Effects of Dispersion Techniques of Flammability and Mechanical Properties of Phenolic/E-Glass Nanocomposites
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Nanomaterials are currently the most researched materials in the scientific world. The term “nanotechnology” or “nanotech” (NT) refers to the ability to measure, manipulate, and organize matter at nano scale (Kobayasi, 2007, p. 13). It influences many aspects of our life, such as social, cultural, and economic. There are more than a thousand NT consumer products on the market and this number is constantly growing (Nanotechnology Consumer Products Inventory, 2009). Manufacturers use the term “nano” in products’ names to increase sales, while these products have no connection to NT. These products are widely known, such as the Indian car Tata Nano or the music player iPod Nano. It shows that the word “nano” and NT in general has a psychological effect and is a new marketing tool to promote new products. However, products made of the true nanomaterials are rare on the market. Nanomaterials have unique properties and, if properly used, can improve properties of existing products. Nevertheless, there are many unsolved problems while using nanomaterials including safety, handling, processing, and disposal. Also, nanomaterials cannot be used “as-is.” The easiest way to use them is as a one of the constituents in other traditional materials such as composite materials, and then it becomes a “nanocomposite.” Nanomaterials blended into polymers can be called “polymer nanocomposite” or simply “nanopolymers.” Fiber reinforced polymer nanocomposites consist of fiber reinforcement and a nanomodified polymer matrix. Nanomodification of polymer matrices using the right kind of nanoparticle in the right percentage, leads to multifunctional composites that enhances two or more properties, such as mechanical, thermal, chemical, and barrier. The major challenge in property enhancement is uniform dispersion of nanoparticles in the polymer matrix. Popular methods used for dispersing nanoparticles into liquid thermoset resins are mechanical stirring, high shear mixing, centrifugal mixing, and sonication. E-glass/phenolic composites have gained popularity due to their excellent fire, smoke, and toxicity (FST) properties. In this research water-based phenolic resin was modified using low-cost montmorillonite nanoclay (Cloisite® Na+ ) to improve flammability properties. Two different dispersion techniques, high-shear mixing and planetary centrifugal mixing, were used to blend nanoclay into phenolic resin, followed by low-cost vacuum assisted resin transfer molding (VARTM) to manufacture glass-reinforced nanocomposites. The loading of nanoclay included 2.5, 5.0, and 7.5 wt.% in both techniques. The degree of dispersion was analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mass loss calorimeter tests were conducted at a heat flux of 35 kW/m2. Mechanical properties such as flexural strength, interlaminar shear strength (ILSS), and compressive strength were evaluated. It is observed that 7.5wt.% loading of Cloisite® Na+ improves flammability properties in both dispersion techniques. Planetary centrifugal mixing techniques did not fully exfoliate nanoclay particles; however it did not adversely affect mechanical properties but still provided near equivalent flammability performance as that of high shear mixing. It can be concluded that cost-effective centrifugal mixing can be used in manufacturing nanocomposites to enhance flammability property without sacrificing mechanical properties.