Investigation of Genetically Modified Soybean Oil for the Synthesis of Pressure Sensitive Adhesives
University of Delaware
Pressure sensitive adhesives are polymer products that are ubiquitous in daily life. They are used in tapes, labels, films, and in many specialty adhesion applications. Demand for adhesives continually increases, and as this happens, it becomes increasingly important to search for a way to move away from petroleum-based starting materials. Such a shift could be performed by moving towards the adoption of vegetable oils for this purpose. Previous work in the Affordable Composites from the Renewable Sources group at the University of Delaware has demonstrated convincing evidence for the possibility of a shift toward the use of vegetable oils and their derivatives in the production of high performance products in the polymer science and chemical engineering industries. In line with this, a method has been developed for synthesizing monomers for pressure sensitive adhesive synthesis from methyl oleate. A mini-emulsion olymerization process, which reduces surfactant use and improves polymer properties over traditional emulsion polymerization, was developed and was shown to yield pressure sensitive adhesives with properties comparable to petroleum based adhesives, using acrylated methyl oleate as a monomer. The use of petroleum for the synthesis of pressure sensitive adhesives and other similar lowly cross-linked polymers has been estimated at 14 billion pound per year. If all pressure sensitive adhesives and similar polymers (including elastomers and coatings) were replaced with versions that use this bio-based technology, the fact that they are 70% bio-based would mean that there would be a reduction in petroleum usage of 10 billion pounds per year. High oleic soybean oil and olive oil were investigated as potential replacements for high purity methyl oleate as a starting product, which is prohibitively expensive. Proton nuclear magnetic resonance was used to determine the average number of double bonds per fatty acid in high-oleic soybean oil (0.9503) and to verify the purity of methyl oleate. The presence of polyunsaturated fatty acids in this oil was also verified. A new procedure that utilizes gas chromatography for the determination of the fatty acid distribution of oils, developed by MIDI Inc. (Newark, DE), was used to obtain a more comprehensive idea of the fatty acid distributions of high-oleic soybean oil and olive oil. The olive oil results agreed with literature, and the high oleic soybean oil results gave mole percent values for fifteen different fatty acids in the oil, and a very complete characterization, which was in close agreement with literature saturation profiles. It was found that the DuPont high oleic soybean oil consists of 85.53% monounsaturated fatty acids, 12.02% saturated fatty acids, and 2.15% poly-unsaturated fatty acids.