This standard specifies additives currently used for determining polypropylene homopolymer formulationsa (PP-H) using liquid chromatography. These additives are extracted with a cyclohexane: methylene chloride mixture using reflux prior to liquid-chromatographic separation. The ultraviolet absorbance (200 nm) of the compound(s) is measured, and quantitation is performed using the internal standard method.
This standard is applicable to determination of erucamide slip additives and phenolic antioxidant in polypropylene homopolymer formulations: a-tocopherol or 3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-benzofuran-6-tocopheryl acetate (hereafter referred to as Vitamin E), Tris-(2,4-di-tert-butyl-pheny)-phosphite (hereafter referred to as Irganox 168), Tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate (hereafter referred to as Irganox 3114), tetrakis [(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester (hereafter referred to as Irganox 1010) and octadecyl-3,5-di-t-butyl-4-hydroxy hydrocinnamate (hereafter referred to as Irganox 1076). This standard may also be used for determination of other antioxidants, such as Ultranox 626, Ethanox 330, Santanox R and BHT, but the applicability of this test method has not been investigated for these aantioxidants.
The detection limit of phenolic antioxidant may be up to 2mg/kg under the optimum detection conditions.
Note: Other methods that have been used successfully to remove additives from the plastics matrix include thin film, microwave, ultrasonic, and supercritical fluid extractions. Other methods have been used successfully to separate additives including SFC and capillary GC.
2 Normative References
The following standards contain provisions which, through reference in this standard, constitute provisions of this standard. For dated reference, subsequent amendments to (excluding corrigendum), or revisions of, any of these publications do not apply. However, all parties coming to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards. For undated references, the latest edition of the normative document referred to applies.
GB/T 6682-2008 Water for Analytical Laboratory Use-Specification and Test Methods (ISO 3696:1987, MOD)
GB/T 12806-1991 Laboratory Glassware-One-mark Volumetric Flask (eqv ISO 1042:1983)
GB/T 12808-1991 Laboratory Glassware-One-Mark Pipettes (eqv ISO 648:1977)
3 Method Summary
Service performance of polymer depends on the composition, so it is necessary to determine the additive in the polypropylene. PP-H is indissoluble in solvents usually used by liquid chromatography, so the additives can be extracted by the solvents. The sample is ground to a 850μm (20-mesh) ~ 425μm (40-mesh) particle size and extracted by refluxing with a mixture of 75:25 methylene chloride: cyclohexane. The extraction liquid is determined relative to an internal standard using reverse-phase liquid chromatography with ultraviolet detection at 200 nm.
