Coatings continued physical properties

While particle size continues to be the physical property most frequently determined by NIR spectroscopy, several other parameters including the dissolution rate and the thickness and hardness of the ethylcellulose coating on theophylline tablets have also been determined using NIR, all with good errors of prediction.94 Tablet hardness, which dictates mechanical stability and dissolution rate, has been determined in hydrochlorothiazide tablets.95... 

Polymers, specifically rubbery, amorphous polymers, have several inherent advantages as chemically sensitive sensor coatings diey can be deposited as thin, adherent, continuous films of fairly uniform thickness by solvent casting or spray coating techniques they are nonvolatile and of homogeneous composition and their chemical and physical properties can be modified to some extent by judicious choice of monomers and synthetic procedures. 

While the design of such coatings is straightforward, selection of appropriate materials is not. Usually materials with the properties required for a particular application are not readily available, and some custom laboratory fabrication is necessary. This usually involves selecting a polymer composite which somewhat approximates the required physical properties. Then minor alterations to the chemical constituents or fillers are used on a trial basis and the acoustic properties (some combination of Young s Modulus and damping factor, sound speed, attenuation, density, and front-face reflectivity) of these sample formulations are measured. This continues until a suitable formulation is achieved. 

Aliuniniiun trihydrate (ATH) should continue to experience strong growth but there is much competition from mineral suppliers all anxious to launch special precipitated grades and those wilh new surface treatments to make them more effective. The drive is the requirement for lower loadings to preserve the balance of mechanical and physical properties for which the particular plastic system has been chosen. The treatment of hydrophilic ATH particles with hydrophobic coatings, such as fatty acids or silanes, provides for more uniform dispersion in the hydrophobic plastic resins. 

Coating and laminating are very exciting technologies with a myriad of possibilities [15]. The aim of coating or laminating a textile substrate with a polymer layer is to significantly influence its external characteristics and physical properties. Textiles coated with, or laminated, bonded with a continuous polymer layer acquire new properties that cannot be achieved by the base fabric alone. 

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