Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D6042-23 – Standard Test Method Technical Guide
🧪 Scope and Applicability
ASTM D6042–23 specifies a liquid chromatography (LC) procedure for the separation and quantitation of phenolic antioxidants and erucamide slip additives in polypropylene homopolymer formulations. The method applies to additives such as Irganox 1010, Irganox 1076, Irganox 3114, Irgafos 168, Kemamide‑E (erucamide), Tinuvin P, and Vitamin E (α‑tocopherol). Additives are extracted from the polymer using a 75:25 (v/v) mixture of methylene chloride and cyclohexane, either by reflux or ultrasonic bath, prior to LC analysis. Ultraviolet absorbance is measured at 200 nm, and quantitation is performed using the internal standard method. The standard is under the jurisdiction of ASTM Committee D20 on Plastics (Subcommittee D20.70 on Analytical Methods) and was approved in 2023.
🔬 Test Procedure and Extraction Methods
The polypropylene sample is first ground to a 20‑mesh particle size (850 µm). Two extraction techniques are permitted:
- Reflux extraction – boiling the ground sample with the methylene chloride/cyclohexane mixture under controlled heating.
- Ultrasonic bath extraction – sonicating the ground sample in the same solvent mixture at ambient temperature.
After extraction, the solvent phase is filtered and injected into a liquid chromatograph equipped with a UV detector set to 200 nm. The internal standard method is used for quantification to compensate for injection and preparation variability. The entire procedure is designed for polypropylene homopolymer formulations and may require adjustment for copolymers or heavily filled grades.
⚠️ Safety Precaution: Methylene chloride and cyclohexane are flammable and pose health hazards. Section 9 of the standard provides specific precautionary statements. Always work in a fume hood and wear appropriate personal protective equipment (PPE) when handling these solvents.
📊 Additive Compounds and Detection Parameters
The following table lists the principal additives addressed by this test method, along with their chemical names and abbreviations as defined in the standard.
| 🟦 Additive (Trade Name) | 📐 Chemical Name | 🔖 Abbreviation |
|---|---|---|
| Irganox 1010 | Tetrakis[methylene(3,5‑di‑tert‑butyl‑4‑hydroxy hydrocinnamate)]methane | — |
| Irganox 1076 | Octadecyl‑3,5‑di‑tert‑butyl‑4‑hydroxy hydrocinnamate | — |
| Irganox 3114 | Tris(3,5‑di‑tert‑butyl‑4‑hydroxybenzyl) isocyanurate | — |
| Irgafos 168 | Tris(2,4‑di‑tert‑butylphenyl) phosphite | — |
| Kemamide‑E | cis‑13‑Docosenamide (erucamide) | — |
| Tinuvin P | 2(2′‑Hydroxy‑5′‑methyl phenyl)benzotriazole | — |
| Vitamin E | α‑Tocopherol (3,4‑dihydro‑2,5,7,8‑tetramethyl‑2‑(4,8,12‑trimethyltridecyl)‑2H‑1‑benzopyran‑6‑ol) | — |
💡 Tip for Method Development: Although the standard specifies UV detection at 200 nm, analysts may confirm peak identity by collecting spectra across 190–400 nm. Always verify that the internal standard does not co‑elute with any target additive.
❓ Frequently Asked Questions
🔍 What sample particle size is required?
The polypropylene must be ground to pass a 20‑mesh sieve, corresponding to a maximum particle size of 850 µm. This ensures efficient extraction of the additives.
💡 Which extraction solvent mixture is used?
A 75:25 (v/v) mixture of methylene chloride and cyclohexane is specified. Both reflux and ultrasonic bath extraction are acceptable; the choice depends on laboratory equipment and safety considerations.
⚡ How are the additives quantified?
Quantitation is performed using the internal standard method. An internal standard of known concentration is added to each sample and calibration standard, and the ratio of analyte peak area to internal standard peak area is used to construct the calibration curve.
📌 What detection wavelength is used?
The ultraviolet absorbance is measured at 200 nm. At this wavelength, both phenolic antioxidants and erucamide provide sufficient response for reliable quantitation.