Pilot-scale production of polylactic acid nanofibers by melt electrospinning

AbstractMelt electrospinning has been used to manufacture fibers with diameters in the low micrometer range, but the production of submicrometer fibers has proven more challenging. In this study, we investigated the feasibility of fabricating polylactic acid nanofibers using polymer grades with the increasing melt flow rates (15–85 g/10 min at 210°C) by melt electrospinning with a 600-nozzle pilot-scale device featuring an integrated climate control system realized as a glass chamber around the spinneret. Previous experiments using this device without appropriate climate control produced fibers exceeding 1 µm in diameter because the drawing of fibers was inhibited by the rapid cooling of the polymer melt. The integrated glass chamber created a temperature gradient exceeding the glass transition temperature of the polymer, which enhanced the drawing of fibers below the spinneret. An average fiber diameter of 810 nm was achieved using Ingeo Biopolymer 6252, and the finest individual fiber (420 nm in diameter) was produced at a spin pump speed of 5 rpm and a spinneret set temperature of 230°C. We have therefore demonstrated the innovative performance of our pilot-scale melt-electrospinning device, which bridges the gap between laboratory-scale and pilot-scale manufacturing and achieves fiber diameters comparable to those produced by conventional solution electrospinning.

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

Textile Research Journal ◽

10.1177/0040517520904019 ◽

2020 ◽

Vol 90 (17-18) ◽

pp. 1948-1961

Author(s):

Kylie Koenig ◽

Stefan Hermanns ◽

Jacqueline Ellerkmann ◽

Katie Saralidze ◽

Fabian Langensiepen ◽

...

Keyword(s):

Polylactic Acid ◽

Fiber Diameter ◽

Sodium Stearate ◽

Polymer Degradation ◽

Pilot Scale ◽

Laboratory Scale ◽

Average Fiber Diameter ◽

Pump Speed ◽

Melt Electrospinning ◽

Spin Pump

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.

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The Effect of Dye and Pigment Concentrations on the Diameter of Melt-Electrospun Polylactic Acid Fibers

Polymers ◽

10.3390/polym12102321 ◽

2020 ◽

Vol 12 (10) ◽

pp. 2321 ◽

Cited By ~ 1

Author(s):

N.K. Balakrishnan ◽

K. Koenig ◽

G. Seide

Keyword(s):

Electrical Conductivity ◽

Polylactic Acid ◽

Electrical Resistance ◽

Polymer Melt ◽

High Viscosity ◽

Electrospinning Process ◽

Polymer Aggregates ◽

Melt Electrospinning ◽

Coarse Fibers ◽

Solution Electrospinning

Sub-microfibers and nanofibers produce more breathable fabrics than coarse fibers and are therefore widely used in the textiles industry. They are prepared by electrospinning using a polymer solution or melt. Solution electrospinning produces finer fibers but requires toxic solvents. Melt electrospinning is more environmentally friendly, but is also technically challenging due to the low electrical conductivity and high viscosity of the polymer melt. Here we describe the use of colorants as additives to improve the electrical conductivity of polylactic acid (PLA). The addition of colorants increased the viscosity of the melt by >100%, but reduced the electrical resistance by >80% compared to pure PLA (5 GΩ). The lowest electrical resistance of 50 MΩ was achieved using a composite containing 3% (w/w) indigo. However, the thinnest fibers (52.5 µm, 53% thinner than pure PLA fibers) were obtained by adding 1% (w/w) alizarin. Scanning electron microscopy revealed that fibers containing indigo featured polymer aggregates that inhibited electrical conductivity, and thus increased the fiber diameter. With further improvements to avoid aggregation, the proposed melt electrospinning process could complement or even replace industrial solution electrospinning and dyeing.

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Factors Influencing Diameter of Polypropylene Fiber in Melt Electrospinning

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.221.129 ◽

2011 ◽

Vol 221 ◽

pp. 129-134 ◽

Cited By ~ 6

Author(s):

Ming Feng Hao ◽

Yong Liu ◽

Xue Tao He ◽

Yu Mei Ding ◽

Wei Min Yang

Keyword(s):

Room Temperature ◽

Polypropylene Fiber ◽

Polymer Melt ◽

Environmentally Friendly ◽

Smooth Surfaces ◽

Optimum Point ◽

Factors Influencing ◽

Melt Electrospinning ◽

Solution Electrospinning ◽

Normal Processing

Melt electrospinning is a safer, more environmentally friendly and cheaper alternative to solution electrospinning in producing superfine fibers. In this paper, a novel melt electrospinning device was used, which has higher efficiency than conventional equipment. Polypropylene is widely used in many fields and it is difficult to find a suitable solvent for its solution electrospinning at room temperature, so it was chosen in this study. The influences of the electrospinning parameters such as temperature and voltage on the diameter of the spinning fibers have been studied. Temperatures higher than normal processing temperatures were used in present electrospinning system in order to reduce the viscosity of the polymer melt sufficiently. Good quality fibers with smooth surfaces and with diameters mostly smaller than 10 microns were spun successfully. It was found that there was an optimum point for the spinning voltage (70-80KV) and the temperature (230-260°C) to get fine fibers.

