PP stands for polypropyleneone of the most widely used plastics in the world. You’ll find the letters “PP” stamped on the bottom of food containersbottle capsand storage binsusually inside or near a triangular recycling symbol with the number 5. It identifies the type of plastic resin the item is made from.
The Number 5 Recycling Symbol
Every common plastic is assigned a resin identification codea number from 1 to 7 inside a triangle of chasing arrows. PP carries the number 5. This system helps recycling facilities sort materials and helps consumers figure out what they’re dealing with. The other codes you’ll see most often are 1 for PET (water bottles)2 for HDPE (milk jugs)3 for PVC4 for LDPE (plastic bags)and 6 for polystyrene (foam cups). If you flip over a yogurt tub or a takeout container and see a 5 or the letters PPyou’re holding polypropylene.
What Polypropylene Actually Is
Polypropylene is a thermoplastic polymer derived from petroleum. “Thermoplastic” means it can be melted down and reshaped without breaking down chemicallywhich is why it’s both moldable during manufacturing andin theoryrecyclable afterward. It resists waterchemicalsand fatigue over timeand it handles heat well compared to many other household plastics. Food containers made from PP won’t warp or melt in the dishwasherand the material can survive autoclave sterilizationwhich is why hospitals and labs rely on it.
PP comes in two main varieties. The homopolymer version is stiffer and has a higher melting point. The copolymer version blends in small amounts of ethylenemaking it more flexible and better at absorbing impactseven in cold temperaturesat the cost of slightly lower heat resistance.
Where You’ll Find PP
Polypropylene is everywhere once you start looking. In the kitchenit shows up as yogurt and cottage cheese tubs (typically sealed with foil lids)reusable food storage containers from brands like Rubbermaid and Sterilitebottle capsdrinking cupscutleryand pitchers. The flip-top lids on ketchup bottles and shampoo caps use PP because it can bend thousands of times at a “living hinge” without cracking.
Beyond foodPP is used in carpets and rugs (it holds color extremely well)ropesstorage boxesring binderswastebasketsand car batteries. In medicineit’s the material behind surgical mesh for hernia repairsnonabsorbable suturesand a wide range of medical devices. It’s also the key raw material in meltblown fabricwhich forms the filter layer in surgical face masks. IndustriallyPP shows up in plumbing pipesroofing membraneselectrical cable insulationsnack food packagingdiapersand wipes.
Heat Resistance and Microwave Safety
One of the biggest practical reasons people search for PP is to figure out whether a container is safe to microwave. Polypropylene handles heat significantly better than most household plastics. If a container has a #5 recycling codeit is generally considered microwave safe. Many containers also carry a separate microwave-safe symbol: a small microwave icon with wavy lines. Look for both the number 5 and the microwave symbol together for the most confidence.
PP containers won’t melt under normal microwave useand they’re dishwasher safe on the top rack. That saidrepeatedly microwaving any plastic at very high temperatures or for very long periods can degrade it over timeso replacing containers that look warped or discolored is a reasonable habit.
Food Safety
Polypropylene does not contain BPAa chemical concern associated with some older plastics (particularly polycarbonateresin code 7). PP also doesn’t typically require phthalates as plasticizers. The FDA has been tightening restrictions on phthalates in food contact materials overalland testing published between 2018 and 2022 found that manufacturers have been steadily replacing phthalates with alternative compounds. Among common food-grade plasticsPP is widely regarded as one of the safer options for everyday use.
How PP Compares to Other Plastics
PP sits in a middle ground among the plastics you encounter daily. PET (number 1)the clear plastic used for water and soda bottlesis stronger and fully transparent. PP is typically translucent or opaqueso you’ll rarely see it used where crystal clarity matters. HDPE (number 2)found in milk jugs and detergent bottlesis slightly tougher and more impact-resistantbut PP offers better heat tolerance and is lighter. PP has moderate overall strength but excellent chemical resistancewhich is why it works so well for containers that hold acidic or fatty foods.
Recycling PP
Polypropylene is picked up through most curbside recycling programsthough acceptance varies by municipality. Despite being technically recyclablePP recycling rates remain lower than those for PET or HDPE. One challenge is contamination: food residue on yogurt cups and takeout containers can make sorting difficult. Another is that recycling polyolefins like PP requires more careful assessment than recycling PETbecause contaminants migrate into the material more readily during repeated processing cycles.
Industry groups like the Polypropylene Recycling Coalition are working to improve these numberswith a goal of a 5% increase in the U.S. polypropylene recycling rate and plans to deploy $10 million in infrastructure investment through 2025. PP products are not biodegradableso items that escape the recycling stream persist in the environment for decades. Rinsing your PP containers before tossing them in the recycling bin is the simplest thing you can do to help them actually get recycled rather than sent to landfill.