Most insulated cups are made of stainless steel material, which is resistant to high temperatures and has good insulation performance. Other materials such as glass, ceramics, purple clay, etc. are only a small part of the “thermos army” due to factors such as insulation, anti drop, and price.
At present, there are three types of stainless steel with code names 201, 304, and 316 that are commonly seen in the thermos cup market.
201 stainless steel
The unqualified insulated cups exposed in the news mostly use 201 stainless steel as the inner liner of the insulated cup. Although 201 stainless steel insulated cups are very cheap, it is not recommended to purchase them. Because this 201 stainless steel is not a food grade material, it belongs to industrial materials and is mostly used to make decorative tubes, industrial tubes, and watch straps.
201 stainless steel has a high manganese content and poor corrosion resistance. If it is used as the inner liner of a thermos cup, long-term storage of acidic substances may lead to the precipitation of manganese elements. Manganese metal is an essential trace element for the human body, but excessive intake of manganese can harm the body, especially the nervous system.
304 stainless steel
The main safety hazard of stainless steel in contact with food is the migration of heavy metals. Therefore, the stainless steel material in contact with food must be food grade. The most commonly used food grade stainless steel is 304 stainless steel, which has good corrosion resistance.
316 stainless steel
304 stainless steel is relatively acid resistant, but it is still prone to pitting corrosion when encountering substances containing chloride ions, such as salt solutions. And 316 stainless steel is an advanced version, which adds molybdenum metal on the basis of 304 stainless steel, allowing it to have better corrosion resistance. 316 stainless steel has a high cost and is mostly used in high-precision fields such as medical and chemical industries.
Therefore, when choosing insulated cups, it is recommended to choose stainless steel that meets safety standards and is labeled as 304, 316, or “food contact” for better safety and corrosion resistance.
Key points for choosing a thermos cup
1.Purchase through legitimate channels and try to choose products from well-known brands. Consumers should pay attention to checking whether the instructions, labels, and product certificates are complete when purchasing to avoid buying “three no products”.
2.Open the thermos and smell it. If it is a qualified product, because the materials used are food grade, there is generally no odor.
3.Check if the surface is smooth. A good insulated cup has a smooth inner liner, outer wall, and cup mouth, without scratches, bumps, or welds.
4.Food grade silicone should be used for accessories such as sealing rings and straws that are prone to contact with liquids.
5.After purchase, leakage and insulation performance tests should be conducted first, and the insulation time usually needs to be at least 6 hours.
Judging the insulation performance of cups
Inject hot water into the cup, tighten the lid, and touch the cup body with your hand after a few minutes. If there is no obvious feeling of heat, it indicates good insulation performance.
Test the sealing of the cup
Fill the cup with water, tighten the lid, place it horizontally and invert it for a moment to see if there is any water overflow. If there is no overflow, it indicates that the sealing of the cup is good.
