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The plastic material burn test serves as a fundamental process for recognizing different plastics through their distinct combustion properties. Multiple industries require knowledge of plastic material burn characteristics for effective recycling processes and material selection while assessing environmental impacts. The simplified guide from Alfa Chemistry enables users to identify common plastic materials by employing a flame source like a lighter, torch, or bottled gas burner.

What is a plastic material burn test?

The burn test requires placing a flame against a plastic sample to monitor its reaction. The straightforward test enables clear identification between thermoplastic and thermoset materials. This burn test provides initial information about the material but fails to deliver a conclusive identification by itself. Advanced methods, including spectral analysis, are necessary to identify complex polymers accurately.

The burn test delivers vital data, including:

• Flame Color: The resulting flame color reveals information when a material undergoes combustion. The material's chemical composition determines the flame color during combustion. A blue flame usually suggests thorough combustion with fewer impurities, but yellow or orange flames demonstrate the presence of carbon or other contaminants in the material.
• Soot Presence: Whether the burning plastic produces soot. The generation of soot during combustion demonstrates incomplete burning, which occurs frequently in plastics containing high carbon content and various additives.
• Odor: The smell produced when the plastic burns. The aroma emitted from burning plastic serves as a diagnostic tool to identify the specific type of polymer used.
• Material Drips: Whether the plastic drips during combustion. Thermoplastics drip during combustion because they become pliable when exposed to heat. Unlike thermoplastics, which drip when heated, thermosets maintain their form and do not drip when exposed to flame.
• Smoke Characteristics: The type and amount of smoke emitted.

How to perform a plastic material burn test?

These steps should guide you through performing the initial burn test for identification.

1. Thermoplastic vs Thermoset Identification

Determining the material type as thermoplastic or thermoset comes before beginning the burn test. To perform this test, you need to use a heated metal or glass rod.

• Bring the rod to a glowing state at approximately 500°F/260°C before proceeding.
• Press the heated rod against the sample.
• Materials that soften when exposed to heat are generally classified as thermoplastics. Materials that remain unchanged after exposure to heat are typically thermoset.

2. Flame Exposure

Place the sample near the edge of flames from sources including cigarette lighters, gas burners, or torches. Hold the material in the flame for a maximum of ten seconds if it fails to ignite right away. Carefully observe:

• Color of the Flame: Analyzing the color of the flame during the test can reveal information about what the material is made of.
• Nature of Smoke: The density and color of the smoke produced during burning serve as indicators for identifying the specific type of plastic.
• Presence of Soot: The development of soot during combustion demonstrates incomplete burning, which suggests the material remains partially unoxidized.

3. Odor Analysis

Once the flame has been extinguished, proceed to carefully smell the resulting fumes. The burning process of each plastic material produces a unique smell. PVC emits a sharp acrid smell when burned, but burning polyethylene releases a sweet and gentle odor. Comparison references provide assistance in determining the sample's identity.

4. Dripping Test

Plastics may release dripping droplets during combustion, with thermoplastic materials being particularly prone to this behavior. The particular feature plays a key role when differentiating among the various plastic kinds.

How do common plastics react under burn test conditions?

The data from plastic burn tests plays a crucial role in choosing appropriate materials and improving recycling methods. This table provides a summary of burn characteristics found in common thermoplastic and thermoset materials.

