Parametric characterization of nano-hybrid wood polymer composites using ANOVA and regression analysis

Abstract

The need to reduce waste is driving the development of new materials and technologies that support the transition of societies towards a more environmentally sustainable world. Wood-polymer composites (WPCs) can be produced by using waste products deriving from wood and plastic manufacturing industries. Enhanced mechanical and physical properties of WPCs also allow for these materials to substitute their conventional counterparts, especially the ones intended to be used in dry and hot environments. This paper examined how the addition of various reinforcements influenced the properties of polymer matrix-based WPC. More closely, this paper focused on assessing the mechanical properties of Polymethylmethacrylate (PMMA) and date palm leaves-based composite samples with different reinforcement types of recycled Polyethylene Terephthalate (PETE) fibers and nano-Aluminum Oxide (nano-Al₂O₃) particles. A two-way ANOVA and multivariate linear regression models are developed to predict and examine the effects and the interaction between the effect of batches and series on density, absorption, strength, modulus and absorbed energy before and after aging. The results suggest that combining the PMMA with recycled date palm leaves and including a mixture of commercially available PETE fiber reinforcements along with nano-Al₂O₃ particles produces samples that show enhanced mechanical and water resistance properties compared to composites without such reinforcements. The analysis used to detect the WPC combination and reinforcements embedded in the composite structure indicated that the reinforcements limited the absorption of water. The mechanical tests conducted on the reinforced WPC samples showed an improvement of mechanical characteristics. Adding both recycled PETE fibers and nano-Al₂O₃ particles to the samples increases the flexural characteristics and shows the largest capacity to absorb energy at impact followed by single reinforcement samples. For samples that underwent aging in chloride solution (offshore simulation), the enhanced capabilities were reduced by 8 and 15%.

Introduction

Plastic and wood residue generated during various manufacturing phases contribute significantly to the overall pollution of the planet. Recycling has become one of the essential contemporary ways to decrease junk materials. The modern technologies have allowed for all parts of plastic and wood to be recycled and used in the manufacturing of various products including the ones that were traditionally considered unusable and thrown away, thus, contributing to lowering the impact of pollution on the environment [1]. Wood-polymer composites or wood-plastic composites (WPCs) are one of the examples of the modern materials produced as an amalgam of two materials that are usually made using recycled base components (wood and plastic) [1]. Wood-polymer composites (WPCs) are defined as a combination of wood in any form and thermoplastic/thermoactivated polymers and can be made using different manufacturing techniques including extrusion, injection, compression and thermal molding. The choice of materials varies greatly and depends on the predefined characteristics of the end product. As environmentally friendly materials, wood fibers are often mixed with various thermoplastic fillers to produce the core of the composite. When used together, this mixture gives a number of desirable properties to the composite such as low density, high toughness, high resistance to decay and rotting as well as good resistance to impact [1]. Increased durability and recycling potential make WPCs one of the materials of choice in sustainable manufacturing that is recognized as an important part of sustainable development described in the United Nations 2030 Agenda for Sustainable Development [2]. WPC is an ideal alternative to traditional materials due to its physical properties that substitute wood effectively, especially in interior design, architecture or constructions. WPCs are materials of choice in manufacturing window frames, doors, benches, fences, ship decks, floors and more due to their durability, malleability and easy maintenance [3], [4], [5]. There has been a growing number of studies in the last decade that assessed the properties of WPCs with a special focus on strength, rigidness, lower cost and low impact on the environment [1], [2], [3], [4], [5], [6], [7], [8]. Contemporary research into the technological manufacturing processes has allowed for the rapid development of composites with good mechanical properties, high dimensional stability, as well as high malleability needed to effectively produce complex shapes [3], [4], [5], [6], [7], [8]. Modern WPCs do not require finalization, withstand weather conditions, are moisture and mold tolerant which are the reason why they are used in open-air conditions where the use of natural wood is contraindicated [3]. Most WPCs have a PVC contents and also have a number of benefits including cheap and widely available base components, competitive prices, the potential for producing products of different shapes and sizes, adequate resistance to wear and tear, and lower maintenance price compared to conventional materials [6], [7], [8]. WPCs have increased the usability of raw wood by 40% because much of WPC is made from waste wood [8]. WPC does not contain formaldehyde or aggressive organic components and it is reusable and can be safely disposed of at landfills along with other waste. The industries that use these composites include construction, infrastructure, and the transport industry [8]. The current literature suggests that WPC has better exploitation characteristics and mechanical properties in the process of making complex profiles compared to its individual components namely wood or plastic [8]. This fact opens up possibilities for the currently used conventional materials to be replaced with cheaper and environmentally friendly WPC alternatives. The type of the thermoplastic matrix determines the thermal stability of WPCs along with the extent of thermal degradation of their lignocellulosic filler [6], [7], [8]. Producing a WPC with predetermined characteristics requires adding reinforcement materials such as PETE fibers, glass fibers or metal wires. The need for this research is supported by the increased demand to develop sustainable hybrid and environmentally friendly wood-polymer composites [2]. This research paper focuses on the ways of improving the properties of WPCs for the end product to have the best characteristics possible. It introduced and analyzed WPC samples manufactured using date palm leaf (DPL), Polymethylmethacrylate (PMMA), toluene diisocyanate (TDI) and either or both commercially recycled PETE and nano-Aluminum Oxide (nano-Al₂O₃) with different content mix by total weight of the mixture. Polymethylmethacrylate (PMMA) matrix gives the composite sample excellent mechanical, chemical and water repellant properties. Using ceramics particles in PMMA-based WPCs advances both mechanical and chemical characteristics. Ceramic particles made of nano-Al₂O₃ can change the properties of composites depending on their crystal structure. Thermoplastic fiber reinforcement can be an ecologically sound alternative to other reinforcing materials and can be made from PETE bottles or other types of recyclable plastic products. The covalent bonding between toluene diisocyanate (TDI) and wood can increase the chemical resilience and enhances the mechanical properties of composites.