Polypropylene is one of the most widely used thermoplastic polymers on the planet. A popular choice for plastic packaging, polypropylene can also be used to make machinery parts and can even help form certain types of textiles. This semi-rigid thermoplastic was first discovered in the 1950s and is today used across many industries.
Polypropylene boasts many properties that make it an ideal alternative to other types of plastic. It’s translucent, making it the obvious choice for packaging, while its heavy-duty nature and impressive chemical resistance also make it suitable for housing more hazardous materials. It also offers excellent fatigue and water resistance, while its heat-resistant credentials also set polypropylene apart from other plastics as a go-to choice for high-temperature situations.
Polypropylene withstands sustained heat better than most commodity plastics. Its melting point sits between roughly 265F and 340F, with a practical continuous operating ceiling closer to 180F. Stiffening additives and fillers raise performance further, which is why PP appears in sterilised medical equipment and hot fill packaging.
Many of polypropylene’s physical properties, including heat resistance, can be improved by incorporating additives into the creation of the material itself. Stabilizers, antioxidants, and fillers can all be used to improve the performance of the material.
Recent innovations have made it possible to produce polypropylene with much higher melting points. By introducing catalysts at certain parts of the manufacturing process, a more crystalline structure is achieved. This results in a far more durable material with substantially improved polypropylene plastic heat resistance.
External factors can also impact the heat resistance of polypropylene. Take UV exposure as one example. When polypropylene is exposed to UV radiation for long enough, the polymer can begin to degrade. Sufficient degradation can significantly reduce the thermal properties of the material.
No, standard polyethylene liners are not suited to hot products. PE liners protect against contamination and moisture but soften and distort well below the temperature the outer polypropylene bag tolerates. For warm discharge, specify a high-temperature liner or run the bag unlined and let product cool first.
Standard polyethylene liners should provide sufficient for many tasks and are a popular choice in the pharmaceutical and food processing sectors. However, while they’re adequate at protecting contents from contamination, the same can’t be said of high temperatures. Generally speaking, polyethylene liners can only withstand temperatures of approximately 170 °F. At higher temperatures, polyethylene begins to break down and lose its integrity. Fortunately, polypropylene liners are on hand to help in these situations.
| Liner Type | Max Temperature | Thickness | Best Applications | Cost |
| Polyethylene (PE) | ~170°F | Standard | Pharmaceuticals, food processing, general use | Lower |
| Polypropylene (PP) | ~295°F | Thicker, sturdier | High-temperature chemicals, demanding applications | Higher |
Thicker and far sturdier than polyethylene liners, polypropylene liners are used for only the most demanding applications. Able to comfortably withstand temperatures as high as 295 °F, these liners can dramatically improve the heat resistance credentials of a standard FIBC.
Polypropylene bulk bags handle product temperatures up to around 200F without a liner. That tolerance suits materials discharged hot from processing, such as resins and minerals. Adding a standard polyethylene liner lowers the ceiling, since PE softens well below the temperature the woven outer bag tolerates.
Thanks to its biological resistance and heat-resistant properties, polypropylene is commonly used for medical applications. Combined with impressive chemical resistance credentials, polypropylene can be used to create everything from specimen bottles to medical equipment that needs to be sterilized at incredibly high temperatures.
Because it’s able to withstand significant levels of heat before melting, polypropylene is also regularly used to create mechanical components that need to be able to function at substantial operating temperatures. The material is also well suited to the food manufacturing industry. As well as being declared safe by the FDA as safe for food contact, polypropylene boasts a high heat tolerance that helps prevent leaching when the material is used to create food and beverage packaging.
| Industry | Application | Why PP? | Temperature Range |
| Medical | Specimen bottles, sterilizable equipment | Biological resistance + heat tolerance | Up to 295°F |
| Food Manufacturing | Food packaging, beverage containers | FDA-safe + prevents leaching | Variable |
| Chemical | Storage/transport of hot chemicals | Chemical + heat resistance | 200-295°F |
| Pharmaceutical | Hot-filled products, sterile packaging | Contamination prevention | 170-295°F |
| Manufacturing | Mechanical components | High operating temperatures | Variable |
The main difference between polypropylene and polyethylene on heat is the melting threshold. Low density polyethylene melts near 230F and high density polyethylene near 260F. Polypropylene runs well above both, which is why processors specify PP for sterilisation, hot fill and any application where packaging meets warm product.
By comparison, polyvinyl chloride has a relatively high melting point. PVC-P begins to melt at temperatures between 338 and 374 °F, while PVC-U begins to melt at temperatures between 320 and 410 °F. Meanwhile, rigid PVC has a comparatively low melting point of 185 °F.
If you’re using polypropylene containers as part of your operation, you can extend the life of your bulk bags by following a few best practices. For starters, only use containers for what they were designed for. You can also enhance the heat-resistant potential of a bulk bag by making use of a container liner made from PP.
If you’re using polypropylene regularly at considerably higher temperatures, ensure you’re regularly inspecting the material for signs of damage. Higher temperatures can lead to warpage and other signs of deformation, with damaged bags needing to be repaired or replaced when necessary.
If you’re working with high-temperature products or need packaging that can cope when exposed to more extreme environments, polypropylene is the obvious choice of material. Its impressive heat resistance aside, polypropylene also delivers when it comes to chemical resistance and is generally one of the most durable materials around when it comes to packaging.
Looking for high-quality polypropylene packaging that will hold up well to repeated use? Codefine is on hand to help. Offering a complete range of innovative packaging solutions, including first-rate polypropylene containers, you won’t struggle to find the perfect packaging for your operation. Explore the full product range online today or contact us with any queries.
At what point does polypropylene begin to degrade from heat exposure?
Is polypropylene suitable for sterilization or autoclave processes?
Do additives or chemicals affect heat resistance?
Does heat resistance vary by product form?
How does repeated heating and cooling impact polypropylene?
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