Sticky point

The sticky point can be determined by using a method developed by Lazar and later by Downton [Downton, Ffores-Luna, and King, "Mechanism of Stickiness in Hygroscopic, Amorphous Powders, Ih-EC Fundamentals 21 447 (1982)]. In the simplest method, a sample of the product, at a specific moisture, is placed in a closed tube which is suspended in a water bath. A small stirrer is used to monitor the torque needed to stir the product. The water bath temperature is slowly increased until the torque increases. This torque increase indicates a sticky point temperature for that specific moisture. The test is repeated with other product moistures until the entire stickiness curve is determined. A typical curve is shown in Fig. 12-23. 

Other sources of problems include electrostatics (most marked with fine and dry powders) and immobile liquid bridges, the so-called sticky-point phenomenon. This latter is sharply temperature-dependent, with only a weak dependence on moisture content, in contrast to mobile... 

Ozmen, L. and Langrish, T.A.G. Comparison of glass transition temperature and sticky point temperature for skim milk powder. Drying Technol., 20,1177,2002. 

DCM and filtering to remove any insoluble components. The products are precipitated using cold diethyl ether, filtered, and dried under high vacuum to yield 4,5 g (90%). The anionic polymerization of macromonomers 11 and 12 (2.6 g) catalyzed by rBuOK (0.10 g) is carried out at 100°C under an argon atmosphere and the sticky point is reached after 30 min. The polymerization is then continued for 12 h. The reaction is quenched by the addition of methanol and the product 13 is granulated through 1-mm sieves. The polymer is stirred in 4 M HCl for 2 h to remove potassium salts and then washed with water and ethanol and dried under high vacuum to yield... 

Stickiness in spray-drying and drum-drying > T sticky point ( )... 

All the double bonds in Figures 3.38 and 3.39 are cis. For some reason this is often a sticky point for students. Make sure you understand why all the double bonds shown in the figures are appropriately called cis. To make the point absolutely clear we will use cyclopentene as an example. Note that the two hydrogens on the double bond are on the same side. The two alkyl groups (part of the ring) are on the other side (Fig. 3.40). The molecule is properly called cis, or (Z). 

The Langmuir adsorption sites can be represented by a collection of sticky sites of the same form as was suggested by Baxter. Only that now we do not have a sphere covered uniformly by a layer of glue, but rather a smooth, hard surface with sticky points, which represent adsorption sites where actual chemical bonding takes place. For a regular crystal lattice face, Eq.(1.136) has to be changed to... 

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