Effect of molecular weight on the properties and structure of biodegradable Poly-lactic acid melt-blown nonwovens

Abstract This work has successfully prepared biodegradable poly-lactic acid (PLA) melt-blown nonwovens with varying molecular weights through the process of melt spinning. To achieve a reduced molecular weight PLA, the Lewis acid Tin (II) 2-ethyl hexanoate (Sn(Oct)2) was employed for degradation. The investigation encompassed the phase morphology, rheological behavior, hydrophobicity, and crystalline characteristics of the melt-blown nonwovens. The examination of crystallization characteristics revealed that PLA molecules with lower molecular weights, comprising shorter-chain segments, exhibit enhanced mobility. Consequently, these molecules tend to crystallize more readily, resulting in a higher degree of crystallinity. Polarized optical microscopy (POM) analysis demonstrates that PLA with lower molecular weights generates the largest spherical crystal size within the same time frame. The storage modulus (G′), loss modulus (G′′), and complex viscosity |η*| were increased with the increase in molecular weight from rheological measurement. The increase in viscosity led to an increase in the distribution of melt-blown nonwoven fiber diameters, and the average diameter increased from 11.86 to 21.07 μm. Furthermore, it triggers a reduction in the water contact angle (WCA), causing it to drop from 128.9° to 114.9°.