Insulated lunch boxes are also daily necessities that will be used in life. Insulated lunch boxes can keep our food warm, and they need to be in direct contact with food in order to preserve the temperature, so we need to pay special attention to the details of materials. Let's take a look at the relevant knowledge of insulated lunch boxes today!

How long can the insulated lunch box keep warm

Under normal circumstances, the insulated lunch box with good quality can be insulated for about 5 hours. The insulation effect of insulated lunch boxes with different quality is different. Now the insulated lunch box on the market is composed of an ordinary lunch box plus an insulation shell, which is filled with foam plastic inside and outside, and then coated with metal film inside. Reduce heat loss from three aspects of conduction, radiation and convection. An electric heating device is added between the lunch box and the shell to supplement the heat loss and keep the food at a certain high temperature.

How to buy insulated lunch boxes

1. For thermal insulation test, you can put boiled water into an insulated lunch box, then cover it, keep it still for about 3 minutes, touch the outer surface of the cup body with your hand. If you feel that the box body is obviously warm, and the bottom is even hotter, it means that the product has lost its vacuum, and can not achieve good thermal insulation effect, while the lower part of the insulated cup is cool.

2. Check the tightness. After adding water, cover the lid. Place the lid flat on the table to see if there is water leaking out. Then check that the screw in and screw out of the lid and the cup mouth should be flexible without gap. Fill a glass of water and turn it upside down for four or five minutes, or shake it vigorously to verify whether there is water leakage.

3. Plastic identification: food grade plastics should have small odor, smooth surface and no barbs, and their life span is often not easy to age.

4. In terms of stainless steel material judgment, there are many specifications of stainless steel, and the ones that meet the standards are selected to meet the national food level. The product is rust proof and corrosion resistant. The body color of ordinary stainless steel is white or dark. If it is immersed in 1% salt water for 24 hours, it will produce rust spots, and some elements contained in it exceed the standard, directly endangering human health.

5. Check whether the products are certified by national standards, and only qualified products can be guaranteed. The name, capacity, caliber, name and address of the manufacturer, standard number used, method of use and precautions in use will be displayed on the insulated lunch box.