC applications
Manufacturing process of Epoxidized soybean oil
Epoxidized linolein, a major component of ESBO.
Epoxidized soybean oil is manufactured from soybean oil through the process of epoxidation.
Polyunsaturated vegetable oils are widely used as precursors to epoxidized oil products because they have high numbers of carbon-carbon double bonds available for epoxidation.
The epoxide group is more reactive than double bond, thus providing a more energetically favorable site for reaction and making the oil a good hydrochloric acid scavenger and plasticizer.
Usually a peroxide or a peracid is used to add an atom of oxygen and convert the -C=C- bond to an epoxide group.
ESO is an epoxidized glycerol fatty ester that is used as a plasticizer and stabilizer in plastic materials.
The substance is especially useful in PVC and its copolymers to keep plastics and rubber soft and pliable.
The epoxy functionality provides excellent heat and light stability.
The term “epoxide” indicates three-membered cyclic ether in which an oxygen atom is jointed to each of two carbon atoms that are already bonded to each other.
The unhindered oxygen atom carries two unshared pairs of electrons, a structure that favors the formation of coordination complexes and the solvation of cations.
Because of equilateral triangle strain in this snall ring, epoxides are more reactive than larger ring ethers.
Epoxides undergo reactions such as C—O bond cleavage, nucleophilic addition, hydrolysis and reduction under mild conditions and more rapidly than other ethers.
Epoxides are formed by some oxidation reactions of alkenes with peracids.
Epoxidized Soybean Oil (ESO) is produced from one of the most readily available and lowest-cost vegetable oils in the world.
ESO is produced through the oxidation of high iodine value unsaturated soybean oil with hydrogen peroxide and organic acids such as acetic acid or formic acid.
Epoxidized Soybean Oil is primarily used as a co-plasticizer for flexible polyvinyl chloride (PVC) and its copolymers to keep these plastics soft and pliable.
The chemical is also used as a pigment dispersing agent and an epoxy reactive diluent.
Epoxidized Soybean Oil acts as a secondary heat and light stabilizer, and it is especially valuable as a low cost and effective synergist to metallic stabilizer compounds in vinyl systems.
In addition, ESO acts as an acid scavenger for soy-based inks, agricultural chemicals, and insecticides.
Epoxidized Soybean Oil can also be used as a chemical intermediate, additive for specialty coatings, adhesives, and urethanes, and in lubricants and cutting oils.
Due to its low cost and biodegradability over traditional phthalate plasticizers, ESO is replacing dioctyl phthalate (DOP) in some applications.
Because ESO is non-toxic, bio-based, bio-degradable, and phthalate-free, it is a prime choice for sustainable and eco-friendly formulations.
Uses of Epoxidized soybean oil:
Food products that are stored in glass jars are usually sealed with gaskets made from PVC.
Epoxidized soybean oil is one of the additives in the PVC gasket.
It serves as a plasticizer and a scavenger for hydrochloric acid released when the PVC degrades thermally, e.g. when the gasket is applied to the lid and food product undergoes sterilization.
ESBO is also used in PVC cling films for wrapping foods and toys.
Applications
Wires & Cables
Leather Cloth
Vinyl Flooring
Medical Equipment
Non-toxic Food Packaging
Footwear
Flexible PVC Films
Adhesives
Perfumery
Automobile Parts
Rubber Belts
Flexible Pipes and Tubings
Paints
Lubricants
Metal Working Fluids
Furniture
Chemical Intermediates, etc.
Applications
• Flexible PVC formulations
• As a co-stabilizing internal lubricant in Rigid PVC formulations
• Soya based inks
• Pesticides
• Insecticides
• As pigment dispersion agent
• As chemical intermediate
• Lubricants
• Cutting oils
• As an epoxy reactive diluent
• Functional fluids
• Fuel additives
• As a polyol replacement
• Agricultural and pharmaceutical molecules
• As a green carrier in flavor and fragrances
• In UV cure applications
• In surfactants
• Adhesives
• Sealants
• Coating
Certain areas where epoxy soybean oil can be used are as follows;
In concrete additives and mortar production
In polyurethane applications and surface adhesives
In furniture and surface applications varnish applications
In toy manufacturing
In artificial leather manufacturing
In PVC cable and cable channels
In PVC granules in hard and soft applications
In PVC pipe, hose and gasket manufacturing
In PVC insulation materials (membrane, shingle, water retaining tape)
PVC tablecloth
In packaging industry
In paneling and curtain springs
Epoxidized Soybean Oil is compatible with a variety of surface coating materials like PVC, PVA, nitro cellulose, chlorinated rubber etc.
Being an acid acceptor, Epoxidized Soybean Oil imparts stability to coating formulations besides better resistance to extraction by soap, detergent and salt solutions.
Epoxidized Soybean Oil also partially imparts resistance to migration compared to conventional plasticizers in surface coating formulations.
In addition, Epoxidized Soybean Oil improves adhesion, toughness, gloss and chemical resistance of the film
Recommended Dosage
Plasticized PVC
In general, Epoxidized Soybean Oil is used at a concentration of 2-5 % and up to 10% of the Plasticizer content has proved to give good results.
