2-3 months. PP plastic raw material, chemical name: polypropylene, characteristics: small density, strength and rigidity, hardness and heat resistance are better than low pressure polyethylene, which can be used at about 100 degrees. It has good electrical performance and high frequency insulation, which is not affected by humidity, but becomes brittle, wear-resistant and easy to age at low temperature. Suitable for making general mechanical parts, corrosion resistant parts and insulating parts
Polypropylene has good heat resistance. The products can be sterilized at a temperature above 100 ℃, and will not deform at 150 ℃ without external force. The embrittlement temperature is minus 35 ℃. When the temperature is below minus 35 ℃, embrittlement will occur. The cold resistance is not as good as polyethylene. The melting temperature of polypropylene is about 40-50% higher than that of polyethylene, about 164-170 ℃, and the melting point of 100% isotactic polypropylene is 176 ℃.
Classification of water cups
1. Plastic cup: Generally speaking, the bottom of the plastic cup is marked with 05, indicating that the material of the cup is PP (polypropylene). The PP cup has good heat resistance. The melting point is 170 ℃~172 ℃, and its chemical properties are also relatively stable. In addition to being eroded by concentrated sulfuric acid and nitric acid, it is relatively stable to other chemical reagents. Plastic is a high molecular chemical material. When hot water or boiled water is filled in a plastic cup, the high molecular is easy to separate out and dissolve into water, which is harmful to human health after drinking. Moreover, the internal microstructure of the plastic has many pores, which hide dirt, and bacteria will breed if it is not cleaned. Therefore, the selection of plastic cups is very important for the selection of plastic materials. We must select food grade plastics that meet the national standards, that is, PP materials.
2. Ceramic cup: The inner wall of a cheap colored ceramic cup is usually coated with a layer of glaze. When the glazed cup is filled with boiling water or drinks with high acid or alkaline content, some aluminum and other heavy metal toxic elements in the glaze are easy to separate out and dissolve into the liquid. At this time, people will be injured if they drink liquid with chemical substances. When using ceramic cups, it is better to choose a cup of natural color, reach out and touch the color surface. If the surface is smooth, it means it is underglaze color or underglaze color, which is relatively safe; If it is uneven and will fall off when you pick it with your fingernails, it means it is overglaze color, and you'd better not buy it.
3. Paper cups: There are three types of paper cups on the market. The first is made of white cardboard, which cannot contain water and oil. The second is the waxed paper cup. As long as the temperature of the water in the cup exceeds 40 ℃, the wax will melt and release the carcinogen polycyclic aromatic hydrocarbons. The third type is paper plastic cup. If the selected material is poor or the processing technology is not up to standard, cracking changes will occur in the process of polyethylene hot melting or coating on the paper cup, resulting in carcinogens. In order to increase the toughness and rigidity of the cup, the paper cup will be added with plasticizer. If the dosage is too large or illegal plasticizers are used, it is difficult to ensure the sanitary condition.
4. Glass: among all the cups made of materials, glass is the most healthy and safe. The glass is made of inorganic silicate, and does not contain organic chemicals in the process of firing. When people drink water or other drinks with glass, they do not need to worry about the chemicals being drunk; Moreover, the glass surface is smooth, easy to clean, and bacteria and dirt are not easy to breed on the glass wall, so it is the healthiest and safest for people to drink water with glass. The only thing to note is that the glass is most afraid of thermal expansion and cold contraction, and the glass with too low temperature should not be filled with hot water immediately to prevent bursting.
5. Stainless steel cup: The advantages of stainless steel cup are firm, durable, rust proof and corrosion proof. However, stainless steel cups belong to alloy products, which contain more heavy metals, such as nickel, chromium, manganese, etc. If they are used improperly, these heavy metals will be easily released and endanger health. Therefore, in daily use, please pay attention not to use stainless steel cups to hold acidic drinks, such as juice, coffee, carbonated drinks, etc; It is also not allowed to keep soy sauce, vinegar, vegetable soup, tea, etc. for a long time, because the electrolyte in these foods may react with the heavy metals in stainless steel, resulting in the separation of heavy metals. When washing stainless steel cups, do not use strong alkaline or strong oxidizing chemicals such as soda, bleaching powder, etc. These substances are also easy to react with stainless steel.
6. Enamel cup: enamel is a kind of composite material that inorganic glass materials are fused and solidified on metal by thousands of degrees. Enamel coating on the metal surface can prevent rust, prevent the metal from forming oxide layer on the surface when heated, and resist the erosion of various liquids. Enamel products do not contain lead and other harmful substances, and are easy to carry and clean. They are widely used as food utensils and washing utensils in daily life. The enamel cup has a disadvantage. The enamel cup is afraid of bumping, and the surface is easy to be damaged. Studies have shown that broken enamel cups are prone to release harmful substances when containing drinks, and should be eliminated decisively.
