A Mini Compilation on Bio Epoxy Resins from Algae Industrial Products

Abstract

The need for water, energy, minerals and other natural resources, particularly in relation to cleaner production, increases with population growth as well as developments in living standards and welfare levels. Intensive resource use consumes and disrupts numerous ecosystem services, increases the risk of sudden and destructive environmental changes, creates significant reductions in biodiversity, and also worsens poverty for certain groups. The key consideration is to meet the increasing energy demand arising from the industrial revolution without pushing natural resources to their limits by employing sustainable methods such as heat recovery and energy production from waste. This study provides a brief review of both the rationale and current technology for the production of epoxy resin, an industrial intermediate, using biotechnological methods based on seaweed and marine algae, which are abundant in nature—even in untreated urban systems, coastal areas and rivers. Section-1: Introduction Microalgae are a potential renewable energy source, but interestingly they have become an alternative source of raw materials for the production of oleochemicals (See figure 1). The unsaturated fats produced from schizochytrium microalgae can also be used in polymer synthesis. After structural analysis of algae oil, it is converted into an active form containing 10 epoxy radicals per molecule through reaction with alternated cation resin. Subsequently, fully bio-based epoxy networks are synthesized with priamine® (oleic acid dimer-derived amine) as hardener. These new algae epoxy materials are characterized and compared with epoxy networks derived from vegetable oils (linseed or soybean oils). Epoxy co-monomers are added to the formulation to improve material properties.

Both trimethylolpropane triglycidyl ether, a conventional cross-linking agent, and triepoxidized floroglucinol derived from algal fluorinations are added.

The addition enables the production of epoxy co-monomers and materials with various properties. Thermal and mechanical properties demonstrate the notable superiority of algae oils due to their high reactive content in reactive functions. Finally, the addition of a blowing agent (MH15 polysiloxane) leads to the synthesis of foams from algae oils with interesting properties. Thus, algae oil shows promising potential as a suitable starting material for fully bio-based thermoset materials and foams. It is important to verify each stage with various quality control methods, regardless of how straightforward a typical synthesis example as described above appears.

Figure 1. Various biopolymer synthesis from algae

Section: 2- Practical Applications

The main reactant, exemplified above, can be reacted with epoxidized algae oil, amines derived from vegetable oil, and another aromatic epoxy co-monomer to provide bio-based aliphatic building blocks for other epoxy foam syntheses (see Figure 2). The epoxy materials and foams obtained are bio-based with various hardeners and high cross-linking rates (see Figure 3). The materials can be used in electronic and electrical systems or for high-performance adhesives. Foams can also be applied as heat and vibration insulation and for the manufacture of lightweight materials or in the transport industry such as aircraft interior panels and crash pads (see Figure 4). Medical applications can also be considered for more flexible foams. Figure 2. Bio-based macromolecular sample produced Figure 3. Macromolecular sample produced  

Figure 4. Bio-based macromolecular

Section: 3- A Detailed Analysis

Thermosetting epoxy materials are widely used in a broad range of applications, including aircraft, automotive and electronic components, due to their high mechanical strength, thermal and chemical stability, and excellent dielectric properties (see Figure 6). Global epoxy thermoset polymer production was estimated at 2 million tons per year in 2010 and is projected to reach 3 million tons by 2017 (for test results of the WNDR algae polymer, see figure 7). More than 60% of global production is used in the coating industry as well as in composites and foam. Indeed, epoxy foams are showing increasing interest in industry due to their insulation and lightweight properties (see Figure 8).

Figure 6. Ski kit produced with coating material obtained from algae

Figure 7. WNDR test results

 

Figure 8. The application process of WNDR algae polymer to the ski suit

Currently, 95% of thermosetting epoxy materials are derived from diglycidyl ether of bisphenol A (DGEBA). The aromatic rings of bisphenol A (BPA) are particularly advantageous as they provide good thermal resistance to epoxy resins. However, this endocrine disruptor can mimic the body's own hormones, and alterations in brain chemistry and structure can lead to a variety of negative health effects that impair male and female reproductive systems in various animals, including fish, frogs and mammals, affecting behavior, immune system, enzyme activity, and other functions. Therefore, there is growing interest in the chemical industry for harmless reactants that allow the synthesis of BPA-free epoxy resins. Uncertainty regarding the price and availability of oil, combined with global trends toward sustainable development principles, encourages the chemical industry to adopt sustainable production and the use of renewable resources, particularly for the synthesis of bio-based chemicals and products.

Therefore, partially or fully bio-based epoxy polymers are nowadays a genuine target both in academic research and industry, though they also pose a real challenge.

Few commercial bio-based epoxy reagents are available, with the exception of epoxidized vegetable oils (such as soybean oil or flaxseed oil) and cardanol, which are the most widely used bio-based monomers. However, polyepoxide networks derived from vegetable oils generally exhibit low glass transition temperatures due to the presence of long aliphatic chains (such as Tg=-38°C for epoxidized flaxseed oil). Some researchers were the first to synthesize polyepoxide foams containing 25% epoxidized soybean oil (ESO), but poor mechanical properties were achieved.

Other researchers subsequently reported the synthesis of polyepoxide foams containing soybean oil with high mechanical properties.

On the other hand, researchers also evaluated the effect of various epoxidized triglycerides on the glass transition temperature of polymers obtained from acrylate content (0 to 9 acrylates per triglyceride). Their methodology demonstrated that increased reactive functions in a triglyceride lead to improved thermal and mechanical properties for polymers. Therefore, the use of algae triglycerides with higher double bond content can be a very interesting alternative for vegetable oil-based polyepoxide networks. Algae oil, or more precisely, microalgal oil, is a source of triglycerides unsuitable for food use that may be suitable for polymer materials. It can be grown on soils where microalgae cannot be planted, in gutter-type pools or in photobioreactors. Additionally, costly food sources such as glucose or peptone are not required. Many microalgae species contain unique products such as carotenoids, antioxidants, fatty acids, enzymes, polymers, peptides, toxins and sterols. More specifically, the fatty acid content in microalgae can be substantial, with high efficiency, reaching 20–50% by weight of dry matter.

Algae oils vary depending on algae type, but in any case, they offer interesting structures enriched with long-chain fatty acids with high unsaturation content, such as docosahexaenoic acid (DHA) containing 22 carbons and 6 double bonds.

Recently, several studies have reported the synthesis of polymers from algae oils. For example, in one study, stepwise polymerization of algae oil-derived diols with dicarboxylic acids was achieved. New polyesters with advantageous high melting and crystallization temperatures were obtained. In another case, algae oil has shown promise as polyol precursors for polyurethanes due to high-yield extractions and various growing conditions compared with vegetable oil sources. In another study, flexible polymer materials from epoxidized algae oil were synthesized. The polyurethane materials and foams obtained exhibit good thermal and mechanical properties comparable to petrochemical polyurethanes. In another study, rigid polyurethane foams were synthesized from Chlorella algal oil. These algae polyols were prepared by oxidation followed by epoxide ring-opening reaction using lactic acid or ethylene glycol. The final polyols were reacted with methylene diphenyl diisocyanate (MDI) using cyclopentane as the blowing agent to produce rigid polyurethane foams. In the same study, a process for the preparation of biopolymer composites from algae oil and natural fibers was patented.