_Applied_  
_sciences_  
**Thermal and Mechanical Characteristics of Okra**  
_(Abelmoschus esculentus)_ **Fibers Obtained via**  
**Water- and Dew-Retting +**  
Footnote †: margin: _Appl. Sci._**2020**, _10_, 5113; doi:10.3390/app10155113  
**[PERSON] 1,*(c), [PERSON] 2, [PERSON] 3 and [PERSON] 1**  
use of natural plant fibers. The increased interest in natural fillers as additives in composite materials is also related to current industry trends, which include recycling plastics, reducing manufacturing costs and controlling the product life cycle through the use of environmentally-friendly materials [6]. Several methods are used to obtain natural plant fibers, including water-retting, dew-retting, chemical-retting, and mechanical decortication [3]. Water-retting and dew-retting are traditional methods that have been widely applied, in fact, dew-retting is thought to be the oldest retting technique. In this technique, plant stems are laid on the ground under a thin layer of soil and kept there for three to four weeks. Plant stems are immersed in water tanks for the water-retting method. The properties of dew-retted fibers have been reported to be inferior and show higher variability compared to water-retted fibers. However, dew-retting still has some advantages, such as ease, low cost, and less environmental impact compared to water-retting [7]. Plant fibers from cotton [8], flax [9], hemp [10], jute [11], and sisal [12] have been the focus of research and commercial interest for their use in composites over the last few decades. However, several other plant varieties that are planted mainly to supply the food industry can also be used as alternative sources of fibers [13]. Unused parts of different edible plants, including okra stems and branches [14], wheat straw [15], nettle stems [16], corn husks [17], and banana pseudo-stems [18] can be used as sources of fiber for composite reinforcement applications. The utilization of agricultural residues for fiber production not only saves the environment because biodegradable materials based on renewable sources are used, but also, developing rural communities prosper as their crops receive added value. Furthermore, more arable land may be allotted for food production to feed our growing world population [19]. Okra (_Abelmoschus esculentus_) is a plant grown in tropical and subtropical regions, mainly for its eatable fruits and its gum, to serve the pharmaceutical industry [14; 20]. The first written mention of okra was recorded in Egypt and dates from 1216. The domesticated form of the species _Abelmoschus esculentus_ spread further to the regions of the Red Sea and the Arabian Peninsula, and then to Southern Europe. In the eighteenth century, okra also appeared in the English dictionary, and slaves brought it from Africa to the United States. Today, apart from Africa, the okra plant is successfully grown in the southern part of the USA, the Caribbean, South America, the Middle East, Greece, and Turkey. However, the okra plant is mainly produced in underdeveloped countries across the globe. According to the Factfish database, total okra production was almost 10 million tons in 2017. That year, the top three okra producers were India, Nigeria, and Sudan. More than half of the ten biggest okra producers were African countries [21]. The main application of okra is food; however, the remaining parts of the plant can be used as a structural element in composite materials. Okra last fibers are considered an alternative to the most commonly used fibers, such as jute, flax, or hemp, which is in line with the general attempt to broaden the number of botanical species from which fibers are extracted [22; 23]. An additional advantage of using okra best fibers is that the inedible parts are used, which are normally recyclable waste. Obtaining okra stalk fibers is, in fact, removing food production waste from the fields. Therefore, okra fiber production is not in competition with food production as both processes take place in parallel in the same area [24].