Studies on polylactide nanocomposites with polyhedral oligomeric silsesquioxane

2020
Meyva Zeybek, Yelda.
The main purpose of the first part of this thesis was to investigate influences of three parameters on the mechanical and thermal properties of the polylactide (PLA) matrix nanocomposites filled with polyhedral oligomeric silsesquioxane (POSS) particles. For the first parameter of “Filler Content”, nanocomposites with 1, 3, 5, 7 wt% basic POSS structure were compared. For the second parameter of “Functional Group”, basic POSS structure having only nonpolar isobutyl groups were compared with three other functionalized POSS structures; i.e. aminopropylisobutyl-POSS (ap-POSS), propanediolisobutyl-POSS (pd-POSS) and octasilane-POSS (os-POSS). For the third parameter of “Copolymer Compatibilization”, all specimens were compared before and after their maleic anhydride (MA) grafted copolymer compatibilization. Specimens were produced with twin-screw extruder melt mixing and shaped under compression molding. Various tests and analyses indicated that the optimum filler content for the improved mechanical properties was 1 wt%; while the optimum structure for strength and modulus was pd-POSS structure, in terms of fracture toughness it was basic POSS structure. Additional use of MA compatibilization was especially effective for the basic POSS and os-POSS particles. Because of the biocompatible and nontoxic character of both PLA and POSS nanoparticles, recently being a significant alternative for biomedical parts; the main purpose of the second part of this thesis was to investigate performance of the 3D-printed PLA/POSS nanocomposites with respect to the compression molded PLA/POSS specimens. Due to the higher uniformity and higher homogeneity in the distribution of POSS nanoparticles in each PLA matrix layer, mechanical tests (tensile, flexural, toughness) revealed that the improvements in the strength, elastic modulus and fracture toughness values of the 3D-printed specimens were much higher compared to their compression molded counterparts, the benefits starting from 13% increasing up to 78%. It was also observed that there was almost no deterioration in the physical structure and mechanical properties of the 3D-printed specimens, even after keeping them 120 days at 37°C in a physiological solution prepared by using the standard PBS (Phosphate Buffered Saline) tablet. It is known that electrospinning is the most practical technique to obtain unique properties of polymer based nanofibrous structures, such as neat PLA and PLA filled with POSS particles. On the other hand, due to the so many different process parameters to consider, production of these fibers are extremely difficult and time consuming. That is, use of a certain statistical optimization technique in the design of experiments would be necessary. Therefore, the main purpose of the third part of this thesis was to determine the optimum electrospinning parameters by applying the Taguchi technique first to neat PLA and then to reveal the applicability of these parameters for the electrospinning of PLA/POSS nanofibers. It was observed that instead of conducting 81 experiments to determine the most significant 4 optimum process parameters for PLA, use of Taguchi L9 orthogonal array experiment matrix, i.e. conducting only 9 experiments, reduced time, labor and material consumption considerably. Moreover, it was generally concluded that these same parameters could be also used for the electrospinning of PLA/POSS nanofibers after addition of only 3 wt% KCl salt into the polymer solution.

Suggestions

Behaviour of PLA/POSS nanocomposites: Effects of filler content, functional group and copolymer compatibilization
Meyva Zeybek, Yelda; Kaynak, Cevdet (2021-04-01)
The main purpose of this study was to investigate influences of three parameters on the mechanical and thermal properties of the polylactide (PLA) matrix nanocomposites filled with polyhedral oligomeric silsesquioxane (POSS) particles. For the first parameter of "Filler Content", nanocomposites with 1, 3, 5, 7 wt% basic POSS structure were compared. For the second parameter of "Functional Group," basic POSS structure having only nonpolar isobutyl groups were compared with three other functionalized POSS str...
Investigation of microstructure inhomogeneity in SiCp-reinforced aluminum matrix composites
Gacsi, Zoltan; Gür, Cemil Hakan; Makszimus, Andrea; Pieczonka, Tadeusz (2007-01-01)
The type, volume fraction, size, shape and arrangement of embedded particles influence the mechanical properties of the particle reinforced metal matrix composites. This presents the investigation of the SiC particle and porosity distributions in various aluminum matrix composites produced by cold- and hot-pressing. The inicrostructures were characterized by optical microscopy and stereological parameters. SiC and porosity volume fractions, and the anisotropy distribution function were measured to establish...
Two-Dimensional Numerical Analysis of Phosphorus Diffused Emitters on Black Silicon Surfaces
TÜRKAY, Deniz; Yerci, Selçuk (2018-07-06)
In this work, we present an analysis on electrical performance of phosphorus diffused emitters on black silicon surfaces through two-dimensional simulations. In particular, we focus on the extraction and analysis of the emitter saturation current density (J(0e)), the sheet resistance (R-sh), spatial collection efficiency profile and relatedly J(sc) of a solar cell. Using process simulations, we form emitters on periodic triangular structures with various aspect ratios (R) and emitter profiles. We show that ...
Studies on the modification of interphase/interfaces by use of plasma in certain polymer composite systems
Akovali, G; Dilsiz, N (Wiley, 1996-04-01)
Calcium carbonate and carbon fiber surfaces were modified by use of a series of plasma polymers at different selected plasma conditions, and the effect of surface modification, mainly on the mechanical properties of composite systems prepared, was investigated. The matrices for the composite systems employed were polypropylene and epoxy, for the chalk and C fiber, respectively. Mechanical and thermal studies and scanning electron microscopy (SEM) pictures revealed that inclusion surfaces, being independent ...
Numerical and experimental investigaton of ultrasonic embossing technique for fabrication of thermoplastic microfluidic devices
Çoğun, Ferah; Arıkan, Mehmet Ali Sahir; Yıldırım, Ender; Department of Mechanical Engineering (2018)
In this study, numerical models and experimental results were presented to describe mechanisms of hot embossing (HE) and ultrasonic embossing (UE) for fabrication of thermoplastic microfluidic chips. The substrates were embossed using micromilled aluminum molds in both techniques. Effects of embossing temperature, time, and force on performance outputs (replication rates and channel symmetry) were investigated numerically and experimentally in HE. Experimental results revealed the importance of temperature ...
Citation Formats
Y. Meyva Zeybek, “Studies on polylactide nanocomposites with polyhedral oligomeric silsesquioxane,” Thesis (Ph.D.) -- Graduate School of Natural and Applied Sciences. Polymer Science and Technology., Middle East Technical University, 2020.