PA Plastic Density: Reference Table & Weight Formula | ICD

Key takeaways

The density of PA plastic (Polyamide) in its unfilled virgin state ranges from 1.13 to 1.15 g/cm3 - slightly heavier than water but much lighter than metals and POM plastic.

However, when reinforcing additives such as glass fiber (GF) are compounded in to increase rigidity, this density can jump to 1.35-1.60 g/cm3. Understanding this figure helps engineers accurately calculate machine-component weights and helps procurement teams correctly estimate raw material input costs.

1. What is the density of PA plastic?

In engineering, when we ask about how “heavy” or “light” a material is, we are referring to its density (also called specific gravity). For PA plastic, this number is not fixed - it varies depending on the molecular structure (PA6 or PA66) and, most importantly, the additives included.

Unfilled virgin PA plastic (no additives):

• PA6 plastic: density approximately 1.13 g/cm3.
• PA66 plastic: density slightly higher, approximately 1.14-1.15 g/cm3.

This means that if you drop a piece of PA plastic into water (density 1.0 g/cm3), it will sink. However, compared to other engineering plastics such as POM or Teflon (PTFE), PA plastic is still classified as a lightweight material.

2. Why is glass-fiber-reinforced PA plastic heavier?

In practice, pure unfilled PA is rarely used for load-bearing components. Instead, glass-fiber-reinforced PA (GF) is used to increase stiffness and heat resistance. Glass fiber is an inorganic material with a high specific gravity (approximately 2.5 g/cm3), so when compounded into the plastic it significantly increases the overall density of the material.

Below is a reference density table for common PA plastic grades:

• Unfilled PA66: 1.14 g/cm3
• PA66 + 15% GF (GF15): 1.23 g/cm3
• PA66 + 30% GF (GF30): 1.36 g/cm3
• PA66 + 50% GF (GF50): 1.57 g/cm3

Knowing these figures is critically important. If you design a mold for unfilled PA plastic but then switch to running PA66-GF30 without recalculating, the product weight will increase by approximately 20%, and raw material costs will rise proportionally.

3. Comparing PA plastic density to other materials

To understand PA plastic’s position on the industrial materials map, here is a comparative table:

4. PA plastic weight calculation formula

Once you know the density, calculating the weight of any PA plastic component is straightforward:

Weight (kg) = Volume (cm3) x Density (g/cm3) / 1000

Example calculation: A PA66-GF30 gear with dimensions 10 cm x 5 cm x 2 cm (approximate volume = 100 cm3):

• Weight = 100 cm3 x 1.36 g/cm3 / 1000 = 0.136 kg = 136 grams

For complex component shapes, calculate the volume using 3D CAD software or use the water displacement method for physical prototypes.

5. Practical applications at ICD Vietnam

Understanding PA plastic density has direct implications for ICD Vietnam’s core product lines:

• Caster wheels for hand pallet trucks: PA6 caster wheels (density 1.13 g/cm3) are 6-7 times lighter than equivalent cast-iron wheels. This reduces the overall weight of the truck, making it easier to maneuver and reducing operator fatigue.
• Machine component replacement: When replacing aluminum parts with PA66-GF30 (density 1.36 vs 2.70 g/cm3), component weight is reduced by approximately 50% while maintaining acceptable mechanical strength for many applications.
• Inventory cost estimation: Procurement teams use density values to estimate raw material consumption per batch and control costs accurately.

Frequently Asked Questions

1. Does the density of PA plastic change with temperature?

Yes, slightly. Like all thermoplastics, PA plastic expands slightly at higher temperatures, which decreases density marginally. However, within normal operating temperature ranges (-40 degrees C to 100 degrees C), this change is negligible for most practical calculations.

2. Is the density of PA plastic the same as its specific gravity?

In engineering practice, these terms are often used interchangeably. Strictly speaking, specific gravity is dimensionless (the ratio of material density to water density), while density has units (g/cm3 or kg/m3). For PA plastic: density = 1.13-1.15 g/cm3 means specific gravity = 1.13-1.15 (since water density = 1.0 g/cm3).

3. How does moisture absorption affect PA plastic density?

PA plastic absorbs moisture from the environment (2.5-9% by weight depending on grade). When fully moisture-conditioned, the absorbed water molecules slightly increase the material’s mass without significantly changing its volume, resulting in a marginally higher density measurement.

References

• Wikipedia: Nylon 6 - Physical Properties
• Wikipedia: Polyoxymethylene (POM) - Density Reference