There are two common plastics: one is polyethylene film […]
There are two common plastics: one is polyethylene film; the other is polyvinyl chloride film. The plastic bag made of polyethylene film is non-toxic and can be used to hold food, but its strength is not good. And can not withstand high temperatures above 80 ℃, and has a certain permeability, not suitable for long-term use to contain tea, spices, etc. Plastic bags made of polyvinyl chloride film are toxic, so it is not suitable for direct contact with food. Polyvinyl chloride plastic is commonly used for raincoats, shoe soles, bed covers, curtains, tablecloths, handbags, etc.
An easy way to identify the above plastic bags:
1. Touch method: It feels lubricating by hand. The surface is coated with a layer of wax (chemically called waxy feeling). This is a non-toxic polyethylene film; while the polyvinyl chloride film feels a little sticky.
2. Shaking method: The sound of hand shaking is crisp, and it is a non-toxic polyethylene film; the low sound of hand shaking is the PVC film plastic bag.
3. Combustion method: Burn in case of fire, the flame is yellow, there is paraffin-like oil dripping when burning. And there is the smell of candle burning, it is a non-toxic polyethylene film; if it is not easy to burn, it will extinguish when it is away from the flame The green color is a PVC film plastic bag.
4. Immersion method: Immerse the plastic bag in the water, press it into the water by hand, and the non-toxic polyethylene film will float out of the water; the plastic bag with the polyvinyl chloride film sinks into the bottom. Polyethylene is abbreviated as PE in English. It is a polymer of ethylene and is non-toxic. Easy to color, good chemical stability, cold resistance, radiation resistance, good electrical insulation. It is suitable for packaging materials for food and medicine, making tableware, medical equipment, and insulation materials for the electronics industry.
Polyvinyl chloride is abbreviated as PVC, which is a polymer of vinyl chloride. It has good chemical stability and is resistant to acid, alkali and some chemicals. It is resistant to moisture, aging, and flame. When it is used, the temperature cannot exceed 60°C, and it will become hard at low temperatures. Polyvinyl chloride is divided into soft plastics and hard plastics. It is mainly made of soft film, used as packaging material, rain-proof products, agricultural seedling-raising film, etc., and can also be used as the insulation layer of cables and wires, and artificial leather products. Hard materials are generally made into pipes and plates. The pipes are used as water pipes and pipes for transporting corrosion-resistant fluids. The plates are used as linings and floors for various storage tanks. Polyvinyl chloride (PVC) resins are non-toxic, polyvinyl chloride monomers are highly toxic, and whether polyvinyl chloride products are toxic depends on whether the residual monomers in the polymerization process are removed to certain requirements. It depends on whether the additives added during processing are toxic. For example, if the content of vinyl chloride monomer in PVC food wrap film is too high, especially in high temperature environments such as microwave ovens, it is easy to decompose substances that have carcinogenic effects on the human body; in addition, plasticizers and stabilizers for processing PVC wrap films If the choice is not good, it will easily cause some harm to the human body.
