Radiation-Cured Polypropylene, Everything You Need to Know
2026-06-01
What is irradiation sterilization?
Irradiation sterilization involves exposing items to gamma rays or high-energy beams generated by accelerators, which directly or indirectly damage the DNA and RNA structures of microorganisms that may be present on the items, causing them to degrade or lose their genetic function, thereby eliminating the microorganisms.
This sterilization method is fast, easy to use, and allows for continuous production line operation. Since the irradiation process takes place at room temperature, it is suitable for temperature-sensitive medical applications, such as plastic packaging products containing special ingredients: medical products containing liquids, such as hydrogels, alcohol swabs, povidone-iodine swabs, and paraffin swabs.
Products sterilized by irradiation can be sterilized after packaging or packaged after sterilization; as long as the packaging is impermeable to bacteria, they can be stored for long periods.
Why is radiation-resistant polypropylene needed:
During irradiation sterilization, all materials—whether the finished products or the packaging materials—must be exposed to high-energy radiation, so choosing the right materials is particularly important.
Most medical devices and packaging materials currently in use contain polypropylene, a material that is prone to changes in its physical and chemical properties when exposed to high-energy radiation, leading to negative effects such as degradation, discoloration, and deterioration of performance. Therefore, radiation-resistant polypropylene materials must be selected for irradiation sterilization applications.
Changes in the Properties of Irradiated Polypropylene
Changes in the properties of irradiated polypropylene are primarily evident in its appearance and mechanical properties.
Appearance and Performance
The irradiated polypropylene has noticeably yellowed, which is likely due to two factors:
- Polypropylene forms chromophores after irradiation;
- Color development in processing aids following irradiation
Yellowing of polypropylene after irradiation not only affects its appearance but also hinders the work of medical staff, making it difficult to accurately read the graduations on containers and severely impacting medical efficiency.
Changes in Mechanical Properties
When polypropylene is exposed to high-energy radiation, the radiation interacts with the molecular chains of the polypropylene, triggering radical reactions that cause structural changes in the polymer. These changes primarily occur through two reaction mechanisms.
Chain scission
Chain scission refers to the breakage of the polypropylene main chain, resulting in a decrease in molecular weight. Its primary effects include:
- Decreased molecular weight
- Reduced material toughness
- Reduced elongation at break
- Reduced impact strength
- Reduced durability
For irradiated polypropylene, chain scission is typically the primary reaction during the irradiation process; therefore, conventional polypropylene is prone to embrittlement, yellowing, and a decline in performance following irradiation sterilization.
Crosslinking
Cross-linking refers to the formation of new chemical bonds between irradiated polypropylene molecular chains, creating a new network structure. Its main effects include:
Higher heat resistance
- High dimensional stability
- High chemical resistance
- Enhanced creep resistance
Although the cross-linking reaction can have some positive effects on irradiated polypropylene, these effects are negligible compared to the negative effects caused by chain scission.
Recommended Irradiated Polypropylene Materials
Since irradiated polypropylene is primarily used in medical applications, polypropylene modified with additives to achieve radiation resistance is unlikely to meet the requirements of medical applications. Therefore, as a supplier of medical grade polypropylene with 20+ years of experience, we recommend the following raw materials that are suitable for irradiated polypropylene applications:
Yungsox 5090R is a random copolymer polypropylene material manufactured by Formosa Plastics specifically for use in medical devices. It is designed for the production of medical devices that require gamma irradiation sterilization, such as disposable syringes.
Formosa 5090R gamma polypropylene received USP Plastic Class VI certification in 2016 and passed the ISO 10993 medical device biocompatibility testing standard in 2019, demonstrating exceptional safety performance in the production of medical devices.
Formosa 5090R PP offers good transparency and impact resistance, with a melt flow rate of 19 g/10 min, and is relatively easy to process.
Topilene R701G is a medical-grade random copolymer polypropylene (PP) developed by Hyosung Chemical specifically for medical devices (particularly those requiring gamma irradiation sterilization).
Compared to conventional irradiated polypropylene materials, Hyosung R701G PP features technical improvements addressing yellowing and reduced mechanical strength in irradiated polypropylene, making it suitable for gamma sterilization at 25–50 kGy. Additionally, R701G PP is certified to USP Class VI and FDA 21 CFR 177.1520, and the material offers excellent medical safety performance.
Ranpelen J-560M is a random copolymer polypropylene material produced by Lotte Chemical and specifically developed for medical devices (disposable syringes) and high-clarity packaging. This material is the first radiation-resistant polypropylene produced in Asia (excluding Japan) and is designed to break the monopoly held by European, American, and Japanese companies in the high-end medical-grade radiation-sterilizable PP market.
Lotte J-560M PP has obtained multiple material certifications, including USP Class VI, FDA 21 CFR 177.1520, and EU Regulation 1935/2004/EC, and has also been registered in the U.S. Master File (Registration No. 27050). In addition, to meet increasingly stringent requirements, the product has obtained certifications confirming it is free of phthalates and bisphenol A. Thanks to its safety and ease of use in production, it is utilized by pharmaceutical companies across Asia, Europe, and South America.
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