ABSTRACT
CONTENTS 18.1 Introduction ........................................................................................................................ 513 18.2 Bio-Based Nanocomposites from Functionalized Plant Oils and Nanoclays ........... 515
18.2.1 Experimental .......................................................................................................... 516 18.2.1.1 Synthesis of Maleinized Acrylated Epoxidized Soybean Oil
(MAESO) .................................................................................................. 516 18.2.1.2 Synthesis of Soybean Oil Pentaerythritol Maleate (SOPERMA) ...... 516 18.2.1.3 Swelling Test ............................................................................................ 517 18.2.1.4 Preparation of Clay Nanocomposites ................................................... 517 18.2.1.5 Characterization and Mechanical Test ................................................ 518
18.2.2 Results and Discussion ......................................................................................... 518 18.2.2.1 Miscibility ................................................................................................ 518 18.2.2.2 Structure and Morphology .................................................................... 519 18.2.2.3 Thermomechanical Properties .............................................................. 520 18.2.2.4 Flexural Properties .................................................................................. 523 18.2.2.5 Thermal Stability ..................................................................................... 526
18.2.3 Summary ................................................................................................................. 526 18.3 Low Dielectric Constant Materials from Plant Oil Resins and Nanostructured
Keratin Fibers ..................................................................................................................... 527 18.3.1 Experimental .......................................................................................................... 527
18.3.1.1 Sample Preparation ................................................................................. 527 18.3.1.2 Characterization ...................................................................................... 528
18.3.2 Results and Discussion ......................................................................................... 528 18.4 Summary ............................................................................................................................. 532 References ..................................................................................................................................... 532
Developing affordable composite materials from renewable sources, such as plant oils, offers economic advantages and also environmental advantages.3-9 The growing demands of polymer materials have increased dependence on petroleum-based resources. With the fast depletion of these resources, replacing some or all of these with readily available, renewable, and inexpensive natural resources, such as plant oils, is becoming important. The use of abundant renewable materials contributes to global sustainability and diminution of global warming gases; and as the number of applications of composite materials continues to increase, an alternative source of petroleum-based composites becomes important. Plant oils are found in abundance in all parts of the world, making them ideal alternatives of petroleum-based materials because of their unlimited resources and potential biodegradability. When bio-based resins derived from natural plant oils are combined with natural fibers, glass fibers, carbon nanotubes (CNTs), nanoclays, and lignin, new low-cost composites can be produced that will be economical in many applications.10-20
Plant oil resins are based on triglycerides, which are the major components of natural oils. Triglycerides, shown in Figure 18.1, are composed of three fatty acids joined at a glycerol juncture.21 Plant oils have been widely used in coatings, inks, plasticizers, lubricants, and agrochemicals in addition to the food industry.22-26 In recent years, extensive work has been done to develop polymers for engineering applications using plant oils as the main component.27-33 Although unmodified triglycerides do not readily polymerize, the chemical functionality necessary to cause polymerization can be easily added to the triglycerides. The active sites on the modified triglycerides can be used to introduce polymerizable groups using the same synthetic techniques that have been applied in the synthesis of petrochemical-based polymers.34-42 Multifunctional triglycerides are produced using active sites, such as the double bonds and the ester groups, which are amenable to chemical reaction; then styrene or other co-monomers are added as reactive diluents. Very detailed synthetic pathways and experimental methods can be found elsewhere.43, 44 In this review, the focus is on three triglyceride monomers, as shown in Figure 18.2: (1) acrylated epoxidized soybean oil (AESO), (2) maleinized acrylated epoxidized soybean oil (MAESO), and (3) soybean oil pentaerythritol maleate (SOPERMA). These monomers, when used as a major component of a molding resin, have shown properties comparable to conventional polymers. The resins from soybean oil can be a substitute for liquid molding resins such as unsaturated polyester resins, vinyl esters, and epoxy resins. With suitable chemical functionalization and viscosity, the molding process of soybean resins is similar to that of conventional thermosetting liquid molding resins, using resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM), sheet molding compound (SMC), etc. The triglyceride-based materials display the necessary rigidity and strength required for structural applications.
