Tyres are highly engineered composite systems. A single tyre contains multiple rubber compounds, each located in a specific zone and each performing a distinct mechanical, thermal, and fatigue-related function. Carbon black selection therefore cannot be generic — it must be zone-specific and application-specific.
At iSTAR, we design three complementary carbon black platforms for tyre applications
PROPELON®
engineered for dynamic performance and heat control
VULCROX®
engineered for structural durability and load endurance
Together, these platforms replace conventional ASTM grades with engineered, zoneoptimized solutions.
Functional Rubber Zones and Their Material Demands
Before discussing tyre segments, it is essential to understand where carbon black is used inside a tyre and why each zone demands different properties.
PROPELON®
The tread is the outermost rubber layer that contacts the road or terrain.
Function
Carbon black role
Provides reinforcement and wear resistance while influencing hysteresis (heat generation)
Undertread (Base Tread)
Located directly beneath the tread.
Function
Carbon black role
Controls hysteresis and stabilizes long-term durability.
Belt
Rubber-coated steel or textile reinforcement layer below the tread.
Function
Carbon black role
Improves rubber-to-cord adhesion and fatigue endurance.
Cap Ply
Protective rubber layer over the belt package.
Function
Carbon black role
Enhances thermal stability and fatigue resistance.
Sidewall
Connects tread to bead and flexes continuously during operation.
Function
Carbon black role
Provides durability and UV protection without excessive stiffness.