Phosphate plasticisers, determination

For direct determination of plasticisers in PVC the sample was dissolved in THF, and phthalate or phosphate plasticisers were measured from absorbance at 240 and 275 nm or 257, 262 and 268 nm, respectively... 

Other plasticiser determinations in PVC include dibutylphthalates, di-2-ethylhexylphthalate, di-iso-decyl phthalate and tricresyl phosphate [18] and di-decylphthalate, di-decyl henzyl phthalate and dihenzyl phthalate [Ij. 

Murray [91] has described a gas chromatographic method for the determination in water of triarylphosphate esters (lmol S-140, tricresyl phosphate, cresol phosphate). These substances are used commercially as lubricant oil and plastic additives, hydraulic fluids and plasticisers. The method involves extraction from the samples, hydrolysis and measurement of the individual phenols by gas chromatography as the trimethylsilyl derivatives. The lower detection limit was about 3ppm. 

Plasticisers are added to PVC to achieve flexibility and workability. The flexibility or softness is determined by the type of plasticiser and level used in relation to the PVC (phr). They also operate as an internal lubricant between the PVC molecules. Based on organic esters, e.g., phthalates, adipates, trimellitates, phosphates, etc., addition levels can be as low as 20 phr for semi-rigid to 100 phr for very flexible applications. The effect on the thermal stability significantly depends on the physical state of the PVC-plasticiser system (260). The relative amount of crystalline PVC in PVC/diethylhexyl phthalate has been identified on the basis of a combination of carbon-13 solution and solid state nuclear magnetic resonance (NMR) (361). 

Various product forms may occur during storage (typical for fatty acid derivatives) or production. DSC has been used for detection of polymorphism of butylated hydroxyanisole (BHA) [91]. Similarly, DSC has allowed to detect various product forms of the hindered phenolic antioxidant octade-cyl 3-(3, 5 -di-f-butyl-4 -hydroxyphenyl) propionate (Anox PP 18), which caused handling problems during production [92]. The DSC method for purity determination as used for curatives, such as 2,2 -benzothiazyldisulfide (MBTS) [93], and for sulfur and accelerators [79], is also applicable to other additives, such as antioxidants and antiozonants. DSC and TGA have been used to establish the oxidation and weight loss characteristics of commercially available triaryl, trialkyl and alkyl-aryl phosphate esters, which are widely used as plasticisers and flame retardants in the polymer industry [94]. 

In many cases, such as in the determination of highly volatile materials (e.g. moisture in nylons or in polysaccharides [412]), or of residual solvents or plasticisers (as in PVB) [413], use of TG-MS is requested. Specifically, there are reports on the entrapment of curing volatiles in bismaleimide laminates [414] and elastomers [415], of plasticisers such as bambuterol hydrochloride [416] or triphenyl phosphate and diethylterephthalate in cellulose acetate [417], on solvent extraction and formaldehyde loss in phenolic resins [418,419]. Carraher et al. [420] have used TG-MS to study the degradation of a fluorescent titanium polyether ester dye. 

---