Gamma Radiation Resistance: Shielding Polymers from Ionizing Rays

Gamma radiation is a form of electromagnetic radiation that is highly energetic. It has a very short wavelength of less than 0.01 nanometers and a frequency higher than 3 × 10¹⁹ hertz. This ionizing radiation has enough energy to remove tightly bound electrons from atoms. This in turn leads to the formation of ions. It is often emitted during certain nuclear reactions and radioactive decay processes.

In polymers, gamma radiation can cause structural changes which can be harmful. They have enough energy to break chemical bonds known as radiation degradation. They can also allow polymer chains to cross-link or undergo other chemical modifications. As a result, the mechanical and thermal properties of the polymer can be altered. This leads to a reduction in its performance.

Understanding these drawbacks is crucial in polymer applications exposed to gamma radiation. Hence, material manufacturers need to ensure that the polymer maintains its desired properties. Additionally, proper testing and evaluation under the anticipated radiation exposure are essential.

Let’s explore more about:

• What is the importance of gamma radiation resistance?
• How to overcome the drawbacks of gamma radiation?
• What is its impact on material properties?
• Which factors affect the gamma radiation resistance of plastics?
• What are the standards for measuring the gamma radiation of plastics?
• How do various polymers rank in gamma radiation resistance?

Importance of Gamma Radiation Resistance

Most polymers can degrade by photolysis to give lower molecular weight molecules. Electromagnetic waves with the energy of visible light or higher are usually involved in such reactions. These EMWs include:

• Ultraviolet light
• X-rays and
• Gamma rays

Out of the above, gamma radiation is most commonly used for material testing. This is because of its high availability in research or industrial irradiators.


Here are some key areas where gamma radiation resistance holds significance:

➢ Medical Industry: Gamma radiation is used to sterilize medical devices and pharmaceuticals. Resistance to gamma radiation maintains the structural integrity & functionality after the sterilization process.

➢ Electronic Devices: Gamma radiation resistance is important to prevent damage to electronic components. It also ensures the reliability of devices.

➢ Packaging industry: Gamma radiation is used in sterilizing food. It extends the shelf life of certain food products. Further, it maintains the properties of packaging materials.

➢ Aerospace & Aviation: Aircraft components may be exposed to ionizing radiation at high altitudes. It ensures the durability and safety of aerospace components.


Browse gamma-resistant grades used in various applications.

Overcoming the Drawbacks of Gamma Radiation

There are ways to deal with the problems of gamma radiation. Here are some solutions:

1. Select polymers that can better handle gamma radiation. Some plastics and composites are more resistant. View materials resistant to gamma radiation.


2. Additive incorporation makes the plastic more resistant to gamma radiation. These additives like stabilizers and antioxidants. They reduce the effects of chain scission and cross-linking.


3. Control crosslinking during manufacturing or processing of the polymer. Do this by changing things like temperature and radiation dose. These balances get the right properties while avoiding too much cross-linking.


4. Blend polymers to make a material that combines the best of each part. This balances desired mechanical properties and radiation resistance.


5. Surface treatment of polymers makes them more resistant to gamma radiation. These treatments act like a protective layer. They reduce the direct impact of radiation on the bulk of the polymer.


6. Use radiation shielding materials to protect sensitive parts from direct radiation.


7. Post-irradiation annealing reverses the effects of radiation-induced damage. This involves heating the material to allow the recombination of broken polymer chains.


8. Quality control & testing materials under gamma radiation. This checks if they meet the needs of the intended use.

Impact of Gamma Radiation on Material Properties

Polymer resins can handle gamma radiation to different degrees. This makes them useful for applications needing sterility. The main industrial sources of gamma radiation are Cobalt 60 (⁶⁰Co) and Cesium 137 (¹³⁷Cs). They give off gamma rays as they decay radioactively. Gamma rays go through plastics easily. They break the bonds in DNA, killing bacteria and microbes.



Ionizing gamma radiation can cause these changes in polymers:

• Color changes in polymers can be induced by gamma radiation. This leads to yellowing or discoloration. This effect is particularly noticeable in polymers that are sensitive to radiation-induced degradation. Color changes can be undesirable in packaging or medical devices.


• Changes in the molecular weight of the polymer can occur due to gamma radiation. This change can affect the polymer's physical and mechanical properties. These include properties such as tensile strength and elongation. It depends on factors such as radiation dose and the specific polymer composition.


• Crosslinking – Gamma radiation can also induce cross-linking in polymers. This process forms covalent bonds between polymer chains, creating a 3D network. Excessive cross-linking can make the polymer stiffer, more rigid, and less flexible. This may lead to a decrease in the material's elasticity and impact resistance. Further, it increases tensile strength and decreases stretching.


• Chain scission – Gamma radiation can lead to the breaking apart of polymer chains, a process called chain scission. The high-energy gamma rays can break the chemical bonds that connect the polymer chains together. This results in shorter polymer chain lengths. Chain scission can considerably alter the mechanical properties of a polymer. It reduces tensile strength and stretching. Specifically, it can make the polymer more brittle and less durable.