Rigid PVC
Recommended concentration is 1-3 %
Epoxidized soybean oil, ESBO or ESO, is a plasticizer which can be used in PVC products (polyvinyl chloride films, gaskets, Masterbatches, compounds, etc...), such as all kinds of food package materials, medical products, different kinds of films, sheet materials, tubing, gaskets, refrigerator sealing strips, artificial leather, plastic wallpaper, electrical wires and cables, other plastic products and for food contact applications. Epoxidized soybean oil (ESO/ESBO) can also be used as special printing ink and liquid composite stabilizer.
Epoxidized Soybean Oil (ESBO) is a plasticizer and stabilizer to maintain softness and flexibility at varying temperature ranges.
Epoxidized Soybean Oil (ESBO) is a bio-degradable and renewable replacement and cost efficient alternative for phthalate plasticizers in PVC compounds, applications and other plastic materials. We can offer several grades of Epoxidized Soybean Oil (ESBO), a regular or medical grade, key difference is the POV value of the product.
Benefits and Features of Epoxidized Soybean Oil:
Bio-degradable, renewable and eco-friendly
Phthalate-free and non-toxic
Good compatibility and flexibility
Excellent heat and light stabilization
Resist migration, volatility is small and not easy to extract
Fo which application can Epoxidized Soybean Oil be used?
Plasticizers (PVC, PVA, Chlorinated Rubber)
Pigment Dispersion Agents
Food & Beverages of Flavor
Functional Fluids
UV Cure applications
Epoxidized Soybean Oil's applications include acid scavenging in soy-based inks, agricultural chemicals and insecticides; monomer compatibilizer, pigment dispersion, chemical intermediate and lubricating and cutting oils.
Soybean Oil Epoxide is frequently used as an additive during poly(vinyl chloride) preparation, displacing harmful phthalates. Soybean Oil Epoxide has also been modified for lubricant formulations with improved oxidative stability and low pour point.
Epoxy oil has the ability to provide stability against heat and sunlight at the same time.
It is not volatile, as well as showing good resistance to dissolution in water and other hydrocarbons. It can be mixed with other main and polymeric plasticizers to perform the desired operations, especially with lower costs. Epoxy oil is acid resistant. In this way, the formation of acid during the process creates a wall.
One of the properties of epoxy soybean oil is increased slider.
Thanks to epoxy soybean oil, which has an internal slider effect in calender and extrusion systems, the fluency of the liquid can be increased.
Epoxy soybean oil is used in combination with stabilizers that are used for PVC.
The reason for this is to increase the features.
Another known feature of epoxy soybean oil is that it is a pigment dispenser and a good internal slider.
The advantages of epoxy soybean oil are that if used together with metal soap stabilizers, it increases heat resistance.
Calcium has a positive effect on the performance of zinc-based stabilizers and some internal sliders.
It increases the heat and light resistance of the products that are used.
By ensuring HCl absorption, it protects the product against external factors.
It can be used safely in all kinds of food packaging applications as it passes food conformity tests.
High compatibility with PVC resin increases migration resistance. It gives brightness to the product.
The quality of epoxidized soybean oil (ESO), industrially used as a plasticizer and heat stabilizer for PVC films, is given by the degree of epoxidation (EI), the number of double bonds expressed as the iodine index (II), and the water percentage in the final product
Epoxidized Soybean Oil is used in the chemical, paints-lacquers-varnishes, and polymers industries;
Epoxidized Soybean Oil is used as a construction materials additive, process regulator, softener, viscosity adjustor, solvent, stabilizer, and plasticizer; [IUCLID]
Epoxidized Soybean Oil is used as a formulation aid, lubricant, and stabilizer or thickener for foods; [FDA]
Epoxidized Soybean Oil has been Permitted for use as an inert ingredient in non-food pesticide products; [EPA]
USAGE OF Epoxidized Soybean Oil AS CORROSION INHIBITOR:
Epoxidized Soybean Oil is a viscous fatty derivative that offers inhibition and protection against the possibility of corrosion and/or staining of ferrous alloys by highly chlorinated cutting or forming oils.
Functions: Acid scavenger, Epoxidized soybean oil
Product Applications: Highly chlorinated cutting oils, Highly chlorinated forming oils
Product Classes: Corrosion Inhibitor, Lubricants, Metalworking & Grease
Safety
Food
A Swiss survey in June 2005 showed that (among many other plasticizers exceeding the legal limits) migration of ESBO into foods reached up to 1,170 mg/kg.
Rapid Alert System in Food and Feed (RASFF) had also reported cases of food product rejection in EU for exceeding SML under EU Legislation (EC/2002/72).
Enforcement authorities took measures to force producers respecting the legal limits.
