Analysis of common materials in plastic bags

Public date： 2021-4-16 14:21:47

   Polyethylene (PE) for short. It is a high molecular organic compound formed by addition polymerization of ethylene. Polyethylene is recognized as the best material in contact with food in the world. Non toxic, tasteless, odorless, in line with food packaging hygiene standards. Polyethylene film, light and transparent, with moisture resistance, oxygen resistance, acid resistance, alkali resistance, general air tightness, excellent heat sealing performance. Known as the "plastic flowers" reputation. Bai is the most important material for plastic packaging printing.

PVC -- PVC

Polyvinyl chloride, abbreviated as PVC, with the molecular formula of (CH-CH) n, is the most important type of vinyl polymer and the second largest plastic variety in the world. In the domestic production of plastics in the first place. In the printing industry, PVC color calendering film and transparent glazing film are often used to make the packaging and decoration of books, magazines, folders, tickets and other covers.

Shrinkfilm -- shrink film

Shrinkfilm is a kind of thermoplastic film which is stretched and oriented in the production process and shrinks when it is exposed to hot air treatment or infrared radiation during use. After heat treatment, the film is tightly wrapped on the package, the shrinkage force reaches the maximum in the cooling stage, and can be stored for a long time.

LDPE -- low density polyethylene

Low density polyethylene (LDPE) is the most widely used variety in plastic packaging and printing industry. The specific gravity is 0.92-0.93, which can float in water. Low crystallinity (60%) and bulk polymerization at pressure of 1000-3000kg / cm2, so it is also called high pressure polyethylene. At 23 ℃, the density is about 0.92. Due to the poor calenderability, it is suitable to be processed into tubular film by blow molding. It is suitable for food packaging, fiber products packaging and daily chemical products packaging.

HDPE -- high density polyethylene

High density polyethylene, HDPE for short. The density is 0.941-0.965g/cm3. It is polymerized with low pressure, so it is also called low pressure polyethylene. It is milky white, indicating poor luster. The film can be processed by blow molding and T-die extrusion. Heat resistant, cooking resistant, cold resistant, freezing resistant, moisture-proof, gas proof, good insulation performance, not easy to damage, the strength is twice that of LDPE. It's very easy to open your mouth. It has strong paper like property and is known as "paper like plastic film".

BOPP -- biaxially oriented polypropylene film

Biaxially oriented polypropylene film, also known as biaxially oriented polypropylene film, abbreviated as BOPP, is characterized by molecular orientation, better mechanical strength, folding strength, air tightness and moisture resistance than ordinary plastic film. Compared with cellophane, the unit price is lower than cellophane. Because of the excellent transparency of this film, the color reproduction after printing is particularly bright and beautiful. It is an important base material for plastic composite flexible packaging.

Toxicity identification of plastic bags

The commonly used food plastic bags are mostly made of polyethylene film, which is non-toxic, so it can be used to hold food. There is also a film made of PVC, PVC itself is non-toxic, but according to the use of the film, the additives are often harmful to human body, with a certain degree of toxicity. Therefore, this kind of film and the plastic bag made of the film are not suitable for holding food. If you want to identify PVC plastic bags and polyethylene plastic bags, you can use the following simple method to identify.

Polyethylene film (non toxic)

The film is milky white and translucent (especially obvious when you stack it up in several layers). It feels greasy. It seems that there is a layer of wax on the surface. It shakes hard and makes a brittle sound. It is flammable when it meets fire. The flame is yellow. There is mucus dripping when it burns and the smell of candle burning.

PVC film (generally toxic)

If there is no pigment, it is transparent. It feels sticky on the surface, shakes with force, and has a low voice. It is not easy to burn when meeting a fire. It goes out when leaving the flame, and the flame is green.