密度對竹材聚乳酸複合材料物理機械及生物降解性質之影響

Effects of Density on Physicomechanical and Biodegradable Properties of Bamboo-Polylactic Acid Composites

本研究利用桂竹（Phyllostachys makinoi）加工廢料、回收型聚乳酸（Recycled polylactic acid，rPLA）製備竹材聚乳酸複合材料（Bamboo-PLA composite，BPC）。同時，利用萬能強度試驗機、示差掃描熱分析儀、膠體滲透層析儀及色差計等儀器，探討密度對複合材料物理機械（Physicomechanical）及生物降解性質之影響。試驗結果顯示，BPC之吸水率隨著密度增加而減少，其抗彎強度及抗彎彈性模數則隨著密度的增加而增加；其中，密度900 kg/m3 者具有最佳之抗彎強度（26.1 MPa）及抗彎彈性模數（3.9 GPa）。而在生物降解性質方面，由BPC之質量損失率試驗結果得知，以密度500 kg/m3 者之損失率最大，經360 d土壤掩埋試驗後，其質量損失率達44%，此現象與複合材吸水率具相關性。此外，不同密度BPC之基質（rPLA）數量平均分子量（Mn），均隨著土壤掩埋時間增加而減少。以密度700 kg/m3 之BPC為例，經360 d的掩埋後，rPLA之Mn由42 kg/mol下降至約16 kg/mol，顯示BPC經土壤掩埋試驗後能有效地降解。 In this study, makino bamboo (Phyllostachys makinoi) residue and recycled polylactic acid (rPLA) were used as raw materials to manufacture bamboo-PLA composite (BPC). Effects of density on flexural, thermal and biodegradable properties of BPC were evaluated by universal testing machine, differential scanning calorimetry (DSC), gel permeation chromatography, and color difference meter, etc. These results showed that the water absorption of BPC decreased and the modulus of rupture (MOR) and modulus of elasticity (MOE) of BPC increased with increasing composite density. Among all BPCs, the BPC with a density of 900 kg/m3 exhibited the strongest MOR (26.1 MPa) and MOE (3.9 GPa). As for the biodegradability, after 360 d of burial soil test, the BPC with a density of 500 kg/m3 exhibited the highest mass loss (44%). This phenomenon may be correlated with water absorption behavior of composites. Regardless of BPC density, the number-average molecular weight (Mn) of PLA matrix in BPC decreased with increasing degradation time. As an example of the BPC with a density of 700 kg/m3, the Mn of rPLA decreased from original 42 to 16 kg/mol after 360 d of burial soil test. This result indicated that BPC can be degraded effectively undergoing burial soil test.