Epoxidized soybean oil
Fatty acid, soybean oil, epoxidized
Flexol EPO
Oils, soybean, epoxidized
Paraplex G-60
Paraplex G-62
PX-800
soybean oil, epoxidised
CAS names: Soybean oil, epoxidized
IUPAC names: 2,3-bis[8-[3-[(3-pentyloxiran-2-yl)methyl]oxiran-2-yl]octanoyloxy]propyl 8-[3-[(3-pentyloxiran-2-yl)methyl]oxiran-2-yl]octanoate
[(2R)-2,3-bis[[(9Z,11Z)-13-hydroperoxyoctadeca-9,11-dienoyl]oxy]propyl] (10Z,12Z)-9-hydroperoxynonadeca-10,12-dienoate
Epoxidised soya bean oil
Epoxidised soya oil
Epoxidized Sojbean oil
Epoxidized Soya Bean Oil
Epoxidized Soyabean Oil
Epoxidized Soybean Oil
ESBO
Plasticizer E
soya been oil, epoxidized
SOYABEAN OIL EPOXIDISED
Soyabean Oil, Epoxidized
Soybean Oil
Soybean oil, epoxidised
Soybean oil, epoxidized - ESBO
Soybean oil, epoxidized; (MERGINAT ESBO)
Trade names
Drapex 39
Drapex 391
Drapex 6.8
Epovinstab H800
Epovinstab H800 D
Epoxidized soyabean oil
Epoxidized Soybean Oil
Epoxol D60
Epoxol D65
Epoxol D65S
Ergoplast ES
ESOPOL
ESOPOL LA
K-PLAST 65
KALFLEX 13
KALFLEX 14
KALFLEX 14 A
KALFLEX 14NP
KALFLEX 14OA
KALFLEX 14OP
Lankroflex E2307
MAKPLAST SN
MAKPLAST SNS
MERGINATE ESBO
Plasticizer E
SDB CIZER E-03
Synonyms
Oils, soybean, epoxidized; Soybean oil, epoxidized; PX-800; Paraplex G-60; Paraplex G-62; Fatty acid, soybean oil, epoxidized; Flexol EPO; [ChemIDplus] Adekacizer O 130L; Adekacizer O 130P; Adekacizer O 130PA; Adekacizer O 130S; Adekacizer O 180P; ADK Cizer O 130L; ADK Cizer O 130P; ADK Cizer O 130PA; ADK Cizer O 130S; ADK Cizer O 180P; Admex 711; ATO Vikoflex 7170; D 130P; Daimac S 300K; Drapex 6.8; E 2000; Ecepox PB 1; Edenol D 81; Edenol D 82; Epocizer P 206; Epocizer W 1000; Epocizer W 100EL; Epocizer W 100S; Epoxidised soya bean oil; Epoxidised soyabean oil; Epoxidized soya oil; Epoxidized Soybean Oil; Epoxol 7–4; Ergoplast ES; ESBO; Estabex 138–A; Estabex 2307; Estabex 2307 DEOD; Flexol Plasticizer EPO; G 62; Hoe S 3680; Intercide ABF 1 ESBO; Intercide ABF 2 ESBO; Interstab Plastoflex 2307; Kapox S 6; Kronox S; Lankroflex GE; Micro–Chek 11; NK 800; O 130P; OLIO DI SOIA EPOSSIDATO; Omacide P–10ESO–5; Paraplex G 61; Pennac TM; Peroxidol 780; Plas–Chek 775; Plastepon 652; Plasthall ESO; Plasticizer E 2000; Plastoflex 2307; Plastol 10; Plastolein 9232; Reoplast 39; Sansocizer E 2000; Sansocizer E 2000H; Scraplube; SOJABOHNENOEL, EPOXIDIERT; Sojabohnenoel, epoxidiert; Sojaoelepoxid; Sojabohnenol, epoxidiert; Sojaol, epoxidiert; Sojaol, epoxydiert; Sojaolepoxid; Soya bean oil, epoxidised; Vikoflex 7170; Vinyzene BP–505; [IUCLID]
Legislation
In Europe, plastics in food contact are regulated by Regulation (EU) 10/2011.
It establishes a specific migration limit (SML) for ESBO of 60 mg/kg.
However, in the case of PVC gaskets used to seal glass jars containing infant formulae and follow-on formulae as defined by Directive 2006/141/EC or processed cereal-based foods and baby foods for infants and young children as defined by Directive 2006/125/EC, the SML is lowered to 30 mg/kg.
This is because babies have higher food consumption per body weight.
Toxicity
The tolerable daily intake (TDI) of ESBO defined by the Scientific Committee on Food (SCF) of the EU is 1 mg/kg body weight.
This value is based on a toxicological assessment performed by the British Industrial Biological Research Association (BIBRA) in the late 1997.
Repeated oral administration had been shown to affect the liver, kidney, testis and uterus of rats.
According to the conventional European rules for food packaging materials, the TDI became a basis for the SML of 60 mg/kg.
Amine hardeners
Functional amines are widely used as curing agents for generating epoxy resin.
For Epoxidized soybean oil, a series of amines used as curing agents are listed in Table 1
Most of the researchers focused on the investigation of the cross-linking process of partially bio-based polymers because of the unsatisfying properties of fully bio-based ones.
Three main methods can be applied to improve the properties of ESO-based thermosets, which are using commercial curing agents, adding commercial epoxy resins to ESO, and adding other materials to make composites
TABLE 1
No. Epoxy resin Hardener
1 ESO Triethylene glycol diamine (TGD)
2 ESO Triethylenetetramine (TETA)
3 ESO Diethylenetriamine (DETA)
4 ESO Jeffamine D-230
5 ESO Jeffamine T-403
6 ESO Jeffamine EDR-148
7 ESO + diglycidyl ether of bisphenol A (DGEBA) TETA
8 ESO + DGEBA DETA
9 ESO + DGEBA Jeffamine D-230
10 ESO + DGEBA Jeffamine T-403
11 ESO + DGEBA Jeffamine EDR-148
12 ESO + DGEBA Linear polyethylenimine
13 ESO, ESO + DGEBA Dicyandiamide (DICY)
14 ESO Decamethylene diamine, succinic anhydride
15 ESO + DGEBA Isophorone diamine(IPDA)
The curing processes of Epoxidized soybean oil or the mixture of Epoxidized soybean oil and commercial epoxy resin have been investigated, and some of these systems have been made into composites through adding fibers, clay and other reinforcement.
