Use of Almond Shells and Rice Husk as Fillers of Poly(Methyl Methacrylate) (PMMA) Composites

Abstract

In recent years, wood fibres have often been applied as the reinforcement of thermoplastic materials, such as polypropylene, whereas their use in combination with thermosetting resin has been less widespread. This study concerns the production of PMMA-based composites by partly replacing alumina trihydrate (ATH) with wood waste fillers, namely rice husks and almond shells, which would otherwise be disposed by incineration. The amount of filler introduced was limited to 10% as regards rice husks and 10 or 15% almond shells, since indications provided by reactivity tests and viscosity measurements did not suggest the feasibility of total replacement of ATH. As a matter of fact, the introduction of these contents of wood waste filler in PMMA-based composite did not result in any significant deterioration of its mechanical properties (Charpy impact, Rockwell M hardness and flexural performance). Some reduction of these properties was only observed in the case of introduction of 15% almond shells. A further issue concerned the yellowing of the organic filler under exposure to UV light. On the other hand, a very limited amount of water was absorbed, never exceeding values around 0.6%, despite the significant porosity revealed by the filler’s microscopic evaluation. These results are particularly interesting in view of the application envisaged for these composites, i.e., wood replacement boards.

Effect of Antibacterial Silver-Releasing Filler on the Physicochemical Properties of Poly(Methyl Methacrylate) Denture Base Material

“…Observed areas showing the presence of spherical shapes, determined by the shape of PMMA pre-polymerized particles of the "powder" component, indicated a significant local reduction in material strength as a consequence of filler aggregations, leading to uprooting of these particles from the cured material and probably accelerated fracture of samples. A similar decrease in the mechanical properties along with the increase in mass concentrations of fillers has been noted after the introduction of particles, e.g., ZrO 2 , nanodiamonds, Al 2 O 3 , hydroxyapatite, titanium oxide, ground fillers of natural origin or even glass fibers [83,[87][88][89]. On the other hand, potential reinforcement in many cases can be achieved by using the synergistic effect of various additives (e.g., different particles, glass meshes, and glass fibers) [90].…”

Effect of Almond Shell Waste on Physicochemical Properties of Polyester-Based Biocomposites

“…This powerful area of interest presents several benefits such as biodegradability in combination with bio-based or natural polymers, light weight, low cost and easy processing [14,15]. Among the wide variety of lignocellulosic wastes, almond shell powder has been already considered as filler for commodity plastics, such as polypropylene [16][17][18][19][20], polyethylene [21], poly(methyl methacrylate) [22] and toughened epoxies [23,24].…”

Identification of properties of recycled high­density polyethylene composites when filled with waste mud solids

“…The publication [9] reviewed the reinforcement of composites with plant waste, such as rice husks and almond shells. It is shown that the greatest improvement of polymer properties is limited by the filler share of 10-15 %, over which there is a deterioration of the mechanical properties and operational characteristics.…”