Analysis of Porous Electrospun Fibers from Poly(l-lactic acid)/Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Blends (original) (raw)
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Tailoring Crystallinity of Electrospun Plla Fibres by Control of Electrospinning Parameters
Polymers, 2012
Poly(L-lactic acid) (PLLA) fibers were fabricated by electrospinning. The effects of various electrospinning process parameters on the thermal properties, especially the crystallinity of the electrospun fibers were investigated. Thermal analysis of the fibers revealed that they exhibited degree of crystallinity ranging from 23% to 46% while that for the as-received granules was approximately 37%, suggesting that the crystallinity of electrospun PLLA fibres can be controlled by optimizing the electrospinning process. This finding is very important because crystallinity affects polymer properties such as degradation, stiffness, yield stress, modulus and tensile strength, solubility, optical and electrical properties which will in turn affect the behavior of these materials when they are utilized in energy, environment, defense and security applications. The results presented in this paper show that the degree of crystallinity of the electrospun fibers decreased with increasing the polymer solution concentration. Furthermore, an optimum electrospinning voltage at which maximum degree of crystallinity can be obtained was observed. At voltages higher or lower than the optimum electrospinning voltage, the degree of crystallinity will decrease or increase, respectively. The effect of the needle tip to collector distance (NTCD) on the degree of crystallinity follows no predictable and consistent pattern.
Porous electrospun polycaprolactone fibers: Effect of process parameters
Journal of Polymer Science Part B: Polymer Physics, 2016
The effect of electrospinning process parameters (solution flow rate, applied voltage, spinning distance) on the size and surface morphology of porous electrospun poly(ε-caprolactone) was investigated in this study. Response surface methodology was implemented for the design and conduction of electrospinning experiments. The feed solution was a 12.5% w/v poly(ε-caprolactone) (PCL) solution in a binary solvent mixture of 90%v/v chloroform/ dimethyl sulfoxide. Spinning distance of 10-25 cm, applied voltage of 10-25 kV and feed flow rate of 0.5-5 ml/h were the range of limiting values of the independent variables used for the development of a central composite design. Second order polynomial equations, correlating electrospinning process parameters to relative pore coverage and fibre average diameter were developed and validated. An increase in any of the electrospinning process parameters favoured pore formation and fibre diameter increase. Under the experimental conditions investigated, the relative pore surface coverage was 15.8-31.9% and the average fibre diameter was in the range of 1.6-3.3 μm. Applied voltage was proven to be the parameter with the strongest impact on both, fibre diameter and surface morphology.
Polymer Engineering & Science, 2013
Poly(hydroxybutyrate) (PHB) obtained from sugar cane was dissolved in a blend of chloroform and dimethylformamide (DMF) and electrospun at 40 ºC. By adding DMF to the solution, the electrospinning process for the PHB polymer becomes more stable, allowing complete polymer crystallization during the jet travelling between the tip and the grounded collector. The influence of processing parameters on fiber size and distribution was systematically studied. It was observed that an increase of tip inner diameter promotes a decrease of the fiber average size and a broader distribution. On the other hand, an increase of the
Open Journal of Polymer Chemistry, 2019
We studied the electrospinning process of the blend of polylactic acid (PLA) and polybutylene succinate (PBS). The blend PLA/PBS ratio 95/5, 90/10, 85/15 and 80/20 wt% were prepared by dissolved in mixture of solvent between dichloromethane (DCM) and N, N-dimethylformamide (DMF) at ratio 3/1. The suitable condition for electrospun of the blend was 17% wt concentration, 16 kV and 18 cm projection distance. The round fiber with pore on the surface was observed. Increasing content of PBS in the blend impact to the diameter of fibril decreased from 1350, 1290, 1210 and 1170 nm, respectively; while the pore on the surface changes from circle to oval shape. Regarding the thermal properties, blending of PBS increases the glass transition temperature (T g) of PLA without affect to the melting temperature (T m) of the electrospun nanofibers. The best tensile properties of PLA/PBS nanofibers were achieved at blend ratio of 95/5, and Young's modulus is increased comparing to those of the pure electrospun fibers.
Organic and Inorganic PCL-Based Electrospun Fibers
Polymers
In this work, different nanocomposite electrospun fiber mats were obtained based on poly(e-caprolactone) (PCL) and reinforced with both organic and inorganic nanoparticles. In particular, on one side, cellulose nanocrystals (CNC) were synthesized and functionalized by “grafting from” reaction, using their superficial OH– group to graft PCL chains. On the other side, commercial chitosan, graphene as organic, while silver, hydroxyapatite, and fumed silica nanoparticles were used as inorganic reinforcements. All the nanoparticles were added at 1 wt% with respect to the PCL polymeric matrix in order to compare the different behavior of the woven no-woven nanocomposite electrospun fibers with a fixed amount of both organic and inorganic nanoparticles. From the thermal point of view, no difference was found between the effect of the addition of organic or inorganic nanoparticles, with no significant variation in the Tg (glass transition temperature), Tm (melting temperature), and the degr...
