【Popular Science Tips on Polymers and Materials】--028 Materials for Household Plastic Wrap + People Watching the Sea
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Plastic wrap is a type of plastic packaging material, typically produced through polymerization reactions using ethylene as the base material. It is mainly used for heating food in microwave ovens, storing food in refrigerators, and packaging fresh as well as cooked foods. It is widely employed in various fields related to food packaging, including household use, supermarkets, hotels and restaurants, and industrial production. Depending on the materials used and the plasticizers added, plastic wrap comes in various types, suitable for different applications. Plastic wrap is favored by people for its convenience, affordability, and aesthetic appeal. However, due to the widespread use of plasticizers in the production process, the impact of plastic wrap on human health has also drawn attention. The vast majority of plastic wrap and common plastic bags available on the market are made from ethylene masterbatch as raw material. Depending on the different types of ethylene masterbatch, plastic wrap can be divided into three categories. The first is polyethylene, abbreviated as PE. This material is mainly used for packaging food; the plastic films used to wrap the fruits and vegetables we buy, as well as the semi-finished products purchased from supermarkets, are all made of this material ； The second is polyvinyl chloride, abbreviated as PVC; this material can also be used for food packaging, but it has certain effects on human safety ； The third is polyvinylidene chloride, abbreviated as PVDC, which is mainly used for packaging products such as cured meats and ham. Among these three types of plastic wrap, those made from PE and PVDC are safe for human use and can be used with confidence, whereas PVC plastic wrap contains carcinogenic substances and is harmful to health; therefore, when choosing plastic wrap, one should opt for PE plastic wrap. From a physical perspective, plastic wrap has a certain degree of oxygen and moisture permeability; it helps regulate the levels of oxygen and moisture around the food being preserved, while also preventing dust from getting in, thereby extending the shelf life of the food. Therefore, it is necessary to use different types of plastic wrap for different foods. Plastic wrap available on the market can be roughly divided into two categories: one is regular plastic wrap, suitable for use in the refrigerator to preserve food ； One type is microwave-safe plastic wrap, which can be used for food preservation in the refrigerator as well as in the microwave oven. The latter type of plastic wrap is far superior to ordinary plastic wrap in terms of heat resistance, non-toxicity, and other aspects. Therefore, consumers should pay special attention when making their choices and use them separately.
This post was last edited by ljtjbx on 2015-11-15 at 10:25. Notes: 1. When heating foods with a high oil content, keep the plastic wrap separate from the food to prevent direct contact between the two. Because when food is heated, the oils in the food can reach very high temperatures, causing the plastic wrap to break and stick to the food. 2. When heating food, cover the container with plastic wrap, then make a few small holes in the wrap using a sharp object, so that moisture can evaporate and the wrap does not burst due to gas expansion. 3. The maximum heat resistance temperatures indicated for plastic wrap of different brands vary; the difference can be around 10°C. The temperature inside a microwave oven is relatively high, often reaching around 110°C. When heating for an extended period of time, it is advisable to choose plastic wrap with higher heat resistance. Special note: PVC plastic wrap has higher transparency, stretchability, and stickiness than PE plastic wrap. When PVC plastic wrap is exposed to fire, the flame turns black, black smoke is produced, and there is a pungent odor; no oil drips from it, and it extinguishes itself once removed from the heat source. When PE plastic wrap burns, the flame is yellow, it is odorless, it drips oil, and it can continue to burn even after being removed from the source of fire. If it is labeled as PVC material or the label is unclear, it is recommended not to purchase or use it. An ideal plastic wrap should meet the following conditions: 1. It should be easy to pull out and cut ； 2. It adheres easily to glass-ceramic and stainless steel tableware (but not to the plastic wrap itself) ； 3. It is nearly transparent, with no wrinkles or uneven thickness ； 4. Can withstand normal pulling stress.
When purchasing storage containers or plastic wrap, be sure to check whether they indicate the specific name or chemical formula. Products that only have an English name without any Chinese labeling should be purchased with caution. At the same time, be sure to choose products labeled as “for food use”. Preservation containers are mainly made of two types of materials: polyethylene (PE) and polypropylene (PP). The price difference between these two types is not significant, but polypropylene (PP) is better at preventing the penetration of oils. When purchasing plastic wrap, it is recommended to choose self-adhesive wrap made of polyethylene (PE), especially for preserving meat, fruits, etc., as from a safety perspective, PE plastic wrap is the safest option. If a longer shelf life is desired, it is recommended to choose polyvinylidene chloride (PVDC), as plastic wrap made from this material has good moisture-retaining properties and provides the longest shelf life among the three types of plastic wrap. Plastic wrap made of PVC is a popular choice for many people due to its good transparency, viscosity, elasticity, and relatively low cost. However, it should not be used to preserve fatty foods, as it is made up of PVC resin, plasticizers, and antioxidants; the resin itself is not toxic. However, the plasticizers, antioxidants, and other additives used have toxic properties. In household polyvinyl chloride plastics, plasticizers such as dibutyl phthalate and dioctyl phthalate are commonly used; these chemicals are toxic. Moreover, the fats present in food can easily dissolve the plasticizer \"ethylamine\" found in plastic wrap, which can cause significant damage to the human endocrine system and disrupt hormone metabolism. Lead stearate, an anti-aging agent for polyvinyl chloride, is also toxic. Polyvinyl chloride (PVC) products containing lead salt antioxidants will release lead when in contact with ethanol, ether, and other solvents. When polyvinyl chloride containing lead salts is used for food packaging and comes into contact with foods such as fried dough sticks, fried pastries, fried fish, cooked meat products, and cakes, lead molecules can diffuse into the fats, so polyvinyl chloride plastic bags should not be used to store oily foods. It must not be heated in a microwave oven, nor used at high temperatures. Because PVC plastic products slowly release hydrogen chloride gas at higher temperatures, such as around 50°C, and this gas is harmful to the human body, PVC products should not be used as packaging for food.
Canned foods, hot foods, and fatty foods, especially meat, should preferably not be stored wrapped in plastic wrap. When these foods come into contact with plastic wrap, it is easy for the chemical compounds contained in the plastic wrap to evaporate and dissolve into the foods, which is harmful to health. The vast majority of plastic wrap available on the market, just like ordinary plastic bags, are made from ethylene masterbatch as raw material. Some types of plastic wrap are made of polyethylene (abbreviated as PE); this material contains no plasticizers, making it relatively safer to use. Other materials are made of polyvinyl chloride (abbreviated as PVC), and such materials often contain stabilizers, lubricants, and other additives, which can be harmful to human health. Therefore, one must be cautious when making a choice. Weight loss using plastic wrap? Some beauty salons offer a weight loss method that involves using plastic wrap made of materials such as PVC to tightly cover the body. It is believed that the low breathability of this plastic wrap can increase the local temperature of the body, thereby helping to burn fat and achieve weight loss. However, some people point out that this is actually a very dangerous behavior, as the large amount of plasticizers contained in PVC can easily enter the body through the skin, and may even affect the body’s endocrine system. Therefore, consumers must be very cautious when choosing this weight loss method.
Do we still need this? Wearing a raincoat will do just fine
If the additives in PVC-type plastic wrap are toxic, why are they still allowed to be produced and circulated in the market? Regarding the production and use of food-grade plastic products, what certifications or qualifications are required from both processing enterprises and raw material suppliers?
These three are different. . . . . . . . . . . . . . .
Zhang has seen it, and indeed there are quite a lot of PVC products in daily life; probably it’s because of their low cost. But when it comes to food safety, one still needs to be cautious