Structure and Properties of Inhibited Plastics

The following fundamental concepts lie at the base of designing inhibited plastics  

These concepts are realized to a greater extent in composites based on thermoplastic polymers incorporating low-molecular plasticizing liquids and Cl [119-121]. Compositions based on HDPE, mineral oil MS-20 (MO) and oil-soluble Cl of metals, e.g. GRM (tar of vegetable oils and inedible fats), 

If the concentration of low-molecular liquids (solvents) in the polymers surpasses their compatibility limit, they isolate and form spherical arrangements with a size of 10-20 pm in the polymer structure. When the solid phase volume exceeds that of the liquid, the formed structures are of the closed-pore kind and the liquid phase is distributed within the solid phase as local spherical inclusions [122]. As soon as the liquid phase content surpasses that of the solid, a new honeycomb structure with communicating cavities is formed whose solid phase builds up thin walls that separate the cells. This feature is to a greater extent typical of tough and crystallizable polymers. This is also relevant for systems like PE-MO where honeycomb structures with a pore size of up to several micrometers can be formed under certain conditions (Fig. 4.22) [123]. Such porous structures are perfect for the impregnation of modified additives, e.g. Cl. 

A characteristic feature of plasticized pol3miers is syneresis, the spontaneous liberation of the liquid phase. S3meresis may take place during both molding of the samples and in complete products. 

Of specific interest from the view point of designing inhibited plastics is the examination of s5meresis in systems with a polymer and mixture of plasticizers. It has been stated in [119] that s3meresis may increase or diminish during combining of PI or may stay at some average level, in contrast to syneresis of polymer blends with each plasticizer individually. The latter case is illustrated in Fig. 4.23, in which the dependencies of the liquid phase liberation from different PE-based blends over 18 days are presented. 

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