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D5991-23 – Standard Test Method Technical Guide
📋 Overview and Scope
This standard practice, designated D5991-23, covers four procedures for the separation and qualitative identification of poly(vinyl chloride) (PVC) contamination in poly(ethylene terephthalate) (PET) flakes. Although not presented as a quantitative method, these procedures can yield quantitative results at the user’s discretion. Independent data suggest a PVC detection level of 200 ppm (w/w) based on an original sample weight of 454 g. There is no known ISO equivalent to this standard.
Safety Note: Users must establish appropriate safety, health, and environmental practices. Specific hazards are detailed in Section 8 of the standard. This international standard was developed in accordance with internationally recognized principles on standardization.
Tip: Although not designed as a quantitative method, with proper validation, users can obtain quantitative results. The reproducibility should be verified by the user.
⚙️ Test Procedures and Conditions
Procedure A uses ultraviolet (UV) light to differentiate PVC from PET based on fluorescence. PET normally fluoresces with a blue or violet color. Flakes fluorescing with different colors are removed, weighed, and identified as PVC if they burn with a bright green flame when heated on a copper wire.
Procedure B is an oven test where PET flakes are heated in air at 235 ± 5°C for a minimum of 45 minutes. PVC charrs and turns black. These charred pieces are removed, weighed, and confirmed as PVC using the Beilstein flame test.
Procedures C and D are dye tests based on differential staining. In Procedure C, PET flakes are soaked in a blue acetone dye solution that preferentially stains PVC flakes. These are visually identified, removed, weighed, and confirmed with the flame test.
| 🟦 Procedure | 📏 Method | 🎯 Key Parameter | ⚡ Confirmation |
|---|---|---|---|
| A | UV Light Fluorescence | Color difference under UV | Flame test (green flame) |
| B | Oven Test | 235 ± 5°C for ≥45 min | Visual charring + flame test |
| C | Blue Acetone Dye Test | Preferential staining of PVC | Visual identification + flame test |
| D | Dye Test (Alternative) | Differential staining | Visual identification + flame test |
📊 Confirmation and Interferences
All procedures include a confirmation step using the Beilstein flame test. Chlorine-containing materials heated in a flame in contact with a copper wire produce a characteristic green flame, confirming PVC. This test is essential for accurate identification.
Interferences can occur, particularly with other polymers such as PETG, which also absorb the stain or brightener used in dye tests. This can result in false positive identification of PVC. Users should be aware of these interferences and perform the flame test for confirmation.
Interference Alert: Polymers like PETG can cause false positives in dye tests. Always confirm with the Beilstein flame test to avoid misidentification.
❓ Frequently Asked Questions
🔍 What is the detection limit for PVC in this practice?
Based on independent data, a PVC detection level of 200 ppm (w/w) is suggested from an original sample weight of 454 g.
💡 How is the Beilstein flame test performed?
Heat the material on a copper wire; a bright green flame indicates chlorine, confirming the presence of PVC.
⚡ What are the specific conditions for Procedure B?
Procedure B requires heating PET flakes in an oven at 235 ± 5°C for a minimum of 45 minutes.
📌 Which materials can interfere with the dye tests?
Other polymers such as PETG can absorb the stain or brightener, leading to false positive identification of PVC. The standard notes that this interference results in false positives.