Under high temperature and high pressure conditions, will the difference in thermal expansion of valve accessory positioning film hardware lead to failure?
Publish Time: 2025-12-26
In industrial settings such as petroleum refining, thermal power generation, and chemical synthesis, valve systems often need to operate for extended periods at temperatures above 300°C and pressures of tens of megapascals. To ensure accurate installation of actuators, positioners, and other accessories, valve accessory positioning film is widely used for temporary fixing or positioning guidance. It is typically directly attached to the surface of metal hardware such as stainless steel and carbon steel.1. Thermal Expansion Mismatch: A Potential Physical Cause of FailureMetal hardware commonly uses positioning film substrates such as polyimide. When the system temperature rises from room temperature to 300°C, the length change rate between the two can differ by 0.3%–0.7%. This mismatch generates shear stress at the interface. If this stress exceeds the cohesive strength or adhesive force of the adhesive, it can lead to edge lifting, bulging, or even complete peeling. Once the positioning film shifts, it not only affects the initial installation accuracy of the accessory but may also become a source of foreign matter in vibration environments, interfering with valve operation.2. Material Matching: Suppressing Thermal Stress at the SourceHigh-end valve accessory positioning films prioritize thermal expansion compatibility with commonly used hardware components during the design phase. For example:Preferring low CTE substrates: Using aromatic polyimide or liquid crystal polymer films, whose CTE is close to that of metals, significantly reducing thermal mismatch;Introducing an elastic interlayer: Adding flexible polymer microspheres or employing a gradient modulus design to give the film a "buffering" capacity, absorbing some thermal strain;Controlling film thickness: Keeping the total thickness within 0.1–0.2 mm reduces thermal deformation moments and avoids large-span warping.3. Adhesive Systems: Balancing High Temperature Resistance and High ToughnessOrdinary acrylic adhesives soften and leak at temperatures above 200℃, necessitating specialized adhesives for high-temperature applications:Silicone Pressure-Sensitive Adhesives: Can be used long-term from -55℃ to +250℃, with a low glass transition temperature, maintaining elasticity even at high temperatures, effectively alleviating thermal stress;Modified Epoxy-Acrylic Hybrid Adhesives: Reinforced with nanofillers, possessing both high Tg and fracture toughness;Cross-linked Structural Adhesives: Form a three-dimensional network through thermosetting after installation, significantly improving high-temperature cohesive strength.These adhesive systems not only offer heat resistance but also excellent creep resistance, preventing slow slippage under long-term loads.4. Structural and Process Optimization: Enhancing Interface ReliabilityBesides materials, structural design is also crucial:Local Spot Bonding Instead of Full Coverage: Apply adhesive only to critical positioning points to reduce continuous interface area and limit thermal stress accumulation;Edge Sealing: Laser sealing or hydrophobic coating of the membrane edges prevents the penetration of humid and hot media along the interface, thus preventing accelerated aging;Pre-Aging Treatment: Some manufacturers perform simulated thermal cycling pretreatment on finished membranes to release internal stress in advance and improve field service stability.While differences in thermal expansion are an objective physical law, they are not insurmountable obstacles. Through the selection of low CTE substrates, high-toughness, high-temperature resistant adhesive systems, intelligent structural design, and rigorous operating condition verification, modern valve accessory positioning films can reliably cope with the thermomechanical challenges of high-temperature and high-pressure environments. It is no longer just a "temporary sticker," but a reliable link in the precision assembly chain—silently safeguarding the macroscopic stability of industrial systems at the microscopic interface between steel and thin film.