Viscoelastic properties, mechanical properties and many other analyses have been studied to evaluate their applicability to be used in industry.
The partially bio-based polymers show great potential to replace fully petroleum-based polymers in many areas according to the testing results.
Glass-transition (Tg) and viscoelastic properties of amine-cured ESO can be enhanced by increasing the amount of triethylenetetramine (TETA) or triethylene glycol diamine (TGD).
TETA endows the polymer with similar viscoelastic properties to a commercial rubber and a higher Tg than TGD does.
In this respect, the biopolymers made from Epoxidized soybean oil and amines have great potential to replace some synthetic rubbers or plastics.
Besides, the quasi-static and dynamic compressive properties of the cured products based on Epoxidized soybean oil and amines and the corresponding composites reinforced by clay have also been investigated to develop compressive one-dimensional stress-strain material models.
Solid freeform fabrication method has been applied to the preparation of ESO-based composites and proved to be a suitable method for this kind of curing system.
Epoxidized soybean oil/TETA/clay composites show controllable biodegradability, low cost, good thermal and mechanical properties, and these properties indicates that the composites may work as alternative to petroleum-based polymers in the field of insulation materials and coating materials.
For clay-reinforced composites based on commercial epoxy resin the addition of Epoxidized soybean oil can enhance the impact strengths.
More interestingly, the product from Epoxidized soybean oil and TETA can be made into an ion-exchange resin through hydrolysis.
Usually, epoxy groups in the internal of the long aliphatic chain exhibits much poorer reactivity than those terminal epoxy groups.
Due to this fact, the reported curing processes of ESO usually needs higher temperature and longer time than commercial petroleum-based epoxy resin, such as bisphenol A epoxy resin.
However, the combination of the hardener, dicyandiamide (DICY), and the accelerator, carbonyldiimidazole (CDI), can make the gelation of ESO occur within 13 min at 190°C.
Moreover, the gelation of the mixture of ESO and DGEBA is achieved with the aid of DICY and CDI within 3 min at 160°C.
Fully or high bio-based polymers are also attractive to researchers owing to people’s strong attention to environment concerns.
A series of fully bio-based elastomers have been synthesized through the ring-opening reaction between ESO and a bio-based amine hardener, decamethylene diamine, and they can be cross-linked by further reaction with another bio-based anhydride hardener, succinic anhydride.
These fully bio-based elastomers have great potential to replace some petroleum-based rubbers in engineering because of their good damping property, low water absorption and weak degradability in phosphate buffer solution.
2.2 Anhydride and acid hardeners
Anhydrides, which are less toxic than amines, are another kind of mainly-used hardeners (Table 2).
TABLE 2
No. Epoxy resin Hardener
1 ESO Maleopimaric acid (MPA)
2 ESO Methyltetrahydrophthalic anhydride (MTHPA)
3 ESO + DGEBA MTHPA
4 ESO ESO + DGEBA Methylhexahydropthalic anhydride (MHHPA)
6 ESO Maleic anhydride (MAL)
7 ESO Phthalic anhydride
8 ESO Nadic methyl anhydride
9 ESO maleinized polybutadiene (MMPBD)
10 ESO terpene-based acid anhydride (TPAn), maleinated linseed oil, hexahydrophthalic anhydride
11 ESO hexahydrophthalic anhydride (CH), MAL, succinic anhydride (SUC), dodecenylsuccinic anhydride (DDS)
12 ESO ESO + DGEBA Sebacic acid
13 ESO Adipic acid, 1,12-dodecanedicarboxylic acid, sebacic acid
14 ESO Citric acid, carboxylic acid functionalized MWCNTs
15 ESO ESO + epoxidized linseed oil (ELO) Carboxyl-terminated polyester
16 ESO Dicarboxyl terminated oligomeric poly(butylene succinate)
17 ESO Dicarboxyl-terminated polymide1010 oligomers
18 ESO + ELO Phosphorylated castor oil
Table 2.
Anhydride and acid for curing Epoxidized soybean oil and Epoxidized soybean oil composites.
The curing process between Epoxidized soybean oil and dicarboxylic acids or anhydrides .
The investigation of green anhydride curing agents is one of the research priorities.
Maleopimaric acid (MPA), which comes from rosin acid, has been used for ESO curing to obtain new polymeric thermosets with a high bio-based content.
The total heat release is only 31.7 kJ/mol epoxy group.
Compared with its petroleum-based analogues, MPA endows the polymer with larger breaking elongation, higher storage modulus and better thermal stability.
Sebacic acid is another bio-based curing agent for ESO in lab.
A fully bio-based composite with highly improved thermal and mechanical properties can be produced through interaction between sebacic-cured ESO and PLA.
What’s more, sebacic acid-cured ESO can be applied in the field of superhydrophobic materials to make a sustainable and biodegradable superhydrophobic material.
Other bio-based chemicals, such as terpene, vegetable oils and citric acid, are all the optional raw material for green curing agents.
A terpene-based acid anhydride has been found to endow ESO with higher Tg, higher tensile strength and greater modulus than maleinated linseed oil and hexahydrophthalic anhydride do.
