Substituted Diene Elastomer Tire Tread Plasticizer Migration
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Solution Overview
Problem
Rubber compositions for tires face compatibility issues with plasticizers, leading to exudation and degradation of performance qualities over time, particularly in the tread area, due to the migration of plasticizers and changes in stiffness and resistance to cracking.
Innovation Solution
Incorporating a substituted diene elastomer with units bearing an aliphatic radical as a plasticizer, grafted to the diene elastomer chain via sulfur or silicon, which reduces migration and crystallization, thereby enhancing compatibility and preventing exudation, resulting in improved endurance and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a plasticizer is added to rubber composition to improve processability and wet grip, then the glass transition temperature is shifted and processability is improved, but compatibility problems occur leading to exudation and performance degradation over time
Solution Approach 1:
The patent combines the plasticizer function with the elastomer structure by grafting plasticizing units directly onto the polybutadiene chain. This merging eliminates the separation between plasticizer and polymer, preventing exudation while maintaining plasticizing effects on Tg and processability.
Solution Approach 2:
The plasticizing units are pre-grafted onto the elastomer chain during polymerization or subsequent modification, ensuring the plasticizer is already integrated into the polymer structure before the rubber composition is formulated and processed, thereby preventing later migration and exudation.
2Temperature
If a free plasticizer is used to shift glass transition temperature, then the Tg is effectively shifted, but the plasticizer crystallizes and exudes from the tire
Solution Approach 1:
The plasticizer units are chemically bonded to the elastomer backbone, merging the plasticizing function with the polymer structure. This prevents the plasticizer from separating, crystallizing, and exuding while maintaining its ability to shift Tg.
Solution Approach 2:
The patent modifies the chemical structure of the plasticizer by grafting it onto the polymer chain, changing its physical state from free-migrating to immobilized, thereby preventing crystallization and exudation while maintaining the Tg-shifting parameter.
3Adaptability or versatility
If plasticizer migrates into adjacent mixtures of the casing, then the plasticizer distributes throughout the tire structure, but the stiffness and resistance to cracking of the casing deteriorate
Solution Approach 1:
By merging the plasticizer with the tread elastomer through grafting, the plasticizer remains localized in the tread composition where it is needed, preventing unwanted migration into casing layers and preserving their mechanical strength and cracking resistance.
Solution Approach 2:
The plasticizing effect is localized to the tread area where the grafted elastomer is present, allowing the plasticizer to perform its function in the tread without migrating to and degrading the mechanical properties of adjacent casing mixtures.
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 grafted plasticizer improves the tire's resistance to separation of plies and maintains performance qualities by reducing exudation and crystallization, enhancing the tire's endurance and maintaining its properties over time.
Implementation Method 1
shift the glass transition temperature (Tg) of an elastomer
Implementation Method 2
prevent crystallization of the plasticizer
Implementation Method 3
A-B are such that the melting point of the analogue, H-A-B, is less than 70° C. and the substituted diene elastomer comprises from 10% to 40% by weight of the said A-B radical
Data Source
AI summary
A tire comprising a rubber composition comprising a substituted diene elastomer is provided. The substituted diene elastomer comprises units bearing an A-B radical, in which:A represents an aliphatic C3-C35 radical which can be interrupted by one or more heteroatom(s), andB represents a linear, branched or cyclic C1-C6 hydrocarbon radical.A and B are such that the melting point of the analogue, H-A-B, is less than 70° C., and the substituted diene elastomer comprises from 10% to 40% by weight of the A-B radical, with respect to the total weight of the elastomer.A tread comprising such a rubber composition is also provided.A rubber composition comprising such a substituted diene elastomer and at least one of the following constituents: a second diene elastomer; a reinforcing filler and, if appropriate, a coupling agent is also provided.