The effect of additives and process parameters on the pilot-scale manufacturing of polylactic acid sub-microfibers by melt electrospinning

Abstract

Sub-microfibers are polymer filaments less than 1 µm in diameter that can be fabricated into highly flexible materials with a large specific surface area. They are often produced by solvent or melt electrospinning. The former is a scalable process that produces thinner fibers but requires hazardous solvents, whereas the latter is more environmentally sustainable due to the absence of solvents but is more challenging to scale up. Here we investigated the manufacturing of biobased polylactic acid (PLA) sub-microfibers by melt electrospinning using a single-nozzle laboratory-scale device and a novel 600-nozzle pilot-scale device combined with conductive and viscosity-reducing additives: sodium stearate (NaSt), sodium chloride (NaCl) and a polyester-based plasticizer. We determined the effect of different additive concentrations on fiber diameter, thermal properties, polymer degradation, and fiber deposition. At the laboratory scale, the minimum average fiber diameter (16.44 µm) was accomplished by adding 2% (w/w) NaCl, but a stable spinning process was not achieved and the plasticizer did not reduce the melt viscosity. NaSt was the most effective additive in terms of adapting the material properties of PLA for melt electrospinning, but extensive polymer degradation occurred at higher temperatures and with higher concentrations of the additive. At the pilot-scale, the minimum average fiber diameter (3.77 µm) was achieved by adding 6% (w/w) NaSt, with a spinneret temperature of 195℃ and a spin pump speed of 0.5 rpm (0.16 cm3), without further improvements such as the integration of a heating chamber. The smallest single-fiber diameter (1.23 µm) was achieved under the same conditions but using a spin pump speed of 2 rpm. The scaled-up melt-electrospinning device therefore offers significant potential for the production of biobased sub-microfibers, bridging the gap between laboratory-scale and pilot-scale manufacturing.

The Effect of Electrical Polarity on the Diameter of Biobased Polybutylene Succinate Fibers during Melt Electrospinning

“…Several challenges must be overcome to achieve the larger-scale production of nanofibers [ 12 , 13 , 14 ]. One of these challenges is the high viscosity and low electrical conductivity of polymer melts [ 13 , 15 , 16 , 17 ], which can be addressed in part by the inclusion of additives [ 18 ]. For example, in our previous study, we investigated the use of curcumin and silver nanoparticles as multifunctional additives to reduce the viscosity of molten polybutylene succinate (PBS) while increasing its electrical conductivity [ 11 ].…”

Detailed Process Analysis of Biobased Polybutylene Succinate Microfibers Produced by Laboratory-Scale Melt Electrospinning

“…Solution electrospinning with PBS and PLA has successfully yielded fibers with average diameters in the sub-micrometer range for biomedical applications such as wound dressings. Melt electrospinning has also been carried out with PLA, but the brittleness and low conductivity of the material hinder the production of nanofibers and their applications, and various machine and material modifications have been tested to overcome this [27][28][29][30][31][32][33][34][35][36][37]. Compared to PLA, PBS is more ductile with a lower glass transition temperature (below room temperature).…”

Detection of Limbal Stem Cells Adhered to Melt Electrospun Silk Fibroin and Gelatin-Modified Polylactic Acid Scaffolds

“…Similarly, studies concerning melt electrowriting of PLA reported difficulties in the accurate positioning of the PLA fibers due to high PLA viscosity [ 44 ]. Some authors reported the addition of sodium stearate to reduce the melt viscosity of PLA during electrospinning, which also resulted in a reduction of fiber diameter [ 45 ].…”