Effects of hot airflow on macromolecular orientation and crystallinity of melt electrospun poly(L-lactic acid) fibers

Xiuhong Li, Yong Liu*, Hao Peng, Xiaojing Ma, Hao Fong*

Abstract：The aim of this study was to prepare melt electrospun poly(L-lactic acid) (PLLA) fibers with relatively high macromolecular orientation and crystallinity (thus relatively high mechanical properties) for future biomedical studies. Upon melt electrospinning PLLA fibers in hot airflow, the elevated environmental temperature was acquired; and the filaments/fibers could be stretched by the hot airflow and/or for a prolonged period of time. The effects of speed and temperature of hot airflow on macromolecular orientation and crystallinity of PLLA fibers were investigated, and the results indicated that the PLLA fibers with higher degrees of macromolecular orientation and crystallinity could be prepared under the condition of hotter airflow having faster speed.

Fig. 1. (A) A schematic representation showing the melt electrospinning apparatus with a hot air flow system,and (B) an illustration depicting the details of spinneret (1: plunger, 2: barrel, 3: heatingcoil, 4: thermalcouple, 5: polymermelt, and 6: frustum nozzle with upper and lower pieces).

Fig. 3. DSC (A) and XRD (B) curves acquired from the PLLA fibers melt electrospun (a) without hot air flow,(b) with 120 °C hot air flow having slow speed, and (c) with 120 °C hot air flow having fast speed.