Journal of Bioresources and Bioproducts. 2018, 3(3) 107-111
Peer-Reviewed
The optical properties of the composite films were determined using ultraviolet spectrophotometer (752N, INESA, shanghai, China). The films were cut into 10 × 50 mm size and tested between 400 nm and 800 nm. 2.3.5. Water absorption properties Dyr composite films were cut into 20 ×20 mm pieces, and soaked in distilled water until the maximum absorption was reached (the films ’ weight changed within 1%). The Water absorption was calculated with the Eq. (3). Where Q was Water absorption. m 0 and m 1 were the weighs of dry and wet film, respectively.
agitator (XH-50E, Xianghu Science and development Co. Ltd, Beijing, China). The film-forming solution was cast onto a rimmed silicone plate and dried at room temperature about 72 h. The films were kept in a constant temperature and humidity chamber (HE-WS-408D8, Haoen Testing Instrument Co., Ltd, Dongguan, China) at 25°C and 50% RH for 48 h before further tests. 2.3. Characterization of gelatin/MFC composite films 2.3.1. Morphological observation The microstructure of gelatin/MFC composite films was characterized by scanning electron microscopy (SEM) (JCM-6000 BENCHTOP SEM, JEOL, Japan) with an accelerating voltage of 15.0 kV. 2.3.2. Mechanical properties The tensile strength and elongation at break were determined by intelligent electronic tensile testing instrument (XLW, Blue Light Electrical and Mechanical Technology Co., Ltd, Jinan, China) according to ASTM D882-02 (ASTM, 1995a), and the thickness was measured by thickness indicator (MX-3, DAKOTA ULTRASONICS, Scott, USA). The composite film samples were cut into 2.30 ×10.0 cm, and kept at 50% relative humidity (RH) for 48 h before analysis. Then, the tensile strength (TS) and elongation at break (E) were calculated with the Eq. (1) and Eq. (2), respectively. Where σ and ε were tensile strength (TS) and elongation at break (EAB), respectively. F , b , and d were tensile force and width and thickness of composite film, respectively. l 0 and l 1 were tensi le elongation and original length, respectively. 100% b u u d F V (1) 100% 0 1 u l l H (2) 2.3.3 . Thermogravimetric and heat shrinkage analysis The thermal analysis of the composite films was characterized by Thermogravimetric analyzer (IRPrestige21, shimadzu corporation, Kyoto, Japan). The composite film samples were about 8-10 mg, and kept at 50% relative humidity (RH) for several days before analysis. The samples were tested with a rate of heating of 10 °C/min, between 25 °C and 800 °C in an inert atmosphere (100 ml/min N 2 ). The heat shrinkage of composite films was characterized by heat shrinkage instrument (RSY-R2, Blue Light Electrical and Mechanical Technology Co., Ltd, Jinan, China). Film samples of 10 × 50 mm dimension were heat treated at 120 °C for twenty seconds. 2.3.4. Optical properties
m
m
m
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0
(3)
100%
Q
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0
3. RESULTS AND DISCUSSION 3.1. Morphology
The surface morphology and cross section of pure gelatin film and gelatin/MFC composite film using scanning electron microscopy are shown Fig.1. In the gelatin/MFC composite film, the surface was much smoother than the pure gelatin film was rough, and the cross section of gelatin/MFC composite film was denser, which might due to cross-linked reaction between gelatin and MFC.
Fig. 1. SEM images of neat gelatin films and gelatin/MFC composite films (top: surface; bottom: cross section; left: neat gelatin films; right: gelatin/MFC composite films) 3.2. Mechanical properties Fig.2 shows the mechanical properties of gelatin/MFC composite films. The tensile strength changed as the MFC mass concentration varied. Among them, the gelatin/MFC composite film of 1.0% MFC had the highest tensile
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