Abstract: Two kinds of PLA with different oligomer contents were used to investigate the specific components of oligomer and the influence of its content on the melt spinning process of PLA. The chemical structure, melting and crystallization behavior and thermal stability of PLA, as well as the mechanical properties of its fibers were studied by using FTIR, 1H NMR, DSC, TG and yarn strength tester, respectively. Results show that the components of oligomer are lactide and PLA with low degree of polymerization. The glass transition temperature, melt temperature and crystallinity are decreased, while the half crystallization time of PLA is increased by the appearance of oligomers. However, the nucleation mode does not change. Besides, the initial degradation temperature of PLA is increased from 134.1 ℃ to 320.7 ℃, and the activation energy during the main stage of degradation is increased from 114.5 kJ/mol to 354.2 kJ/mol when oligomers are removed. What’s more, the strength-at-break of PLA fibers reaches up to 4.1 cN/dtex while the elongation-at-break maintains at 17.1% when drafted by 2.3 times.

Key words: oligomer, non-isothermal crystallization, thermal stability, melt spinning, PLA fiber