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Polymer Science: Peer Review Journal

Microwave Synthesis of Vegetable Oil- Based Polymers for Coating Applications - A Mini Review

Antonella Hadzich, Daniel Obregón and Santiago Flores*

Institute of Corrosion and Protection (ICP-PUCP), Pontificia Universidad Católica del Perú (PUCP), Peru

*Corresponding author:Santiago Flores, Institute of Corrosion and Protection (ICPPUCP), Pontificia Universidad Católica del Perú (PUCP), Avenida Universitaria 1801, San Miguel, 15088 Lima, Peru

Submission: August 23, 2023;Published: September 05, 2023

DOI: 10.31031/PSPRJ.2023.05.000607

ISSN: 2770-6613
Volume5 Issue2


Microwave processing technology has spread its use rapidly in various areas due to its higher efficient reactions, rapid and controlled heating, and safe use with precise temperature and pressure control. Nowadays, this green alternative has triggered enormous interest in organic synthesis, specifically in developing vegetable oil-based polymers for coating applications such as alkyds, epoxies, esteramides and urethanes. The present summary aims to highlight recent investigations that have used microwave heating to obtain polymers from vegetable oil sources for diverse coating applications.

Keywords:Microwave-assisted synthesis; Resins; Vegetable oil; Coating

Microwave-Assisted Synthesis of Oil-Based Resins

Alkyd resins

Alkyd resins are polyester resins modified with unsaturated fatty acids obtained from semi-drying or drying vegetable oils [1-3]. Specific properties, characteristics, and applications depend on the degree of unsaturation of the fatty acid source, oil proportion, and selected polyalcohol’s or polyacids [4]. Alkyd resins continue to be one of the largest types of coatings used worldwide and have expanded its domestic and industrial use to innovative applications like artistic mediums [5], textile printing, and self-healing coatings. Extensive research has been made on alkyd resins synthesized with oils of different kinds, being a recent trend the use of non-traditional or non-edible plants to take advantage of native resources, look for better properties, or replace high-consumption sources. Recently, conventional synthesis processes are being replaced by Microwave (MW) heating for the manufacturing of oil-based resins. Long-chain alkyd resins were prepared by microwave irradiation and characterized as oil-based artistic mediums using a non-traditional source, Sacha inchi oil [6]. Reaction times were reduced by around 12-13 hours when using microwave heating instead of the conventional system. Also, more homogeneous heating allowed control of chain cross-linking avoiding polymer gelation. Furthermore, sunflower oil-based alkyd resins were also synthesized by microwave irradiation with the incorporation of recycled Polyethylene Terephthalate (PET) for textile printing [7]. Authors emphasized that microwave exposure did not affect the elongation of polymers and its application properties. The energy efficiency of the microwave treatment process, and reduction of reaction time for sample preparation from hours to minutes was also highlighted. Otherwise, PET glycolyzates are used as a partial substitute for phthalic anhydride, the only component of an alkyd resin that is non-renewable. There are more studies that take advantage of microwave power to recycle PET by chemical depolymerisation [8-10]. Chemical-recycled PET obtained through microwave-assisted extraction could produce sustainable coatings such as epoxy, polyesters, alkyd, acrylic, and polyurethanes [11].

Epoxy resins

Epoxy resins are thermoset polymers that are derived commonly from diglycidyl ethers of bisphenol-A (or F) and epichlorohydrin [12], components that provide high-performance film properties [13]. Just before application, epoxy resins must be mixed with cross-linking agents such as amines or polyamides, and the surface must be properly prepared to ensure its durability [12,14]. Epoxy resins have found widespread usage in relatively mature markets like marine and industrial maintenance, due to its superior adhesion and chemical resistance to metals [14]. However, its main components and cross-linkers have been related to health and environmental problems [15]. High processing costs and toxicity issues of epoxy resins have increased the need to find renewable alternatives. In this context, vegetable oils have been transformed into high-value-added bio-based epoxy resins by epoxidation, a chemical process that converts double bonds into oxiranes (epoxides) with an oxidizing agent and oxygen carriers [16,17].