But maleinated linseed oil makes the thermoset easier to biodegrade.
Biodegradable and biocompatible elastomers, which may be competitive in the field of implantable materials, can be obtained by curing Epoxidized soybean oil and Epoxidized linseed oil (ELO) with phosphorylated castor oil.
Carboxylic acid functionalized MWCNTs are always used as the filler for fully bio-based ESO/citric acid system.
The produced composites with good mechanical properties and high bio-based content may be applied in the field of industry.
Physical tests of fully sustainable polymers obtained from curing ESO with different dicarboxylic acids show the decreases of Tg and elongation at break, and the increases of tensile strength and Young’s modulus with the increasing of chain-length of the curing agents.
In this respect, besides bio-based micromolecular chemicals, bio-based dicarboxyl-terminated polymers are also able to work as green curing agents for ESO to make fully bio-based polymers.
Polymer curing agents with long chain length can avoid the short, brittle and amorphous cross-link structures which may be the reason for the poor performance of ESO-based thermosets [23].
Like the situation occurring in amine-cured systems, anhydride-cured ESO with a high bio-based content usually cannot exhibit excellent properties as petroleum-based polymers do.
In order to overcome this deficiency, ESO usually works together with some petroleum-based chemicals.
For this kind of complicated reaction systems, many factors are worth investigations. We are going to discuss this kind of reaction systems in terms of the properties of epoxides, the addition of commercial curing agents, the influence of the catalysts and the incorporation of fillers.
The internal epoxy rings in Epoxidized soybean oil exhibits lower reactivity than terminal ones do and the epoxy equivalent weight of ESO is usually higher than commercial epoxy resins.
The addition of Epoxidized soybean oil in the mixture of DGEBA and ESO results in the increase of peak exothermic temperature, and activation energy and the decrease of enthalpy of reaction.
Tensile strength, modulus, fracture toughness, impact strength, storage modulus (E′) in the glassy state and Tg of the cured products decrease because of the addition of ESO.
Besides, the thermal and mechanical properties of the cured products has a positive correlation with the epoxide content of ESO.
Aside from the alteration of epoxides, the properties of the cured products can be enhanced with the aid of commercial curing agents.
Bio-based foams based on methyltetrahydrophthalic anhydride (MTHPA)-cured ESO show similar mechanical properties to synthetic epoxy foams and the contents of ESO can be larger than 55 wt%, which indicates that this kind of green foams can be valuable alternative for commercial epoxy foams.
Polymers with anhydride groups and dicarboxylic acids are also able to work as curing agents for Epoxidized soybean oil.
The carboxylic acid-terminated polyesters can work with ESO to produce green pressure-sensitive adhesives, which are environmentally friendly, thermal stable and with flame retardance.
In this kind of curing systems, the molecular weight of the polymer curing agents obviously have a great influence on the curing process and the physical properties of the cured bio-based products.
One of the remarkable advantages of bio-based polymers is their potential biodegradability. Lower crosslink density usually means higher biodegradability for ESO-based thermosets.
The cross-link density of the cured product reaches maximum at stoichiometric ratio between ESO and hardener.
Not only the properties of the main reactants, but the loading and type of the catalyst have a great influence on the on the curing process final polymers.
The curing kinetics of ESO/methyl hexahydrophthalic anhydride (MHHPA) system show a significantly autocatalytic characteristic and ESO with 1.5 phr (parts per hundreds of resin) of 2-ethyl-4-methylimidazole (EMI) catalyst is a recommended composition for ESO/MHHPA system to be cured effectively at relative low temperature and short time.
ESO-based thermosets can also be used as good matrixes for organoclays, organo-montmorillonite clay, proteins, regenerated cellulose and other fillers.
These works show that the thermal and mechanical properties of the composites can be improved significantly with the addition of different fillers.
2.3 Initiators for chain-growth polymerization
Besides adding curing agents, ESO can also be cross-linked only by initiators
Fluoroantimonic acid hexahydrate (HSbF6·6H2O) and boron trifluoride diethyl etherate (BF3·OEt2) mare commonly employed to initiate the ring-opening polymerization of ESO.
As the special macromolecular structure and mechanical properties, the products have the potential to be made into hydrogels and applied in the areas of personal and health care.
Besides, the cross-linked ESO initiated by BF3·OEt2 can be used to synthesize bio-based surfactants, which can help produce microbubbles effectively and may take the place of petroleum-based detergents and surfactants.
Figure 3.
Chain-growth polymerization of Epoxidized soybean oil under initiators.
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3. Introducing hydroxyl groups
Besides the curing, introducing hydroxyl groups is one of the most important chemical modification of ESO.
Hydroxyl groups are functional groups that can be compatible with matrixes through hydrogen bonding or can be able to covalently bond with matrixes using some active chemicals.
3.1 ESO-based polyols
Bio-based polyols with two or more hydroxyl groups can be synthesized from Epoxidized soybean oil by epoxy ring opening applying different approaches
Ring opening reagents mainly include in mono-functional amines, alcohols (such as methanol, ethylene glycol, propylene glycol or butanol), acids (such as acrylic acid, acetic acid, phosphoric acid, fatty acids, carboxylic acid, hexanoic acids, or octanoic acids), thioethers or ketones.
