Ecscuba said:From Livestrong site:
"PP stands for polypropylene, a strong plastic mostly used in caps and lids. You can identify polypropylene by a triangle and the number 5 on the bottom of your container, although many lids do not include this "resin number". PP has a high melting point and can be "hot-filled" or used with products that need to incubate. It also does not transmit any known chemicals into food. This makes it an ideal material for a garden container, though large PP containers may be hard to find."