The impact of plasticizer migration on long-term performance in PVC insulated wire and how to suppress migration.
Release Time : 2026-02-04
PVC insulated wire, with its excellent electrical properties and processing characteristics, is widely used in power transmission, equipment connection, and other fields. However, plasticizer migration, as a key factor affecting its long-term performance, has become a core issue restricting product reliability. Plasticizers, as key additives for improving the flexibility of PVC, bind to PVC molecules through hydrogen bonds or van der Waals forces. This non-chemical bonding method makes it easy for plasticizers to migrate from the matrix to the surface or contact medium during long-term use, leading to degradation of the insulation layer performance.
The impact of plasticizer migration on the long-term performance of PVC insulated wire exhibits multi-dimensional characteristics. In terms of electrical performance, plasticizer enrichment on the insulation surface caused by migration reduces surface resistivity, increases the risk of leakage current, and may cause partial discharge, especially in humid environments, accelerating insulation aging. In terms of mechanical performance, plasticizer loss increases the hardness and brittleness of the insulation layer, making it prone to cracking when the wire is bent or vibrated, and even leading to insulation peeling. In terms of environmental adaptability, migrating plasticizers can contaminate contact materials. For example, they may cause electrochemical corrosion when in contact with metal conductors, and swelling or adhesion when in contact with rubber parts. Furthermore, plasticizer migration can alter the thermal stability of the insulation layer, reducing its high-temperature resistance and increasing fire hazards.
Inhibiting plasticizer migration requires starting with material formulation design. Using high molecular weight plasticizers can significantly reduce the migration rate because their longer molecular chains result in stronger entanglement with the PVC matrix, making it less likely for them to diffuse through chain segment gaps. Polyester plasticizers, due to their excellent compatibility with PVC, can form a stable hydrogen bond network, effectively fixing other small molecule plasticizers and reducing migration. Ionic liquids, as novel plasticizers, possess high-temperature low volatility and UV stability, and can replace traditional phthalate plasticizers, reducing migration risks at the source.
Nanoparticle modification is an important technical approach to inhibiting migration. Nano-sized SiO₂, montmorillonite, and other inorganic particles form a "maze structure" in the PVC matrix, reducing the migration rate by extending the plasticizer diffusion path. After organic modification, montmorillonite exhibits increased interlayer spacing, allowing for uniform dispersion within PVC. Its layered structure provides a physical barrier to plasticizer molecules. Nanoparticles can also form physical cross-linking points with PVC molecular chains, restricting chain segment movement and further inhibiting plasticizer migration. However, careful control of the nanoparticle addition is necessary to avoid localized defects in the insulation layer due to agglomeration.
Surface modification techniques prevent plasticizer migration by constructing physical barriers. Coating the PVC surface with non-migratory substances, such as water-soluble polymers or inorganic oxide layers, forms a dense protective film, blocking channels for plasticizer volatilization or extraction. Photo-initiated surface cross-linking technology, through sodium sulfide treatment, creates a network structure on the insulation layer surface, significantly improving surface density. This method is widely used in medical PVC applications, effectively extending product lifespan, but a balance must be struck between surface hardness and flexibility.
Process optimization plays a supporting role in inhibiting migration. Controlling mixing temperature and shear force prevents premature plasticizer precipitation, ensuring uniform dispersion within the PVC matrix. Gradient cooling processes promote PVC crystallization through staged cooling, reducing the proportion of amorphous regions and thus minimizing plasticizer migration pathways. Using a zoned temperature-controlled extruder allows for differentiated processing of the insulation and conductor layers, preventing plasticizer degradation caused by localized overheating.
The development of PVC insulated wire will focus on the development of environmentally friendly plasticizers and multifunctional composite technologies. Bio-based plasticizers have become a research hotspot due to their degradability and low toxicity, but their compatibility with PVC still needs optimization. Molecular imprinting technology, by introducing specific binding sites into the PVC matrix, can achieve precise binding of plasticizer molecules. Smart responsive materials can automatically adjust the plasticizer release rate according to environmental conditions, providing solutions for wire applications in extreme environments. These innovations will drive the evolution of PVC insulated wire towards high performance, long lifespan, and environmental friendliness.