Why does PO film maintain good flexibility and crack resistance in cold regions?
Publish Time: 2025-12-03
PO film (polyolefin film), as a high-performance agricultural covering material, has been widely used in greenhouses worldwide in recent years, especially in high-latitude or frigid winter regions. One of its core advantages is its ability to maintain excellent flexibility and crack resistance even at low temperatures. This characteristic not only extends the film's lifespan but also ensures the continuity and stability of agricultural production. So, why can PO film maintain such excellent mechanical properties under cold conditions? This is mainly due to its unique molecular structure, advanced co-extrusion process, and scientific additive system.1. Low-Temperature Toughness Advantage of Polyolefin SubstratePO film uses ethylene-octene copolymer or ethylene-butene copolymer as its main raw materials. These polyolefin materials have a highly regular molecular chain structure and low crystallinity. Compared with traditional polyethylene, the short branches introduced into its molecular chain effectively hinder excessive crystal growth, thereby lowering the material's glass transition temperature. This means that even in environments as low as -20°C or even lower, the molecular chains of PO film retain sufficient mobility and do not become brittle, thus maintaining good flexibility and impact resistance.2. Optimized Mechanical Distribution Through Multilayer Co-extrusionPO film commonly employs three-layer or multilayer co-extrusion technology, with each functional layer having a clear role: the outer layer focuses on weather resistance and anti-fogging, the core layer provides strength and toughness, and the inner layer balances insulation and anti-dripping. The core layer typically uses a high-toughness polyolefin elastomer or a specific ratio of mLLDPE as a "buffer layer" to absorb external stress. This structural design not only improves overall tear resistance but also effectively disperses localized stress concentration at low temperatures, preventing micro-cracks from propagating into macroscopic damage. Even when subjected to ice and snow loads or strong winds, the film is not prone to brittle fracture.3. Synergistic Effect of Anti-aging and Toughening AdditivesTo cope with the intense ultraviolet radiation and drastic temperature differences in cold regions, high-efficiency antioxidants, light stabilizers, and specialized toughening additives are added to PO film during the production process. These additives not only delay the oxidative embrittlement of polymer chains at low temperatures but also improve intermolecular forces at the microscopic level, enhancing the material's elongation at break. In particular, some novel nanoscale toughening agents can significantly improve low-temperature impact strength without sacrificing transparency, allowing the film to maintain structural integrity during repeated freeze-thaw cycles.4. Low-Temperature Flexibility Testing Verifies Actual PerformanceIndustry standards specify clear requirements for the low-temperature embrittlement temperature of agricultural films, and the embrittlement temperature of high-quality PO film can typically be as low as -50℃. This means that in most cold or high-altitude winters, the film remains in a "highly elastic state" rather than a "glassy state," able to bend with slight deformation of the frame without cracking due to cold contraction stress. Furthermore, the elongation at break of PO film generally exceeds 400%, far higher than ordinary PE film, allowing it to withstand significant deformation at low temperatures without breaking.5. Environmental Adaptability in Practical ApplicationsLong-term feedback from cold agricultural regions such as Northeast Asia, Northern Europe, and Canada shows that PO film exhibits a significantly lower breakage rate than traditional agricultural films under harsh conditions such as snow cover, large diurnal temperature variations, and frequent strong winds. Its flexibility not only reduces the risk of tearing during installation but also lowers winter maintenance costs. Farmers do not need to frequently replace the film, saving resources and ensuring a safe microenvironment for crop overwintering.In summary, the excellent flexibility and crack resistance of PO film in cold regions is the result of the combined efforts of materials chemistry, structural engineering, and formulation science. From molecular design to multilayer composites and additive optimization, each step provides solid support for low-temperature performance. With the continuous advancement of materials technology, PO film is expected to play a greater role in special scenarios such as extremely cold agriculture and high-altitude planting, becoming one of the key materials for the sustainable development of modern agriculture.