Epoxidized oils are green materials that can be used as intermediates or monomers in the surface coating field [18]. Several oils have been chemically transformed to prepare bio-based epoxy resins under conventional heating [19,20], but few studies have used microwave technology for this purpose. Epoxidation is an exothermic reaction that can have heat/mass transfer limitations in conventional reactors, which can be overcome by the power and temperature control of microwave devices [21]. Also, higher temperatures can be achieved to ensure the reduction of the reaction time and increase the rate of oxirane group content [22]. Soybean oil was epoxidized by microwave heating, producing higher yields and uniform oil-aqueous suspensions, and diminishing by half the reaction time in comparison with traditional processes [23]. Nevertheless, authors pointed out that the stirring speed is limited in microwave devices. Moreover, epoxidized derivatives were obtained from tall oil fatty acids, by-products from Kraft pulping process, with microwave irradiation [24].

Authors found that microwave heating power apparently accelerates ring opening reactions during epoxidation of fatty acid chains that have more than one unsaturation. Microalgal oils were also epoxidized with formic acid and hydrogen peroxide under microwave-assisted conditions and controlled pressure for the production of epoxy thermosetting resins [22]. Some deficiencies of epoxidized oils are strongly related to the length or degree of unsaturation of the aliphatic chains; for example, providing flexibility but reducing the mechanical strength of bio-based epoxy [25]. However, cross-linkers of epoxidized oils can be enhanced by the addition of maleinized oils, unsaturated oils reacted with maleic anhydride [26]. Maleinization of grape, hemp, and linseed oils was successfully achieved by microwave heating in shorter times and with higher viscosity products in comparison with conventional synthesis [27]. Similar results were obtained with soybean [28], and grape seed [29] oils.

Polyesteramide resins

Polyesteramides are high performance polymers that combine good properties of polyamides and polyesters [30]. These resins have attracted great attention because of the effective antibacterial and anticorrosive protection they provide [31] and their stability at high temperatures [32]. But their application as coatings is limited due to their high curing temperatures, high melting point and low chemical resistance [32]. Polyesteramides have been synthesized from seed oils to ensure faster drying, better thermal stability, resistance against chemicals and water, hardness, corrosion protective efficiency [32,33]. First, vegetable oils undergo a base-catalyzed aminolysis to obtain N, N-bis (2-hydroxy ethyl) fatty amides, which are subsequently reacted with different dibasic acids through polycondensation [32,34]. These bio-based polyesteramides are attractive protective resins, but their conventional heating method is very time consuming due to its multiple steps [35]. Only a few studies were carried out using microwave heating to transform vegetable oils into polyesteramides, despite being a greener route.

Cottonseed oil was converted to polyesteramide precursors through microwave technique [36]. Researchers observed that microwave energy saves time and generates better product yields. Microwaved bio-based polyesteramides were synthesized with Jatropha oil, a non-edible source, and reacted again under MW irradiation conditions to produce urethane-modified polyesteramide resins [37], and polyetheramide and urethanemodified polyetheramide coatings [38]. The resins had a good protective behavior under various corrosive media and good immersion performance in water, xylene and HCl, respectively. A waterborne linseed oil-based polyesteramide was prepared with a domestic microwave oven as a promising biodegradable coating [35]. The reaction was reduced to less steps and did not require the addition of any solvent.

Polyurethane resins

Polyurethanes (PU) are polymers obtained by combining hydroxyl bases (polyols) with diisocyanato’s [39], usually Toluene Diisocyanate (TDI) or Methylene Diphenyl Diisocyanate (MDI). Their versatility due to many raw materials available on the market with extreme properties (from soft to rigid structures), has made them suitable materials for many applications [40]. Polyurethanes are applied as a high-performance coating in automotive appliances and wood industries [41]. Environmental concerns and depletion and high costs of petroleum-based resources have forced researchers to use bio-based materials for the manufacturing of polyurethanes [39]. Vegetable oils have been extensively used for PU applications by introducing hydroxyl groups into unsaturated bonds of fatty acid chains, components known as polyols. Polyols derived from oils have been synthesized with different pathways such as amidation-esterification, hydroformylation, epoxidationring opening, ozonolysis, and metathesis, among others [42]. Properties of these bio-based polyurethanes are related to the type and amount of oil, polyol (the number and distribution of hydroxyl groups), and isocyanate [43]. Vegetable oil-based polyurethane coatings have shown to have excellent toughness, abrasion resistance, low-temperature flexibility, corrosion and chemical resistance, [42].

