engleski

DEVELOPMENT OF ADVANCED POLYLACTIDE NANOBIOCOMPOSITE REINFORCED WITH Spartium junceum L. FIBRES

The main goal of this thesis was to develop biodegradable composite material of sustainable origin for possible usage in automotive industry. Increased demand for usage of sustainable and biodegradable natural materials initiated wider production of biocomposites. For that reason, composite materials made of sustainable polylactide (PLA) polymer and Spartium junceum L. (SJL) bast fibres were designed and produced in the course of research for this thesis. Three fibre extraction (maceration) methods were investigated: water retting (WR), osmotic degumming (OD) and alkali retting under the influence of microwave energy (MW). It was proven that long lasting conventional maceration method can be succesfully replaced by ecologically favourable method using microwaves. Tensile strength of MW treated fibres show approximately 60 % higher strength compared to conventional WR and 30 % compared to novel OD method. Functionalization of fibres was carried out using montmorillonite (MMT) nanoclay particles added as a flame retardant nanofiller, and citric acid (CA) as an environmentally friendly crosslinker. Effectiveness of the conducted modifications was examined according to the relevant standardized methods used in current industrial and manufacturing processes (testing of morphological, mechanical, chemical and thermal properties of the final composite material). MMT/CA modified fibres show better thermal stability in comparison to the reference fibre (MWR) which is confirmed with the increase in crystallinity and proved by thermogravimetric analysis by shifting of fibre's onset decomposition temperature to higher value. Fibre/polymer interface was also positively influenced by MMT/CA fibre modification. Therefore, such material has showed higher decomposition temperature at certain weight loss, as well as higher strength and modulus values in comparison to samples without CA. The results indicate formation of crosslinking caused by interactions between the carboxylic acid and –OH groups of cellulose fibre or PLA. Biodegradability of developed composite materials was examined with serine endopeptidase. Concentration of 50 wt% enzyme reveals very positive result of composite degradation. After 5 days of enzymatic treatment, composite material reinforced with MMT/CA modified fibres lost 2.5 % of its initial weight. Additionally, the possibility of residue stem utilization in bioenergy production was investigated. Proximate and ultimate analysis of residues after MW maceration showed increase in content of positive biomass quality indicators. The obtained results confirmed SJL biomass as promising feedstock for solid biofuel production. The significance of the proposed research lies in the application of innovative, sustainable raw materials for the production of new advanced products of wide application.

Spartium junceum L. ; PLA ; sustainability ; green composites ; nanoparticles ; flame retardant ; biodegradation ; bioenergy ; solid biofuel

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