Lewis acid is known as a kind of useful initiator for the hydroxyl reaction with epoxides.
ESO-based polyether polyols are capable to be prepared by Lewis acids catalyzing ring opening with propylene glycol.
After that, the ESO-based polyether polyols with higher molecular weight can be cured with phenolic, melamine and other conventional crosslinkers to give reasonable film properties.
Besides, Epoxidized soybean oil phosphate ester polyols have been synthesized by using super phosphoric acid phosphorylated Epoxidized soybean oil, which is able to be incorporated in bake coatings with excellent performance.
A series of methoxylated soybean oil polyols (MSOLs) have been prepared with different hydroxyl functionalities by the ring opening of ESO with methanol.
These polyols have been applied to synthesize the environmentally friendly vegetable-oil-based polyurethane dispersions (PUDs) with very promising properties.
Thioglycolic acid (TGA) bearing thiol and carboxylic acid as two different functional groups, glycolic acid (GA) containing hydroxyl and carboxyl functionality and methyl ester of thioglycolic acid (TGAME) have been also used as ring opening agents of ESO to synthesize novel bio-based polyols.
Using TGA and GA, the epoxy rings are opened by the carboxylic acid group, while the epoxy rings are opened by the thiol group primarily when using TGAME.
In addition, polyols obtained by ring opening with TGA have higher molecular weight comparing to GA and TGAME.
That is because some of the thiol groups of TGA initially remain intact and then are involved in ring opening of other epoxy groups resulting in chain coupling.
There are some side reactions occurring during the ring-opening of ESO epoxide groups, and these side reactions often depend on reaction parameters.
A substantial degree of oligomerization due to oxirane-oxirane, and oxirane-hydroxyl reaction will take place in the presence of phosphoric acid.
It is possible to synthesize ESO-based polyols having varying hydroxyl content and phosphate-ester functionality by controlling the type and amount of polar solvent and phosphoric acid content.
Inter-esterification or intermolecular ether formation are also observed as side reactions, depending on the molar proportion of the hydrogen donor.
Different catalysts for the ring opening of the epoxide groups in ESO have been evaluated in many works.
The most common catalysts are sulfuric acid, p-toluenesulfonic acid, perchloric acid, tetrafluoroboric acid (HBF4) and activated clays.
HBF4 have been found to produce polyols with a higher OH content, and lower viscosity than other catalysts in the ring opening reaction of ESO with methanol.
And, triflic acid is a very effective catalyst for preparing ESO polyether polyols.
As alcohol concentration relative to ESO is reduced, higher molecular weight polyether polyols can be produced in a controlled way.
3.2 Epoxidized soybean oil-based polyurethanes
Currently, vegetable oils-based polyols are gradually replacing petroleum-based hydroxyl for preparing PUs, which are considered as sustainable and environmentally friendly polymers from biomass industry.
Epoxidized soybean oil based polyols can be co-polymerized with some commercial isocyanates, such as toluene di-isocyanate (TDI), methylene-4,49-diphenyldiisocyanate (MDI) or others, to obtain bio-based PUs with useful properties, including enhanced hydrolytic and thermal stability
Synthesis of soybean-oil-based PUs.
The structure-property relationships between ESO based polyols and PUs have been extensively investigated.
Several factors have important influences on the properties of the PUs, such as chemical structure of the segment, chemical composition, hydroxyl group position, hydroxyl values of polyols and cross-linking densities of the PUs networks.
The structure and properties of PUs prepared from halogenated as well as non-halogenated soybean polyols with commercial isocyanates have been studied which shows that brominated polyols and their corresponding PUs have the highest densities and Tg while their thermal stabilities are lowest.
Chlorinated polyols have comparable glass transition and strength to brominated polyols, somewhat higher than the methoxy-containing and hydrogenated polyols.
Besides, the NCO/OH mole ratios also show effects on the properties of the PUs networks that the cross-linking densities, Tg, and tensile strengths deteriorate as the NCO/OH ratios decrease and glassy polymers can be produced when the NCO/OH ratio is between 0.8 and 1.05.
The studies on polyurethane resins from a blend of glycerol and polyol show that the increasing of Tg caused by the incorporation of glycerol into soy polyols obviously enhances the rigidity of PUs.
The polyurethanes elastomers synthesized from ESO based polyols obtained by ring opening with Ricinoleic acid (RA) and sebacic acid with citric acid as the cross-linker display biocompatibility and biodegradability and are very suitable for bone tissue engineering.
Furthermore, Epoxidized soybean oil is able to be effectively converted to carbonated soybean oil (CSBO) containing five-membered cyclic carbonates by reacting with carbon dioxide in the presence of tetra-butylammonium bromide at 110°C in high yield.
Then, CSBO can easily react with diamines to give the corresponding non-isocyanate polyurethane networks(NIPUs), and the thermal and mechanical properties of NIPUs can be well adjusted and controlled by changing the CSBO/amine ratio.
4. Acrylated epoxidized soybean oil (AESO)
4.1 Synthesis of AESO
AESO is commercially-manufactured derivative of ESO and has been extensively used in coatings, resins and composites.
The acid catalyst promotes the formation of an oxonium ion, which can be stabilized by local epoxide group.
And the ring-opening reaction happened between acrylic acid and the oxonium ion.
Inhibitor is needed in this reaction to prevent polymerization of vinyl groups.