Also, the use of oils has reduced or eliminated the use of solvents in the synthesis of this type of resin [42]. It has been reported that urethane linkages provide a faster drying, better toughness and resistance to abrasion, chemicals, and UV irradiation than alkyd resins [41]. Recently, a few studies have applied microwave technology to convert vegetable oils into multifunctional polyols. Rapeseed oil-based polyols were synthesized in a mixed conventional and microwave two step heating process to obtain flexible foams [44]. First, epoxidized oils were obtained with conventional equipment, and then, the ring opening of the epoxy groups to hydroxyls was carried out under microwave irradiation. Microwave heating reduced reaction time by 75% compared to a traditional synthesis process. Other oil-based PU polyols were also prepared with an adapted domestic microwave oven with rapeseed oil but recycled Polyethylene Terephthalate (PET) components [45]. MW polyols had properties similar to traditionally synthesized polyols. However, the MW process required shorter times and consumed much lower energy than conventional electrical heating.


A wide variety of polymers based on vegetable oils have been obtained with microwave heating for coating applications. Vegetable oils and renewable monomer sources appear as a more promising alternative due to their wide availability, low cost, and versatile properties in comparison with traditional petroleumbased products. Microwave irradiation, a technique that aligns with the principles of green chemistry, has been shown to provide many advantages such as fast reactions, high yields, homogenous products, and reduced side reactions over conventional heating. Overcoming new challenges such as the synthesis of high-viscosity polymers is one of the next steps for the industrial scale-up of the microwave synthesis process. Efficient reactions with biodegradable sources are the key to a sustainable future.


