How Does Scratch Sniff and Carbonless Copy Paper Work

21 How Does Scratch Sniff and Carbonless Copy Paper Work  

The clever combination of chemistry and microsphere technology enables advertisers to take advantage of the incredible marketing power of scent. These innovations have also modernized paper-based recordkeeping and business transactions. 

These two seemingly dissimilar applications have a common basis—both are examples of the pressure-sensitive release of a chemical. How are these products designed Tiny spherical capsules (microcapsules or microspheres) with a glass or polymer shell are filled with a liquid core and glued onto paper. For a scratch-and-sniff ad, the core of the microcapsules contains a liquid with the desired scent for carbonless paper, a liquid ink or dye is encapsulated within the 

The polymer and glass microspheres employed in the pressure-sensitive release of chemicals range in size from 1 //m to 1 mm in diameter. (For comparison, a human hair is typically 80-100 lim in diameter.) A scanning electron micrograph illustrating the morphology of the particles appears in color Fig. 14.2.1 

In the coacervation process, the core substance is first added to a homogeneous solution of the selected solvent and polymer. Mechanical agitation is used to disperse the immiscible core to create tiny droplets suspended in solution (i.e., an emulsion). The coacervation or phase separation phenomenon is then induced by several means, such as changing the temperature and/or acidity of the polymer solution or adding salts, nonsolvents, or incompatible (immiscible) polymers to 

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