precautions for using PVC foam board in high-temperature and high-humidity environments
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Softening and Deformation: The thermal deformation temperature of PVC typically ranges from 60-80°C. If the ambient temperature continuously exceeds 70°C, the board may soften, warp, or experience dimensional expansion (linear expansion coefficient approx. (5-8)×10⁻⁵/°C), affecting structural stability.
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Reduced Mechanical Strength: High temperatures accelerate the movement of PVC molecular chains, potentially decreasing tensile and flexural strength by 10%-30% (e.g., tensile strength at room temperature is about 20MPa, dropping to 14-18MPa at 70°C).
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Damage to Foam Structure: The cellular pores in the foam core may rupture under high-temperature pressure, causing uneven board density and reducing thermal and acoustic insulation properties.
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Moisture Absorption and Hydrolysis: While PVC itself is water-resistant, the porous foam structure may adsorb water vapor. Prolonged high humidity (humidity >85%) can cause slight surface hydrolysis, leading to stickiness and loss of gloss.
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Mold Growth: In poorly ventilated wet environments, the surface of PVC foam board may become a breeding ground for mold due to residual organic matter (e.g., processing aids), affecting hygiene and appearance.
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Additive Migration: Plasticizers in PVC (such as phthalates) may slowly migrate to the surface in high humidity, causing the board to harden, become brittle, and release odors.
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Avoid Prolonged Outdoor Exposure: When used for outdoor sunshades or canopies, pair with a sunscreen coating (e.g., acrylic paint) or choose modified PVC foam boards with UV absorbers to prevent dual aging from heat and UV (unmodified boards typically last <2 years outdoors).
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Restrictions in Indoor Wet Areas: In bathrooms, kitchens, etc., ensure good ventilation and prevent direct contact with standing water (e.g., bathroom partitions should be ≥10cm above the floor) to avoid core softening from prolonged moisture penetration.
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预留 Expansion Gaps During Installation: In high-temperature environments, leave 0.5-1mm expansion gaps between boards (e.g., 1mm for a 1m-long board) and fill with elastic sealant to prevent cracking from thermal expansion/contraction.
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Application as Equipment Insulation: When used as insulation for high-temperature equipment (e.g., ovens, pipes), ensure the equipment surface temperature is <60°C and cover the outer layer with aluminum foil or other reflective materials to avoid direct heat contact (thermal conductivity approx. 0.04-0.06W/(m·K), which may increase by 20% at high temperatures).
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Moisture-Proof Packaging Treatment: For packaging in wet environments, cover the board with PE film or waterproof paper to prevent moisture from penetrating the foam pores and reducing packaging strength (e.g., condensate accumulation in cold chain transport).
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Caution for Outdoor Billboards: In high-temperature and high-humidity regions (e.g., tropical monsoon climates), prefer PET foam or XPS foam over PVC. If PVC is necessary, inspect edges quarterly for powdering or cracking and replace promptly (typical unprotected outdoor lifespan: ~1 year).
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Indoor Display Maintenance: In humid exhibition halls or showrooms, prevent contact with condensate (e.g., below air conditioner vents) and regularly wipe the surface with a dry cloth to prevent mold spots.
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Cutting and Drilling: High temperatures soften the board, so increase tool speed (e.g., circular saw ≥3000r/min) and use cooling water to prevent cut edges from melting and sticking; drill holes 0.2-0.3mm larger than at room temperature to avoid cracking from thermal expansion when installing bolts.
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Welding and Bonding: PVC foam board commonly uses hot gas welding or chloroprene adhesive. In high temperatures, reduce welding temperature by 10-20°C (e.g., from 200-220°C to 180-200°C) to avoid material overheating and decomposition; use moisture-resistant adhesives (e.g., polyurethane) as ordinary glues may lose 50%+ bonding strength in high humidity.
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Temperature Monitoring: Ensure the environment is <35°C during storage and installation, avoiding direct sunlight (e.g., cover transport vehicles with sunshades).
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Humidity Management: If the board is damp before installation (moisture content >0.5%), dry it in a 40°C ventilated environment for 24 hours; in humid areas, treat the wall or base with a moisture barrier (e.g., asphalt coating) to prevent bottom-up moisture penetration.
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Regular Inspection Cycle: Inspect every 3 months in high-temperature and high-humidity environments, focusing on surface discoloration (yellowing, blackening), bulges, softening, and mold growth in corners and joints.
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Cleaning Methods: Use a neutral detergent (pH 6-8) and soft cloth for surface stains, avoiding organic solvents like alcohol or gasoline (which may dissolve the PVC surface); treat mold spots with a chlorine-based disinfectant (e.g., 10x diluted bleach) followed by ventilation.
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Random Performance Testing: For critical applications (e.g., structural components), sample boards for thermal deformation testing (per GB/T 1633, load 1.82MPa and test deflection at 70°C). Replace if deformation exceeds 5%.
For strict high-temperature and high-humidity environments (e.g., temperature >80°C or prolonged immersion), prioritize:
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PE (Polyethylene) Foam Board: Temperature resistance -40-80°C, water absorption <0.01%, superior moisture and heat resistance.
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PIR (Polyisocyanurate) Foam Board: Temperature resistance -196-120°C, closed-cell rate >95%, suitable for high-temperature wet industrial scenarios (e.g., cold storage, chemical equipment).
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Metal Honeycomb Panels: Aluminum or stainless steel surface with aluminum honeycomb core, temperature resistance up to 200°C+, waterproof, but higher cost.
