In this study, composite system was developed to enhance mechanical properties of plastic pallets. The potential of graphite nanoplatelets (GnP)/PP composites for the application in packaging was scrutinized by examining mechanical properties, thermal properties, flow properties, and morphology as a function of GnP loading and by comparison of two mixing methods: physical melt compounding (PMC) and chemical pretreatment compounding (CPC) processes. Incorporation of the GnP into PP resulted in a significant enhancement in the mechanical strength (tensile, impact, and flexural strength) and thermal decomposition temperature compared to the neat PP specimen. The CPC process clearly shows good exfoliation and better distribution on the PP matrix compared to the PMC method based on morphological evaluation measured by SEM. The impact test at low temperature revealed that the composites made by the CPC process showed 64% higher impact strength than neat PP due to higher even-distribution of GnP molecules into the PP matrix.
We attempted to discover the degree of dispersion of natural fiber (kenaf) and graphite nanoplatelets (GnP) into the polypropylene (PP) polymer matrix and the effect of filler-adding sequence on physical and mechanical properties. Tensile strength of the composites was increased up to 25%. In the case of Young's modulus, composites showed a 56% enhancement compared to the control. However, the impact strength decreased as a result of the increased brittleness when kenaf fiber was added. Another study investigated the effects of hybrid filler systems (graphite nanoplatelets (GnP)/commercially available modified calcium carbonate (mCaCO3) nanoparticles) on mechanical and physical properties of polypropylene nanocomposites with three variables, filler loading amount, the number of compounding processes, and the compounding order of two different fillers. The impact strength of composite samples, containing 1wt% of GnP and mCaCO3 nanoparticles, increased up to 64% compared to neat PP. Among all tested samples, the highest tensile strength was found at 1wt% of mCaCO3 nanoparticles regardless of the presence or absence of GnP addition. There was no significant difference in flexural strength regardless of any nano-filler addition. However, both the flexural modulus and Young's modulus increased significantly when 10wt% of mCaCO3 nanoparticles were added. The number of compounding processes did not affect any strength, and the single compounding process was found to be more effective than the double compounding process. It may be contributed by thermal degradation of polymeric structure by double heat processing. This study can be able to provide a solution for value-added high-end products in various industries such as application in logistics, aerospace or electric automobile, where carbon-based nanomaterials are more affordable. / Doctor of Philosophy / Pallets are the basic structure of a unit load which allows handling and storage efficiency. The advantages of plastic pallets are durability, cleanliness, and performance reliability, However, those are expensive and have lower mechanical properties than that of wood, such as low strength, creeps and deformation. Therefore, hybrid composites were fabricated using various fillers, such as graphite nanoplatelets, kenaf fiber or calcium carbonate on polypropylene matrix to enhance mechanical properties for plastic pallets. In order to fabricate the composites, two methods were utilized and compared: physical melt compounding (PMC) and chemical pretreatment compounding (CPC) processes. Graphite nanoplatelets (GnP) reinforced polypropylene (PP) composites made by both PMC and CPC process showed significance in the mechanical process compared to the neat PP. Moreover, the CPC process showed better dispersion on the PP matrix resulting in higher impact strength in low temperature.
Based on the first chapter, we attempted to focus on reducing weight and sustainability using natural fiber. At the same time, when two or more fillers are reinforced in a polymer matrix, I wondered if the order in which the fillers were added could affect properties. Kenaf fiber and GnP were reinforced in the PP matrix through the CPC process to discover the degree of dispersion of fillers and the effect of filler-adding sequence on physical and mechanical properties. Tensile strength of the composites was increased up to 25%. In the case of Young's modulus, composites showed a 56% enhancement compared to the control. However, the impact strength decreased as a result of the increased brittleness when kenaf fiber was added.
Another study investigated the effects of hybrid filler systems (GnP/commercially available modified calcium carbonate (mCaCO3) nanoparticles) on mechanical and physical properties of polypropylene nanocomposites with three variables, filler loading amount, the number of compounding processes, and the compounding order of two different fillers. This study was concentrating on the impact strength based on the result that the material adding sequence affects the mechanical strength when manufacturing the hybrid composites. The hybrid composite system on GnP/mCaCO3/PP resulted in enhancement of impact strength, tensile strength, flexural modulus and Young's modulus. The number of compounding processes did not affect any strength, and the single compounding process was found to be more effective than the double compounding process.
Enhancement of impact strength in low temperature, and effect of filler-adding sequence on mechanical properties in hybrid composite system can be able to provide a solution for value-added high-end products in various industries such as application in logistics, aerospace or electric automobiles, where carbon-based nanomaterials are more affordable.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/113531 |
| Date | 26 January 2023 |
| Creators | Lee, Soohyung |
| Contributors | Forest Resources and Environmental Conservation, Kim, Young Teck, Moore, Robert Bowen, Lee, Seul-Yi, White, Marshall S. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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