Nanocellulose Fiber Sizing for Fiberglass Composites

Abstract

The transportation industry produces the most greenhouse gas emissions of any economic sector in the United States due in large part to the burning of fossil fuels in road, rail, air, and marine transportation. Industry-wide initiatives to combat these emissions have resulted in increasing use of lightweight materials in automotive production, such as fiber-reinforced polymer composites, for the purpose of improving vehicle fuel economy. However, the displacement of heavier metal materials in these manufacturing processes is limited by the failure of existing composite technologies to exhibit a favorable balance between weight, cost, and performance. Enhancing these qualities is key to developing the materials that will be used in the lightweight cars of the future. A promising approach involves the incorporation of high-performance nanomaterial additives into the composite system. Some success has been achieved in this regard using cellulose nanocrystals (CNC), a lightweight, renewable biomaterial derived from plants. However, proposed methods of CNC composite development are limited in their scalability due to demanding processing conditions, as well as the tendency of CNC to aggregate and lose their high inherent properties in polymeric matrices. A processing path that utilizes the strengths of CNC while maintaining scalability is thus highly desirable. In this study, we have developed coating solutions for glass fibers that contain CNC. Incorporation of CNC in the fiber sizing potentially improves scalability by circumventing the need to process the CNC in the epoxy matrix. Improvements in composite strength were monitored using the single fiber fragmentation test to assess the strength of the fiber-matrix interface. Observed changes were hypothesized to be the result of alterations to fiber surface characteristics such as coating thickness, morphology, and surface energy. Tests for these parameters revealed that CNC strengthen the interface, and this phenomenon is likely related to improvements in spreading behavior.