I. Combustion Method (Most Common and Intuitive)
PVC materials have distinct characteristics when burning:
Flame Color: The flame is yellow with a distinctive green edge.
Smoke: Produces thick black smoke in large quantities, a typical characteristic.
Removal from Flame: Self-extinguishes after being removed from the flame source, indicating it is a flame-retardant material.
Odor: Emits a strong, pungent hydrochloric acid odor (similar to hydrogen chloride), a hallmark of chlorinated plastics.
✅ Comparison: PU conveyor belts produce less smoke, mostly white smoke, with a milder odor and a slight fragrance or isocyanate smell. After burning, it leaves a black, viscous substance with a stringy appearance.
II. Solvent Solubility Test
This test utilizes the solubility of PVC in specific solvents:
Soluble Solvents: Tetrahydrofuran, cyclohexanone, methyl ketone, dimethylformamide, etc. Heating enhances the solubility.
Insoluble Solvents: Methanol, acetone, heptane, etc. PVC is essentially insoluble in these solvents.
Operational Suggestion: Take a small sample and place it in tetrahydrofuran. If it swells or dissolves significantly, it is likely PVC; PU is usually insoluble or reacts differently in these solvents.
III. Physical Properties and Tactile Observation Preliminary judgment can be made using everyday methods:
Elastic Recovery: PVC conveyor belts rebound slowly after folding, with a long recovery time; PU rebounds quickly.
Surface Scratch Resistance: Scratching the surface with a fingernail, PVC easily leaves a dent that recovers slowly; PU leaves virtually no mark.
Texture Changes: Inferior PVC may contain a large amount of filler, feeling harder, brittle, and prone to cracking at low temperatures.
IV. Professional Testing Methods (Applicable to High-Requirement Scenarios)
For authoritative determination, the following laboratory methods can be used:
FTIR Infrared Spectroscopy: Precisely identifies the chemical structure of the material to confirm whether it is polyvinyl chloride.
Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC): Analyze thermal decomposition behavior and processing temperature characteristics.
Chlorine determination: Detect chlorine content using a pyridine colorimetric reaction, further distinguishing PVC from other chlorine-containing materials.
