Abstract
In this work, the suitability for the production of sustainable and lightweight materials with specific mechanical properties and potentially lower costs was studied. Agave fiber (AF), an agro-industrial waste, was used as a reinforcement and azodicarbonamide (ACA) as a chemical blowing agent (CBA) in the production of bilayer materials via rotational molding. The external layer was a composite of linear medium density polyethylene (LMDPE) with different AF contents (0–15 wt %), while the internal layer was foamed LMDPE (using 0–0.75 wt % ACA). The samples were characterized in terms of thermal, morphological and mechanical properties to obtain a complete understanding of the structure-properties relationships. Increases in the thicknesses of the parts (up to 127%) and a bulk density reduction were obtained by using ACA (0.75 wt %) and AF (15 wt %). Further, the addition of AF increased the tensile (23%) and flexural (29%) moduli compared to the neat LMDPE, but when ACA was used, lower values (75% and 56% for the tensile and flexural moduli, respectively) were obtained. Based on these results, a balance between mechanical properties and lightweight can be achieved by selecting the AF and ACA contents, as well as the performance and aesthetics properties of the rotomolded parts.
Highlights
In recent times, conventional plastics have become indispensable for an increasing number of human activities; for this reason, it is difficult to imagine a modern society without plastics because of its uses in several areas such as construction, packaging, medicine, electronics, etc. [1]
The use of natural fibers as reinforcement of thermoplastics has drawn a great deal of attention due to their interesting specific mechanical properties, low environmental impact and cost, wide availability, biodegradability and lightweight compared to synthetic fibers and other fillers which are still widely used in the industry [6]
2a) indicating good thermal stability started at around 420 °C and finished around 500 °C (Figure 2a) indicating good thermal stability for for the range of conditions used in rotational molding
Summary
Conventional plastics have become indispensable for an increasing number of human activities; for this reason, it is difficult to imagine a modern society without plastics because of its uses in several areas such as construction, packaging, medicine, electronics, etc. [1]. Due to the environmental concerns caused by the accumulation of plastics wastes, academic, industrial and government sectors are developing strategies to increase the sustainability of the plastic industry including the reduction of plastics in single-use applications, recycling and the production of more sustainable materials such as composites based on biobased fillers (flax, hemp, pine, coir or agave fibers) [3,4,5]. The main limitation of natural fibers is their low compatibility with most hydrophobic polymers, leading to poor filler-matrix adhesion. They are susceptible to moisture absorption, which affects the dimensional stability and overall performance of the composites [7]. Under optimized processing parameters, they can be processed via injection [8], compression [9] and rotational molding, with properties and design suitable for any particular application [10]
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