Mechanical Properties of Poly (lactic acid) Composites Reinforced with CaCO 3 Eggshell Based Fillers
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Mechanical Properties of Poly (lactic acid) Composites Reinforced with CaCO3 Eggshell Based Fillers Nicholas G. Betancourt1 and Duncan E. Cree1 1
Department of Mechanical Engineering, University of Saskatoon, 57 Campus Drive, Saskatoon, SK S7N 5A9, Canada.
ABSTRACT Poly (lactic acid) (PLA) bioplastics are recyclable and biodegradable thermoplastics. They are derived from environmentally friendly sources such as potatoes, cornstarch and sugarcane. However, PLA is inherently brittle with low impact strength. The goal of this study is to improve mechanical properties of PLA by the addition of calcium carbonate (CaCO3) fillers. PLA composites were prepared by injection molding conventional limestone (LS) and white chicken eggshell (WES) powders with particle sizes of 63 μm and 32 μm in amounts of 5 wt. %, 10 wt. % and 20 wt. %. Mechanical properties such as, tensile strength, tensile modulus, and Charpy impact strengths were investigated. These three properties were evaluated and the results statistically analyzed using ANOVA F-test. For both particle sizes, the tensile strength decreased as the filler content increased, but was highest for a filler loading of 5 wt. %. In general, the 32 μm powder fillers had better tensile strengths than 63 μm sized fillers. The tensile modulus increased with filler content and was highest at 20 wt. % for both particle sizes. The LS/PLA composites had better toughness than the WES/PLA composites. The particle filler morphology and fractured surfaces were observed by scanning electron microscopy (SEM) and determined to have well dispersed particles with smooth fractured surfaces. Water absorption behavior of PLA/CaCO3 composites were studied by immersion in distilled water at room temperature for 56 days. Virgin PLA absorbed the least amount of water while the water absorption of CaCO3 composites were a function of powder type and content.
INTRODUCTION For the past two decades, the area of sustainable, green polymers has been growing quickly [1]. A common bio-polymer that has gained interest in the research community for the past 25 years is polylactic acid (PLA) [2]. PLA is a biopolymer that can be recycled or provided with the right environmental conditions can safely degrade back into the environment. Adding conventional calcium carbonate (CaCO3) fillers to polymers is known to have a reinforcing effect [3]. Industrial limestone could potentially be replaced fully or partially with a renewable source such as white chicken eggshells (WES). Eggshells are a source of calcium carbonate as they contain 96-97 % CaCO3 with the remaining 3-4 % consisting of membrane [4]. The majority of investigations on polymer composites containing eggshell fillers were conducted on polypropylene matrices [5]. One study examined the mechanical and thermal properties of thin (50 μm thick) PLA/eggshell films [6] but research using PLA/eggshell composites with sheet thicknesses (> 500 μm) are lacking. This work examines the production of PLA/eggshell
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