If you put a plastic cup in the freezer, several things can happen depending on the type of plastic used to make the cup and the duration of its exposure to the freezing temperatures. Here are the possible outcomes:
No noticeable effects: Some types of plastic cups, especially those made from high-density polyethylene (HDPE) or polypropylene (PP), are more resistant to low temperatures and may not show any significant changes when placed in the freezer for a short period.
Brittleness and cracking: Certain types of plastics, like polystyrene (PS) or polyvinyl chloride (PVC), can become brittle at freezing temperatures. Prolonged exposure to the cold environment may cause the cup to develop cracks or even shatter.
Deformation: Some plastic cups, such as those made from low-density polyethylene (LDPE) or polyethylene terephthalate (PET), can deform under freezing conditions. The cup may lose its original shape or become slightly warped.
Odor and taste absorption: Plastics with more porous surfaces, like polypropylene or polystyrene, might absorb odors from the freezer or from other food items, affecting the taste of beverages or food placed in the cup later.
Leaching of chemicals: In rare cases, certain types of plastics may release potentially harmful chemicals when exposed to extreme temperatures, including freezing. While food-grade plastics are generally considered safe, using non-food-safe plastics in the freezer can be hazardous.
To minimize potential issues when putting a plastic cup in the freezer:
Use food-grade plastic cups: Ensure that the cup is labeled as food-safe or designed for freezer use.
Avoid extended exposure: If you plan to freeze the cup for a short time, such as to chill a beverage, it should be fine. However, avoid leaving it in the freezer for an extended period.
Check the plastic type: Look for the recycling symbol on the cup's bottom, which should have a number inside the triangle of arrows. Avoid putting cups with recycling codes 3 (PVC), 6 (PS), and 7 (Other) in the freezer, as they are more prone to issues.
Allow for expansion: When freezing liquids in a plastic cup, leave some room at the top to account for the liquid's expansion as it freezes, reducing the risk of cracking or spilling.
If you're uncertain about the safety of freezing a particular plastic cup, it's best to choose an alternative container that is explicitly labeled as freezer-safe or use glass or stainless steel containers, which are generally safe for freezing.