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Abstract:
In the current study, the key role of incorporation of starch nanocrystals (SNC) and modified acetylated starch nanocrystals (ASNC) on mechanical, physical, and biological properties of low-density polyethylene/thermoplastic starch/polyethylene-grafted-maleic anhydride (LDPE/TPS/PE-g-MA) blend was individually investigated. To achieve this, SNC was successfully extracted from waxy maize starch by chemical treatment utilizing acid hydrolysis. The results of solubility of the modified specimens showed that the hydrophilicity of ASNC was well reduced by dispersion enhancement in non-polar solvents, which was also proved by increasing considerably the contact angle, after modification, 37.9° ± 3.5° to 59.9° ± 3.1°. It was noticed that the mechanical properties of the ASNC nanocomposites were significantly affected by the filler type and content. Furthermore, by adding 3.0 wt% ASNC (3ASNC), the ultimate tensile strength of the nanocomposite was considerably enhanced from 9.0 ± 0.1 to 12.0 ± 0.3 MPa; it may be due to homogeneous dispersion of the ASNC. Moreover, the water absorption capacity was remarkably enhanced from 0.1% for the pure polymer, low-density polyethylene (LDPE), to 1.9% for modified nanocomposite (3.0 wt% ASNC) and 4.1% for unmodified nanocomposite (5 wt% SNC). In addition, the degradation rate of 3ASNC nanocomposite was improved by 1% compared with LDPE. In conclusion, LDPE/TPS/PE-g-MA nanocomposite reinforced by ASNC shows excellent potential as a promising candidate for polyethylene packaging applications, thanks to the combination of biodegradability and superior mechanical properties.

Keywords:
acetylation, biodegradability, low-density polyethylene, mechanical properties, thermoplastic starch, waxy maize starch

Abstract:
In this study, the effective role of incorporation of cellulose nanofibers (CNF) and modified acetylated cellulose nanofibers (ACNF) on mechanical, physical, and biological properties of poly (ε-caprolactone) (PCL)/gelatin (Gel) electrospun nanofibrous scaffold was individually investigated. It was noticed that mechanical and biological properties of the scaffolds were considerably affected by the filler type and content. Although, by addition of 2 wt% ACNF, the ultimate tensile strength (UTS) of the PCL/Gel was remarkably enhanced from 2.5 ± 0.1 MPa to 4.3 ± 0.1 MPa due to homogeneous dispersion of the ACNF, however, the degradation rate of PCL/Gel scaffold was reduced about 1.66 times. Moreover, the studies on the interactions between hybrid scaffolds and fibroblast cells revealed that the incorporation of ACNF into scaffold not only showed no cytotoxic, but also promoted cell proliferation. In conclusion, PCL/Gel nanocomposite scaffolds reinforced by ACNFs show an excellent potential as a promising candidate for soft tissue engineering applications.

Keywords:
Electrospinning, Poly (ε-caprolactone), Gelatin, Cellulose nanofibers, Acetylated cellulose nanofibers, Tissue engineering

Abstract:
In the current study, a mixture of formic acid (FA), acetic acid (AA), and acetone was used, for the first time, as a ternary solvent system to dissolve poly(ɛ-caprolactone) (PCL). In addition, as a biomaterial reinforcement, various amounts of cellulose microfibrils (CMF) (1.5, 3, and 5 wt.%), extracted from rice husk, were added to PCL solution, and subsequently the prepared suspensions were individually electrospun. Adding acetone to FA/AA solvent system led to fabrication of uniform electrospun nanofibers with the average diameter of 178 ± 38 nm. Upon CMF incorporation, the mean electrospun fiber diameter was increased to 320 ± 132 nm at 5 wt.% CMF mostly due to the solution viscosity rise. In addition, scanning electron microscopy (SEM) confirmed wider diameter distribution in the presence of CMF. The electrospun fibers were also analyzed via wide angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC) to study the supermolecular structure and thermal behavior of fibrous bionanocomposites, respectively. Both the characterizations positively affect the PCL crystallinity as a result of CMF incorporation. The DSC measurements showed the highest crystallinity (70.11%) at 1.5 wt.% CMF incorporation. The effect of CMF addition on the hydrophilicity of PCL was also investigated by contact angle measurement, where a decreasing trend in contact angle was observed upon CMF loading. Moreover, in vitro degradability of the bionanocomposite nonwoven mats was studied in PBS solution. The rate of degradation was enhanced in the presence of CMF. Moreover, tensile mechanical analysis was carried out and CMF inclusion had a reinforcing impact on electrospun PCL. The highest modulus (19.17 ± 0.8 MPa) and ultimate tensile strength (UTS) (4.45 ± 0.32 MPa) were achieved at 1.5 wt.% CMF addition to PCL.

Keywords:
Biocomposite, poly(Ecaprolactone), cellulose microfibrils, ternary solvent mixture, electrospinning

Abstract:
To proceed with the electrospun poly (caprolactone) (PCL)/gelatin (Gel) combinations, the current research was aimed to explore the incorporation of cellulose nanofibers (CNF) into the PCL/Gel blends for the first time. Accordingly, various amounts of CNF were added to different ratios of PCL/Gel, and the corresponding electrospun nanocomposites were examined. Observing morphology via scanning electron microscopy proved, unexpectedly, increasing fibers diameter upon CNF addition into PCL/Gel blends. Mechanical analysis in tensile mode revealed more brittle electrospun PCL/Gel when more Gel was included into the blend due to higher Young’s modulus and lower ultimate tensile strength and strain at break. Addition of various contents of CNF led to strain reduction while displayed a summit-like curve for UTS and modulus, where registered maximum values at 2 wt% CNF for all PCL/Gel/CNF. Among the electrospun nanocomposites the highest UTS (3.24 ± 0.22 MPa) belonged to sample including 70 wt% PCL, 30 wt% Gel, and 2 wt% CNF (P70/2CNF), while P30/2CNF recorded maximum modulus (93.89 ± 10.44 MPa). The wide-angle X-ray scattering confirmed increase in PCL crystallinity upon CNF incorporation Furthermore, the presence of PCL, Gel, and CNF in electrospun composites was confirmed with Fourier transform infrared spectroscopy. Degradability of electrospun nanocomposites was carried out in PBS solution, which showed that CNF addition reduced degradation rate of PCL/Gel blends.

Keywords:
Poly (caprolactone), Gelatin, Cellulose nanofibers, Electrospun nanocomposite