Insight into the Effects of Solvent Treatment of Natural Fibers Prior to Structural Composite Casting: Chemical, Physical and Mechanical Evaluation

Design of Strain-Hardening Natural TRM Composites: Current Challenges and Future Research Paths

This paper discusses the challenges in using natural fibers for the development of textile-reinforced mortar (TRM) composites with pseudo-strain-hardening and multiple cracking behavior. The particular characteristics of natural vegetal fibers are analyzed with reference to data from the literature. It is concluded that the efficient use of these fibers as composite reinforcement requires the development of treatment or impregnation protocols for overcoming durability issues, eliminating crimping effects in tensile response and imparting dimensional stability. Relevant experimental research on the synthesis and performance of natural TRMs is reviewed, showing that the fabrication of such systems is, at present, largely based on empirical rather than engineering design. In order to set a framework regarding the properties that the constituents of natural TRM must meet, a comparative analysis is performed against inorganic matrix composites comprising synthetic, mineral and metallic reinforcement. This highlights the need for selecting matrix materials compatible with natural fibers in terms of stiffness and strength. Furthermore, a rational methodology for the theoretical design of natural TRM composites is proposed. First-order analysis tools based on rule-of-mixtures and fracture mechanics concepts are considered. Based on the findings of this study, paths for future research are discussed.

Extraction and Characterization of Fiber and Cellulose from Ethiopian Linseed Straw: Determination of Retting Period and Optimization of Multi-Step Alkaline Peroxide Process

Flax is a commercial crop grown in many parts of the world both for its seeds and for its fibers. The seed-based flax variety (linseed) is considered less for its fiber after the seed is extracted. In this study, linseed straw was utilized and processed to extract fiber and cellulose through optimization of retting time and a multi-step alkaline peroxide extraction process using the Taguchi design of experiment (DOE). Effects of retting duration on fiber properties as well as effects of solvent concentration, reaction temperature, and time on removal of non-cellulosic fiber components were studied using the gravimetric technique, Fourier transform infrared (FTIR) spectroscopy and thermal studies. Based on these findings, retting for 216 h at room temperature should offer adequate retting efficiency and fiber characteristics; 70% cellulose yield was extracted successfully from linseed straw fiber using 75% ethanol-toluene at 98 °C for 4 h, 6% NaOH at 75 °C for 30 min, and 6% H₂O₂ at 90 °C for 120 min.

Evaluation of Novel Compatibility Strategies for Improving the Performance of Recycled Low-Density Polyethylene Based Biocomposites

The interfacial compatibility of the natural filler and synthetic polymer is the key performance characteristic of biocomposites. The fillers are chemically modified, or coupling agents and compatibilisers are used to ensure optimal filler-polymer compatibility. Hence, we have investigated the effect of compatibilisation strategies of olive pits (OP) flour content (10, 20, 30, and 40%wt.) filled with recycled low-density polyethylene (rLDPE) on the chemical, physical, mechanical, and thermal behaviour of the developed biocomposites. In this study, we aim to investigate the filler-polymer compatibility in biocomposites by employing novel strategies for the functionalisation of OP filler and/or rLDPE matrix. Specifically, four cases are considered: untreated OP filled rLDPE (Case 1), treated OP filled rLDPE (Case 2), treated OP filled functionalised rLDPE (Case 3), and treated and functionalised OP filled functionalised rLDPE (Case 4). In general, the evaluation of the performance of biocomposites facilitated the application of OP industrial waste as an eco-friendly reinforcing agent for rLDPE-based biocomposites. Furthermore, surface treatment and compatibilisation improved the properties of the developed biocomposites over untreated filler or uncoupled biocomposites. Besides that, the compatibilisers used aided in reducing water uptake and improving thermal behaviour, which contributed to the stability of the manufactured biocomposites.