The triangular symbol with the number 5, known as a resin identification code, indicates the material is Polypropylene (PP). This material is broadly considered one of the safer plastics available for food contact applications. Polypropylene’s inherent properties make it a reliable choice for packaging and storage, often mitigating the concerns associated with other types of plastic.
Defining Plastic #5
Plastic with the resin code 5 is chemically known as Polypropylene (PP), a thermoplastic polymer valued for its robust physical characteristics. This material is lightweight yet durable, possessing a higher melting point and greater chemical resistance than many other common plastics. PP is flexible and resistant to stress cracking, which contributes to its long lifespan in applications requiring repeated use.
This combination of strength and resilience makes PP a popular choice for items that must withstand regular handling and different temperature extremes. Consumers encounter Polypropylene in everyday items such as yogurt and cottage cheese tubs, syrup and medicine bottles, and many reusable food storage containers.
Food Contact Safety and Regulatory Approval
Polypropylene has received approval from major regulatory bodies, including the U.S. Food and Drug Administration (FDA), for use in direct food contact. Its molecular structure provides excellent chemical inertness, meaning it is non-reactive when exposed to most foods, including acidic, alkaline, and alcoholic contents. This stability is the primary reason PP is classified as food-grade.
The safety profile of PP is supported by the fact that it is naturally free of Bisphenol A (BPA) and phthalates, chemicals that have raised public health concerns in other plastic types. Migration of substances from the plastic into the food is the central safety consideration for any food-contact material. Because PP is highly stable, the risk of chemical migration at ambient and refrigerated temperatures is extremely low.
The FDA’s approval process for food-contact materials is rigorous, requiring manufacturers to demonstrate that any migrating components remain below established safety thresholds. Polypropylene meets these stringent requirements because it is composed of high molecular weight polymers that do not readily diffuse into food matrices.
Thermal Stability and Microwave Use
Polypropylene has high thermal stability, with a melting point around 160 degrees Celsius. This property means that PP containers will not easily warp or melt when exposed to high heat, such as in a dishwasher or a microwave oven. This heat endurance is why many containers intended for reheating leftovers are made from PP.
However, the ability to withstand heat without melting is not the only factor in determining “microwave safety.” Research shows that subjecting PP to microwave energy, particularly with fatty foods, can accelerate the migration of trace additives, such as antioxidants, incorporated during manufacturing. These additives are present in minute quantities to protect the plastic but can migrate at higher temperatures.
Consumers should always look for a clear “microwave safe” label, which indicates the finished product has been tested for safety under heating conditions. Heating food in any plastic can increase the potential for chemical transfer, even if the levels remain within regulated limits. It is advisable to use PP containers only for reheating, not for prolonged cooking, and to avoid microwaving the plastic if the food is high in fat.
Practical Handling and Recycling
To maintain the safety and integrity of Polypropylene food containers, users should regularly inspect the plastic for physical damage. Deep scratches, cracks, or excessive cloudiness can compromise the material’s surface, creating pathways for potential chemical transfer or providing areas where bacteria can harbor. Containers showing these signs of wear should be replaced.
Polypropylene is a recyclable material, and its resin code 5 is an indicator to recycling facilities. While accepted in many municipal programs, it is not as universally collected as plastics with codes 1 (PET) or 2 (HDPE). Consumers should check their local waste management guidelines to confirm whether PP is accepted in their curbside collection.
The recycling rate for PP remains lower than for other common plastics, but the material is sought after for applications like battery casings, brooms, and signal lights. Proper cleaning and disposal of PP containers contribute to the supply chain for recycled plastic, ensuring the material can be repurposed for new products.