Softening range techniques

Softening ranges are dependent on the technique and procedure used to determine them. Thus information on softening ranges should be accompanied by information on the specific technique and procedure employed for the determination. 

Experimental techniques such as those used to measure specific values of viscosity (e.g. softening point) are still in common use, but are not as powerful as those in which a range of viscosities can be measured. Hence, only the Margules (1 to 106 Pa-s), parallel plate (103 to 108), and beam bending viscometers (107 to 1014 Pa-s) will be discussed here. These devices are manufactured and marketed by Theta Industries. 

The final action required is reheating the molded part at which time the plastic softens and the gas expands to form a closed-cell foam. With this technique it is possible to produce foams with densities as low as 2 lb/ft3, although the usual range is 10 to 50 lb/ft3. Because of this two-step procedure the process is much slower than the foaming procedure for open-cell foams. Close cell use includes athletic mats and marine flotation products. 

Ion-exchange chromatography Has a wide range of uses in the food industry, medicine and life and health sciences. This technique has been extensively used in the food industry as a quality control measure and to detect contamination with metals and organic acids. Another important use of this method is in the purification of blood products such as human albumin, growth factors and enzymes. Perhaps the most common application of this technique is the deionization of water and water softening/purification. 

Polymeric thin films in this thickness range can easily be prepared from solution by spin coating or doctor blading techniques. Drying the films at elevated temperatures under high vacuum or under inert atmosphere is necessary to remove residual solvent traces, which cause softening of the material and contribute to fast relaxation of the oriented chromophores to an isotropic state. 

Other important uses are adhesives and coatings. A wide variety of resins, plasticizers, fillers, and other ingredients commonly used in adhesives and coatings can be used with styrene-diene-styrene triblock copolymers. With these ingredients properties such as tack, stiflfiiess, softening temperatures, and cohesive strength can be varied over a wide range. With aliphatic resin additives the block copolymers are used for permanently tacky pressure-sensitive adhesives, and in conjunction with aromatic resins they are used for contact adhesives. The copolymers can be compounded into these adhesives by solution or hot-melt techniques. 

---