Phenols interaction with packaging

Preservative availability may be appreciably reduced by interaction with packaging materials. Examples include the permeation of phenolic preservatives into the rubber wads and teats of multi-dose injection or eye-drop containers and by their interaction with flexible nylon tubes for creams. Quaternary ammonium preservative levels in formulations have been significantly reduced by adsorption onto the surfaces of plastic and glass containers. Volatile preservatives such as chloroform are so readily lost by the routine opening and closing of containers that their usefulness is somewhat restricted to preservation of medicines in sealed, impervious containers during storage, with quite short use lives once opened. 

Cyclodextrins have had valuable industrial uses for a considerable time, particularly as agents to bind or release volatile molecules. Accurate predictions concerning the selectivity and stability of cyclodextrin-guest complexes are therefore of considerable interest both academically and practically." MD was used to simulate cyclodextrin hydrates" as a test of the applicability of the GROMOS program package to systems beyond proteins and nucleic acids. Other early MD simulations focused on interactions with guests such as enantiomers of methyl-2-chloropropionate. Comparisons between calculated thermodynamic properties for complexes formed by O -cyclodextrin with para-substituted phenols and the results of MM simulations led to improvements in force fields that described the interactions. MM2 simulations were used to support NMR data for the -cyclodextrin inclusion complex with benzoic acid. " The well-known catalytic effect of cyclodextrins has been modeled. For example, the relative rate increase of hydrolysis of S over R phenyl ester stereoisomers in the presence of -cyclodextrin... 

Many applications of novolacs are found in the electronics industry. Examples include microchip module packaging, circuit board adhesives, and photoresists for microchip etching. These applications are very sensitive to trace metal contamination. Therefore the applicable novolacs have stringent metal-content specifications, often in the low ppb range. Low level restrictions may also be applied to free phenol, acid, moisture, and other monomers. There is often a strong interaction between the monomers and catalysts chosen and attainment of low metals levels. These requirements, in combination with the high temperature requirements mentioned above, often dictate special materials be used for reactor vessel construction. Whereas many resoles can be processed in mild steel reactors, novolacs require special alloys (e.g. Inconel ), titanium, or glass for contact surfaces. These materials are very expensive and most have associated maintenance problems as well. 

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