# Effect of MDI on the Mechanical Properties of Fibers in Poly(lactic acid)/Poly(butylene succinate) Blends During Melt Spinning

## TL;DR

This study shows that adding MDI improves the mechanical properties of PLA/PBS blend fibers during melt spinning.

## Contribution

The novel finding is that MDI enhances the miscibility and mechanical performance of PLA/PBS blends in fiber production.

## Key findings

- Increasing MDI content improved thermal stability, viscosity, and elastic properties of the blend.
- Tensile strength and elongation of fibers increased by 17% and 85%, respectively, with higher MDI content.
- MDI addition reduced phase separation and enhanced the practical usability of PLA/PBS fibers.

## Abstract

In this study, the properties of poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) blends were analyzed according to the PBS content during the manufacture of the blend. However, the inherent immiscibility between PLA and PBS often leads to phase separation and limited mechanical performance, particularly in melt-spun fiber applications, which restrict their practical use. To increase the miscibility of the PLA/PBS blend, methylene diphenyl diisocyanate (MDI) was added up to 0.8 wt.%, and the characteristics were analyzed via thermogravimetric analysis, differential scanning calorimetry, viscosity measurements, dynamic mechanical analysis, and Fourier-transform infrared spectroscopy. As the PBS content in the blend increased, the thermal stability, viscosity, elastic properties, and glass transition temperature decreased. In contrast, as the MDI content in the PLA/PBS blend increased, the thermal stability, viscosity, elastic properties, and glass transition temperature increased. The results revealed that the miscibility of the PLA/PBS blend increased as the MDI content in the blend increased. Additionally, the tensile strength and elongation of the PLA/PBS blend fibers manufactured through melt spinning were analyzed. While the tensile strength decreased as the PBS content increased, the tensile strength and elongation considerably improved as the MDI content in the blend increased. Specifically, the tensile strength of the PLA/PBS blend fibers increased from 2.55 to 2.99 gf/de, corresponding to an improvement of approximately 17%, while the elongation at break increased from 22.48% to 41.64%, representing an enhancement of approximately 85% with increasing MDI content.