Butyl Rubber Composition for Tire Curing Bladder Durability
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Solution Overview
Problem
Conventional tire curing bladders made from butyl rubber or EPDM/IIR blends have limited De Mattia flex fatigue and heat aging resistance, leading to a short lifespan in tire manufacturing.
Innovation Solution
A rubber composition comprising 20-50 phr of a copolymer of ethylene and α-olefins with a specific Mooney viscosity, combined with 50-80 phr of butyl-type rubber and a resin-based curative system using phenol formaldehyde resin as the curing agent, along with a halogen donor and metal oxide activator package, enhancing flex fatigue and heat aging resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional butyl rubber or EPDM/IIR blends are used for tire curing bladders, then the bladder can be manufactured with standard materials, but the De Mattia flex fatigue and heat aging resistance is limited, leading to short lifespan
Solution Approach 1:
The patent uses a composite rubber composition combining butyl rubber (IIR) with EPDM copolymer in a specific ratio (30-70 phr EPDM, 70-30 phr butyl rubber). This composite formulation synergistically improves both flex fatigue resistance and heat aging resistance while maintaining processability, resolving the contradiction between using standard materials and achieving extended lifespan.
Solution Approach 2:
The patent specifies precise parameter ranges for the rubber composition including Mooney viscosity (20-60 at 100°C), EPDM content (30-70 phr), and curative ratios. By optimizing these parameters, the composition achieves superior durability and heat aging resistance, transforming the lifespan limitation into a solved problem.
2Reliability
If high amounts of EPDM with high ENB content are used to improve flex fatigue resistance, then the bladder shows better durability, but the composition becomes difficult to process and cure
Solution Approach 1:
The patent limits ENB content to 1-6 wt% of copolymer (A) and controls Mooney viscosity to 20-60 at 100°C. This parameter optimization ensures sufficient unsaturation for curing while maintaining processability and avoiding the difficulties associated with high ENB content, thus resolving the contradiction between durability and ease of manufacture.
Solution Approach 2:
The patent introduces a specific curative system (triazole-based curing agents like 2,4,6-tris(dimethylaminosulfonylethyl)resorcinol) that targets the specific unsaturation level of the rubber composition. This localized curing approach ensures effective crosslinking without requiring excessive ENB content, maintaining both processability and durability.
3Ease of manufacture
If the Mooney viscosity of the copolymer is reduced to improve processability, then the rubber is easier to manufacture, but the flex fatigue resistance and heat aging resistance decrease
Solution Approach 1:
The patent establishes an optimal Mooney viscosity range of 20-60 at 100°C, balancing processability with performance. Within this range, the rubber remains sufficiently viscous to maintain molecular structure integrity for fatigue resistance, while being processable for manufacturing, thus resolving the contradiction between ease of manufacture and reliability.
Solution Approach 2:
The composite of butyl rubber and EPDM in specific ratios provides a synergistic effect where the butyl rubber base maintains good processability even when EPDM viscosity is optimized for durability. This composite approach allows achieving both ease of manufacture and high reliability 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 composition exhibits improved tensile strength retention after aging and extended flex fatigue life, outperforming traditional formulations in terms of durability and performance.
Implementation Method 1
a resin-based curative, containing a phenol formaldehyde resin cross-linker as the only curing agent
Implementation Method 2
an activator package comprising of metal oxide and a halogen donor where a halogenated component (B) or halogenated cross-linker as part of component (C) is not already present
Data Source
AI summary
A rubber composition containing based upon parts by weight per 100 parts by weight rubber (phr): (A) 20 - 50 phr of a copolymer of ethylene, at least one C3 to C23 α-olefin and a least one polyene monomer, whereby the copolymer unit derived from the polyene is 1 to 5 wt.%, by weight of the copolymer (A) and has a Mooney viscosity ML (1+4) at 100 °C from 51 or greater, in particular from 55 to 90 at 100 °C, (B) 50 - 80 phr of butyl-type rubber and (C) a resin-based curative, containing a phenol formaldehyde resin cross-linker as only curing agent and an activator package comprising of metal oxide and a halogen donor where a halogenated component (B) or halogenated cross-linker as part of component (C) not already present.