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Научни трудове на Съюза на учените в България-Пловдив. Серия В. Техника и технологии, т. XV, ISSN 1311 -9419 (Print), ISSN 2534-9384 (On- line), 2017. Scientific Works of the Union of Scientists in Bulgaria-Plovdiv, series C. Technics and Technologies, Vol. XV., ISSN 1311 -9419 (Print), ISSN 2534-9384 (On- line), 2017.
ПОЛУЧАВАНЕ И ОХАРАКТЕРИЗИРАНЕ НА НЕТЪКАНИ Ш1АКНЕСТИ МАГЕРИАЛИ ОТ ПОЛИ (З-ХИДРОКСИБУТИРАТ)
ВЪРХУ КИЛЕКТОРИ С РАЗЛИЧНА ГЕОМЕТРИЯ Ирена Борисова, Оля Стоилова, Илия Рашков, Невена Манолова Лаборатория Биологично активни полимери, Институт но полимери, Българска аридемия на наукоте, ул. акад.Л.Бончеврбл.ТРЗА, ON1P
Слфия, Бълггрия
PRECAI^TIONAND CHAIVaCTEbPATION OF NON-WOVEN FIBROUS MATERIALS FROM POLY(3-HYDROXYBUTYRATE) ONTO PDTTERNED COLLECTORS Inna Bnrisora, Olya Iliya
Laboratory of Bioactive Polymers , Institute of Polymers, Bulgarian Academy of Sciences, Acad. G. Bonchev St, bl. 103A, 1113 Sofia, Bulgaria
Abstract
Phc extensive and dynamic development iL the nanitechniIigies has led ti the creation iL a new generation advanced materials with unique features. NaoiLiarias pilymer materials prepared by cIcrtrIsp]oo]og - a cattingaedge technique fir simple and efficient eabricatiin if pilymer Liaers with diameters in the micro- and naniscale, and extremeIy high aspect ratii are such kind if materials. Phe present research is ficased in study if the pissiailities fir improving the phDsirIaTcrhaoiraI properties if pIID(3ahDdroxDaatDrate) (LH4) materials iatained ay cIcrtrosp]oo]og using twi types if patterned rotating cillectirs - drum and aiade cillectiri Phe materials are hased in LH4 matrix auilt if micro- ir oaoIe]aroas oio-wivco textile with tailired structurei PhcrcaD, the effect if the cillectir gCIтctrD in the structure if LH4 oio-wivco textile, as well as the dependence in the rIтpIsitiIo-strartarc-propcrtics if these materials is studied.
Keywirds: eIectrisp]nn]ng, pIID(3ahDdroxDaatDrate), patterned rotating ciIIectirs, mechanical properties.
Introductiin
Recently, an abrupt increase in the number of studies on electraspun materials has been observed, since they possess specific properties related to their size and their exceptionally large specific area. It is well known that the mechanical properties of the electrospun materials depend on diverse parameters [1]. A key factor is the structure and the achievement of a certain alignment of the fibers that compose the non-woven textile during the electrospinning process [2].
Poly(3-hydroxybutyrate) (PHB) is worthy of special interest as promising polymer obtained from renewable sources. Because of its high crystallinity, PHB materials are stiff and brittle, and thus results in very poor mechanical properties with a low extension at break [3,4]. In this respect, the present research is focused on study of the possibilities for improving the
mechanical properties of PHB-based materials obtained by electrospinning using different types of patterned rotating collectors - drum and blade. The effect of the collector rotation rate and geometry onto the alignment of the fibers and on the mechanical properties (tensile strength) of the electrospun PHB-based materials is studied. The effect of the position of cutting the specimens in respect to the direction of collector rotation on the tensile properties is assessed.
Materials and methods
Poly(3-hydroxybutyrate) (PHB, 330000 g/mol), chloroform (CHCls) and N,N-dimethylformamide (DMF) were of analytical grade and used without further purification. For the fabrication of PHB-based non-woven fibrous materials a solution of PHB (14% w/v) in CHQ3/DMF (4/1 v/v) was prepared by heating at 60°C and further were used as a spinning solution. Electrospinning of the PHB was performed at 25 kV applied voltage, spinneret-to-collector distance of 25 cm and feeding rate of 3 ml/h. For the fabrication of non-woven textile with tailored structure two types of patterned rotating collectors - drum (conventional) and blade, were used. In order to achieve desired alignment of the PHB fibers, the speed of the collectors was varied (600 or 2200 rpm).