  1. Flores S, Flores A, Calderón C, Obregón D (2019) Synthesis and characterization of sacha inchi (Plukenetia volubilis L.). oil-based alkyd resin. Prog Org Coat 136: 105289.
  2. Hadzich A, Alexander G, Leimbach M, Ispas A, Bund A, et al. (2020) Characterization of Plukenetia volubilis L. fatty acid-based alkyd resins. Polym Test 82: 106296.
  3. Obregón D, Toledo C, Hadzich A, Flores S (2021) Low viscosity alkyd resins based on trimethylolpropane and Peruvian oil. J Polym Res 28(6): 1-10.
  4. Hadzich A, Flores S, Masucci AE, Gomez ED, Groß GA (2023) NMR and GPC analysis of alkyd resins: Influence of synthesis method, vegetable oil and polyol content. Polymer 15(9):1993.
  5. Bellatin L, Meza R, Obregon D, Hadzich A, Costa M, et al. (2023) Alkyds with artistic applications based on drying oils, multifunctional polyalcohols and different polybasic acids. J Appl Polym Sci 140(6): e53746.
  6. Obregón D, Hadzich A, Bellatin L, Flores S (2023) Microwave-assisted synthesis of alkyd resins using response surface methodology. Chem Eng Process: Process Intensif 183: 109221.
  7. Haggag K, Elshemy NS, Niazy W (2014) Recycling of waste PET into useful alkyd resin synthesis by microwave irradiation and applied in textile printing. Res J Text Appar 18(1): 80‑88.
  8. Attallah O, Azeem M, Nikolaivits E, Topakas E, Fournet MB (2021) Progressing ultragreen, energy-efficient biobased depolymerization of poly(ethylene terephthalate) via microwave‑assisted green deep eutectic solvent and enzymatic treatment. Polym 14(1): 109.
  9. Zangana K, Fernandez A, Holmes J (2022) Simplified, fast, and efficient microwave assisted chemical recycling of poly (ethylene terephthalate) waste. Mater Today Commun 33: 104588.
  10. Saravari O, Potiyaraj P, Phunphoem S (2011) Preparation of urethane oils from microwave‑assisted glycolyzed products of waste PET bottles. Energy Procedia 9: 491-497.
  11. Ghosal K, Nayak C (2022) Recent advances in chemical recycling of polyethylene terephthalate waste into value added products for sustainable coating solutions - hope vs. hype. Mater Adv 4(3): 1974-1992.
  12. Oldring P (2003) Coatings, Colorants, and Paints, In: Meyers RA (Edn.), Encyclopedia of Physical Science and Technology (Third Edition). Academic Press, USA, pp. 175-190.
  13. Breitsameter J, Reinhardt N, Feigel M, Hinrichsen O, Drechsler K, et al. (2023) Synthesis of a sustainable and bisphenol a‐free epoxy resin based on sorbic acid and characterization of the cured thermoset. Macromol. Mater Eng 2300068.
  14. Sørensen P, Kill S, Dam-Johansen K, Weinell C (2009) Anticorrosive coatings: a review. J Coat Technol Res 6: 135-176.
  15. Pawar M, Kadam A, Yemul O, Thamke V, Kodam K (2016) Biodegradable bioepoxy resins based on epoxidized natural oil (cottonseed & algae) cured with citric and tartaric acids through solution polymerization: A renewable approach. Ind Crops Prod 89: 434-447.
  16. Aguilera A, Tolvanen P, Heredia S, Muñoz M, Samson T, et al. (2018) Epoxidation of fatty acids and vegetable oils assisted by microwaves catalyzed by a cation exchange resin. Ind Eng Chem Res 57(11): 3876-3886.
  17. Wai P, Jiang P, Shen Y, Zhang P, Gu Q, et al. (2019) Catalytic developments in the epoxidation of vegetable oils and the analysis methods of epoxidized products. RSC Adv 9(65): 38119-38136
  18. Silva R, Maia D, Fernandes F (2021) Production of tung oil epoxy resin using low-frequency high power ultrasound. Ultrason Sonochem 79: 105765.
  19. Kumar S, Samal S, Mohanty S, Nayak S (2018) Recent development of biobased epoxy resins: a review. Polym Plast Technol Eng 57(3): 133-155.
  20. Sreehari H, Gopika V, Jayan J, Sethulekshmi A, Saritha A (2022) A comprehensive review on bio epoxy based IPN: Synthesis, properties and applications. Polym 252: 124950.
  21. Bhattacharya M, Basak T, Senagala R (2011) A comprehensive theoretical analysis for the effect of microwave heating on the progress of a first order endothermic reaction. Chem Eng Sci 66(23): 5832-5851.
  22. Hidalgo P, Echeverria A, Romero L, Navia R, Hunter R (2023) Microwave-assisted epoxidized oil production from the wet microalga Nannochloropsis gaditana to obtain environmentally friendly epoxy resins. Chem Eng Process - Process Intensif 183: 109215.
