Coefficients of Friction (Static) Ranges for Various Materials

 Static Coefficients of Friction for Various Engineering Materials

Material	Coefficient of Friction (Static) Range
Plastics
PTFE (Teflon)	0.10–0.25
PE (Polyethylene, Rigid)	0.40–0.50
PE (Polyethylene, Flexible)	0.65–0.75
PP (Polypropylene)	0.35–0.45
POM (Polyoxymethylene)	0.25–0.50
PA (Polyamide, Nylon)	0.30–0.50
PBT (Polybutylene Terephthalate)	0.30–0.40
PS (Polystyrene)	0.45–0.60
SAN (Styrene-Acrylonitrile)	0.45–0.65
PC (Polycarbonate)	0.40–0.65
PMMA (Acrylic)	0.60–0.70
ABS (Acrylonitrile Butadiene Styrene)	0.60–0.75
PVC (Polyvinyl Chloride)	0.55–0.60
Metals
Aluminum	0.30–0.45
Steel (Mild)	0.60–0.80
Stainless Steel	0.50–0.60
Copper	0.30–0.40
Brass	0.30–0.35
Titanium	0.30–0.35
Composites and Other Materials
GFRP (Glass-Fiber Reinforced Polymer)	0.30–0.35
CFRP (Carbon-Fiber Reinforced Polymer)	0.25–0.30
Rubber (Natural)	1.0–4.0 (varies widely)
Wood (Dry)	0.30–0.50
Wood (Wet)	0.40–0.60
Ceramics
Alumina	0.20–0.25
Silicon Carbide	0.25–0.30
Zirconia	0.20–0.30

---

Explanation of Static Friction Coefficient

The static friction coefficient ($\mu_s$) is a dimensionless quantity that represents the ratio between the force needed to start moving an object on a surface and the normal (perpendicular) force pressing the two surfaces together. It is calculated as:

$$\mu_s = \frac{F_s}{N}$$

where:

• $F_s$ is the force required to overcome the static friction and start movement.
• $N$ is the normal force.

 

Importance of the Static Friction Coefficient

• Design Applications: Knowing the static friction coefficients helps engineers determine the force needed to initiate motion in components, essential for designing machinery with moving parts.
• Material Selection: The coefficient helps in selecting materials for parts that contact each other, affecting wear and efficiency.
• Safety and Stability: For applications requiring stability (e.g., structural supports), materials with higher static friction can prevent sliding and ensure safety.