Results and discussion
It is known that the fibrous materials from PHB prepared by electrospinning by means of conventional rotating collector are characterized by poor mechanical properties [5]. Thus, the working hypothesis is that the electrospinning of PHB onto patterned rotating blade collector and at various speeds will enable the preparation of a non-woven textile with well-defined morphology and tailored fibers alignment as shown in Figure 1. In this respect, a series of electrospun non-woven fibrous materials based on PHB onto drum and blade rotating collectors and at various collector speeds were fabricated.
Figure 1. Schematic representation of fibers obtained at rotation rate below (left) and above (right) 1500 rpm
Morphological and structural characteristics, as well fiber orientation of these materials were observed by scanning electron microscopy (using a Philips SEM 515). The electrospinning onto drum rotating collector at 600 rpm caused obtaining of randomly oriented PHB fibers (Figure 2A). As can be seen, the increase of the drum collector speed to 2200 rpm resulted in an arrangement of the PHB fibers along the drum collector rotation direction (Figure 2B). It was found that between the blades, PHB fibers were randomly deposited at 600 rpm (Figure 2C), whereas at 2200 rpm they were aligned along the blade collector rotation direction (Figure 2D). Therefore, by varying the collector speed and the type of the collector an additional fibers alignment in collector rotation direction was achieved.
Figure 2. SEM micrographs of PHB fibrous materials obtained onto drum (A, B) and blade rotating collectors (C, D) at 600 rpm (A, C) and 2200 rpm (B, D) collector rotating rate. The arrows show collector rotation direction
In order to study the effect of the collector geometry on the mechanical properties of PHB non-woven textile, the tensile testing was performed on a single column system for mechanical testing INSTRON 3344, equipped with a loading cell of 50 N, at room temperature and extension rate of 20 mm/min. The testing was carried out using specimens cut out with 20x60 mm dimensions, at a constant loading rate based on 10 measurements. All specimens were cut in the direction of collector rotation, since cutting the specimens in this direction yields the best results for mechanical properties of the electrospun materials [6]. The obtained stress-strain curves are shown in Figure 3. Clearly, the increasing the collector speed from 600 rpm to 2200 rpm leads to enhancement of the strength of the electrospun PHB materials obtained onto patterned collectors. Based on the obtained stress-strain curves the values of the modulus of elasticity (E, MPa), tensile strength (a, MPa) and the elongation at break (eb, %) were determined, as well. It should be noted that the materials prepared at higher collector speed (2200 rpm) were characterized by higher values of the modulus of elasticity compared to those at lower speed (600 rpm). It was found that the Young's modulus in both types of PHB materials obtained at 2200 rpm increased two times compared to that at 600 rpm. In addition, the elongation at break also increased 1.4 times at higher collector rotation rate.
A B
Figure 3. Stress-strain curves of PHB fibrous materials obtained onto drum (A) and blade (B) rotating collectors at 600 rpm and 2200 rpm collector rotation rates
Conclusions
Non-woven fibrous materials from PHB onto patterned collectors were prepared by electrospinning and characterized. It was shown that certain alignment of the fibers that compose the PHB non-woven textile might be successfully achieved by using the patterned collectors and by varying their rotation rate. Moreover, it is a suitable approach for improvement the strength of the electrospun PHB materials.
References
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2. F. Chen, Y. Su, X. Mo, C. He, H. Wang, Y. Ikada, J. Biomat. Sci. 20, 2117-2128, 2009.
3. Y. Poirier, D. E. Dennis, Ch. Nawrath, Ch. Somerville, Adv. Mater. 5, 30-37, 1993.
4. Y. Kumagai, Y. Doi, Polym. Degrad. Stability, 36, 241-248, 1992.
5. M.P. Arrieta, J. Lopez, D. Lopez, J.M. Kenny, L. Peponi, Eur. Polym. J. 73, 433-446, 2015.
6. M. Kancheva, A. Toncheva, N. Manolova, I. Rashkov, eXPRESSPolym. Lett. 9, 49-65, 2015.
Acknowledgements: Financial support from the National Science Fund (Grant DN 09/2, 14.12.2016) is kindly acknowledged.
e-mail stoilova@polymer.bas.bg