Surface morphology of electrospun PLA fibers: mechanisms of pore formation
The article elucidates the mechanisms of formation of varying degrees of surface pores/pits on polylactic acid (PLA) fibers during electrospinning. The role of a combination of different parameters in governing pore formation was demonstrated. They include solvent vapor pressure (pv), solvent miscibility/interaction with water, solubility parameter, and relative humidity (RH) within the spinning unit. Our results indicated that traditional mechanisms like thermally induced phase separation (TIPS) and vapor induced phase separation (VIPS) were not responsible in the generation of surface porosity/pits. Instead, higher RH (water vapor, a non-solvent of the polymer), and its miscibility/interaction with solvent(s) were concluded to be relatively more important than the simple presence of a high pv solvent or a combination of high pv and low pv solvent system. Further, content of high pv solvent in solution determined the spherical or elliptical nature of pores/pits by affecting the level of saturation of nearby region of the interface between jet and air during the electrospinning process.
Porous electrospun polycaprolactone (PCL) fibres by phase separation
European Polymer Journal, 2015
Porous electrospun poly(e-caprolactone) (PCL) fibres were produced through a non-solvent induced phase separation mechanism, using binary solvent systems with different properties. The effect of the solvent properties on the size and surface morphology of electrospun PCL fibres was investigated. Chloroform (CF), dichloromethane (DCM), tetrahydrofuran (THF) and formic acid (FA) were used as good solvents in mixtures with a poor solvent, dimethyl sulfoxide (DMSO), in order to generate pores on the fibre surface. The production of porous, bead free fibres with an average diameter ranging from 1470 to 2270 nm was achieved using 12.5% w/v PCL in CF/DMSO solution with good/poor solvent ratios varying from 75% to 90% v/v at the applied voltage of 15 kV, a spinning distance of 20 cm, and the feed flow rate of 1 ml/h. DCM and THF were proven to be less suitable good solvents for the process due to the formation of a solid skin on the jet surface, caused by the limited diffusivity of the polymer molecules from the jet surface to the liquid core and its subsequent collapse. FA was found to be unsuitable due to its similar evaporation rate to DMSO. The pore formation was favoured at high good/poor solvent ratios, whereas, the production of fibres with ribbon cross sections or fibres with beads was more pronounced at low good/poor solvent ratios. Data fitting was used for the development of a second order polynomial equation, correlating the produced fibre average diameter to the solution parameters (conductivity, surface tension, and viscosity), for the given polymer and solvent systems, under the specific experimental conditions used in this study. The ternary mixture compositions that lead to the formation of porous fibres were mapped on a ternary graph.
Applied Sciences
Polycaprolactone (PCL) is one of the most used synthetic polymers for medical applications due to its biocompatibility and slow biodegradation character. Combining the inherent properties of the PCL matrix with the characteristic of nanofibrous particles, result into promising materials that can be suitable for different applications, including the biomedical applications. The advantages of nanofibrous structures include large surface area, a small diameter of pores and a high porosity, which make them of great interest in different applications. Electrospinning, as technique, has been heavily used for the preparation of nano- and micro-sized fibers. This review discusses the different methods for the electrospinning of PCL and its composites for advanced applications. Furthermore, the steady state conditions as well as the effect of the electrospinning parameters on the resultant morphology of the electrospun fiber are also reported.
Effect of Polymer Concentrations on Pores Mechanism in Electrospun Fibre
Journal of Materials & Environmental Sustainability Research
Advanced material science has resulted in materials with atomic-scale dimensions whose tremendous application includes filtration, drug delivery, membrane, sensor, and encapsulation. Nanoporous fibre has been formed using temperature-induced phase separation (TIPS) and vapour-induced phase separation (VIPS) mechanism, but polymer concentration has been underestimated in the electrospinning parameter. This work aims at showcasing the effect of electrospinning parameters including polymer concentration and resultant phases on pore formation on fibre. Pore formation in electrospun fibre was carried out by electrospinning expanded polystyrene (EPS). The surface morphology of the resulting nanoporous fibre was characterized with Scanning Electron Microscope (SEM) while the pore distribution was analyzed with a BET (Brunauer, Emmet, Teller) micromeritics analyzer. From the result, an increased concentration of polymer from 10 % decreased bead population to zero, meanwhile, bombardment wit...