Polyester separation methods

The oligomer distribution is highly dependent on the method of isolation of the oligomers (TLC, Soxhlet or dissolution/precipitation). Jung and Lee [513] have determined a dimer of 2-phenylbenzoxazole in a polyester resin by means of TLC. A comparative study of the separation of styrene oligomers (up to dodecamers) by TLC and OPLC has appeared [514]. 

Many substances can serve as the stationary phase for gas chromatographic separations of methyl esters in most cases polyester, polyether, or silicone greases are used. Percival (18) has investigated the composition of polyesters by methanolysis with sodium methyl oxide. The dimethyl esters of the dicarboxylic acids present in the composition and free glycols are formed and subsequently are separated at temperatures between 110° and 180° C. on a column of GE silicone SF-96 and Fluoropak 80. It should be possible to adapt this method to the analysis of polyesters used as plasticizers. 

We, in most cases, have used a 2-meter column of polypropylene glycol (Ucon LB-550 X) on Celite 545 at 191° C. in helium flow and have succeeded in separating the aliphatic alcohols and diols. D. F. Percival s method (18) for separating diols from saponified polyesters should be adaptable to plasticizer analysis. 

Liquid-liquid extraction (LLE) is the traditional method to extract organic compounds from water. The low molecular weight compounds are transferred from one liquid phase to another immiscible or partially immiscible liquid by shaking them in a separation funnel. LLE is still a common method, but has several drawbacks such as low selectivity, labor intensivity, and the use of large amount, of organic solvent. LLE has been used to extract hydrolysis products of degradable polyesters such as PLA and its copolymers from the buffer solution [115]. 

Cadotte ( ) presents a comprehensive review of the development of the composite membrane with emphasis on the pros and cons of the four preparation methods mentioned above and on the polymer chemistry Involved. Cadotte points out that while each of the four methods continues to receive some attention, the Interfaclal polymerization method appears to be the most versatile. This method can be used to produce skin layers from polyamines, polylmlnes, polyurethanes, polyesters and other polymers. Elsewhere In this volume, Lee and co-workers (45) discuss the advantages and problems associated with using these composite membranes for ethanol-water separations via counter-current reverse osmosis. Also, Cabasso (44) discusses double-layer composite membranes. 

Klingsberg (jf.S.D.C., 1954, 70, 563) describes a method specially designed for the chromatographic examination of vat dyes. Owing to the insolubility in virtually all solvents of the pigment form, the separation must be carried out in the leuco state. The reduced vat dyes, however, have such a marked affinity for cellulose that paper chromatography must be ruled out, but strips of material made of hydrophobic synthetic fibres, of which polyesters are the best, may be substituted. Rao, Shah, and Venka-... 

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