Properties

Glass fiber-reinforced polyamide (PA66+GF) is a composite material made from polyamide 66 (PA66) and reinforced with glass fibers for improved mechanical properties. Polyamide 66 is a type of nylon that is manufactured through the polycondensation of two monomers: hexamethylenediamine and adipic acid, each containing six carbon atoms—hence the PA66 name. In addition to superior mechanical characteristics compared with earlier nylon variants, PA66 offers the advantage of low-cost starting materials. 

• Glass fiber-reinforced polyamide (PA66+GF) is a composite material derived from PA66 (nylon 66) and glass fibers.
• PA66+GF demonstrates superior mechanical properties compared to earlier nylon variants.

 History

Discovered and brought to the mainstream market between the 1930s and 1940s by DuPont, polyamide 66 (PA66 or nylon 66) quickly became a popular choice for mass-produced goods due to its durability, chemical resistance, and versatility as a synthetic plastic. As demand for high-strength, heat-resistant, and lightweight materials grew, composites such as PA66+GF were created by adding glass fiber reinforcements to polyamide-type polymers. PA66+GF achieved an excellent combination of glass fiber’s strength and heat resistance with nylon 66’s versatility. By the 1970s and 1980s, the PA66+GF composite had gained significant popularity in the automotive and electronics sectors, where it was used as an alternative for heavier metals. Its applications have since expanded across many industries, with technological advancements allowing for further refinement of its properties. The characteristics of PA66+GF can be fine-tuned to meet end-product requirements by varying the glass fiber content (e.g., 10%, 30%, 50%) and using specific compounding methods to achieve optimal performance. 

• PA66 was developed in the early 1930s by DuPont. Glass fiber reinforcements were added to PA66 to create composites that combine the strength and heat resistance of glass fibers with the versatility of nylon.
• The characteristics of the end product can be fine-tuned by varying the glass fiber content and using specific compounding methods.

Tensile Strength

PA66+GF demonstrates superior performance in terms of tensile and flexural strength as well as impact resistance. The addition of glass fibers increases PA66’s tensile strength from 75 MPa to 180 MPa or more when the composite contains 30% glass fiber, enabling its use in load-bearing applications. Flexural strength is enhanced compared with PA66; for example, a 30% glass fiber content translates to a flexural strength of roughly 250 MPa. Furthermore, impact resistance and durability are improved, although the composite becomes more brittle compared to the polymer alone. PA66+GF is suitable for applications involving friction or stress, as the composite exhibits superior hardness with improved surface durability and wear resistance. 

• PA66+GF demonstrates superior tensile and flexural strength, as well as impact resistance, enabling its use in load-bearing applications.
• The composite also possesses superior hardness, surface durability, and wear resistance compared to PA66. 

While glass fiber reinforcements do not alter the melting point of PA66 dramatically, they significantly improve the heat deflection temperature, i.e., the temperature at which the material begins to deform under load. This property translates to improved heat resistance compared with PA66 alone, making the composite suitable for high-heat applications. Although PA66+GF remains an insulator, its thermal conductivity is enhanced. Dimensional stability is also improved due to a lower coefficient of thermal expansion, meaning that the material undergoes expansion to a lesser extent with temperature changes as glass fiber content increases. 

• While the melting point remains mostly unchanged, PA66+GF’s heat deflection temperature is superior to that of PA66, meaning the composite can withstand higher temperatures before it begins to deform under load.
• The composite demonstrates superior heat resistance, dimensional stability, and improved thermal conductivity compared with PA66.

Chemical Resistance

The excellent chemical resistance of PA66 to oils, fuels, and solvents is retained in PA66+GF. However, the composite is susceptible to degradation by strong acids and bases, which can damage both the polyamide matrix and the glass fibers. The addition of glass fiber also improves one significant limitation of PA66: moisture absorption. Although PA66 tends to absorb moisture, which can affect its mechanical properties, PA66+GF demonstrates reduced moisture absorption, though it does not become moisture-resistant.

• PA66+GF demonstrates excellent chemical resistance to oils, fuels, and most solvents, but it is susceptible to degradation by strong acids and bases, which can damage the matrix and glass fibers.
• The composite demonstrates reduced moisture absorption, a significant improvement over PA66’s susceptibility to moisture.

Since glass fibers are not electrically insulating, PA66+GF has a lower dielectric strength than PA66, meaning the composite is a poorer insulator than PA66 Although glass fiber-reinforced PA66 resists electrical conductivity, it is unsuitable for high-voltage applications where insulation is required.

• Glass fiber reinforcements diminish PA66’s insulation capacity.
• PA66+GF resists electrical conductivity and, thus, is unsuitable for high-voltage applications requiring insulation. 

While glass fiber reinforcements yield improved mechanical properties for PA66+GF composites, it is important to consider their environmental impact. The production process of PA66 is energy-intensive, a process that becomes even more demanding when incorporating glass fibers. PA66 is a downstream product of the petrochemical industry, and extracting glass fibers from raw materials, such as silica sand, limestone, or soda ash, also has environmental impacts, for example, habitat disruption and pollution. Like most synthetic polymers, PA66+GF is non-biodegradable, and as such, proper waste management is key to limiting associated pollution.

Reducing PA66+GF’s carbon footprint poses challenges, as recycling the material involves technical difficulties. Glass fibers can degrade during recycling, resulting in products that demonstrate diminished mechanical properties. Mechanical recycling may also damage the matrix and glass fibers. Finally, while in theory, chemical recycling of the composite into PA66 and GF can be achieved, the associated costs and technical limitations make this a complex process and impede large-scale implementation. Advancements in recycling technology, sustainable alternatives to PA66 and glass fibers, and responsible end-of-life management are essential in minimizing the environmental impact. 

• As a downstream product of the petrochemical industry, PA66+GF has an energy-intensive production process. Sourcing glass fiber from raw materials also has environmental impacts, such as habitat disruption and pollution.

• Recycling is challenging due to the degradation of mechanical properties, damage to the PA matrix and glass fibers, and associated cost and technical limitations, making large-scale recycling of PA66+GF complex and costly. Therefore, proper energy and waste management, improved recycling technologies, sustainable alternatives to PA66 and glass fibers, and responsible end-of-life management are essential for minimizing environmental impact.