In 1988, labeling was introduced for the processing of plastic waste. On it there are only 7 types of plastic. Such marking is most often used on containers. For other products, abbreviations of plastics, for example ABS, PS, etc., may be used.
Typically, marking is applied on the back of the product, for example, on plastic bottles on the bottom.
Number 1. This is polyethylene terephthalate, PET or PET (Ф). It is used for the manufacture of containers, fibers or films. It was originally developed for the production of fibers and the production of both technical and household fabrics (fleece). But with the improvement of polymerization technology, it is increasingly used for food packaging.
Figure 2. High-density low-density polyethylene, HDPE. From it make packaging bags, shrink film.
Number 3. Polyvinyl chloride (PVC), PVC. Mainly for the production of linoleum and plastic windows. For the use of food packaging, its use is prohibited, although often liners for bottle caps are made from it.
Figure 4. High-density low-density polyethylene, LDPE. For the manufacture of packaging containers, greenhouse films, pipes and toys.
Figure 5. Polypropylene PP is widely used for food packaging because of its complete chemical inertness and heat resistance. It is used in the manufacture of disposable syringes, catheters, disposable dishes for hot dishes, household appliances. It can be steamed and boiled, so pipes are made from it for hot water supply.
Number 6. Polystyrene PS. Disposable dishes, glasses for yogurt, inner lining and filling of refrigerators. Foaming of special grades of polystyrene with pentane allows to obtain expanded polystyrene, an insulating material.
Figure 7. Other materials, such as multilayer foil packaging for milk and juices, combining paper, foil and polymers. More recently, chlorinated CPE polyethylene has been added to this group. These materials are virtually recyclable.
There are hardware types of studies, for example, infrared spectroscopy. Well, if there are no devices at hand, then you can use quick and uncomplicated methods.
After all, plastics of different types:
the smell during their burning is different,
solvents act differently on them,
when immersed in water, they also behave differently.
It is on this difference that the basic methods of self-determination of the type of plastic are based.
The flotation method is based on different densities and different behaviors in water – the separation of various types of plastics in flotation baths.
Burning and dissolving plastics
Polyethylene Terephthalate (PET). Durable, tough, heat resistant material. Drowning in water. It burns with a smoky flame, it softens without flow, self-extinguishing, that is, when removed from the combustion zone, it attenuates. The smell is pungent.
Polyethylene. All types of polyethylene burn very well with a bright, bluish flame without soot, with the smell of paraffin. In this case, streaks and drops form.
Polyethylene floats on the surface of the water and does not dissolve in most organic solvents. For this reason, and because of its surface tension, parts made of polyethylene cannot be glued.
Polypropylene. When introduced into the flame, polypropylene burns with a brightly glowing flame. Burning is similar to burning polyethylene, that is, when burning, polymer streaks are formed, the smell is sharper, similar to the smell of burnt rubber or sealing wax. If you touch the melt with a match, you can stretch a long thread.
It practically does not dissolve in organic solvents at room temperature, only slightly swells. For this reason, it does not adhere well. He is swimming in the water.
Polystyrene. When bending a strip of polystyrene, it easily bends with the appearance of a white zone, then sharply breaks with a characteristic crack. It burns with a bright, very smoky flame, with flakes and cobwebs of soot. The smell is sweet.
Polystyrene is highly soluble in organic solvents (acetone, benzene), carbon tetrachloride and chladones (in dichloethane). Drowning in water.
Polyvinyl chloride (PVC). Elastic. Hard-burning, self-extinguishing, that is, when removed from the fire zone it goes out. When burning, it smokes heavily, at the base of the flame you can observe a bright bluish-green glow.
Very sharp, pungent smell of smoke with an admixture of chlorine, so the combustion products are very toxic. Upon combustion, a black, carbon-like substance is formed. Drowning in water.
It is soluble in chladones and polyesters (dichloroethane, chloroform), swells in gasoline and acetone.
Polyacrylate (organic glass). Transparent, fragile material. It burns with a bluish-glowing smoky flame with a slight crackle. Smoke has a sharp fruity smell (ether).
Easily soluble in dichloroethane and acetone, which is used for bonding it. Drowning in water.