• Change in mechanical properties lessens the polymer strength. All the above factors can result in the loss of mechanical properties in polymers. These include elongation at break, tensile strength, and impact resistance.

Each polymer reacts differently to ionizing radiation. So, the overall dose rate varies and must be limited based on the polymer.



Radiation resistance is measured by the half-value dose. This is the amount of radiation that causes a 50% change in important mechanical properties. These properties include elongation at break and flexural strength at break. This measurement applies to thermoplastics, elastomers, aromatic polymers, and composite materials. The loss of a material's ability to elongate is used to measure the effects of irradiation. This is because loss of elongation equates to brittleness failure.

Irradiation and Polymers

• Polyethylene generally crosslinks when irradiated, although some chain scission also occurs. Crosslinking increases its tensile strength. However, polyethylene can be stabilized to make it radiation-resistant. High-density polyethylene is less stable than medium-density, linear low-density, and low-density polyethylene grades.


• Aromatic polymers with benzene rings resist radiation. They can be easily sterilized due to the benzene ring.


• Aliphatic polymers show varying radiation resistance depending on their unsaturation and substitution levels.


• Highly amorphous polymers resist radiation better than semi-crystalline ones. Their chain structure can stretch more before breaking.


• Polymers with butylene backbones like ABS and PBT lose impact strength when irradiated.


• Nylons 10, 11, 12, and 6-6 are more stable than nylon 6. Nylon films and fibers have lower resistance. View polyamides with high gamma resistance.


• Polymethylmethacrylate can withstand a single sterilization dose as a high molecular weight cast sheet or molded item. However, it is not suitable for repeated doses.


• PVC works for single-dose radiation sterilization, both unplasticized and plasticized.


• Thermosets like phenol and urea formaldehyde are suitable for irradiation sterilization. View other thermosets with high gamma resistance.


• PTFE, PVDF, polyacetals, and polypropylene do not withstand gamma radiation sterilization well. PP degrades slowly after irradiation.

Factors Affecting Gamma Radiation Resistance of Plastics

A material's radiation resistance depends a lot on:

Polymer formulation

1. Additives reduce the effects of irradiation on mechanical properties. They also reduce the appearance and prevent yellowing. For example, tint-based stabilizers added to PVC help stop color change. Some additives protect plastics and reduce the effects of radiation.


2. Reinforcement: Fillers can alter the polymer's radiation resistance. Inorganic fillers increase resistance to gamma rays while organic fillers usually decrease it.


3. Crosslinking: Excessive cross-linking can make the polymer stiffer. This may further alter the mechanical properties of the polymer.

Conditions during radiation

1. Environmental conditions can impact the material's response to gamma radiation. Some materials are more sensitive to oxidative degradation in the presence of oxygen. While others may exhibit different behaviors under varying environmental conditions.


2. Temperature can influence the material's response to radiation. Specific operating conditions can vary from ambient to elevated temperatures.


3. Dose rate refers to the rate at which the material is exposed to gamma radiation. It is measured in units of absorbed dose per unit time (e.g., Grays per hour). Dose rates can vary widely depending on the application.


4. Stress: Materials used in structural components or devices subject to mechanical forces.

Important things to note:

→ Thin sections, films, or fibers in a product allow too much exposure. This in turn causes polymer degradation.

→ Moldings that are strong lengthwise but weak sideways become even weaker after irradiation.

Standards to Measure Gamma Radiation of Plastics

There are a few international standards to measure the radiation resistance of plastics. Here are some examples:

1. ISO 11357: Checks how radiation affects plastics using differential scanning calorimetry (DSC).


2. ISO 10437: Has procedures to expose plastics to gamma radiation and measure the dose.


3. ISO 15540: Outlines how to evaluate changes in plastics from gamma rays.

It's key to pick the right standard for what you need. Ask experts or regulators if you are unsure of which standard to choose.

Gamma Radiation Resistances of Various Polymers

Click to find polymer you are looking for:
A-C     |      E-M     |      PA-PC     |      PE-PL     |      PM-PP     |      PS-X

