Plasticizers polar aromatic

Polarity Parameter. Despite their appareat simplicity, these parameters, ( ), show a good correlatioa with plasticizer activity for nonpolymeric plasticizers (10). The parameter is defiaed 2ls (j) = [M A j Po)]/1000 where M = molar mass of plasticizer, = number of carboa atoms ia the plasticizer excluding aromatic and carboxyHc acid carbon atoms, and Pg — number of polar (eg, carbonyl) groups present. The 1000 factor is used to produce values of convenient magnitude. Polarity parameters provide useful predictions of the activity of monomeric plasticizers, but are not able to compare activity of plasticizers from different families. 

Chlorinated insecticides The analysis of chlorinated pesticides in residue samples in complicated by the fact that they usually occur along with polychlorinated biphenyls (PCBs). The latter compounds occur widely in the environment due to their use as plasticizers, dye stuff additives and hydraulic oils, and both chlorinated pesticides and polychlorinated biphenyls are persistent in the environment. Since both compound classes include non-polar aromatic molecules, adsorption chromatography has been the mode of choice for the HPLC separation of these compounds. 

Polar aliphatic plasticizers mis less well with polymers than do polar aromatics and, consequently, may exude (bloom) from the plasticized polymer more easily. Their polymer miscibility temperature is higher than that for the first group. These plasticizers are called oil-type plasticizers, and their kerosene extraction index is high. Their plasticization action is, however, more pronounced than that of polar aromatic plasticizers at the same molar concentration. Moreover, since the aliphatic portions of the molecules retain their flexibility over a large temperature range, these plasticizers give a better elasticity to finished products at low temperature, as compared to polar aromatic plasticizers, and allow the production of better cold-resistant materials. In PVC they also cause less coloration under heat exposure. 

FIGURE 1.44 Action of (a) a polar aromatic plasticizer and (b) a polar aliphatic plasticizer on PVC chains. 

One of the most difficult elastomer families to plasticize with any confidence in the results is polychloroprene. The CR grades respond differently to plasticizers than most elastomers due to the ability of polar plasticizers and aromatic process oils to attack the molecular backbone of the CR. In addition, plain unsaturated vegetable oils (e.g., rapeseed, corn, and castor), which are relatively incompatible in most specialty elastomers, are seemingly quite compatible in CR up to about 30 phr. 

Attacked or dissolved by polar, aromatic and halogenated solvents unfilled grades not UV resistant absorbs water which acts as a plasticizer more expensive than PSU. 

Rubbers. Plasticizers have been used in mbber processing and formulations for many years (8), although phthaHc and adipic esters have found Htde use since cheaper alternatives, eg, heavy petroleum oils, coal tars, and other predominandy hydrocarbon products, are available for many types of mbber. Esters, eg, DOA, DOP, and DOS, can be used with latex mbber to produce large reductions in T. It has been noted (9) that the more polar elastomers such as nitrile mbber and chloroprene are insufficiendy compatible with hydrocarbons and requite a more specialized type of plasticizer, eg, a phthalate or adipate ester. Approximately 50% of nitrile mbber used in Western Europe is plasticized at 10—15 phr (a total of 5000—6000 t/yr), and 25% of chloroprene at ca 10 phr (ca 2000 t/yr) is plasticized. Usage in other elastomers is very low although may increase due to toxicological concerns over polynuclear aromatic compounds (9). 

Solvents. Solvents are added for the same purposes as oils and plasticizers, and additionally may interact with the substrate (e.g. by partially dissolving the substrate surface). Aromatic and polar solvents are the most suitable. 

It was also found that better plasticization occurs if the polar group is on an aliphatic molecule (because of its greater mobility) rather than on an aromatic molecule. 

Plasticizers include the esters of a few aliphatic and aromatic mono and dicarboxylic acids, aliphatic and aromatic phosphorus acid esters, ethers, alcohols, ketones, amines, amides, and non-polar and chlorinated hydrocarbons. These additives are used in various mixtures. For their separation and qualitative detection, thin-layer chromatography (TLC) is preferred. Usually Kieselgur plates, 0.25 mm thick, activated at 110°C for 30 min, in the saturated vapor are used. Methylene chloride and mixtures of diisopropyl ether/petether at temperatures between 40 to 60°C have been successfully used as the mobile phase. Refer to Table 1. 

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