Waste Plastic Recycling Solutions

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How to sort and identify waste plastic recycling?

1. Plastic classification


1. According to the different properties of plastics after being heated, they are divided into thermoplastic plastics and thermoset plastics. The waste plastics that we can usually recycle are thermoplastic plastics, because the molecular structure of thermoplastics is linear, which softens or melts when heated. It can be molded into a certain shape, and it becomes hard after cooling. It softens again after being heated to a certain extent, and then becomes hard after cooling. This process can be repeated many times. Such as polyvinyl chloride, polyethylene, polystyrene, etc.


The molecular structure of thermosetting plastics is a body structure. It is hardened and shaped after heating to a certain degree or adding a small amount of curing agent. It will not become soft and change shape after heating, so it cannot be recycled and reused, such as phenolic plastic, amino plastic, ring Oxygen resins are all such plastics.


2. According to different uses of plastics, it is divided into general plastics and engineering plastics


General-purpose plastics refer to plastics with large output, low prices and a wide range of applications, mainly including polyolefins, polyvinyl chloride, polystyrene, phenolic plastics and amino plastics.


Engineering plastics are plastics that can be used as engineering structural materials and to replace metal manufacturing machine parts, such as polyamide, polycarbonate, polyoxymethylene, ABS resin, polytetrafluoroethylene, polyester, polysulfone, polyimide, etc.


2. Identification of waste plastics


Waste plastics are mainly CaC03 (stone powder) content that determines the utilization value of waste plastics. The more CaC03 content, the lower the price.


Generally, there are several steps to identify waste plastics:


1. Look at the color and brightness (transparent material can be removed in this step); Look at the feel (weight, smoothness);


PE: Polyethylene The raw material of LDPE is white waxy, transparent; HDPE is white powder or white translucent granular resin. It floats in water, is odorless and tasteless, has a waxy smooth feel, has traces after scratching, and the film is soft and stretchable. LDPE is soft, extensible, bendable, but easy to break; MDPE and HDPE are harder, have better rigidity and toughness, and have low sound.


PP: Polypropylene raw material is white waxy, translucent, floating in water, odorless and tasteless, smooth to the touch, no trace after scratching, bendable, not easy to break, good tensile strength and rigidity, bright sound.


PS: Polystyrene is transparent like standard glass; impact-resistant, matt, sinking in water, odorless and tasteless, smooth to the touch, brittle, and easy to break. There is a metallic sound when nailed, commonly known as "sound glue".


ABS: Milky white or beige, amorphous, opaque, dull, odorless and tasteless when sinking in water, tough, hard, and rigid. It is not easy to break, and the sound is clear and crisp.


Pvc: Polyvinyl chloride products vary depending on the plasticization and filler conditions, and some are opaque. It sinks in the water and varies with the type. Hard products will be soft and bendable when heated to 50℃; soft products will sag, and some are flexible. Hard products such as doors and windows, sewer pipes, etc.


Pmma: Polymethyl methacrylate (plexiglass), transparent like glass, beautiful appearance. It sinks in water, is odorless and tasteless. It can be bent freely when heated to 120°C. It can be processed by hand. It is hard and not fragile. It has a dull and heavy sound when hit with fingers.


PU has five forms: foam, elastomer, coating, synthetic leather, and adhesive, with different forms, some sink in water, some float. It is odorless and tasteless, and varies with the shape, and the sound is low.


PC: The raw material of polycarbonate is white crystalline powder, light yellow to amber, transparent solid, and the product is almost colorless. It is a high-grade insulating material, odorless, tasteless, metallic, hard, resistant to bending, impact resistance, toughness, and louder.


2. Ignite (check whether the color of the flame is smoking, whether it contains burning away from the fire or not burning at all);


You can cut a small piece of plastic sample, hold it with tweezers, and burn it on a lit alcohol lamp or lighter. Observe the difficulty of burning carefully. Whether it continues to burn after leaving the fire source or extinguished immediately, the color of the flame, Smoke, what is the status change of the plastic during and after burning, what smell is there when burning, etc. According to the burning characteristics of plastic, determine its type.


PE burns brightly, the bottom is blue, the top is yellow, it continues to burn after the melt dripping, and there is no smoke that melts dripping


PP is yellow at the top, blue at the bottom, a small amount of black smoke, soft, foamy, spicy oil smell


PS is flammable, bright, orange-yellow, thick black smoke, soot. Melting, foaming, slightly charred. Aromatic smell (styrene monomer smell)


ABS yellow flame, bright, black smoke softened, melted, burnt, no dripping, rubbery smell


PA (Polyamide) Burns slowly, extinguishes slowly, yellow-orange, blue at the edge Melting, dripping, blistering, special smell like burnt wool and nails


PC yellow, bright, soaking, softening, melting, foaming, coking, flower and fruit smell


PVC is non-flammable and extinguishes after the fire is yellow-orange, green at the edge, white smoke, and light green and yellow flame is softened, can be drawn, has a pungent hydrogen chloride smell


UF self-extinguishing yellow, light blue at the top, swelling, cracking, turning white, coking Formaldehyde smell, ammonia smell


MF Light yellow, whitish edges, swelling, cracking, whitening, coking Formaldehyde smell, light fishy smell


PF glows, yellow sparks, cracks, darkening, smell of phenol and formaldehyde


PF (wood powder) slow burning yellow, black smoke swelling, cracking wood and phenol smell


Only by understanding the classification and identification methods of plastics can we better recycle and sell waste plastics!


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