Extraction and Quantification of Polyolefin Additives

Roberson et al. [42] have reported an extrae-tion recovery rate of 90-99% for one-step extrae-tion of PP samples. Desrosiers [23] deseribed extrae-tion and quantification of in-polymer additives from polyolefinic materials. The problems eneountered in the extraction step are release of low-MW waxes or oligomers, and formation of hydrolysis, oxidation and degradation products. Undesirable ehemieal reactions may also take place during the extraetion process. 

Quantitation limits (defined as the monomer concentration necessary to produce a peak at least three times the baseline noise or 3% of full scale) for residual monomers (such as vinylchloride, butadiene, acrylonitrile, styrene and 2-ethylhexylacrylate) as low as 0.05 ppm have been reported for solution headspaee, as eompared to 1 ppm for direct solution injection GC [43], Quantification of volatiles by solid headspaee sampling can be challenging. Solid headspace provides about 10-fold more sensitivity than solution headspace. 

Nielson [28] has compared microwave (MAE) and ultrasonic (US) extraction of HDPE/(BHT, Irganox 1010, Irganox 1076) pellets using cyclohexane/iso-propyl alcohol (IPA) and methylene chloride/IPA mixtures in various ratios. Results are eolleeted in Table 6.14. 

The data reported correspond to an RSD of 1.8% for the three additives over six separate extractions or to an RSD of 1.9% for three separate extractions. The same author [28] has also compared US and MAE for several PP resins that contained a variety of additive packages. The PP formulations consisted of antistats, pigments, fillers, slip agents, and antiox-idants/UV degradants. Table 6.15 shows the MAE recoveries for a selection of additives in four resins. 

Results were also reported for LDPE/erucamide andLDPE/(BHT, BHEB, Isonox 129, Irganox 1010/ 1076) [28]. Similar detailed quantitative reports are rare. The results give a good indication of the expectations of careful quantitative extraction. 

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