by What is Epoxidized Soybean Oil?
Epoxidized soybean oil (ESBO) is a specialized form of soybean oil that has undergone a chemical process known as epoxidation. Soybean oil, which is extracted from the seeds of the soybean plant, is a vegetable oil composed largely of fatty acids like oleic acid and linoleic acid. During epoxidation, some of the double bonds present in the unsaturated fatty acids are reacted with peroxides to introduce epoxide groups into the structure. This modification alters the physical and chemical properties of the oil.
Chemical Structure and Properties
The epoxidation process results in the formation of oxirane rings, or Epoxidized Soybean Oil, at the sites of some of the double bonds in the fatty acid chains. This imparts a more rigid cyclic structure compared to regular soybean oil. ESBO has a higher molecular weight and lower iodine value as some of the double bonds are saturated during epoxidation. It has a higher viscosity than unmodified soybean oil due to the bulkier epoxide groups. The oil is pale yellow in color and is described as being odorless with a mild odor.
Epoxidized soybean oil is non-toxic and approved by the FDA for indirect food contact applications. However, in its undiluted form it may cause mild skin and eye irritation. It is insoluble in water but soluble in many organic solvents like chlorinated solvents and esters. ESBO is also thermoplastic and will soften and melt at higher temperatures without decomposing.
Applications in Plastics and Elastomers
The unique blend of properties that ESBO acquires following epoxidation make it well-suited for use as a plasticizer and reactive diluent in various polymers and composites. Some key applications include:
– PVC Plasticizers: As a semi-plasticizer, ESBO is used to make polyvinyl chloride (PVC) plastics more flexible. It replaces some of the phthalate plasticizers to provide lower toxicity.
– Epoxy Resins: The epoxide groups allow ESBO to react into epoxy resin networks during curing, acting as a reactive diluent. This enhances toughness and reduces costs.
– Unsaturated Polyester Resins: Epoxidized soybean oil is blended into unsaturated polyester resins used to make fiberglass and other reinforced composites for the automotive and construction industries.
– Adhesives and Sealants: The oil adds flexibility and extends various acrylic-based and urethane adhesives as well as silicone and polysulfide sealants.
– Coatings: ESBO improves the flexibility and durability of coating formulations for applications like caulks, cement cracks, and traffic line paints.
Regulations and Sustainability
As a derivatives of soybean oil, ESBO is considered to be biobased and renewable. According to the USDA BioPreferred program, products containing ESBO can qualify for Federal preferred procurement. It has also been approved by the FDA for food contact applications which helps plasticizers made from it replace other non-renewable petroleum-based plasticizers.
However, like other epoxides, ESBO does have some associated health concerns. The epoxide groups make it a skin and eye irritant. It is therefore important to follow safety precautions and use it only as recommended by product SDS. Some jurisdictions may also place limitations around its use in toys and childcare products. Overall though, ESBO remains a sustainable and eco-friendly plasticizer option.
With continued environmental regulations and societal push for greener materials, the market for epoxidized soybean oil is expected to grow steadily in the coming years.
Key factors fueling this include:
– Regulations banning phthalates and other harmful plasticizers will boost demand for ESBO as a safer bio-based alternative.
– Growing construction activities especially in developing nations will spur consumption of ESBO in composites, coatings and sealants.
– Increased focus on sustainability in end-use industries like automotive, consumer goods will raise popularity of plant-oil based chemicals like ESBO.
– Technological advances may optimize epoxidation processes to enhance properties and lower production costs of ESBO.
Provided it is manufactured and used responsibly with necessary precautions, epoxidized soybean oil appears poised to take on a bigger role as a versatile bio-plasticizer and polymer additive in the future. Continuous R&D also holds promise to further improve its performance characteristics.
