Polypropylene (PP) and polyethylene (PE) are the two most widely produced and traded plastics in the world. Both belong to the polyolefin family, both are light, chemically resistant and recyclable, and both arrive at factories as small pellets. Yet they behave very differently once moulded. Choosing the wrong one can mean cracked parts, deformed packaging or unnecessary cost. This guide explains the practical differences.
What are polypropylene and polyethylene?
Polyethylene is made by polymerising ethylene. Depending on its density it is sold mainly as LDPE (low density), LLDPE (linear low density) and HDPE (high density). Polypropylene is made from propylene and is sold as homopolymer, random copolymer and impact (block) copolymer grades.
Key differences at a glance
| Property | Polypropylene (PP) | Polyethylene (PE) |
|---|---|---|
| Stiffness | Higher, more rigid | Lower, more flexible (HDPE is the stiffest grade) |
| Heat resistance | Higher melting point, suitable for hot filling and dishwashers | Lower melting point, softens earlier |
| Low-temperature impact | Homopolymer becomes brittle in cold; copolymers improve this | Keeps impact strength well below freezing |
| Fatigue resistance | Excellent, ideal for living hinges | Moderate |
| Density | Among the lightest plastics | Slightly higher; varies by grade |
| Recycling code | 5 | 2 (HDPE), 4 (LDPE) |
Typical applications
Where polypropylene wins
- Food containers and caps that must survive hot filling or microwaving
- Automotive interior parts, bumpers and battery cases (see polymers in automotive)
- Living hinges on bottle caps and boxes
- Kitchenware and household goods (see polymer kitchenware)
- Non-woven fabrics, raffia bags and fibres
Where polyethylene wins
- Films and bags (LDPE and LLDPE)
- Bottles for milk, detergents and chemicals (HDPE)
- Pipes for water and gas
- Products used in cold environments, such as freezer packaging
- Toys and squeezable containers that need flexibility
How to choose between PP and PE
- Define the temperature range. If the product sees heat, PP is usually safer; if it sees freezing temperatures, PE or a PP copolymer is the better choice.
- Decide between stiffness and flexibility. Rigid housings and hinged lids favour PP; films, squeeze bottles and impact-loaded parts favour PE.
- Check the process. Both run on injection moulding, extrusion and blow moulding lines, but the melt flow index (MFI) of the grade must match your machine and mould.
- Confirm regulatory needs. For food contact, medical or toy applications, ask for the grade’s compliance documents.
- Compare total cost. Price per tonne is only part of the picture; density, cycle time and scrap rate change the real cost per part.
What to ask your polymer supplier
- The exact grade name and producer, with the technical data sheet (TDS)
- Safety data sheet (SDS) and certificate of analysis (CoA) for each lot
- Melt flow index, density and additive package
- Packaging (25 kg bags, octabins or bulk), lead time and Incoterms
The Atlantic Trade supplies polymer raw materials to manufacturers and helps them compare grades for their application. Learn more about our polymer trade service or contact our Dubai team with your product requirements.
Frequently asked questions
Is polypropylene better than polyethylene?
Neither is better in every case. Polypropylene is stiffer and withstands higher temperatures, while polyethylene is more flexible and keeps its impact strength at low temperatures. The right choice depends on the product and process.
How can I tell if a plastic is PP or PE?
The resin identification code helps: 2 is HDPE, 4 is LDPE and 5 is PP. In the lab, density and melting point tests separate them reliably; PP melts at a noticeably higher temperature than PE.
Are PP and PE food safe?
Both are widely used in food packaging when produced in food-contact grades that meet the relevant regulations. Always request the supplier’s food-contact compliance documents.