Characterization and statistical study of compatibilized poly (lactic acid) /polypropylene / graphene nanoplatelets nanocomposites / Farah Hafidzah Ahmad

Faculty of Chemical and Process Engineering Technology

Thesis (Master of Science) -- Universiti Malaysia Pahang – 2021

Includes bibliographical references

Many researchers gave much attention to new biodegradable material from a renewable source to ease the impact of petroleum-based conventional materials. One of them is poly (lactic acid) (PLA), a commonly used material nowadays due to its high strength and modulus. However, its brittle thermoplastic features have led to limit its wide application. Polypropylene (PP) polymer was chosen to be blended with PLA to overcome the limitation. But, the combination of both materials was immiscible, which led to poor tensile strength. Various amount of polypropylene-grafted-maleic anhydride (PP-g-MA) and graphene nanoplatelets (GNP) were used to investigate their influence on the PLA/PP blends. Both of PP-g-MA and GNP were loaded into PLA/PP blends at 1 to 7phr and 1 to 5phr respectively. In this study, all the samples were fabricated using injection moulding machine and characterized for the mechanical properties, thermal properties, crystallinity, chemical structure changes, and morphology. Besides that, a statistical study also conducted to study the relationship between PP-g-MA and GNP in various ratio of PLA/PP blends using a full-factorial design (FFD). A remarkable improvement in the ductility of PLA/PP blend was achieved by adding a PP-g-MA up to 5phr. The elongation at break of the compatibilized PLA/PP blend are 18% and 59% higher than those of uncompatibilized PLA/PP and PLA, respectively. The tensile strength of compatibilized blends also improved as well but Young's modulus reduced. The thermogravimetric analysis (TGA) showed that the thermal stability significantly increased as the PP-g-MA was loaded in blends. Differential scanning calorimetry (DSC) results showed changed in the glass transition temperature (Tg) and cold-crystallization temperature (Tcc), but maintaining its melting temperature (Tm). PP-g-MA had dropped the degree of crystallinity (Xc), but it still does not affect the strength of the blends produced. The Fourier- Transform Infra-red (FTIR) spectrum was also confirmed that there was the interaction between PP-g-MA and PLA/PP blends. In that case, it was observed that PP had more dispersed in the matrix blends. The reinforcement of GNP also provided significant improvement in the blend's properties. GNP incorporation has increased the Young’s modulus and strength from 1 to 3phr, but the percentage elongation at break was reduced. The thermal stability and properties of the blend nanocomposites also were improved as well. However, Xc values were reduced. The Raman spectra were confirmed that no GNP damage after the injection molding process since D, G, and 2D were detected. The surface morphology showed significant changes, which indicates that the blend had been reinforced with GNP. Besides all these analyses, the statistical study also proved that there had an interaction factor of PP-g-MA with GNP at various PP/PLA blends ratios that causes a positive impact on the tensile strength of PLA/PP blends. Lastly, the PLA/PP/PP-g-MA/GNP nanocomposites with 5phr PP-g-MA and 3phr GNP was the best composition among others