Polymer Name	Gamma Resistance
ABS - Acrylonitrile Butadiene Styrene	Good
ABS Flame Retardant	Poor
ABS High Heat	Good
ABS High Impact	Fair
ABS/PC Blend - Acrylonitrile Butadiene Styrene/Polycarbonate Blend	Good
ABS/PC Blend 20% Glass Fiber	Good
ABS/PC Flame Retardant	Poor
ASA - Acrylonitrile Styrene Acrylate	Good
ASA/PC Blend - Acrylonitrile Styrene Acrylate/Polycarbonate Blend	Good
ASA/PC Flame Retardant	Poor
ECTFE - Ethylene Chlorotrifluoroethylene	Good
ETFE - Ethylene Tetrafluoroethylene	Good
EVA - Ethylene Vinyl Acetate	Fair
FEP - Fluorinated Ethylene Propylene	Good
HDPE - High Density Polyethylene	Fair
HIPS - High Impact Polystyrene	Poor
HIPS Flame Retardant V0	Poor
LCP - Liquid Crystal Polymer	Good
LCP Carbon Fiber-reinforced	Good
LCP Glass Fiber-reinforced	Good
LCP Mineral-filled	Good
MABS - Transparent Acrylonitrile Butadiene Styrene	Fair
PA 11 - (Polyamide 11) 30% Glass fiber reinforced	Fair
PA 11, Conductive	Fair
PA 11, Flexible	Fair
PA 11, Glass Filled	Fair
PPA 11 or 12	Fair
PA 11, Rigid	Fair
PA 12 (Polyamide 12), Conductive	Fair
PA 12, Fiber-reinforced	Fair
PA 12, Flexible	Fair
PA 12, Glass Filled	Fair
PA 12, Rigid	Fair
PA 46 - Polyamide 46	Fair
PA 46, 30% Glass Fiber	Fair
PA 6 - Polyamide 6	Fair
PA 6-10 - Polyamide 6-10	Fair
PA 66 - Polyamide 6-6	Fair
PA 66, 30% Glass Fiber	Fair
PA 66, 30% Mineral filled	Fair
PA 66, Impact Modified, 15-30% Glass Fiber	Poor
PA 66, Impact Modified	Fair - Poor
Polyamide semi-aromatic	Fair
PAI - Polyamide-Imide	Good
PAI, 30% Glass Fiber	Good
PAI, Low Friction	Good
PAR - Polyarylate	Good
PARA (Polyarylamide), 30-60% glass fiber	Fair
PBT - Polybutylene Terephthalate	Good
PBT, 30% Glass Fiber	Good
PC (Polycarbonate)	Good
PC (Polycarbonate) 20-40% Glass Fiber	Good
PC (Polycarbonate) 20-40% Glass Fiber Flame Retardant	Poor
PC - Polycarbonate, high heat	Good
PC/PBT Blend - Polycarbonate/Polybutylene Terephthalate Blend	Good
PE - Polyethylene 30% Glass Fiber	Fair
PEEK - Polyetheretherketone	Excellent
PEEK 30% Carbon Fiber-reinforced	Excellent
PEEK 30% Glass Fiber-reinforced	Excellent
PEI - Polyetherimide	Good
PEI, 30% Glass Fiber-reinforced	Good
PEI, Mineral Filled	Good
PESU - Polyethersulfone	Good
PESU 10-30% glass fiber	Good
PET - Polyethylene Terephthalate	Good
PET, 30% Glass Fiber-reinforced	Good
PET, 30/35% Glass Fiber-reinforced, Impact Modified	Fair
PET, 30/35% Glass Fiber-reinforced, Impact Modified	Poor
PETG - Polyethylene Terephthalate Glycol	Good
PE-UHMW - Polyethylene - Ultra High Molecular Weight	Fair
PFA - Perfluoroalkoxy	Good
PI - Polyimide	Excellent
PMMA - Polymethylmethacrylate/Acrylic	Good
PMMA (Acrylic) High Heat	Good
PMMA (Acrylic) Impact Modified	Fair - Good
PMP - Polymethylpentene	Good
PMP 30% Glass Fiber-reinforced	Good
PMP Mineral Filled	Good
POM - Polyoxymethylene (Acetal)	Fair
POM (Acetal) Impact Modified	Fair
POM (Acetal) Low Friction	Fair
POM (Acetal) Mineral Filled	Fair
PP - Polypropylene	Poor
PP - Polypropylene 10-20% Glass Fiber	Poor
PP, 10-40% Mineral Filled	Poor
PP, 10-40% Talc Filled	Poor
PP, 30-40% Glass Fiber-reinforced	Poor
PP (Polypropylene) Copolymer	Poor
PP (Polypropylene) Homopolymer	Poor
PP, Impact Modified	Poor
PPA - Polyphthalamide	Good
PPE - Polyphenylene Ether	Fair
PPE, 30% Glass Fiber-reinforced	Fair
PPE, Flame Retardant	Poor
PPE, Impact Modified	Fair
PPE, Impact Modified	Poor
PPE, Mineral Filled	Fair
PPS - Polyphenylene Sulfide	Good
PPS, 20-30% Glass Fiber-reinforced	Good
PPS, 40% Glass Fiber-reinforced	Good
PPS, Conductive	Good
PPS, Glass fiber & Mineral-filled	Good
PPSU - Polyphenylene Sulfone	Excellent
PS (Polystyrene) 30% glass fiber	Good
PS (Polystyrene) Crystal	Good
PS, High Heat	Good
PSU - Polysulfone	Good
PSU, 30% Glass finer-reinforced	Good
PSU Mineral Filled	Good
PTFE - Polytetrafluoroethylene	Good
PTFE, 25% Glass Fiber-reinforced	Good
PVDF - Polyvinylidene Fluoride	Good
SAN - Styrene Acrylonitrile	Good
SAN, 20% Glass Fiber-reinforced	Good
SMMA - Styrene Methyl Methacrylate	Good
SRP - Self-reinforced Polyphenylene	Good
XLPE - Crosslinked Polyethylene	Good