Biorefinery lignin as filler material in polylactic acid composite

In natural world, lignin is unique and the most abundant renewable carbon source after cellulose, therefore, more applications of adding commercial value of lignin are needed. Polylactic acid (PLA), which has the second highest consumption of bioplastic in the world, is a biodegradable composite with widely application in industry. A filler adding into PLA can decrease the cost of the composite, and change the mechanical and thermal properties compared with original pure PLA. In this thesis report, the objective is to analysis how a lignin-based filler could influence the mechanical and thermal properties of PLA composite. In Chapter 2, hydrochloric acid wash was applied to reduce the ash content of Lignin from 7% to 4% and 2%. TGA, FTIR, ICP, MPT and elemental analysis tests were applied to analysis the basic properties of lignin and pure PLA. Then, lignin with 2%, 4% and 7% ash content were applied as fillers in PLA composite with 5%, 10% and 15% weight percentage, respectively. The extruded mixed composite was produced into films to test thermal and mechanical properties by TGA, FTIR and MPT tests, including decomposition temperature, tensile strength, modulus, and strain of lignin-PLA composite. Same tests were also applied in Chapter 3. In Chapter 3, lignin with 4% ash content was acetylated to remove hydroxyl group before it was added into PLA as filler to produce films. The results were compared with the ones in Chapter 2. Also, films made by pure PLA, 4% ash content and 5wt% lignin filler, and 4% ash content and 10wt% acetylated lignin filler were heated at 40C for 48 and 72 hours. Results showed that compared to pure PLA, adding lignin-based filler would decrease