What material is best for household food wrap? Which is safer, PP or PE cling film?

　　The thin, transparent cling film brings great convenience to food preservation and has become an indispensable item in kitchen and home life. Now that there are so many types of cling film on the market, do you know how cling film is classified? Which type of cling film material is safe and healthy? 
　　I. Common materials of cling film 
　　There are many food preservation materials, such as plastic plates, cardboard, and metal materials, which belong to hard materials, while cling film belongs to soft materials. In addition, there are preservatives. Among them, cling film is accepted by families, but while cling film brings convenience, the safety of cling film itself should also be taken seriously by consumers. The safety of cling film is closely related to the material, 
　　1. PE (Polyethylene) cling film 
　　The main component of PE cling film is polyethylene resin, which is an odorless, non-toxic, waxy solid with a milky white appearance. Although ethylene monomer is slightly toxic, the residue in PE cling film is extremely small, and the content of additives is very small, so it is generally considered a safe packaging material. 
　　It is mainly used for packaging ordinary fruits and vegetables. PE cling film has good moisture resistance and air permeability, and is especially suitable for packaging peanuts, biscuits, etc. for short-term storage; due to its good air permeability, it is not suitable for packaging high-fat foods that are easily damaged by oxygen. such as wine, tea and other flavor foods, edible oil, dairy products, etc. 
　　2. PP (Polypropylene) cling film 
　　PP (polypropylene) cling film is currently available in several types: uniaxially oriented PP, biaxially oriented PP (OPP), and ordinary thin film (CPP). The hygiene and safety of PP (polypropylene) cling film are better than PE. 
　　It should be noted that both PP and PE are food-grade plastics. PE is commonly used in cling film and plastic film, etc., and is not heat-resistant, so it cannot be heated in a microwave oven. PP plastic is safe and non-toxic, and is not afraid of high and low temperatures, and is the only plastic that can be heated in a microwave oven. 
　　In order to prevent buying cling film made of PVC material, the following methods can be used to distinguish between PE and PVC cling film: 
　　1. PE cling film has poor stickiness and transparency, and is easy to open after being rubbed by hand, while PVC cling film has better transparency and stickiness. It is difficult to unfold after being rubbed by hand, and it is easy to stick to the hand. 
　　2. When PE cling film is ignited with fire, the flame is yellow, and it will not extinguish even when it leaves the fire source, and there is oil dripping phenomenon, and there is no pungent odor, while PVC cling film contains nitrogen elements, and when ignited with fire, the flame is yellowish-green, the smoke is relatively large, there is no oil dripping phenomenon, and it will extinguish after leaving the fire source, and there is a strong pungent odor. 
　　3. PVC (Polyvinyl chloride) cling film 
　　PVC cling film is a high molecular compound synthesized by polymerization of vinyl chloride monomers. It has good transparency, high viscosity, good elasticity, and is not easy to break, but PVC has poor thermal stability, and improper use can cause great harm to people. Some PVC cling films may contain di(2-ethylhexyl)phthalate (DEHA) as a plasticizer, which can damage the human endocrine system and is carcinogenic. It is easy to leach from the packaging material and enter the human body with food. Therefore, the state prohibits the use of DEHA in the production of PVC cling film, but PVC cling film is low in cost and cheap. Therefore, the production and sales volume is very large, 
　　Because PVC cling film is not heat-resistant, high temperatures will cause the already polymerized VC to be released, polluting food. Therefore, PVC cling film cannot be used to cover hot food, and it cannot be used in a microwave oven. At the same time, PVC cling film cannot be directly covered on high-fat foods, fish, meat, eggs and dairy products, and can only be used for the outer packaging of fruits and vegetables. 
　　4. PVDC (Polyvinylidene chloride) cling film 
　　PVDC cling film is composed of polyvinylidene chloride and a small amount of plasticizers, stabilizers and other additives. The content of vinylidene chloride monomer is extremely low. It has good freshness retention, is strong and easy to adhere to, and can prevent water evaporation. It is superior to PVC cling film in terms of heat resistance and safety. 
　　However, since PVDC cling film also uses stabilizers and plasticizers, there are hygiene and safety issues when used as food packaging, just like PVC. Attention should be paid to the selection, but it is also said that PVDC cling film is far superior to ordinary cling film in terms of heat resistance and non-toxicity (this point is reserved for now, and professional friends are expected to provide popular science). PVDC cling film is mainly used for packaging some cooked food, ham, etc. The PVDC cling film has a usable temperature range of -60℃~140℃. 
　　Some people believe that if you want to steam or put it in a microwave oven, it is better to choose PVDC or PMP cling film. 
　　II. Which foods are suitable for cling film? 
　　Medical experts and nutritionists point out that only scientific use of cling film can ensure both freshness and safety. Cling film can adjust the oxygen and water content around the preserved food, and block dust in the air, thereby extending the shelf life of food. 
　　Cling film is mainly used for preserving fruits and vegetables with high water content, such as apples, pears, tomatoes, rapeseed, chives, etc., but cooked food, hot food, and oily food, especially meat, should not be packaged and stored with cling film. These foods, after contacting cling film, easily cause the chemical components contained in the material to volatilize and dissolve into the food, which is detrimental to health. 
　　III. How to choose cling film 
　　The State Administration of Quality Supervision, Inspection and Quarantine requires food cling film manufacturers to clearly indicate the material and scope of application on the product packaging. Therefore, if the cling film packaging does not indicate the material, it may be a suspicious inferior product. 
　　At present, most of the cling films sold in supermarkets for household use are PE cling films. This material does not contain plasticizers and is relatively safe to use.