Compact face powders

The majority of the analytical techniques used for determining elements in cosmetic samples require the dissolution and dilution of samples in an appropriate solvent, with some exceptions such as X-ray fluorescence spectrometry or neutron activation analysis (NAA) which allow, in the case of solid samples, direct measurement. For example, iron and zinc have been determined in compact eye-shadow, face-powder, and rouge by NAA without prior treatment of samples. 

Tinted dry powders form the second type of facial makeup. Commonly, the blended soHds are compressed into compacts. The finished products, sold as compressed powders, rouges, or blushers, are appHed to the face with the aid of powder puffs, bmshes, or similar devices. Facial makeup compositions have been pubHshed for rouge (57), powder (58), and makeup (59). 

In the disc method, the powder is compressed by a punch in a die to produce a compacted disc, or tablet. The disc, with one face exposed, is then rotated at a constant speed without wobble in the dissolution medium. For this purpose the disc may be placed in a holder, such as the Wood et al. [Ill] apparatus, or may be left in the die [112]. The dissolution rate, dmldt, is determined as in a batch method, while the wetted surface area is simply the area of the disc exposed to the dissolution medium. The powder x-ray diffraction patterns of the solid after compaction and of the residual solid after dissolution should be compared with that of the original powder to test for possible phase changes during compaction or dissolution. Such phase changes would include polymorphism, solvate formation, or crystallization of an amorphous solid [113],... 

One very common beneficial interaction involving an excipient is the interaction between magnesium stearate and the metal of tablet punches and dies, or the equivalent parts on a powder encapsulation machine. Magnesium stearate is an example of a boundary lubricant. As such it has a polar head and a fatty acid tail. It is believed that the polar head of the magnesium stearate is oriented toward the die wall or tablet punch face. In these ways it is able to reduce the ejection force (the force required to eject the tablet from the die after compaction) and prevent sticking to the punch faces. The other boundary lubricants, e.g., calcium stearate and sodium stearyl fumarate, will also function in a similar manner. However, the so-called liquid film lubricants function in a very different manner (19). 

Compaction properties of each material were determined with a standardized test performed on a custom-built hydraulic compaction simulator using 8 mm (0.3150 in.) round flat-faced punches. A linear saw-tooth upper punch position profile was selected with a punch velocity of 300 mm/sec for both punch extension and retraction. The lower punch position was at a fixed position within the die during the compaction event. The powder weight loaded into the die for each compression was calculated from the equation below so as to form a cylindrical tablet having a thickness-to-diameter ratio of 0.30 at a theoretical SF of 1.0. These dimensions are typical of commercially elegant tablets. 

A major challenge is the densification of the graded powder compacts. The processing of FGM materials by powder metallurgy methods often faced undesirable excessive bending or warping of the component after sintering (Miyamoto et al., 1999). Due to excessive thermal residual stresses, cracks and other defects may often be observed in the final FGM component unless properly manufactured. 

The intrinsic dissolution profiles in water for both hemihydrate forms and the monohydrate form of aspartame were determined using 1 cm diameter compacts [23]. The compacts were mounted so that only one face was exposed to the medium, which was stirred at 50 rpm by a paddle near the solid surface. The three forms gave essentially identical profiles, corresponding to an intrinsic dissolution rate of about 7.3 x 10"4 mg/mL/min/cm2. X-ray powder patterns for the solid recovered from the measurements showed that the two hemihydrate forms had converted in situ to the monohydrate. As all intrinsic dissolution profiles were quite linear, the conversion to the monohydrate appears to be so rapid as to preclude assessment of the dissolution rates for the unaltered hemihydrates. 

There are three types of lubricants employed in solid dosage form manufacture. The first class of lubricant is the glidant. The flow properties of a powder can be enhanced by the inclusion of a glidant. These are added to overcome powder cohesiveness. The two other classes of lubricant are antiadherent excipients, which reduce the friction between the tablet punch faces and tablet punches, and die wall lubricant excipients, which reduce the friction between the tablet surface and the die wall during and after compaction to enable easy ejection of the tablet. The level of a lubricant required in a tablet is formulation dependent and can be optimized using an instrumented tableting machine. 

Sinka IC, Cunningham JC, Zavaliangos A. The effect of wall friction in the compaction of pharmaceutical tablets with curved faces a validation study of the Dracker-Prager Cap model. Powder Technol 2003 133 33-43. 

Stiver-white metal, face-centered cubic structure occurs also as black powder and as spongy masses which can be compressed to a compact mass, mp 1555 bp 3167. dj 12.02. Hardness on Mohs scale 4.8, Brindl hardness 61.0. Spec heat 0.0584 cal/g at 0 C, Electrical resistivity at 0 -10.0 microohms-cm. Appreciably volatile at high temps. At a red heat is converted into the monoxide. Forms dihalides with fluorine or chlorine at a red heat. Reacts with nitric acid, sulfuric acid, a mixture of hydrochloric and chloric acids. Reacts slightly with coned HCI more readily in the presence of air or free chlorine. Forms a sulfide when heated with sulfur, a phosphide when heated with phosphorus. Absorbs a considerable amount of hydrogen. 

In the disc method for conducting intrinsic dissolution studies, the powder is compressed in a die to produce a compact. One face of the disc is exposed to the dissolution medium and rotated at a constant speed without wobble. The dissolution rate is determined as for a batch method, while the wetted surface area is simply the area of the disc exposed to the dissolution medium. 

Matrices were made by directly compressing an uniform aspirin-polymer powders mixture (10 w/w of the drug) using an instrumented compaction machine (Nassovia, Germany), with a single 13 mm flat face punch and die. 

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