Thickness swell measurements

Thickness swell measurements were made on 2 x 12 x 7/l6" (51x 305 x 11mm) specimens after conditioning at 21 C (70 F) and 90 relative humidity for two months. 

Tablets coated with the Eudragit-PEG 400 mixture were made with three different polymer film thicknesses 6, 10 and 15 mg (KET-R, 10 and 15 tablets). For these tablets it was not possible to obtain swelling measurements because this was prevented by the lake coating.

After the boards were removed from the hot press they were conditioned at room temperature for several days before testing. Three 2 x 10-inch strips were cut from each board for determining breaking load. A 0.24-inch-per-minute loading rate and a 9-inch span were used. Thickness of each strip was measured at the point where the load was to be applied, and after the strip had been "broken each half was cut into two 2 x 2-inch samples. These samples were used to obtain data necessary for determination of oven-dry density, water absorption and thickness swelling, internal bond, and a 2-hour boiling-in-water thickness swelling test. 

The effects of a test substance on the cornea are measured quantitatively as an increase in thickness (swelling), subjectively as scores for corneal opacity, the area of corneal involvement, fluorescein penetration, and morphological changes to the corneal epithelium. Two additional endpoints may be incorporated into the protocol or used ad hoc to supplement existing data. This includes the use of histopathology to confirm or identify the extent of irritancy at the histology level (especially if the irritancy fells between moderate and severe) and the use of confocal microscopy to determine the extent and depth of ocular injury [69, 70], see also Section 4.2.3. 

Swelling measurements were done in heptane. Disc shaped samples of about 0.5 mm in thickness which were immersed in heptane were weighed periodically after wiping all liquid from the sample surface. Results were converted to volume swell in percent. 

The pattern used for cutting test specimens is shown in Figure 3. The property values given in this report are mean values of the number of specimens indicated times two since each board was duplicated. Densities were measured on all thickness swell, internal bond (IB) and bending modulus specimens before those respective tests were run. 

A comparison of the durability of the adhesive bonds formed by the two binders is provided by the wet internal bond and by the thickness swell values shown graphically in Figures 5 and 6, respectively. The former, measured after a 2 hour water boil, are strikingly superior for the Desmodur PU-1520A 20 vs. the phenolic binder at all press times. The same can be said for thickness swell after 2 and 2k hour water soaks. 

A method was described by Burton et al. (1981) involving the direct application of irritant test substance to the cornea of eyes removed immediately after sacrifice of rabbits and subsequent evaluation of the cornea for swelling, opacity, and fluorescein staining, The eye is mounted on a clamp in a temperature-controlled superfusion chamber with isotonic saline dripped onto the surface of the cornea, After an equilibrium period of 30-45 min, the test material is applied to the surface of the cornea and then washed off. Eyes are inspected macroscopically. Then, with a slit-lamp biomicroscope, the comeal thickness is measured and any fluorescein staining noted. The predictive value of the method has been confirmed in several studies (Commission of the European Communities, 1991 Koeter and Prinsen, 1985 Price and Andrews, 1985 Whittle et al., 1992), By using comeal thickness measurement, fluorescein retention, and comeal opacity as criteria for ocular injury, the suitability of the chicken eye as an enucleated model was confirmed by Prinsen and Kocier (1993) and Prinsen (1996). 

Note that for the particleboards produced with all resins, other physical properties were also measured, namely, density, moisture content, and thickness swelling. All the results obtained comply with standard specifications for particleboards (EN 312). 

The phenomenon of die swell is complex, and the method for incorporating it into die design calculations is unclear. In most cases the processing die geometry is considerably different from that used to make die swell measurements. For example, in the extrusion of a parison used in blow molding there is swell of both the thickness and outer diameter of the parison. How to translate die swell from a capillary to that of a parison is certainly not straightforward. 

To illustrate one possible way of translating capillary die swell measurements to some other die geometry we consider the swell of extrudate leaving an annular die. In the swell of polymer extruded from an annular die as shown back in Figure 3.1 (this figure is associated with Design Problem II), there is swell of the diameter as well as the thickness of the extrudate. The two most eommon swell parameters are the diameter swell, Bi, and the thiekness swell, B2, defined, respectively, as... 

Solvent Resistance. At temperatures below the melting of the crystallites, the parylenes resist all attempts to dissolve them. Although the solvents permeate the continuous amorphous phase, they are virtually excluded from the crystalline domains. Consequently, when a parylene film is exposed to a solvent a slight swelling is observed as the solvent invades the amorphous phase. In the thin films commonly encountered, equilibrium is reached fairly quickly, within minutes to hours. The change in thickness is conveniently and precisely measured by an interference technique. As indicated in Table 6, the best solvents, specifically those chemically most like the polymer (eg, aromatics such as xylene), cause a swelling of no more than 3%. 

The physiological effect of a particular lens can be determined by measuring the increased thickness of the cornea after lens wear studies have shown the relationship between the DkjD of a lens and the subsequent swelling of the underlying cornea (20,21). 

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