Hygroscopic plastic

HOCHj CHjOH. Colourless, odourless, rather viscous hygroscopic liquid having a sweet taste, b.p. 197 C. Manufactured from ethylene chlorohydrin and NaHC03 solution, or by the hydration of ethylene oxide with dilute sulphuric acid or water under pressure at 195°C. Used in anti-freezes and coolants for engines (50 %) and in manufacture of polyester fibres (e.g. Terylene) and in the manufacture of various esters used as plasticizers. U.S. production 1979 1 900 000 tonnes. 

Plasticized PVB interlayer is hygroscopic. In addition, Ts are in the neighborhood of 30°C thus, interlayer tends to adhere to itself, or block, when roUs or stacks of cut blanks are stored at ambient conditions. For these reasons handling and shipping must be carried out under controUed humidity and at temperatures weU below the sheet s T. Precut interlayer blanks and roUs are usually stored or shipped refrigerated (3—I0°C), and when roUs need to be stored or shipped at ambient conditions, the sheet is interleaved with a thin sheet of nonadhering plastic such as polyethylene. 

Dicyandiamide forms white, non-hygroscopic crystals which melt with decomposition at 209°. Its most important reaction is conversion to melamine (Fig. 8.25) by pyrolysis above the mp under a pressure of NH3 to counteract the tendency to deammonation. Melamine is mainly used for melamine-formaldehyde plastics. Total annual production of both H2NCN and NCNC(NH2)2 is on the 30 000 tonne scale. 

Of the various plastics available, such TPs as nylon, PC, PMMA, PUR, PET, and ABS are among those categorized as hygroscopic. 

These absorb moisture, which then has to be carefully removed before the plastics can be fabricated into acceptable products (2,3). Low concentrations, as specified by the plastic supplier, can be achieved through efficient drying systems and properly handling the dried plastic prior to and during molding, extrusion, etc. (Figs. 7-24 and 7-25). When desired processor can have these hygroscopic plastics properly dried and shipped in sealed containers. 

Drying hygroscopic plastics should not be taken casually. The simple tray dryers or mechanical convection hot-air dryers that are... 

Fig. 7-26 Example of the effects of moisture on the mechanical properties of an IM hygroscopic PET plastic.

Nylon (Polyamide) PA is a crystalline plastic and the first and largest consumption of the engineering thermoplastic. This family of TPs are tough, slippery, with good electrical properties, but hygroscopic and with dimensional stability lower than most other engineering types. Also offered in reinforced and filled grades as a moderately priced metal replacement. 

The effectiveness of an internal antistatic agent incorporated in the melt depends primarily on its molecular structure. This determines properties vital to the antistatic effect such as polarity and migration. The aliphatic C)4-C,7 chain in the alkanesulfonates imparts the required migration property to polar plastics, whereas the polar group is responsible for their hygroscopic behav-... 

Cellulose acetate CAP Acetone, ethyl acetate/IPA, alkalies, if pH 6.0 Dissolves in distal end of duodenum requires presence of plasticizer such as triacetin or castor oil is somewhat hygroscopic... 

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