Water heating history

Polyethylene terephthalate also has the tendency, because it is produced by a condensation polymerization process, to depolymerize under high pressure and temperatures in the presence of water. Although this is usually a negative attribute, it can be utilized to regenerate pure monomers which can be repolymerized to make fresh polymer. This avoids the issues experienced by reprocessing resins, as the new resin has not experienced a previous heat history. A major drawback to this process is the requirement that the monomers used in polymerization processes must be highly pure, Unfortunately, this process is extremely costly and not performed on a commercial scale. 

Clean and efficient heat exchangers are a prerequisite if the water treater wishes to retain business, and therefore some considerable effort must be made to properly understand not only the design characteristics of this equipment but also the current and previous water treatment history. 

In compounding Neoprene AF adhesives the polymer interaction with metal oxides must be considered. Variables which are important include resin type, solvent system, water content, polymer heat history and the order of addition of compounding ingredients. A typical Neoprene AF formulation is shown in Table 5. A comparison of the bond properties of Neoprene AF and Neoprene AD is shown in Table 6. 

The heat exchanger had a history of fouling with silt and precipitates. Water pH was decreased to reduce fouling, with some success. 

Small organisms frequently become embedded within corrosion products and deposits. The organisms may make up a sizable fraction of the deposit and corrosion product. Seed hairs and other small fibers often blow into cooling towers, where they are transported into heat exchangers. The fibers stick to surfaces, acting like sieves by straining particulate matter from the water. Deposit mounds form, reinforced by the fibers (see Case History 11.5). 

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