Use of Commercial Non-Hazardous Air Pollutant Monomers to Optimize the Properties of Fatty Acid-Based Resins

摘要

Vinyl ester (VE) resins are used to make polymer matrix composites in military and commercial applications because of their good properties, low weight, and low cost. These resins typically contain high concentrations of reactive diluents, such as styrene, to allow these resins to be molded using resin transfer molding and other inexpensive liquid molding techniques. Because styrene is a hazardous air pollutant (HAP) and a volatile organic compound (VOC), the Federal Environmental Protection Agency of the United States of America introduced legislation to limit styrene emissions from composite manufacturing (1). Unfortunately, decreasing the styrene content in VE resins does not offer an acceptable solution to this problem. As the styrene content is reduced, the fracture toughness decreases and the resin viscosity increases, making it difficult to use inexpensive molding techniques (2, 3). For example, Dow Derakane 441-400 uses 27% less styrene than Derakane 411-C50 (4, 5), but has less than half the fracture toughness (6, 7). Various monomers with volatilities lower than that of styrene have been used as styrene replacements, such as vinyl toluene (8). First of all, these styrene replacements still produce significant VOC emissions, and are therefore still regulated by the EPA (1). In addition, few monomers yield resins with properties comparable to styrene based resins, and even fewer can match the low cost of styrene. Recently, fatty acid-based monomers have been used in VE resins to reduce the styrene content (9, 10). Fatty acid monomers are excellent alternatives to styrene because of their low cost and low volatility. Fatty acids are renewable resources because they are derived from plant oils. Therefore, not only would the use of fatty acids in liquid molding resins reduce VOC emissions, thereby reducing health and environmental risks, but it also would promote global sustainability. On the other hand, fatty acid monomers tend to lower the glass transition te.