Antioxidants and Erucamide Slip Additives in Polyethylene ASTM D6953-18

Scope:

The ASTM D6953 test method specifies a liquid chromatographic approach for separating various polyethylene additives currently in use. Isopropanol and cyclohexane in this method have excellent extraction efficiencies. UV absorbance of the eluting solvent is measured and quantification is done using external calibration. BHT, BHEB, Isonox 129, erucamide slip,  Irgafos 168, Irganox 1076, Irganox 1010 and TNPP levels in polyethylene samples can be determined using this method. Other antioxidants such as Ultranox 626, Santanox R, Ethanox 330 and Topanol CA ought to be detectable using this test method. 

Procedure:

The polyethylene sample is ground to a particle size of 1-mm (20 mesh) or 0.5-mm (40 mesh)  and extracted with isopropanol or cyclohexane, according to ASTM D6953. Liquid chromatography is then used to evaluate the solvent extract. Reverse-phase chromatography (C-8  or C-18 column) with ultraviolet (UV) detection at wavelengths corresponding to the absorption apex of each additive will be used to estimate additive levels using external calibration curves. 

Specimen size:

Grinded particle size specimen of 1 mm, that is, ~20 mesh (density < 0.94 g/cm3) or 0.5 mm,  that is, ~40 mesh (density > 0.94 g/cm3) is used in this ASTM D6953 test method. 

Data:

The concentration in mg/kg (that is, ppm) of each additive in the polyethylene sample is  computed as follows for additive peaks with a resolution R > 1: 

where,

A = area of additive peak, 

K = slope of a calibration curve, that is, linear regression line [Sample]sol = concentration of the sample in solution