The acrylation reaction has a first-order dependence on the concentration of epoxy groups, but the rate constant increases with the decreasing of epoxides per fatty acid due to steric hindrance and the stabilization effect of local epoxide group on oxonium groups.
4.2 Thermal initiation of AESO
Through reversible addition-fragmentation chain transfer (RAFT) polymerization, AESO can be made into a hyper-branched bio-based polymer without macro-gelation.
The conversion of vinyl is usually over 50%, which indicates that it is possible for multifunctional renewable feed stocks to be made into bio-based thermoplastics polymers at a high conversion without gelation.
Most of the researches focused on the cross-linking reaction of AESO through free radical polymerization.
Like the Epoxidized soybean oil, the cross-linked homopolymers from AESO also have the shortage that the polymers exhibit poor mechanical properties.
One of the common methods used to enhance its mechanical properties is adding reinforcements to make polymer composites.
There are many polar groups in the structure of AESO, including C〓O, ▬OH and epoxy groups.
These polar groups provide the possibility for the formation of hydrogen bonds between AESO and fillers.
Thermoplastic polyurethane, microcrystalline cellulose (MCC) and cellulose fiber are the common reinforcements worth investigation for poly(acrylated epoxidized soybean oil)(PAESO).
The interaction between PAESO and polyurethane can be enhanced by the formation of hydrogen bonds between hydrophilic functional groups from both of the two components which give rise to the result of improving the toughness and increasing the elongation of PAESO.
As a green filler, microcrystalline cellulose will increase the density, hardness, flexural strength and modulus of the material without decreasing the bio-based content.
Cellulose-reinforced PAESO can also be successfully made into bio-based foams with enhanced mechanical properties, which shows the great potential to replace petroleum-based foams.
Another common way to adjust the properties of AESO-based materials is the incorporation of co-monomers.
Styrene, N-vinyl-2-pyrrolidone (NVP), 3-isopropenyldimethylbenzyl isocyanate (TMI) , isocyanatoethyl methacrylate (IEM), 1,6-hexanediol diacrylate, divinylbenzene and unsaturated polyester are widely used as co-monomers for AESO.
The diblock copolymers based on AESO and styrene are able to work as an additive for asphalt to modify the rheological performance so that the corresponding stiffness, elasticity and rutting resistance of the asphalt can be substantially improved.
The copolymer based on AESO and styrene can also be reinforced by natural fibers and denim to obtain bio-based composites for structural applications, such as roof structure and safety helmets. Due to the toxicity of styrene, styrene-free polymers become more attractive recently.
NVP is an alternative to styrene in the synthesis of copolymer based on AESO, and the corresponding hemp fibers (HFs) composites exhibit superior static and dynamic mechanical properties.
As both AESO and HFs contains ▬OH groups in their structures, the addition of isophorone diisocyanate, whose isocyanate groups can react with ▬OH groups, to the AESO/HFs/NVP system can improve the properties by working as both a cross-linker and a coupling agent.
Accordingly, TMI and IEM bringing both C〓C double bonds and isocyanate groups into the reaction systems may also be good co-monomers for AESO/HFs system.
Besides the free radical polymerization of vinyl groups, the reactions between isocyanate groups and the ▬OH groups of AESO and HFs also occurred at the same time in this bio-based polymer composite systems.
Consequently, the crosslinking density and interfacial reaction between reinforcement and the matrix can be improved significantly, leading to the enhancement of storage modulus, Tg and water resistance.
As a nonvolatile and nonhazardous chemical, AESO is a suitable replacement for styrene in unsaturated polyester (UPE) resin to obtain hybrid polymer networks.
The UPE with unsaturated sites works as the co-monomer for AESO, and the final products usually exhibit comparable properties to correspondingly styrene-based products.
The combination of a variety of co-monomers may provide AESO based copolymers with more possibilities.
The thermosets based on the combination of AESO, styrene and divinylbenzene can be the potential replacements for commercial electronic materials.
The combination of AESO, 1,6-hexanediol diacrylate and divinylbenzene is able to make into the matrix for bacterial cellulose nanocomposite foams and the properties of the composites can be tailored by adjusting the compositions.
Although petroleum-based co-monomers can bring excellent properties, the decrease of the bio-based content is still not expected.
Functional bio-based co-monomers are desired in consequence.
Isosorbide can be used to synthesize a bio-based co-monomer for AESO through the reaction with methacrylate anhydride.
The product, isosorbide-methacrylate (IM), which has stiff structure, endows the bio-based networks with ideal thermal and mechanical properties.
Similarly, rosin is also a bio-based raw material with a rigid molecular structure.
Its derivative, N-dehydroabietic acrylamide (DHA-AM), can enhance the storage modulus, Tg, thermal stability, tensile strength and hydrophobicity of AESO/DHA-AM thermosets.
Methacrylated lauric acid (MLAU) is another bio-based reactive diluent for AESO.
The mixture exhibits a suitable viscosity for liquid molding techniques to get AESO based thermoset specimens with low densities and Tg around room temperature.
4.3 UV curing of AESO
AESO has been widely applied in the UV curing systems for their lower volatility and relatively higher reactivity of C〓C bonds which are able to conduct free-radical polymerization in the presence of functional initiator.
In general, residual internal stress in the UV-curing coating film often leads to poor adhesion with substrate.
