Dwell time INDEX

A large difference between the two indices may predict sensitivity to scale-up of the tableting process relating to dwell time of the machine. This tendency, is described as the VI, as shown in Equation (4). However, no correlation of this index to scale-up has been shown to date in the literature. 

The XRD patterns of the samples obtained by calcining the gel powder and the boehmite powder at 1000 °C for different hours are shown in figure 2. The gel powder is possibly amorphous indicated by its XRD pattern. The solid squares signify the peaks of the a-alumina according to JCPDS data (card No. 10-173). When the gel powder was calcined for 0.5 h, a-alumina coexisted with 0-alumina. When the dwell time was increased to 6 h, 0-alumina was transformed to a-alumina completely. On the other hand, when the gel powder was reacted with water, boehmite was formed as revealed by the XRD pattern indexed according to the JCPDS card 74-1895. When such boehmite powder was calcined at 1000 °C, no peaks of a-alumina were observed for 1 h. a-Alumina started to form after 5 h and pure a-alumina was obtained in 40 h. That is, the boehmite powder needs much longer dwell time than the gel powder to transform completely to a-alumina at 1000°C. 

The physical, chemical and structural changes created in stabilization can be detected by various analyzing techniques include X-ray diffraction (XRD), Differential scanning calorimetery (DSC) and Fourier transform infrared (FTIR) spectroscopy, which can be considered as standard evaluation techniques for the extent of stabilization [14, 21, 22]. In this study, different methods are employed to measure stabilization index of electrospun PAN nanofibers after heat treating to obtain the desired conditions for stabilizing temperature, dwell time and heating rate. 

TABLE 5 Enthalpies and stabilization indexes of stabilized samples in different dwell times (constant temperature of 270°C, and heating rate of l°C/min). ... 

Figure 4 The development of seal strength as a function of sealant resin melt index (I2) for a 0.915 g/cm LLDPE at various sealing dwell times. The preferred melt index operating range bracketed by the vertical broken lines within the plot.

Figure 5 The relationship between the sealing dwell time and the melt index I2) for a specified maximum heat sealing rate as computed by HEATSEAL for a 0.915 g/cm LLDPE. The preferred operating ranges are brackrted by the vertical broken lines.

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