Effects of Extractives on Dimensional Stability, Dynamic Mechanical Properties, Creep, and Stress Relaxation of Rice Straw/High-Density Polyethylene Composites

Modification of Fibres and Matrices in Natural Fibre Reinforced Polymer Composites: A Comprehensive Review

Composite materials derived from eco-friendly natural fibres and other biodegradable materials have gained prominence in industrial applications due to their sustainability and reduced greenhouse gas emissions attributes in comparison with conventional reinforcements such as glass and carbon fibres. Application of natural fibre-polymer composites (NFPCs) in different industrial applications provides competitive edge due to its lightweight, higher specific mechanical properties than glass fibres, sustainability and lesser cost involved in production. There are certain challenges associated with natural fibers and its reinforcement in composites such as poor bonding between the fibres and matrix due to its contradictory nature of characteristics, moisture absorption, lower thermal properties and poor interfacial adhesion between the natural fibre and polymer matrix. The challenges involved in NFPCs needs to be overcome to produce materials with relatively equivalent properties to that of conventional compositesand other metallic structures. Several researchers around the globe have conducted investigations with the primary attention being paid to the modification of natural fibers and matrix by employing surface treatments and other chemical treatment methods. In order to address the need for eco-friendly and sustainable materials in different domains, a comprehensive review on natural fibers and its sources, available matrix materials, modification techniques, mechanical and thermal properties of NFPCs is needed for better understanding of behavior of NFPCs.This work provides the information and wholistic view of natural fibre reinforced composites based on the results obtained from modification techniques,with the view of focusing the review in terms of different chemical and physical treatment techniques, modification of fibers and matrix and enhanced mechanical and thermal properties in the composites. This article is protected by copyright. All rights reserved.

Non-Isothermal Crystallization of Titanium-Dioxide-Incorporated Rice Straw Fiber/Poly(butylene succinate) Biocomposites

In this work, titanium dioxide (TiO2)-incorporated rice straw fiber (RS)/poly(butylene succinate) (PBS) biocomposites were prepared by injection molding with different TiO2 powder loadings. The RS/PBS with 1 wt% TiO2 demonstrated the best mechanical properties, where the flexural strength and modulus increased by 30.34% and 28.39%, respectively, compared with RS/PBS. The non-isothermal crystallization of neat PBS, RS/PBS composites, and titanium-dioxide-incorporated RS/PBS composites was investigated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The non-isothermal crystallization data were analyzed using several theoretical models. The Avrami and Mo kinetic models described the non-isothermal crystallization behavior of neat PBS and the composites; however, the Ozawa model was inapplicable. The crystallization temperature (Tc), half-time of crystallization (t1/2), and kinetic parameters (FT) showed that the crystallizability followed the order: TiO2-incorporated RS/PBS composites > RS/PBS > PBS. The RS/PBS with 1 wt% TiO2 showed the best crystallization properties. The Friedman model was used to evaluate the effective activation energy of the non-isothermal crystallization of PBS and its composites. Rice straw fiber and TiO2 acted as nucleating agents for PBS. The XRD results showed that the addition of rice straw fiber and TiO2 did not substantially affect the crystal parameters of the PBS matrix. Overall, this study shows that RS and TiO2 can significantly improve the crystallization and mechanical properties of PBS composites.

Chemical composition of Luffa aegyptiaca Mill., Agave durangensis Gentry and Pennisetum sp

The particleboard industry faces problems of wood shortage, which has led to the use of non-wood lignocellulosic materials. Furthermore, there is also interest in looking for materials that improve their physical and mechanical properties. The species Luffa aegyptiaca Mill. (fruit), Agave durangensis Gentry (bagasse) and Pennisetum sp. (plant, leaves and stem) could be used in the elaboration of wood-based particleboards. The aim of this study is to determine the feasibility of using these materials to produce particleboards in accordance with their chemical composition. Five materials were studied, A. durangensis (bagasse), L. aegyptiaca (fruit) and Pennisetum sp. (whole plant, leaves and stem). Extractives, holocellulose, Runkel lignin and ash content was determined. The pH of the fibers was also measured and a microanalysis of the ash was performed. ANOVA and Kruskal-Wallis tests were carried out, in addition Tukey and Dunn tests for group comparison were performed. Pennisetum sp. leaves presented the highest total extractives and ash content, while L. aegyptiaca fruit and A. durangensis bagasse had the highest both content of holocellulose and Runkel lignin respectively. The lowest pH was presented by the L. aegyptiaca fruit, while the highest was from the Pennisetum sp. stem. The element with the greatest presence in the five materials was potassium, except in A. durangensis bagasse showing calcium. L. aegyptiaca fruit has better characteristics to be used in particleboards with greater mechanical resistance because of its higher holocellulose content. However, Pennisetum sp. (plant, leaves and stem) could be used to make particleboards with high resistance to water absorption.

Leather Waste to Enhance Mechanical Performance of High-Density Polyethylene

Leather buffing dust (BF) is a waste from tannery which is usually disposed on landfills. The interest in using wastes as fillers or reinforcements for composites has raised recently due to environmental concerns. This study investigates the potential use of BF waste as filler for a high density polyethylene matrix (HDPE). A series of HDPE-BF composites, containing filler concentrations ranging from 20 to 50wt%, were formulated, injection molded and tested. The effect of filler contents on the mechanical properties of the composites were evaluated and discussed. Composites with BF contents up to 30wt% improved the tensile strength and Young’s modulus of the matrix, achieving similar mechanical properties to polypropylene (PP). In the case of flexural strength, it was found to be proportionally enhanced by increasing reinforcement content, maintaining high impact strength. These composites present great opportunities for PP application areas that require higher impact resistance. The materials were submitted to a series of closed-loop recycling cycles in order to assess their recyclability, being able to maintain better tensile strength than virgin HDPE after 5 cycles. The study develops new low-cost and sustainable composites by using a waste as composite filler.

Synthesis of developed rice straw sheets and glass fiber-reinforced polyester composites

In this study, a sheet of random rice straw fiber was developed. These rice straw sheets were used to reinforce polyester matrix. Synthesis of rice straw sheets and glass fibers as synthetic fibers-reinforced polyester composites were investigated. Several new stacking sequences were fabricated with random glass fiber mats with different areal densities (225 g/m2, 300 g/m2, and 450 g/m2) and rice straw sheets. The specific mechanical properties of these natural/synthetic fiber composites were investigated. Scanning electron microscopy was used to study the morphology of the fracture surfaces of the fabricated hybrid composites. Experimental results showed that specific tensile and flexural stiffness of rice straw fiber composite is better those obtained with glass fiber composites. The hybrid natural/synthesis composites with alternating glass fiber mat with areal densities 300 g/m2, and rice straw shows higher specific tensile strength than rice straw and other hybrid composites. Hybrid composites with high areal density on the outer surfaces yield a significant increase in flexural-specific strength and hardness as compared to other fabricated composites.