Pneumatic Tire Innerliner Segmentation for Adhesion and Air Retention
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Solution Overview
Problem
Pneumatic tires with innerliners containing thermoplastic elastomers like styrene-isobutylene-styrene block copolymer experience poor vulcanized adhesion to other rubber compounds, leading to peeling and cracking, especially at the joint portions during tire operation.
Innovation Solution
A pneumatic tire design featuring a carcass with a third layer continuously provided from the bead apex tip to the tire-axially outermost end of the breaker, a second layer containing butyl-based and isoprene-based rubbers, and a first layer with thermoplastic elastomer and butyl-based rubber, ensuring improved adhesion and resistance to cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermoplastic elastomer such as styrene-isobutylene-styrene block copolymer is used in the innerliner to improve air retention, then air retention is improved, but vulcanized adhesion to other rubber compounds deteriorates, causing peeling at interfaces
Solution Approach 1:
The innerliner is divided into multiple layers: a first innerliner layer containing thermoplastic elastomer for air retention, and a second innerliner layer containing butyl-based rubber with good adhesion properties. This segmentation allows each layer to perform its specialized function without compromising the other.
Solution Approach 2:
The invention uses a composite structure combining thermoplastic elastomer (for low air permeability) with butyl-based rubber (for good vulcanized adhesion). The composite material approach leverages the complementary strengths of both materials to achieve both excellent air retention and adhesion simultaneously.
2Reliability
If thermoplastic elastomer is used in the innerliner to reduce air permeability, then air retention is improved, but the first layer becomes prone to cracking under stress concentration during running
Solution Approach 1:
The innerliner is segmented into multiple layers with different material properties. The first layer (thermoplastic elastomer) provides air retention, while the second layer (butyl-based rubber) provides crack resistance and flexibility, absorbing stress concentrations that would otherwise propagate through the thermoplastic layer.
Solution Approach 2:
The second innerliner layer acts as a cushioning layer that absorbs and distributes stress concentrations before they can reach the first layer. This beforehand cushioning prevents crack initiation and propagation in the thermoplastic elastomer layer during tire operation.
3Strength
If butyl tape is attached to joint portions to improve adhesion, then adhesion at joint portions is improved, but peeling may still occur in portions other than joint portions
Solution Approach 1:
Instead of locally reinforcing only the joint portions, the invention segments the innerliner into functional layers that provide continuous reinforcement throughout the entire tire structure. The second innerliner layer extends continuously to provide uniform adhesion and stress distribution across all areas, not just at joints.
Data Source
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AI summary
Provided is a pneumatic tire which is excellent in air retention and adhesion at the interface between first and second layers, particularly in the joint portion, and which is resistant to cracking in the first layer. Included is a pneumatic tire including: a carcass; a third layer adjacent to the carcass on its tire-radially inner side; a second layer adjacent to the third layer on its tire-radially inner side; and a first layer adjacent to the second layer on its tire-radially inner side, the third layer being continuously provided along the carcass at least from a bead apex tip portion to a portion below a tire-axially outermost end of a breaker, the first layer including a first layer rubber composition containing a thermoplastic elastomer and a butyl-based rubber, the second layer including a second layer rubber composition containing a butyl-based rubber and an isoprene-based rubber, the third layer including a third layer rubber composition containing an isoprene-based rubber.