Failing Photovoltaic Cable Thermal Aging? – High‑Temperature Stability Analysis of POE‑g‑MAH Compatibilizers

Global photovoltaic installations continue to rise, and the long‑term reliability of photovoltaic cables directly affects the life‑cycle revenue of power plants. The IEC 62930:2017 standard clearly specifies that photovoltaic cables are expected to have a service life of at least 25 years under normal operating conditions, with a maximum continuous conductor temperature of 90 °C for normal operation, and a permitted operating time of 20,000 hours at a maximum conductor temperature of 120 °C. This imposes extremely demanding requirements on the thermal aging performance of cable materials—the insulation and sheath materials must undergo long‑term exposure tests in high‑temperature air aging ovens, and after aging, the change rates of tensile strength and elongation at break must be controlled within specified limits. This means that every component in the cable compound, including the compatibilizer—although used in small quantities but critically important—must withstand long‑term high temperatures without significant degradation.

I. Why Can Conventional Compatibilizers Not Withstand High‑Temperature Aging?

The core function of a compatibilizer is to establish an interfacial anchoring layer between polar inorganic fillers and the non‑polar polyolefin matrix. However, during the long‑term high‑temperature aging tests required for photovoltaic cables, conventional compatibilizers face three major challenges:

The first challenge: thermal scission of grafted chains.
Maleic anhydride is chemically grafted onto the polyolefin backbone. Studies have confirmed that as the grafting reaction temperature rises, the grafting ratio initially increases and then decreases, eventually reaching equilibrium, but high temperatures exacerbate crosslinking side reactions. During long‑term high‑temperature aging, the carbon‑carbon bonds near the grafting points are more prone to scission due to steric hindrance. Once the grafted chains break, the maleic anhydride functional groups detach from the backbone, the grafting ratio drops, anchoring sites at the interface diminish, and the "molecular bridge" between the filler and the matrix gradually collapses.

The second challenge: uncontrolled gel content.
High temperatures not only trigger grafted chain scission but also activate residual peroxide initiator fragments or promote new free‑radical reactions. Studies have confirmed that when the initiator dosage is increased, the gel fraction continues to rise until complete gelation occurs, which severely affects processability and mechanical properties.

The third challenge: aggravated migration of small‑molecule extractables.
High temperatures accelerate the migration rate of residual unreacted monomers, initiator fragments, and low‑molecular‑weight oligomers in the compatibilizer. These substances gain sufficient kinetic energy at elevated temperatures, accelerating their migration to the sheath surface, where they form oily or powdery deposits. This not only affects appearance but may also reduce the insulation performance of the sheath surface.

These three challenges act simultaneously—grafted chain scission destroys interfacial anchoring, increasing gel content leads to embrittlement, and small‑molecule migration deteriorates insulation properties—making it difficult for conventional compatibilizers to survive the long‑term high‑temperature aging tests required for photovoltaic cables.

II. How to Enhance Thermal Stability at the Source to Withstand High‑Temperature Aging?

The key to solving the problem lies in strengthening thermal stability from the very design of the compatibilizer.

The JP‑M13 cable compound compatibilizer from Shanghai Jiuju Polymer Materials Co., Ltd. is a POE‑based maleic anhydride grafted compatibilizer specifically developed for the high‑temperature aging scenarios of photovoltaic cable compounds. It incorporates, at the synthesis stage, an antioxidant compounding system tailored for high‑temperature applications—a primary antioxidant (hindered phenol) that scavenges alkoxy radicals and terminates chain oxidation reactions, and a secondary antioxidant (phosphite) that decomposes hydroperoxides and regenerates the primary antioxidant activity. Their synergistic action establishes a three‑dimensional "thermal‑oxidative protection barrier" within the compatibilizer, effectively inhibiting grafted chain scission, radical‑induced crosslinking side reactions, and the formation of small‑molecule migrants.

After long‑term high‑temperature thermal aging, JP‑M13 maintains a high retention rate of the grafting ratio, effectively suppresses gel content, and ensures that the retention rate of elongation at break of the sheath meets the requirements of IEC 62930—guaranteeing that the compatibilizer still retains sufficient interfacial anchoring capability after the stringent thermal aging tests specified for photovoltaic cables, that the filler dispersion remains intact, and that the flexibility and crack resistance of the sheath are preserved.

III. Selection Recommendations for Photovoltaic Cable Compound Formulators

For the development of photovoltaic cable compounds, the following points deserve special attention:

• Request suppliers to provide grafting‑ratio retention data after long‑term high‑temperature thermal aging—this is the most direct basis for judging the heat resistance of a compatibilizer. A truly good product should maintain a high grafting‑ratio retention after aging.

• Pay attention to gel content indicators—improper formulation design may cause gel content to become uncontrolled during long‑term aging, directly affecting both processability and mechanical properties.

• Conduct complete thermal aging validation—perform thermal aging tests in the laboratory according to IEC 62930 requirements to verify that the change rates of tensile strength and elongation at break of the aged sheath meet the standard specifications.

JP‑M13 incorporates an antioxidant compounding system specifically developed for high‑temperature applications in its formulation design. After long‑term high‑temperature thermal aging, it maintains a high grafting‑ratio retention and effectively suppresses gel content, ensuring that the retention rate of elongation at break meets the photovoltaic cable standard requirements—making it a key technical guarantee for fulfilling the 25‑year service‑life promise.

If you are also developing photovoltaic cable compounds and need a POE‑g‑MAH compatibilizer that can withstand high‑temperature aging, please feel free to contact us. We have been steadily serving a number of leading cable companies, and we can provide aging test data reports and free samples, with direct technical engineer support.