Polyamide (PA). Very durable plastic, which is attributed to engineering, structural materials. Burns with a bluish flame. When burning, it swells, smokes, “puffs”, forms burning streaks. Smoke with an easily recognizable smell of singed hair, feathers. Frozen drops are very hard and brittle. Drowning in water.
Polyurethane. Very flexible and flexible material (at room temperature). In the cold – fragile. It burns with a smoky, luminous flame, with a pungent odor. At the base, the flame is blue. When burning, burning droplets are formed. After cooling, these drops are a sticky, greasy to the touch substance. Drowning in water.
Plastic ABC. All combustion properties are similar to polystyrene, but a caustic note is mixed with the sweet smell of styrene. It is easy to confuse with impact-resistant polystyrene, but differs from it in higher rigidity, which can be felt when bent.
Unlike polystyrene, it practically does not dissolve in freons and gasoline, it can only swell a little. Drowning in water.
Ftoroplast. Not combustible, with strong heating, charred with the release of a very pungent odor. It is strictly forbidden for contact with food, because the smell can be felt without heating.
It is poorly soluble in organic solvents and may swell.
Polycarbonate Transparent high-strength plastic is increasingly being used for greenhouses, stopping pavilions and advertising structures (especially cellular). It is steady against blows, but it is easily scratched. Self-extinguishing, that is, when removed from the flame it goes out. When burning, a sweet floral smell appears.
It softens in gasoline, acetone and in most organic solvents. It sinks in water.
Polyacetal And it burns polyacetal. Dense, durable, “slippery” plastic with a very pungent odor when burning. There is a group of non-combustible acetals. Therefore, you can use the express test to avoid major troubles with consumers.
Unfortunately, manufacturers do not always mark products, and then you have to resort to other methods of determining the brand of plastic:
To determine the type of plastic from which the product is made, a piece of this material is carefully heated with a match flame. If the material melts, then the product is made of thermoplastic plastic, if it does not melt, thermoset plastic is used. If after the lit match is removed, the plastic material continues to burn, polyethylene, polypropylene, polystyrene, polymethylene, organic glass, cellulose acetate or nitrocellulose (celluloid) were used to make the product. If the material does not burn, the product is made of polyvinyl chloride, polyamide or polytetrafluoroethylene.
Flammable plastics. The color of the flame and the smell formed during combustion determine the type of plastic. Polyethylene burns with a faint bluish flame. When the flame is blown out, the smell of a burning candle is felt, and the combustion product is a soft, greasy to the touch substance. The same can be said about polypropylene. Polystyrene when consumed strongly fumes, while a sweetish smell appears.
Cellulose acetate, which in an unheated state is an elastic and viscous substance, burns with a non-smoking flame, cracking, spreading the smell of vinegar. Cracking on burning, with the smell of fruit, solid polymethyl methacrylate burns. Nitrocellulose (celluloid) burns with a bright strong flame.
Non-combustible plastics. After the flame is brought to the polyamide, bursts form, crackling is heard, and the burnt sample smells of burnt wool. If a PVC sample is heated in a flame, the end of the tongue of the flame will turn green and a pungent odor similar to that of hydrochloric acid will spread.
Non-consumable plastics. After removal of the flame, the phenoplast goes out and has a specific smell. The aminoplast, heated in a flame, burns with a smoky flame, cracking, after being removed from the flame it continues to burn, spreading the smell of ammonia (ammonia). The polyester in the flame cracks, after blowing out the flame a sweetish smell is formed, reminiscent of the smell of fruit. The epoxy does not crack when the flame is presented, and after being removed from the flame, it continues to burn for a short time. After blowing out the flame smells like burnt wool.
Compiled by Logvinenko V.V.
As you know, certain types of plastics are characterized by a certain set of indirect features, the knowledge of which will help in the field to attribute the latter to one or another group of polymers: color, texture, light transmission, elasticity, elasticity, fracture nature.
The technique is simple and consists in analyzing the behavior of a plastic sample in an open source of fire, as well as the products of a concomitant oxidation process (nature of combustion, emitted smell, sound).
This method should be considered conditional, since the sample may contain additives that change the structure, color and smell of the polymer during combustion.