Effect of Rice Husk and Wood Flour on the Structural, Mechanical, and Fire-Retardant Characteristics of Recycled High-Density Polyethylene

Abstract

Given the rising consumption of plastic products, it is becoming imperative to prioritize the recycling of plastic items as a solution to reducing plastic waste and environmental pollution. In this context, this research focuses on assessing the impact of incorporating rice husk and wood flour into recycled high-density polyethylene (rec-HDPE) to analyze its mechanical properties, flammability, and thermal stability. The combined rec-HDPE content of wood flour and rice husk varied between 0% and 20%. The rec-HDPE content of maleic anhydride grafted polyethylene (MAPE) was fixed at 3%. Mechanical characteristics such as flexural, tensile, and impact strengths were assessed. Cone calorimetry (CC) tests, limited oxygen index (LOI) tests, and horizontal and vertical burning tests were performed to determine the flammability or fire retardancy of these composites. On the other hand, to characterize the thermal characteristics of these composites, thermogravimetric analysis (TGA) was used. To further characterize the fluctuation in these characteristics, scanning electron microscopy (SEM) and infrared spectroscopy (FTIR) studies were carried out. The mechanical characteristics were found to be increased in response to adding rice husk or wood flour. An 8% increase in tensile strength and a 20% increase in elastic modulus enhancement were recorded for a 20% rice husk-added composite. SEM revealed the reason for the variation in tensile properties, based on the extent of agglomeration and the extent of uniform distribution of fillers in rec-HDPE. Following these lines, the 20% rice husk-added composite also showed a maximum increase of around 6% in its flexural strength and a maximum increase of 50% in its flexural modulus. A decrease in impact strength was recorded for rice husk and wood flour-reinforced composites, compared with unreinforced rec-HDPE. Hybrid composites displayed a lack of mechanical strength due to changes in their nature. FTIR tests were performed for a much more elaborate analysis to confirm these results. Twenty percent of rice husk-added rec-HDPE displayed the best thermal properties that were tested, based on TGA and derivative thermogravimetric (DTG) analysis. This 20% composite also displayed the best fire-retardancy characteristics according to UL 94 tests, cone calorimetry tests, and limited oxygen index tests, due to the barrier created by the silica protective layer. These tests demonstrated that the incorporation of both fillers—rice husk and wood flour—effectively enhanced the thermal, mechanical, and fire-retardant attributes of recycled HDPE.

Developing Eco-Friendly 3D-Printing Composite Filament: Utilizing Palm Midrib to Reinforce High-Density Polyethylene Matrix in Design Applications

“…The peaks at 2842 and 2908 cm −1 are attributed to the C-H symmetric and asymmetric stretching vibration, respectively, which are caused by aliphatic structures [ 30 ]. Conversely, the presence of alkanes is indicated by the peak at 1468 cm -1 , which is brought on by the C–H bond bending [ 31 , 32 ], and the presence of previous peaks is attributed to HDPE. Nevertheless, an extra broad peak was detected in the HDPE/DPFNP composites at a wavenumber of 1084 cm −1 , and its intensity increased when the DPFNP weight ratio increased from 10% to 50%.…”

Modifications of Phase Morphology, Physical Properties, and Burning Anti-Dripping Performance of Compatibilized Poly(butylene succinate)/High-Density Polyethylene Blend by Adding Nanofillers

“…The widespread utilization of non-sustainable PE has resulted in severe, long-lasting environmental and waste management issues [9]. The applications of PE have been further broadened by blending with other polymers and/or loading with various fillers [10][11][12]. A realistic solution to mitigate the harmful effects is to produce PE blends with biopolymers such as poly(butylene succinate) PBS.…”