2.3 Characterization
Fourier transform infrared spectroscopic (FTIR) spectra were obtained by Nexus 670 (Thermo Nicolet, America). The data was collected in attenuated total reflection (ATR) mode with the wavenumber range from 400 cm-1 to 4000 cm-1. XRD spectra were recorded on Rigaku SmartLab diffractometer with the Cu Kα at the voltage of 40 kV and current of 30 mA over the 2θ angular range of 2 o~30 o at the scanning speed of 10 o/min. SEM image was processed on S-4800 (Hitachi, Japan) at an accelerating voltage of 10 kV. Oxygen transmission rate (OTR) was conducted on G2/132 (Labthink, China) based on the differential pressure method. Water vapor transmission rate (WVTR) was determined using W3/330 (Labthink, China) with a sample test area of 5 cm2 at 37.8oC and 77.0 %RH (±1 %RH). The limiting oxygen index (LOI) values were collected by the YZS-75A oxygen index meter (Bei Guang Jing Yi, China) according to GB/T 2406.1-2008. MMT-PI film was fixed 2 cm above the heat source (alcohol lamp flame) and the pseudocolor thermal imager was set at a specific distance for fire-resistance measurement. The thermal infrared imager VH-780 (Infra Tec, Germany) was used the capture pseudocolor thermal images during the 90 s video recording. The test method for water absorption is as follows. The MMT film, MMT-PI, MMT-PVA, and MMT-CMC were completely immersed in deionized water and placed under room temperature and pressure for 3 days. The films were then taken out, and water adhering to the surface of the films was quickly wiped off and weighed immediately. The water absorption rate (WA%) was calculated accruing to Eq. 1 .