(CNFs) ซึ่งสร้างโดยกระบวณการ electrospinningของเซลลูโลสอะซิเตทที่ได้มาจากเซลลูโลสของไม้ไผ่ (B-CA) ตามด้วยกระบวณการ Deacetylation ซึ่งจะช่วยในการเป็นกำลังเสริมที่จะทำให้ฟิล์มคอมโพสิตโปร่งใสสายตา เราตรวจสอบผลของความเข้มข้นของ B-CA และไฟฟ้าสถิตพารามิเตอร์ (เช่นระยะทางปั่นและความเร็ว) สัณฐานเส้นใยและการวางแนว ซึ่งทำหน้าที่เกี่ยวกับคุณสมบัติทางกลการแสงของคอมโพสิต CNFs เสริม ดังนั้นผลลัพธ์จะทำให้ ฟิล์มคอมโพสิตมีการการส่งผ่านแสงที่มองเห็นได้สูง แม้จะมีปริมาณเส้นใยมากรวมทั้งยังทำให้ สมบัติเชิงกลที่ดีขึ้นอีกด้วย ความเข้าใจที่ได้รับจากการศึกษาครั้งนี้อาจจะอำนวยความสะดวกในการพัฒนาของวัสดุ nanofibrous นวนิยายสำหรับการใช้แสงต่างๆ
Nanofiber morphology
ลักษณะของสมบัติทางกล
3.3. Mechanical characterization
The mechanical property of fiber as a reinforcement in polymeric matrices is directly concerned with the overall performance of the composite. In this study, the mechanical performance of
a-CNFs and r-CNFs mats was first compared (see Supporting information) and had demonstrated obviously different results. Aligned cellulose nanofibrous mats showed a substantially high tensile
strength, which was approximately 7 times that of nano fibrous mats with a random fiber orientation. The uniaxial orientation of electrospun cellulose fibers positively influenced on the improvement of mechanical strength. Therefore, a-CNFs were used as the reinforcements to further reinforce the PVA resin matrix in the following experiment. The tensile property of a-CNFs@PVA was measured by cutting the composite film into strips along the impregnated fiber direction. As shown in Fig. 5, the fiber content influences the tensile properties. The pure PVA film showed poor mechanical properties, and the tensile strength and modulus were ∼25 MPa and
∼129 MPa, respectively. The tensile strength of the composite evidently increases when the cellulose fibers are embedded in the PVA matrix. The maximum mechanical strength of ∼39 MPa was achieved for the a-CNFs@PVA composite with CNFs content of 32%.
This value is 1.6 times that of neat PVA film, whereas the modulus significantly increased from 129 MPa to 1.1 GPa. The modulus of composite films increases substantially with fiber content in
the range studied in this work. Notably, the increase in modulus is not in accordance with the moderate gain of tensile strength. A similar finding was also reported in the literature (Bergshoef &
Vancso, 1999; Tang & Liu, 2008). These results demonstrate that electrospun cellulose nanofibers provide effective reinforcement, as explained by strong intermolecular forces between the CNFs and PVA matrix. As such, a large amount of hydroxyl groups on CNFs surfaces forms strong hydrogen-bonding with PVA matrices. This formation consequently results in intimate adhesion force at the CNFs@PVA interfaces, as evidenced in the fractured SEM images (Fig. 4). When a PVA composite film was stretched, this interaction structure can lead to stress transfer from PVA to CNFs. The occurrence of nanofiber bowing derived from the stress transfer, and in turn it improves the mechanical properties of the composite. With further increase in a-CNFs content, the tensile strength of the composite film gradually decreased, but remained higher than those of
pristine PVA film. Given that the strength of the CNFs is smaller than that of PVA matrix, the excessively high content of CNFs is not expected to effectively reinforce the composite film. Instead, it was J. Cai et al. / Carbohydrate Polymers 140 (2016) 238–245 243 Fig. 5. Mechanical performance of a-CNFs@PVA composite films corresponding with the changes of fiber content. possible to weak the overall mechanical properties of the composite film. Fig. 5 also shows a decrease in strain at break values after CNFs were impregnated into PVA matrix. The unexpected decrease in stain originates from the rigidity effect of the cellulose fiber. To further examine the effects of the CNFs embedding into matrix on the mechanical property of the composite film, aCNFs@PVA was subjected to dynamical mechanical analysis (DMA). Fig. S7 (in the Supporting Information) shows the storage modulus (E0) of the a-CNFs@PVA as a function of temperature and fiber content. The studied pure PVA shows a typical mechanical behavior of an amorphous polymer material. With increasing temperature, the E0 of samples decreased because of the easier movement of polymer chains at elevated temperature. Compared with the fairly low E0 of neat PVA, the value significantly increased for composite films, such as those with increasing a-CNF content. This finding suggests that the incorporation of aligned nanofibers in the matrix enhances the stiffness and thermal stability. The shift of Eo to a higher value could be explained by intimate fiber/PVA interfaces, which impart mechanical limitations to the matrix and reduces mobility and deformation. The height of tanı peaks substantially declined for CNFs@PVA composite films, indicating that the dampening effect decreased with the loading of
