Abstract
Tung oil is uniquely reactive among plant-based natural oils due to the series ofconjugated carbon-carbon double bonds in its fatty acid chains. These conjugatedcarbon-carbon double bonds impart a high reactivity towards cationic polymerization in thepresence of other reactive co-monomers, such as divinylbenzene and styrene. An impressivedecrease in the cure time of tung oil-based thermosets has been achieved when the resinsinvestigated were microwaved in the presence of carbon nanotubes (CNTs). However, thefast cure compromised the overall thermo-mechanical properties of the materialsinvestigated. Microwave power, exposure time, and CNT loading effects have been assessedby means of dielectric analysis (DEA), thermogravimetric analysis (TGA), differentialscanning calorimetry (DSC), dynamic mechanical analysis (DMA), and proton nuclearmagnetic resonance (1H NMR) spectroscopy of extracts obtained by Soxhlet extraction.Possible reasons were proposed to explain the overall inferior properties observed wheneverfaster cure rates were achieved.
Highlights
The partial replacement of petroleum-derived plastics and composites by bio-based materials from inexpensive, renewable, and natural resources has the potential to greatly impact the plastics and composites industries
The findings reported in this manuscript are relevant for furthering the understanding of the fundamentals of microwave effects in the cure-kinetics of thermosets in the presence of carbon nanotubes (CNTs)
In a related work, evaluating the concentration of DVB in conjugated vegetable oil-based resins cured by free radical polymerization, it has been shown that samples containing 15 wt % of DVB exhibit good mechanical properties [5]
Summary
The partial replacement of petroleum-derived plastics and composites by bio-based materials from inexpensive, renewable, and natural resources has the potential to greatly impact the plastics and composites industries Natural starting materials, such as vegetable oils, are readily available in large quantities, low cost, and have the potential to offer properties not currently available in commercial petroleum-based products. A variety of vegetable oil-based polymers with tunable thermal and mechanical properties have been developed by the free radical, or cationic co-polymerization of regular and modified vegetable oils in the presence of divinylbenzene (DVB), styrene (ST), and/or maleic anhydride [3,4] In such systems, the reactive sites in the triglyceride units are the carbon-carbon double bonds along the fatty acid chains. The higher the degree of unsaturation of an oil, the higher the crosslink density of its resulting co-polymer, and the better its mechanical properties [3]
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