Pellets, preparation

For poor solubility as well as poor film forming nature of the rigid conjugated polymer and its nanocomposites, generally pellet is used as 

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J. J. Fitzgibbon. Sintered, spherical, composite pellets prepared from clay as a major ingredient useful for oil and gas well proppants. Patent CA 1232751, 1988. 

R Bodmeier, HG Chen. Evaluation of biodegradable poly(lactide) pellets prepared by direct compression. J Pharm Sci 78 819-822, 1989. 

Hlukhyy and Pottgen (2004) prepared Pd-Mg compounds (Pd2Mg5) and Ir-Mg-In alloys. Pd2Mg5 was synthesized from cold pressed pellets prepared from Pd powder and Mg small pieces. The pellets were sealed under an argon pressure of 800 mbar in niobium tubes. The niobium tubes placed in the water-cooled sample chamber of an induction furnace were first heated at about 1000K for half a minute and then cooled down to 700 K within 30 minutes and quenched by switching off the furnace. The samples could easily be separated from the niobium tubes, and no reaction with the crucible material was observed. 

The effect of KBr pellet preparation discussed above brings about a well known - and possibly overlooked - class of mechanochemical reactions those between alkaline halogenides, such as KBr and Csl, used for IR pellets, and species, such as molecules carrying -COOH groups, which may cause an alteration of the absorption frequencies with respect to those measured in solution or Nujol [70]. The mechanochemical reactions that take place when milhng and pressing analytes with KBr to form discs for IR experiments have been recently reviewed by Fernandez-Bertran and Reguera [71]. 

At the start of the cycle, the lower piston is in the upper position. The pellet prepared in the previous cycle is pushed out as the die passes under the feeder mechanism. 

Lovgren K, Lundberg PJ. Determination of sphericity of pellets prepared by extrusion-spheronization and the impact of some process parameters. Drug Dev Ind Pharm 1989 15 2375-2392. 

Nitrodipenta resembles PETN in its physical and chemical properties. Nitro-dipenta dissolves in acetone more readily than PETN, and this is used to separate the two nitrates. The specific gravity of single crystals of nitrodipenta is 1.630 at 15°C, while pellets prepared under a pressure of 2500 kg/cm2 acquire a specific gravity of 1.589. Nitrodipenta is less sensitive to impact and to friction than PETN and its temperature of initiation is higher. In spite of this, its chemical stability at 100°C is distinctly less than that of PETN. This is the main reason why the presence of nitrodipenta in PETN is undesirable. 

The technique of pellet preparation and the guard-ring electrode cell were described previously (8). The density of the pellets is 61% of the real zeolite density. No structural damage is observed with x-ray diffraction after pellets are made. 

Table II lists the thermodynamic parameters for the conduction process. For the Na+ samples the activation energies are on the average 3.5 kcal lower than those for the conduction process of the corresponding dehydrated zeolites (<8). For K+-zeolites this difference averages 2.1 kcal. NaF69.8 is not included because of experimental difficulties in pellet preparation. The activation entropies are negative for the X-type zeolites and positive for the Y-type. The activation entropies are higher than those of the dehydrated samples (8) except for KF86.5. The effect of AS on E...

The infrared spectrum given in Figure 1 was determined for a KBr pellet preparation of silver sulfadiazine with the use of a Beckman IR 10 spectrometer. The assignments for important absorption bands are presented — as far as possible — in Table I. The assignments are based on various literature references (4, 8,9). In practice it is found that different batches of silver sulfadiazine do produce slightly different IR spectra, while the batches assay closely to the theoretical values (4,5,9). 

Test 3 Examine by infrared absorption spectrophotometry, comparing with the spectrum obtained with dipyridamole CRS. Examine the substances as pellets prepared using potassium bromide R. 

Recently, Castiglioni, et al. have devised a new method, diffuse reflectance CD (DRCD), to measure the solid-state CD of a pure microcrystallite sample or one mixed with KBr [42,43] and checked their performance. An integrating sphere used for UV-Vis and IR spectroscopy was introduced (Fig. 6). The advantage of this technique is to remove possible artifact elements such as reactions with the KBr, the effect of pressure required for the pellet preparation, or sample dissolution in nujol. Further, samples can be recovered after the spectral measurement, in contrast to both KBr pellet and nujol mull methods. 

The contact angle of mercury on the various materials was measured using two different methods. Prior to the pellet preparation, the samples were milled to obtain a particle size < 10 pm. 

Follonier, N. Doelker, E. Cole, E.T. Various ways of modulating the release of diltiazem hydrochloride from hot-melt extruded sustained release pellets prepared using polymeric materials. J. Controlled Release 1995, 36, 243-250. 

Fig. 22 Pellets prepared by different methods. Cross-sectional view of a pellet prepared by powder layering (A), cross-sectional view of a pellet prepared by extrusion/spher-onization (B), and size and shape of pellets prepared by extrusion/spheronization (C).

Fig. 23 Pellets prepared by spherical agglomeration. Overview about ascorbic acid pellets prepared from powder of a mean particle diameter of 8.8 pm. The bar is 1 mm (A). SEM picture from left (B). Ascorbic acid pellet prepared from powder of a mean diameter of 8.8 pm without the addition of povidone (C). Pellet from left prepared with the addition of 2% PVP (D). Ascorbic acid pellet prepared from powder of a mean particle diameter of 3.0 pm without the addition of povidone (E). Pellet from left with the addition of 2.0% povidone (F).

Fig. 25 Differences observed in the deformation of substances during tableting. Potassium chloride at low (A) and high com-pressional forces (B), pellets prepared by spherical agglomeration in a tablet surface (C) and in the inner part of a broken tablet (D), surface of an acetyl salicylic acid (ASA) tablet containing 10% sodium carbox5methyl starch (E) and the same surface after moistening with a finger (F). (From Ref...

Pellets prepared by extrusion/spheronization have uniform cross-sectional area (Fig. 22B) but differ slightly in shape and size, which is based on the spheronization process following extrusion (Fig. 22C). 

Fig. 27 Infiuence of the type of polymer application on film properties (top and side view). HP55 (HPMCP)-coated pellet, prepared from a micronized film dispersion (A). HP55 [hydroxypropyl methylcellulose (HPMCP)]-coated pellet, prepared from an organic solution (B).

Thomsen LJ, Schaefer T, Sonnergaard JM, Kristensen HG. Prolonged release matrix pellets prepared by melt pelletization. I. Process variables. Drug Dev Ind Pharm 1993 19 1867-1887. 

It is usually by standard tray or fluid bed systems. For specific use, freeze-drying has been used. The pellets prepared from MCC (Avicel PH 101) mixed with a water/ethanol system, were found to have different porosity and mechanical strength depending upon how they were dried (55). 

An immediate release product would require some special feature to warrant the increased cost of production when compared to a conventional capsule or tablet. Therefore, the major commercial use of pellets prepared by extrusion/spheronization is in the preparation of controlled release products and there are several highly successful products available. In particular the ability to produce pellets with a high drug loading offers advantages over alternative methods of forming pellets. 

Perez JP, Rabiskova M. Influence of the drying technique on theophylline pellets prepared by extrusion-spheronization. Int J Riarm 2002 242 349-51. 

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