(CNFs) ซึ่งสร้างโดยกระบวณการ electrospinningของเซลลูโลสอะซิเตทที่ได้มาจากเซลลูโลสของไม้ไผ่ (B-CA) ตามด้วยกระบวณการ Deacetylation ซึ่งจะช่วยในการเป็นกำลังเสริมที่จะทำให้ฟิล์มคอมโพสิตโปร่งใสสายตาเราตรวจสอบผลของความเข้มข้นของ B-CA และไฟฟ้าสถิตพารามิเตอร์ (เช่นระยะทางปั่นและความเร็ว) สัณฐานเส้นใยและการวางแนวซึ่งทำหน้าที่เกี่ยวกับคุณสมบัติทางกลการแสงของคอมโพสิต CNFs เสริมดังนั้นผลลัพธ์จะทำให้ฟิล์มคอมโพสิตมีการการส่งผ่านแสงที่มองเห็นได้สูงแม้จะมีปริมาณเส้นใยมากรวมทั้งยังทำให้สมบัติเชิงกลที่ดีขึ้นอีกด้วยความเข้าใจที่ได้รับจากการศึกษาครั้งนี้อาจจะอำนวยความสะดวกในการพัฒนาของวัสดุ nanofibrous นวนิยายสำหรับการใช้แสงต่าง ๆNanofiber morphologyลักษณะของสมบัติทางกล3.3. Mechanical characterizationThe mechanical property of fiber as a reinforcement in polymeric matrices is directly concerned with the overall performance of the composite. In this study, the mechanical performance ofa-CNFs and r-CNFs mats was first compared (see Supporting information) and had demonstrated obviously different results. Aligned cellulose nanofibrous mats showed a substantially high tensilestrength, which was approximately 7 times that of nano fibrous mats with a random fiber orientation. The uniaxial orientation of electrospun cellulose fibers positively influenced on the improvement of mechanical strength. Therefore, a-CNFs were used as the reinforcements to further reinforce the PVA resin matrix in the following experiment. The tensile property of a-CNFs@PVA was measured by cutting the composite film into strips along the impregnated fiber direction. As shown in Fig. 5, the fiber content influences the tensile properties. The pure PVA film showed poor mechanical properties, and the tensile strength and modulus were ∼25 MPa and∼129 MPa, respectively. The tensile strength of the composite evidently increases when the cellulose fibers are embedded in the PVA matrix. The maximum mechanical strength of ∼39 MPa was achieved for the a-CNFs@PVA composite with CNFs content of 32%.This value is 1.6 times that of neat PVA film, whereas the modulus significantly increased from 129 MPa to 1.1 GPa. The modulus of composite films increases substantially with fiber content inthe range studied in this work. Notably, the increase in modulus is not in accordance with the moderate gain of tensile strength. A similar finding was also reported in the literature (Bergshoef &Vancso, 1999; Tang & Liu, 2008). These results demonstrate that electrospun cellulose nanofibers provide effective reinforcement, as explained by strong intermolecular forces between the CNFs and PVA matrix. As such, a large amount of hydroxyl groups on CNFs surfaces forms strong hydrogen-bonding with PVA matrices. This formation consequently results in intimate adhesion force at the CNFs@PVA interfaces, as evidenced in the fractured SEM images (Fig. 4). When a PVA composite film was stretched, this interaction structure can lead to stress transfer from PVA to CNFs. The occurrence of nanofiber bowing derived from the stress transfer, and in turn it improves the mechanical properties of the composite. With further increase in a-CNFs content, the tensile strength of the composite film gradually decreased, but remained higher than those ofpristine PVA film. Given that the strength of the CNFs is smaller than that of PVA matrix, the excessively high content of CNFs is not expected to effectively reinforce the composite film. Instead, it was J. Cai et al. / Carbohydrate Polymers 140 (2016) 238–245 243 Fig. 5. Mechanical performance of a-CNFs@PVA composite films corresponding with the changes of fiber content. possible to weak the overall mechanical properties of the composite film. Fig. 5 also shows a decrease in strain at break values after CNFs were impregnated into PVA matrix. The unexpected decrease in stain originates from the rigidity effect of the cellulose fiber. To further examine the effects of the CNFs embedding into matrix on the mechanical property of the composite film, aCNFs@PVA was subjected to dynamical mechanical analysis (DMA). Fig. S7 (in the Supporting Information) shows the storage modulus (E0) of the a-CNFs@PVA as a function of temperature and fiber content. The studied pure PVA shows a typical mechanical behavior of an amorphous polymer material. With increasing temperature, the E0 of samples decreased because of the easier movement of polymer chains at elevated temperature. Compared with the fairly low E0 of neat PVA, the value significantly increased for composite films, such as those with increasing a-CNF content. This finding suggests that the incorporation of aligned nanofibers in the matrix enhances the stiffness and thermal stability. The shift of Eo to a higher value could be explained by intimate fiber/PVA interfaces, which impart mechanical limitations to the matrix and reduces mobility and deformation. The height of tanı peaks substantially declined for CNFs@PVA composite films, indicating that the dampening effect decreased with the loading of
การแปล กรุณารอสักครู่..