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Solvent-free preparation of polylactic acid fibers by melt electrospinning using umbrella-like spray head and alleviation of problematic thermal degradation

Journal of the Serbian Chemical Society ◽

10.2298/jsc110711027l ◽

2012 ◽

Vol 77 (8) ◽

pp. 1071-1082 ◽

Cited By ~ 26

Author(s):

Yong Liu ◽

Fengwen Zhao ◽

Chi Zhang ◽

Jianming Zhang ◽

Weimin Yang

Keyword(s):

Thermal Degradation ◽

Molecular Mass ◽

Polylactic Acid ◽

Relative Molecular Mass ◽

Degradation Temperature ◽

Melt Electrospinning ◽

High Efficient ◽

Before And After ◽

Diffraction Patterns ◽

Solution Electrospinning

Melt electrospinning is an even simpler and safer method compared with the solution electrospinning in the production of ultra-fine fibers. Polylactic acid (PLA) is a biodegradable and resorbable aliphatic ester that has received significant attention in recent years. PLA is easily degradable at high temperature in the process of melt electrospinning. High efficient fibers were made using our designed umbrella-like spray head spinning facility in this work. To find how to alleviate the problematic degradation and what factors could be relevant to degradation, temperature, relative molecular mass, Differential Scanning Calorimeter and X-ray Diffraction patterns before and after spinning were investigated and compared with each other. Results showed that fibers were facile shorten and fractured when spun at 245?C while the relative molecular mass of PLA fibers decreased markedly as compared with that spun at 210?C. To hinder the degradation, couple of experimental efforts were implemented with adding antioxidants, raising spinning voltage, lowering temperature, and reducing residence time. After such efforts, it was observed that the relative molecular mass of the PLA fibers was higher than those without inputting any efforts. The effect of antioxidant 1010 was found the most promising on the alleviation of PLA problematic thermal degradation.

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Effect of melt and solution electrospinning on the formation and structure of poly(vinylidene fluoride) fibres

RSC Advances ◽

10.1039/c7ra01299c ◽

2017 ◽

Vol 7 (29) ◽

pp. 17593-17598 ◽

Cited By ~ 12

Author(s):

Hanako Asai ◽

Marina Kikuchi ◽

Naoki Shimada ◽

Koji Nakane

Keyword(s):

Vinylidene Fluoride ◽

Melt Electrospinning ◽

Poly Vinylidene Fluoride ◽

Solution Electrospinning ◽

Conventional Solution ◽

Linear Laser

Linear laser melt electrospinning and conventional solution electrospinning.

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Pilot-Scale Production of Chito-Oligosaccharides Using an Innovative Recombinant Chitosanase Preparation Approach

Polymers ◽

10.3390/polym13020290 ◽

2021 ◽

Vol 13 (2) ◽

pp. 290

Author(s):

Chih-Yu Cheng ◽

Chia-Huang Tsai ◽

Pei-Jyun Liou ◽

Chi-Hang Wang

Keyword(s):

Cell Density ◽

Scale Up ◽

Cost Effective ◽

Pilot Scale ◽

Ionic Concentration ◽

Dihydrogen Phosphate ◽

Scale Production ◽

Sodium Dihydrogen Phosphate ◽

Selective Precipitation ◽

Pilot Scale Production

For pilot-scale production of chito-oligosaccharides, it must be cost-effective to prepare designable recombinant chitosanase. Herein, an efficient method for preparing recombinant Bacillus chitosanase from Escherichia coli by elimination of undesirable substances as a precipitate is proposed. After an optimized culture with IPTG (Isopropyl β-d-1-thiogalactopyranoside) induction, the harvested cells were resuspended, disrupted by sonication, divided by selective precipitation, and stored using the same solution conditions. Several factors involved in these procedures, including ion types, ionic concentration, pH, and bacterial cell density, were examined. The optimal conditions were inferred to be pH = 4.5, 300 mM sodium dihydrogen phosphate, and cell density below 1011 cells/mL. Finally, recombinant chitosanase was purified to >70% homogeneity with an activity recovery and enzyme yield of 90% and 106 mg/L, respectively. When 10 L of 5% chitosan was hydrolyzed with 2500 units of chitosanase at ambient temperature for 72 h, hydrolyzed products having molar masses of 833 ± 222 g/mol with multiple degrees of polymerization (chito-dimer to tetramer) were obtained. This work provided an economical and eco-friendly preparation of recombinant chitosanase to scale up the hydrolysis of chitosan towards tailored oligosaccharides in the near future.

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