There are a lot of types of products on the market made of HDPE or LDPE and this has lead to a saturation in the quality of these items. It has become necessary to have some sort of standard and identification mark to identify them. This is very important from the perspective of customers so that they know very well the thing they have in hand, and what all they can be used for?
In order to make it more convenient, there have been a number of regulations and drafts passed that formalizes and legalizes vendors and manufacturers to use them on their products so that the customers are not unaware of its use. This is extremely important for some of the products where they are used even in food processing industry, packaging and parcel industry, and used as carrying bags in almost every part of the world. This ensures that the right kind of PET is used for the right kind of work. For example, the containers used for packaging milk and other liquid food items are made with PET 2. That is, they are safe to keep those food items without any worries. Also, they have a date of expiry too in the given storage conditions that must be strictly followed.
What are some of these examples?
One very commonly used food grade plastic storage is labeled as PET 1. This is the most commonly found quality too, I guess. You might have seen them in packaging your peanut butter, the jelly jars, and in the sandwich mix/spread packaging. There is also another slightly low-density material used as a pouch instead of non-flexible structures.
Apart from them, we have another category of items that are made of more durable and toughened PET. They are excellent to chemical corrosion, resistant to them and suitable for a whole range of food.
But, mainly they are found as alternatives for transferring milk, water and even as great drums on top of buildings and towers to piped water. These are all HDPE and fall in PET 1 label.
The labels are such that the highest one is best and the lowest one is disposable kind of or not to be used at all. This also tells its recycling capacity. The PET 1 can be reused and recycled while the PET 7 cannot be done that easily and must not be reused, in any manner of course, not for food. The others in between have their own benefits and limitations that can be found easily.