The radiation resistance of high-temperature tape is closely and directly linked to the molecular structure of its substrate. This relationship is reflected in multiple aspects, including molecular chain stability, the role of aromatic groups, the balance between crosslinking and chain scission, and the influence of specific structures. These factors collectively determine the tape's performance in radiation environments.
The stability of the substrate's molecular structure is a key factor influencing its radiation resistance. When exposed to radiation, the substrate's molecular chains are impacted by high-energy radiation, causing breakage or crosslinking reactions. Substrates with dense molecular chains and high chemical bond energy, such as polyimide, have aromatic rings within their molecular chains that effectively disperse radiation energy, reducing the risk of main chain breakage and thus maintaining the material's physical integrity. Conversely, if the substrate's molecular chains contain weak links, such as side chains containing easily cleavable groups, radiation can cause the molecular chains to rapidly decompose, resulting in a loss of adhesion and mechanical strength.
The role of aromatic groups in the substrate's molecular structure significantly influences radiation resistance. Polymers containing aromatic structures, such as benzene rings, such as polystyrene and polyimide, exhibit excellent stability during radiation exposure. This is because the conjugated system of aromatic rings absorbs radiation energy and converts it into heat through electron delocalization, preventing main chain breakage. For example, the imide ring and benzene ring in polyimide molecules form a rigid conjugated structure, which not only improves heat resistance but also significantly enhances radiation resistance, making it widely used in high-radiation environments such as aerospace.
The balance between crosslinking and chain scission in the substrate's molecular structure is a key mechanism determining radiation resistance. Under radiation, substrate molecules may undergo crosslinking reactions, forming a three-dimensional network structure that improves the material's strength and heat resistance; they may also undergo chain scission reactions, causing embrittlement. The ideal substrate molecular structure should enhance performance through moderate crosslinking during the initial radiation phase while limiting the spread of chain scission reactions. For example, when an aromatic curing agent is added to epoxy resin, the benzene rings in its molecular structure stabilize the crosslinked network, making the material stable even at radiation doses exceeding 1000 Mrad. However, aliphatic curing agents cannot provide the same level of radiation stability.
The influence of specific molecular structures on the radiation resistance of high-temperature tape is reflected in steric hindrance and electron cloud distribution. Quaternary carbon atoms or large-diameter atoms in the substrate molecules can easily break the molecular chains due to steric hindrance. For example, butyl rubber, due to the steric hindrance created by the isobutyl side chains in its molecular structure, is extremely susceptible to chain scission under radiation, making it the least radiation-resistant elastomer. In contrast, polymers with regular molecular structures and fewer side chains, such as polytetrafluoroethylene, have a uniform electron cloud distribution, effectively resisting radiation damage and exhibiting excellent radiation resistance.
The compatibility of the substrate's molecular structure with the type of radiation also affects the radiation resistance of high-temperature tape. Different types of radiation (such as gamma rays, X-rays, and neutrons) have different molecular damage mechanisms. For example, gamma rays primarily cause molecular chain breakage and crosslinking, while neutrons degrade material properties through collisions with atomic nuclei. Factors such as the hydrogen atom content and crystal structure in the substrate's molecular structure determine its sensitivity to specific radiation types. Therefore, choosing a substrate with a molecular structure that matches the radiation environment is crucial to optimize the radiation resistance of high-temperature tape.
Modifying the substrate's molecular structure is an important means of improving the radiation resistance of high-temperature tape. The radiation resistance of a substrate can be significantly enhanced by introducing radiation-resistant groups (such as aromatic rings or halogen atoms) or adding stabilizers (such as light-shielding agents or excited-state quenchers). For example, adding inorganic fillers or glass fibers to polyester can increase its radiation resistance to doses exceeding 1000 Mrad. Adding highly aromatic oil-based softeners to rubber can mitigate radiation-induced crosslinking reactions and improve the material's radiation stability.
From an application perspective, matching the substrate's molecular structure with its radiation resistance is a core principle in high-temperature tape design. High-radiation applications, such as aerospace and nuclear industries, require substrates with stable molecular structures and aromatic groups (such as polyimide and polyetherketone). In general industrial radiation environments, the radiation resistance of conventional substrates (such as epoxy resin and acrylate) can be enhanced through molecular structure modification. This targeted design, based on molecular structure, enables high-temperature tape to maintain stable performance under varying radiation conditions, meeting diverse industrial needs.