AESO can be used to synthesize cured films with reduced internal stress and its flexible triglyceride structure can improve adhesion.
UV-curable materials based on AESO have been found many applications like coatings, adhesives and composite materials.
As petroleum-based fiber composites often swell after water absorption resulting in deterioration of mechanical properties, the dried distillers grains (DDGS)-flax mat coated with AESO polymerized by UV light with the initiation of irgacure 819 shows improved water resistance property.
Besides, AESO-based UV-cured PUDs with higher functionality can be used in textiles printing.
Different content of AESO based UV-curable PUDs pigment prints adhesive have been successfully synthesized with isophorone diisocyanate (IPDI), poly(caprolactone glycol) and 2-hydroxyethyl methacrylate, and all UV-curing films have excellent thermal stability.
With the increasing of AESO content, the color strength of printed fabrics can be enhanced correspondingly.
Conversely, the increasing of UV radiation time shows positive impact on the color fastness.
UV-curable, AESO-based organic shape-stabilized phase change materials also can be obtained by UV technique with enhanced thermal performance, decreased melting and freezing temperature, which verify the promising application of UV-curable material for thermal energy storage.
However, the existing of soft long aliphatic chains usually results in low mechanical or thermal properties and some rigid compounds are often added as the co-monomers to improve the performances of AESO-based UV-curable materials.
Acrylate acid is one of the most common-used petroleum-based rigid compounds.
The performances of AESO-based UV curable coating materials by using petroleum-based hyper-branched acrylates (HBAs) as co-photo-polymerization monomer, using acrylated sucrose (AS) as tougheners and using tetra-hydrofurfural acrylate (THFA) as reactive diluents show the increased coating hardness, adhesion, modulus, solvent resistance and glass transition temperature.
Nowadays, many researchers are devoted to exploit bio-based co-monomers to develop high bio-based content UV-curable coatings.
Monomer acrylated betulin (AB) synthesized from botulin, unsaturated monomer (named IG) synthesized from itaconic acid and glycidyl methacrylate, monomers (named EM2G and EM3G) synthesized from eugenol via a thiol-ene reaction and epoxide ring-opening reaction have been all evaluated to be successfully used with AESO matrix polymer and have great potential to improve the properties of UV curable coating.
Coating films containing AB from 5 to 10 wt% contents have better modulus of elasticity, tensile strength, abrasion resistance and hardness, higher Tg and lower strain at break value, while the transmittance of the cured films is reduced with increasing AB loading, especially for wavelengths below 650 nm.
In comparison, the polycyclic structure of betulin imposes a more rigid structure on AESO matrix polymer to enhance the applied performance.
In the presence of irgacure 184 as initiator, a series of UV-cured coatings without any solvent can be successfully prepared with IG (EM2G or EM3G) and AESO, and EM2G and EM3G show higher reactivity when copolymerized with AESO.
The introduction of IG, EM2G and EM3G in the UV-curing system results in significantly improved mechanical and thermal properties as well as coating performances such as hardness, flexibility, adhesion, solvent resistance.
5. Epoxidized soybean oil-based polymer composites
Epoxidized soybean oil is initially used as a plasticizer in industry for poly(vinyl chloride) chlorinated (PVC) rubber, and poly(vinyl alcohol) (PVA) emulsions to improve stability and flexibility, and ESO is also considered to be potential nontoxic biocompatible plasticizers for poly(3-hydroxybutyrate) (PHB) and polylactic acid (PLA) when combined with other plasticizers.
Moreover, it is an interesting trend to prepare composites of ESO or its homo-polymers with other materials because of their special properties.
A double network composites with Epoxidized soybean oil and a di-hydrocoumarin derived network can been synthesized with toughening effect, which make the ESO-based polymer possible to be applied in the fields of coatings and films.
The composites of cross-linked Epoxidized soybean oil and acrylic monolith or poly(lactic acid) apparently exhibit much larger Young’s modulus and tensile strength than ESO homo-polymer and can work as shape memory materials, which makes ESO a potential component for manufacture of intelligent polymer materials.
Interestingly, the long chain alkane fatty acid residues in ESO can give the composites hydrophobicity, so cross-linked ESO can also work as a water-resistant film for paper that the obtained composites may be competitive in the field of packaging considering their good properties.
An efficient method has been reported for the formation of cellulose-based materials grafting with poly epoxidized soybean oil (PESO) with controllable hydrophobic properties 1–2.
A kind of PESO coated paper composites with good water-resistant property have been obtained via in situ polymerization of ESO on the surface of the paper cellulose fibers.
6. Conclusions
This chapter summarizes the most recent advances in the application of ESO and its derivatives for preparation of bio-based polymeric materials.
The multiple reactive epoxy groups from triglycerides of unsaturated fatty acids imply its great potential in the bio-based polymer preparation fields with controllable biodegradability, thermal and mechanical properties.
Epoxidized soybean oil can crosslink directly with variety curing agents to form permanent network, or to introducing reactive function groups by chemical modifications.
Two most important modifications are introducing hydroxyl groups and esterification to produce acrylates.
Based on these, varieties of new polymeric materials have been prepared recently from Epoxidized soybean oil and derivatives that exhibit industrially viable thermos-physical and mechanical properties and thus may find many possible applications.
It is believed that Epoxidized soybean oil based compounds will gain continuously strong interest and allow new developments both in academic and industrial points of view.