  23. Piccolo D, Vianello, C, Lorenzetti A, Maschio G (2019) Epoxidation of soybean oil enhanced by microwave radiation. Chem Eng J 377: 120113.
  24. Aguilera A, Rahkila J, Hemming J, Nurmi M, Torres G, et al. (2020) Epoxidation of tall oil catalyzed by an ion exchange resin under conventional heating and microwave irradiation. Ind Eng Chem Res 59(22): 10397-10406.
  25. Qi M, Xu Y, Rao WH, Luo X, Chen L, et al. (2018). Epoxidized soybean oil cured with tannic acid for fully bio-based epoxy resin. RSC Adv 8(47): 26948-26958.
  26. Lerma-Canto A, Samper MD, Dominguez-Candela I, Garcia-Garcia D, Fombuena V (2023) Epoxidized and maleinized hemp oil to develop fully bio-based epoxy resin based on anhydride hardeners. Polym 15: 1404.
  27. Lanero F, Bresolin BM, Scettri A, Nogarole M, Schievano E, et al. (2022) Activation of vegetable oils by reaction with maleic anhydride as renewable source in chemical processes: New experimental and computational NMR evidence. Molecules 27(23): 8142.
  28. Alarcon R, Gaglieri C, de Souza O, Rinaldo D, Bannach G (2020) Microwave-assisted syntheses of vegetable oil-based monomer: A Cleaner, faster, and more energy efficient route. J Polym Environ 28(4): 1265-1278.
  29. Gaglieri C, Alarcon R, Moura A, Magri R, Silva-Filho L, et al. (2021) Green and efficient modification of grape seed oil to synthesize renewable monomers. J Braz Chem Soc 32(11): 2120‑2131.
  30. Rodríguez-Galán A, Franco L, Puiggalí J (2011) Biodegradable poly (ester amide) s: synthesis and applications. Biodegradable polymers: processing, degradation, and applications. In: Felton GP (Edn.), Nova Science Publishers Inc, USA.
  31. Aqeel S, Abd El-WH, Mahdy A, Abd El-HF, Abd El-FM (2010) New modified polyesteramide resin for industrial applications. Prog Org Coat 68(3): 219-224.
  32. Meshram P, Puri R, Patil A, Gite V (2013) Synthesis and characterization of modified cottonseed oil based polyesteramide for coating applications. Prog Org Coat 76(9): 1144-1150.
  33. Mohamed A, Mustafa A, Elgaby M, Abd El-WH, Abed S, et al. (2021) New modified poly (ester amide) resins and their uses as a binder for surface coating with different applications. Pigm Resin Technol 50(2): 146-156.
  34. Pramanik S, Sagar K, Konwar B, Karak N (2012) Synthesis, characterization and properties of a castor oil modified biodegradable poly (ester amide) resin. Prog Org Coat 75(4): 569-578.
  35. Zafar F, Zafar H, Yaseen M, Sharmin E, Ahmad S (2012) Vegetable seed oil based waterborne polyesteramide: A “green” material. In: Khemani L, Srivastava M, Srivastava S (Eds.), Chemistry of Phytopotentials: Health, Energy and Environmental Perspectives. Springer, Berlin, Heidelberg, New York, USA.
  36. Azcan N, Danisman A (2007) Alkali catalyzed transesterification of cottonseed oil by microwave irradiation. Fuel 86(17-18): 2639-2644.
  37. Alam M, Alandis N (2011) Microwave assisted synthesis of urethane modified polyesteramide coatings from jatropha seed oil. J Polym Environ 19: 784-792.
  38. Alam M, Alandis N (2012) Microwave-assisted preparation of urethane-modified polyetheramide coatings from Jatropha seed oil. High Perform Polym 24(6): 538-545.
  39. Zhang C, Madbouly S, Kessler S (2015) Biobased polyurethanes prepared from different vegetable oils, ACS Appl Mater Interfaces 7(2): 1226-1233.
  40. Das A, Mahanwar P (2020) A brief discussion on advances in polyurethane applications. Adv Ind Eng Polym 3(3): 93-101.
  41. Ling J, Ahmed I, Ghazali A, Khairuddean M (2014) Novel poly(alkyd-urethane)s from vegetable oils: Synthesis and properties. Ind Crops Prod 52: 74-84.
  42. Paraskar P, Prabhudesai M, Hatkar V, Kulkarni R (2021) Vegetable oil based polyurethane coatings–A sustainable approach: A review. Prog Org Coat 156: 106267.
  43. Saravari O, Praditvatanakit S (2013) Preparation and properties of urethane alkyd based on a castor oil/jatropha oil mixture. Prog Org Coat 76(4): 698-704.
  44. Dworakowska S, Bogdal D, Prociak A (2012) Microwave-assisted synthesis of polyols from rapeseed oil and properties of flexible polyurethane foams. Polym 4(3): 1462-1477.
  45. Zeltins V, Cabulis U, Avolins A, Gaidukovs S (2016) Microwave synthesis of polyols for urethane materials. IOP Conf Ser: Mater Sci Eng 111(1): 012015

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