Polyolefin-Polybutadiene Block Copolymer for Tire Tread
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Solution Overview
Problem
Current tire tread compounds face challenges in achieving excellent wet traction without increasing rolling resistance and tread wear, as existing additives either improve silica dispersion or raise wet traction but often degrade mechanical performance or have limited effectiveness.
Innovation Solution
A polyolefin-polybutadiene block-copolymer with specific molecular weight ranges and cross-linking moieties is used to enhance silica dispersion and improve wet traction without affecting rolling resistance, forming nano-micelles that preserve fatigue and cut resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If functionalized SBR is used to enhance silica filler dispersion and reduce rolling resistance, then rolling resistance is reduced, but wet traction is not improved
Solution Approach 1:
The invention uses a block copolymer structure with distinct polyolefin blocks and polybutadiene blocks separated by crosslinking moieties. This segmentation allows each block to perform its specific function: polyolefin for silica interaction and rolling resistance reduction, polybutadiene for wet traction enhancement, without interfering with each other's performance.
Solution Approach 2:
Different blocks of the copolymer provide different local properties: the polyolefin block provides polarity for silica interaction and low Tg for rolling resistance, while the polybutadiene block provides elasticity and adhesion for wet traction. This local differentiation resolves the contradiction by assigning specific functions to specific parts of the molecule.
2Reliability
If Nanoprene gels are used to raise wet traction, then wet traction is improved, but mechanical performance in fatigue and cut resistance is degraded
Solution Approach 1:
The invention changes the size parameter of the additive from micron-sized gels (Nanoprene) to nanometer-sized micelles (block copolymer aggregates). This size reduction from microns to nanometers allows the material to improve wet traction while being too small to cause the mechanical degradation associated with larger gel particles.
Solution Approach 2:
The block copolymer forms a composite structure with polyolefin cores and polybutadiene coronas, creating nanoscale micelles that combine the benefits of both blocks while avoiding the drawbacks of micron-sized gel particles. This composite approach resolves the contradiction between wet traction improvement and mechanical strength preservation.
3Reliability
If compound Tg is raised to provide good wet traction, then wet traction is improved, but rolling resistance and tread wear increase
Solution Approach 1:
The block copolymer provides local polybutadiene regions with appropriate Tg for wet traction while the polyolefin blocks maintain low Tg for rolling resistance. This local differentiation allows the compound to have multiple Tg characteristics simultaneously, resolving the contradiction between wet traction and rolling resistance.
Solution Approach 2:
The copolymer creates a composite molecular structure combining high-Tg polybutadiene segments for wet traction with low-Tg polyolefin segments for rolling resistance reduction. This molecular-level composite allows the compound to exhibit both high wet traction and low rolling resistance properties simultaneously.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The polyolefin-polybutadiene block-copolymer effectively enhances wet traction while maintaining low rolling resistance and mechanical performance, with micelle sizes less than 20 microns to prevent detrimental effects on the tread compound.
Implementation Method 1
forming nano-micelles that preserve fatigue and cut resistance
Implementation Method 2
the 'fPB' is a functionalized polar polybutadiene block
Implementation Method 3
XL is a cross-linking moiety that covalently links the PO and fPB blocks
Data Source
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AI summary
A polyolefin-polybutadiene block-copolymer and a tire tread composition comprising the polyolefin-polybutadiene block-copolymer, the composition comprising, by weight of the composition, within the range from 15 to 60 wt% of a styrenic copolymer, processing oil, filler, a curative agent, and from 4 to 20 wt% of a polyolefin-polybutadiene block-copolymer, wherein the polyolefin-polybutadiene block-copolymer is a block copolymer having the general formula PO— XL— fPB; where "PO" is a polyolefin block having a weight average molecular weight within the range from 1000 to 150,000 g/mole, the "fPB" is a functionalized polar polybutadiene block having a weight average molecular weight within the range from 500 to 30,000 g/mole, and "XL" is a cross-linking moiety that covalently links the PO and fPB blocks; and wherein the maximum Energy Loss (Tangent Delta) of the immiscible polyolefin domain is a temperature within the range from -30°C to 10°C.