Materials	No Flame	Burns, but goes out when the source of fire is removed			Continues to burn when the source of fire is removed				Remarks
	Odor	Odor	Flame Color	Drips	Odor	Flame Color	Drips	Speed of Burning
Thermoplastics
ABS		Acrid	Yellow, blue edges	No	Acrid	Yellow, blue edges	Yes	Slow	Black smoke with soot in air
ABS/Polycarbonate	-	-	-	-	-	Yellow, blue edges	No	-	Black smoke
ABS/PVC	-	Acrid	Yellow, blue edges	No	-	-	-	-	Black smoke with soot in air
Acetals	-	-	-	-	Formaldehyde	Blue, no smoke	Yes	Slow
Acetate	-	Vinegar	Yellow with sparks	No	Vinegar	Yellow	Yes	Slow	Flame may spark
Acetate Butyrate	-	-	-	-	Rancid butter	Blue, yellow tip	Yes	Slow	Flame may spark
Acrylics	-	-	-	-	Fruity	Blue, yellow tip	No (cast) Yes (molded)	Slow	Flame may spurt if rubber modified
Chlorinated Polyether	-		Green, yellow tip	No	-	-	-	-	Black smoke with soot in air
CTFE	Faint odor of acetic acid	-	-	-	-	-	-	-	Deforms; no combustion, but drips
Ethyl Cellulose	-	-	-	-	Burnt sugar	Yellow, blue edges	Yes	Rapid	-
FEP	Faint odor of burnt hair	-	-	-	-	-	-	-	Deforms; no combustion, but drips
Modified Grade	-	Phenol	Yellow-orange	No	-	-	-	-	Flame spurts; difficult to ignite, soot in air
Nitrate	-	-	-	-	camphor	White	No	Rapid	-
Oxides (PPO)	-	Phenol	Yellow-orange	No	-	-	-	-	Flame spurts; very difficult to ignite
Phenoxies	-	Acrid	Yellowc	No	Acrid	Yellow	Yes	Slow	Black smoke with soot in air
Polycarbonates	-	Faint, sweet aromatic ester	Orange	Yes	-	-	-	-	Black smoke with soot in air
Polyethylenes	-	-	-	-	Paraffin	Blue, yellow tip	Yes	Slow	Floats in water
Polyimides	-	-	-	-	-	-	-	-	Chars; material very rigid
Polypropylenes	-	Acrid	Yellow	Yellow	Sweet	Blue, yellow tip	Yes	Slow	Floats in water; more difficult to scratch than polyethylene
Polystyrenes	-	-	-	-	Illuminating Gas	Yellow	Yes	Rapid	Dense black smoke with soot in air
Polysulfones	-	-	Orange	Orange	-	-	-	-	Black smoke
Polyurethanes	-	-	-	-	-	Yellow	No	Slow	Black smoke
Propionate	-	-	-	-	Burnt sugar	Blue, yellow tip	Yes	Rapid	-
PTFE	Faint odor of burnt hair	-	-	-	-	-	-	-	Deforms; does not drip
PVC/Acrylic	-	Fruity	Blue, yellow tip	No	-	-	-	-
PVDF	acidic	-	-	-	-	-	-	-	Deforms
Rigid	-	Hydrochloric acid	Yellow with green spurts	No	-	-	-	-	Chars, melts
Type 6	-	-	-	-	Burnt wool	Blue, yellow tip	Yes	Slow	-
Type 6/6	-	Burnt wool or hair	Blue, yellow tip	Yes	-	-	-	Slow	More rigid than Type 6 nylon
Vinyls Flexible	-	Hydrochloric acid	Yellow with green spurts	No	-	-	-	-	Chars, melts
Thermosetting plastics
Diallyl Phthalates	-	-	-	-	Phenolic	Yellow	No	Slow	Black smoke, cracks
Diglycol Carbonate	-	-	-	-	Acrid	Yellow	No	Slow	Black smoke with soot
Epoxies	-	-	-	-	Phenol	Black smoke	No	Slow	Black smoke with soot in air
Melamines	Formaldehyde and fish		-	-	-	-	-	-	-
Phenolics	Formaldehyde and phenolc	Phenol and wood or paperd	Yellow	No	-	-	-	-	May crack
Polyesters	-	Hydrochloric acida	Yellow	No	-	Yellow, blue edges	No	Slow	Cracks and breaks
Silicones	-	-	-	-	-	-	-	-	Deforms
Ureas	Formaldehyde	-	-	-	-	-	-	-	-

How accurate is the plastic burn test for identification?

The burn test offers a rapid preliminary plastic identification technique but is not completely reliable. The presence of additives like flame retardants modifies how materials behave when burned. Composite materials that include multiple plastics or fillers exhibit burn behaviors that blend together, making identification hard without detailed examination.

Alfa Chemistry advises using the burn test together with advanced techniques like infrared spectroscopy or pyrolysis-gas chromatography to achieve accurate material identification. These methods enable a detailed chemical analysis of plastic materials, which leads to accurate identification of complex and composite materials.