What are the thermal properties of glass fiber?
Core Thermal Performance Characteristics:
1. Excellent Thermal Insulation (Low Thermal Conductivity)
Glass fiber has extremely low thermal conductivity. At room temperature (approximately 25°C), its typical thermal conductivity is about 0.027 W/(m·K).
This value is significantly lower than most metallic materials (e.g., steel approximately 50 W/(m·K), aluminum approximately 237 W/(m·K)), and also significantly lower than many commonly used building and industrial materials (e.g., concrete approximately 1.7 W/(m·K), wood approximately 0.1-0.2 W/(m·K)).
This extremely low thermal conductivity means that glass fiber effectively impedes heat transfer, making it a high-performance thermal insulation material.
Temperature Effect: As ambient temperature increases, the thermal conductivity of glass fiber increases slightly, but its fundamental low thermal conductivity characteristic is maintained over a fairly wide temperature range, making it suitable for thermal insulation in medium to high temperature conditions.
2. Excellent High-Temperature Resistance and Non-combustibility
Compared to organic fibers (such as cotton, wool, polyester, nylon, aramid, etc.), glass fiber exhibits extremely high heat resistance.
Its softening temperature is as high as 550°C - 750°C. This means that below this temperature range, glass fiber maintains sufficient structural strength and morphological stability without softening or deforming.
Key Advantage: Non-combustible. Glass fiber is an inorganic silicate material that does not burn at high temperatures and does not release toxic fumes. This characteristic makes it ideal for fire safety applications (such as fireproof insulation in buildings, fire blankets, fire curtains, and high-temperature pipe cladding).
3. Thermal Shrinkage and Its Impact on Composite Materials
Although the mechanical properties of glass fiber itself do not change significantly when heated to temperatures far below its softening point, thermal shrinkage occurs.
Associative Risks in Composite Materials: This thermal shrinkage behavior is critical for resin-based composites (fiberglass) reinforced with glass fiber. If the interfacial bonding between glass fiber and the resin matrix is poor (e.g., inappropriate sizing agent selection or uneven coating leading to poor coupling), during repeated heating and cooling cycles (thermal cycling) of the product:
· The fiber and resin will deform differently due to the difference in their coefficients of thermal expansion/contraction.
· The poor interface cannot effectively transfer stress or coordinate deformation.
· This may eventually lead to interfacial debonding between the fiber and the resin matrix.
· Consequences: Interfacial debonding severely weakens the integrity of the composite material, becoming a stress concentration point and crack initiation source, resulting in a significant decrease in the mechanical strength of the product (especially interlaminar shear strength and fatigue strength), affecting its long-term reliability and durability.
Application Areas: Solutions for High Temperature and Thermal Insulation Needs
Based on the above unique thermal properties, glass fiber is widely used in:
· Building thermal insulation: Glass wool, insulation felt/boards, used for wall, roof, and pipe insulation, saving energy and reducing consumption.
• Industrial High-Temperature Insulation: Insulation layers for high-temperature kilns, pipelines, and equipment; thermal system insulation; energy saving.
• Fire Safety: Fireproof door core materials, fireproof partitions, fire blankets, insulation layers for fire suits, and fireproof cable wrapping.
• Aerospace and Transportation: Thermal insulation, sound insulation, and fireproofing materials for aircraft, ships, and high-speed trains.
• Household Appliances: Thermal insulation pads for high-temperature appliances such as ovens, grills, and dryers.