Abstract
Composites reinforced with natural lignocellulosic fibers (NLFs) are gaining relevance as the worldwide demand for renewable and sustainable materials increases. To develop novel natural composites with satisfactory properties, less common NLFs should also be investigated. Among these, the Cyperus malaccensis (CM), a type of sedge fiber, is already used in simple items like ropes, furniture, and paper, but has not yet been investigated as composite reinforcement for possible engineering applications. Therefore, the present work evaluated for the first time the properties of novel epoxy composites incorporated with 10, 20, and 30 vol.% of CM sedge fibers. Tensile, Izod-impact, and ballistic impact tests were performed, as well as Fourier transform infrared (FT-IR) spectroscopy and thermal analysis of the composites. Results disclosed a decrease (−55%) in tensile strengths as compared to the neat epoxy. However, the elastic modulus of the 30 vol.% sedge fiber composite increased (+127%). The total strain and absorbed ballistic energy did not show significant variation. The Izod impact energy of the 30 vol.% composite was found to be 181% higher than the values obtained for the neat epoxy as a control sample. An increase in both stiffness and toughness characterized a reinforcement effect of the sedge fiber. The thermal analysis revealed a slight decrease (−15%) in the degradation temperature of the CM sedge fiber composites compared to the neat epoxy. The glass-transition temperatures were determined to be in the range of 67 to 81 °C.
Highlights
Synthetic fibers experienced exponential growth after the Second World War and became a successful class of engineering materials, mainly as reinforcement of polymer matrix composites.They have been applied in several technological fields of human interest, from surgical prostheses to aerospace components [1,2,3]
An absorption band appears at 3430 cm−1, which is attributed to the axial vibration of hydroxyl groups (O-H) of the cellulose [54]
The relatively small amplitude of this band in the Cyperus malaccensis (CM) sedge fiber might justify a low interaction with the polymer matrix during the eventual manufacture of composites [54]
Summary
Synthetic fibers experienced exponential growth after the Second World War and became a successful class of engineering materials, mainly as reinforcement of polymer matrix composites.They have been applied in several technological fields of human interest, from surgical prostheses to aerospace components [1,2,3]. Polymers 2020, 12, 1776 pollution caused by non-degradable materials, such as common plastics, as well as climate changes resulting from carbon dioxide emissions, motivated a tendency to replace synthetic by natural fibers in composite materials. As compared to synthetic fibers, the NLFs display better characteristics, such as lower density and cost, as well as superior specific strength and elastic modulus [18,19] Such characteristics are motivating applications in automotive, packaging, civil construction, and aerospace industries associated with NLF composites [20,21,22,23,24,25,26]. Several researchers have been investigating the NLF waste as a source of nanocrystalline cellulose (NCC) [31,32,33,34,35,36], a strong nanomaterial, which can be used to produce several important products, such as nanocomposites, ion exchange membranes, films for electronics devices, and others [36]
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