To identify plastic
- Jan 05, 2019 -

Most of the waste plastics need to be sorted before they are reused by various plastic recycling methods. As a result of plastic consumption channel is much and complex, the plastic after some consumption is difficult to pass exterior to distinguish its simply again, accordingly, had better be able to mark material breed on plastic product. China with reference to the American society of plastic (SPE) is put forward and implement the material varieties tag made the GB/T16288-2008 "plastic packaging products recycling symbol", although can use the tag above method for sorting, but because there are many Chinese sign of plastic products, bring difficulty to the sorting, respectively for different varieties of plastic, so that classification recycling, the first thing to have knowledge to identify different plastic, plastic simple identification method introduces below:



Folded appearance identification


By observing the appearance of plastics, it can be preliminarily identified that the plastic products belong to the following categories: thermoplastics, thermosetting plastics or elastomers.



Thermoplastics are usually either crystalline or amorphous. Crystalline plastic appearance is translucent, opacified or opaque, only in the film state is transparent, hardness from soft to horny. Amorphous is colorless commonly, it is completely transparent when do not add additive, hardness from hard at corneous rubber shape (this often adds additive such as plasticizer). Thermosetting plastics usually contain fillers and are opaque, as in the absence of fillers they are transparent. Elastomers have a rubbery feel and a certain stretch rate.



Simple folding identification


The first is to see, because dark colors are generally very toxic, so generally the darker the color of the plastic is more toxic. Another important reason to dye plastics is that the raw material is waste plastic, to cover up the original color.



The 2nd it is to smell, want plastic to have peculiar smell only, no matter how absolutely cannot load food, peculiar smell is to add additive commonly in the product, color makings wait for other additional makings or the flavour of residual monomer.



The 3rd it is to touch, the plastic that holds food feels commonly smooth and have burnish, if feel is not smooth, especially the hair is sticky must not hold food, because this inside auxiliary agent is too much, much you cannot imagine, may account for 50 above.



Say a few material simply next, of the PP that packaging food USES commonly (polypropylene), PE(polyethylene), these two are safer, the plastic wrap of supermarket is PP commonly, still have the hot water pipe in the home also is PP, because want to assure avirous. Plastic cups that hold hot water are usually made from PC(polycarbonate), but use this for compact discs as well. Sewer is used commonly PVC did not hinder greatly.



Folding identification method


1, density method: through the density of all kinds of plastic, with the liquid as the medium to see its subsidence phenomenon, can roughly identify the plastic belongs to a large class, assuming that plastic in the water can float in the water, then you can determine that the raw material is not PVC.



2. Combustion method: the flame color, smell and smoke are observed through the burning of plastics. Generally, the flame of polyolefin raw materials is mostly blue or light blue with mild smell and white smoke. Additional, if PE, PP has drop to burn a phenomenon, and PVC does not have drop to burn, but have since extinguish a phenomenon.



3. Optical method: through observing the transparency of raw materials for identification, the commonly used transparent raw materials are PS, PC, PMMA and AS; The semi-transparent raw materials are PE, random copolymerization PP, homopolymerization PP, soft PVC, transparent ABS, etc. The other raw materials are basically opaque.



4. Color discrimination: generally speaking, if the raw materials without additives contain double bonds, the color will be slightly yellow, such as ABS. Because of butadiene copolymerization, the polymer still contains double bonds after polymerization, so the color will be slightly yellow.



Folding identification summary


1. PTFE



Appearance: translucent to opaque, flexible and elastic.



Flammability: noncombustible. Pungent odor in hot condition (HF).



2. Polyamide (PA)



Appearance: translucent to opaque.



Flammability: hard to ignite and goes out immediately after leaving the flame. When burning in the flame there is blue smoke, the top is orange red; Melting, dripping, bubbling phenomenon; The smell of burning wool.



3. Polycarbonate (PC)



Appearance: transparent to opaque, hard.



Flammability: difficult to ignite. In the flame burning black smoke, bright, carbonization, bubbling phenomenon; The smell of phenol.



4. Phenolic resin (PF)



Appearance: dark tone.



Flammability: difficult to ignite. Burning in the flame can be seen bright yellow flame, black smoke, cracking and color deepening phenomenon.



5. Polyvinyl chloride (PVC)



Appearance :(same as polycarbonate)



Flammability: difficult to ignite. In the flames burning yellow, flame edge green, white smoke; There is softening. I can smell burning.



6. Amino resin (UF urea/formaldehyde); MF melamine/formaldehyde



Appearance :(with stuffing) hard.



Flammability: difficult to ignite. Burning bright yellow in flames; There are carbonization, expansion, cracking phenomenon. Can smell ammonia, formaldehyde, fishy smell.



7. Polyethylene (PE)



Appearance: translucent to opaque, hard; Transparent film.



Combustibility: combustible in flame, slowly extinguished or continued to burn after leaving the flame. When burning, the upper end of the flame is yellow and the lower end is blue. There is melting, dripping phenomenon. You can smell paraffin.



8. Polypropylene (PP)



(same appearance and flammability as polyethylene)