INDEX time-dependent deformation

Substituting the appropriate values shows that the capillary pressure drop will increase from 78% to 100% of the applied pressure as the melt flow indexer goes from completely filled to empty. Thus, a 50% increase in the output rate is possible, as has been shown for polyethylene (PE) by Skinner [13]. With PF, the position is shown to be worse by Charley [IS], who performed extensive experiments for using the MFI test for molten PP. Despite this time-dependent deformation behavior, there is no conection recommended for entrance and exit abnormalities. This would also be difficult to specify, because the conections would be expected to vary from polymer to polymer. 

Here the index s runs over the relevant saddle points, those that are visited by an appropriate deformation of the real integration contour, which is the real five-dimensional (t,t, k) space, to complex values, and Sp(t,t, k) s denotes the five-dimensional matrix of the second derivatives of the action (4.5) with respect to t,t and fc, evaluated at the saddle points. The time dependence of the form factors (4.6) and (4.7) is considered as slow, unless stated otherwise (see Sect. 4.5 and [27]). 

Hiestand Tableting Indices Likelihood of failure during decompression depends on the ability of the material to relieve elastic stress by plastic deformation without undergoing brittle fracture, and this is time-dependent. Those which relieve stress rapidly are less likely to cap or delaminate. Hiestand and Smith [Powder Technol., 38, 145 (1984)] developed three pharmaceutical tableting indices, which are applicable for gener characterization of powder com-pactiability. The strain index (SI) is a measure of the elastic recovery following plastic deformation, the bonding index (BI) is a measure of plastic deFormation at contacts and bond survival, and the brittle fracture index (BFI) is a measure of compact brittleness. 

Creep is the change in shape of a material while subject to a stress it is time-dependent. Elasticity, the ability of a fiber to return to its original dimensions upon release of a deformation stress, is described by the tenacity of the 5deld point on the stress-strain curve. Toughness, the ability of a fiber to absorb work before it ruptures, is evaluated from the area under the total stress-strain curve. The toughness index is defined as one-half the product of the stress and strain at break... 

First, the rate of shear, which is not linear with the shearing stress due to the non-Newtonian behaviour, varies with the different types of polymer. The processability of different polymers with an equal value of the MI may therefore differ widely. An illustration of this behaviour is given in Fig. 15.14. Furthermore the standard temperature (190 °C) was chosen for polyethylenes for other thermoplastics it is often less suitable. Finally, the deformation of the polymer melt under the given stress is also dependent on time, and in the measurements of the melt index no corrections are allowed for entrance and exit abnormalities in the flow behaviour. The corrections would be expected to vary for polymers of different flow characteristics. The length-diameter ratio of the melt indexer is too small to obtain a uniform flow pattern. 

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