Controlled release additive

Stein, J. and Eckberg, R.P., UV Curable silicone release coatings and controlled release additives. J. Coat. Fabr., 20, 24 (1990). 

Phospholipid molecules form bilayer films or membranes about 5 nm in thickness as illustrated in Fig. XV-10. Vesicles or liposomes are closed bilayer shells in the 100-1000-nm size range formed on sonication of bilayer forming amphiphiles. Vesicles find use as controlled release and delivery vehicles in cosmetic lotions, agrochemicals, and, potentially, drugs. The advances in cryoelec-tron microscopy (see Section VIII-2A) in recent years have aided their characterization [70-72]. Additional light and x-ray scattering measurements reveal bilayer thickness and phase transitions [70, 71]. Differential thermal analysis... 

Cosmetics and Pharmaceuticals. The main use of hexadecanol (cetyl alcohol) is in cosmetics (qv) and pharmaceuticals (qv), where it and octadecanol (stearyl alcohol) are used extensively as emoUient additives and as bases for creams, Hpsticks, ointments, and suppositories. Octadecenol (oleyl alcohol) is also widely used (47), as are the nonlinear alcohols. The compatibiHty of heavy cut alcohols and other cosmetic materials or active dmg agents, their mildness, skin feel, and low toxicity have made them the preferred materials for these appHcations. Higher alcohols and their derivatives are used in conditioning shampoos, in other personal care products, and in ingested materials such as vitamins (qv) and sustained release tablets (see Controlled RELEASE technology). 

Amine-containing cellulose esters, eg, the acetate A/A/-diethylaminoacetate (36) and propionate morpholinobutyrate (35), are of interest because of their unique solubiHty in dilute acid. Such esters are prepared by the addition of the appropriate amine to the cellulose acrylate crotonate esters or by replacement of the chlorine on cellulose acrylate chloroacetate esters with amines. This type of ester has been suggested for use in controlled release, mmen-protected feed supplements for mminants (36,37). 

Although the field of controlled release technology is only a few decades old, the late 1980s and early 1990s have seen an explosion in research aimed at creating new dmg dehvery systems (12) as well as numerous pubHcations that discuss controlled release. In addition, journals and societies have been estabUshed that are devoted to the advancement of dmg dehvery systems. 

Electrotransport technology offers a number of benefits for therapeutic appHcations, including systemic or local adininistration of a wide variety of therapeutic agents with the potential adininistration of peptides and proteins long-term noninvasive administration, improving convenience and compliance controlled release, providing a desired deflvery profile over an extended period with rapid onset of efficacious plasma dmg levels and in some cases reduced side effects and a transport rate relatively independent of skin type or site. Additional benefits include easy inception and discontinuation of treatment, patterned and feedback-controlled deflvery, and avoidance of first-pass hepatic metaboHsm. 

Cyclopentadiene oligomers have been formed by vapor deposition of CPD on kaolin to afford a sorbant for removal of oil from water (71). They are also employed as coatings for controlling release rates of fertilizers (72). Thermal addition of sulfur to a mixture of DCPD and CPD oligomers has led to a number of beneficial appHcations such as waste water oil adsorbant powdery foams (73), plasticized backing for carpets and artificial turfs (74), and in modified sulfur cements for encapsulating low-level radioactive wastes (75). 

The most important of the phosphate bonded cements are the zinc phosphate, dental silicate and magnesium ammonium phosphate cements. The first two are used in dentistry and the last as a building material. Copper(II) oxide forms a good cement, but it is of minor practical value. In addition, certain phosphate cements have been suggested for use as controlled release agents. The various phosphate cements are described in more detail in the remainder of this chapter. 

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