Plasticizer exudation

The plasticizer content of a polymer may be increased by the suppression of crystallization in the polymer, but if crystallization subsequently occurs the plasticizer exudes. For highly crystalline resins, the small amounts of plasticizer allowable can change the nature of the small amorphous regions with a consequent overall change in properties. 

Phase segregation. Incompatibility of polymer and plasticizer causes plasticizer exudation. Often such an effect is a function of temperature and it can be reversible. It can take place not only as a result of a temperature change, bnt also because of humidity change, mechanical stress, and chemical crosslinking. Exndation of plasticizer is observed visually or by paper absorption Plasticizers that have an excellent compatibility with the polymer are much less likely to be extracted by solvent or oil. 

In addition, caseinate-based films were crosslinked with formaldehyde (HCHO). The occurrence of covalent bridges between protein chains allows water-insoluble three-dimensional network to be achieved. The crossHnking was combined with plasticizing to produce caseinate films with improved mechanical properties and water resistance which are able to replace synthetic films and to overcome protein film deficiencies. Nevertheless, in spite of crosslinked protein material being water insoluble, it was also shown that during water immersion, plasticizer exuded out of the film, even for highly crosslinked samples. 

Fifty percent of TEA plasticized NaCAS films with various ratios of crosslinker were immersed into distilled water. The exudation ratio of TEA (percentage of initial dry weight of TEA initially present in films) versus immersion time is shown in Fig. 5. As suspected, the water-soluble plasticizer exudes out of the film and after 10 min immersion in distilled water 80% of the TEA migrated out of the film, whatever the crosslinking. For all the NaCAS films, the whole TEA exuded out of the film after 24 h in water. Nevertheless, for short time of contact with water (2 min), the plasticizer... 

Even in the copolymers there is extensive crystallization and so the materials have high specific gravity (1.7 for 85% vinylidene chloride — 15% vinyl chloride copolymer) and low permeability to moisture vapour and gases. The copolymers also have high tensile strengths, namely about 10 000 Ib/in for unoriented material and about 30 000 Ib/in for oriented filament. It may be noted that the copolymers are not readily plasticized as all but small amounts of plasticizer exude from the finished product. 

Moth Balls naphthalene 38 2 4 Plasticizer exudation generally unsatisfactory 1.01 ... 

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