Pneumatic Tire Inner Liner Multilayer Structure
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Solution Overview
Problem
Conventional inner liners for pneumatic tires face challenges in achieving high gas barrier properties and crack resistance while maintaining a reduced thickness, with ethylene-vinyl alcohol copolymer-based liners experiencing deformation and cracking under bending stress due to their high elastic modulus.
Innovation Solution
A multilayer structure comprising a barrier layer and an elastomer layer, where the elastomer layer accounts for 60% or more of the thickness, with seven or more layers laminated, providing high flexibility and reducing fatigue, and using specific resins and thermoplastic elastomers for enhanced gas barrier and crack resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EVOH is used for the inner liner to improve gas barrier property, then internal pressure retention is improved, but the inner liner breaks or causes cracks due to high elastic modulus
Solution Approach 1:
The invention uses a composite structure consisting of an EVOH layer for gas barrier property and a rubber layer for flexibility and crack resistance. This composite material approach allows the inner liner to simultaneously achieve high gas barrier performance and resistance to cracking under bending deformation, resolving the contradiction between these two properties.
2Strength
If butyl rubber is used for the inner liner to improve crack resistance, then flexibility is maintained, but air barrier property is low requiring increased thickness
Solution Approach 1:
The invention combines butyl rubber or halogenated butyl rubber with EVOH in a laminated structure. The rubber layer provides flexibility and crack resistance while the EVOH layer provides superior gas barrier properties, allowing the inner liner to achieve both properties without requiring increased thickness.
Solution Approach 2:
The inner liner is segmented into multiple functional layers: a rubber layer for mechanical properties and an EVOH layer for gas barrier properties. This segmentation allows each layer to specialize in its function, with the rubber layer handling deformation and the EVOH layer handling gas permeation, achieving both goals simultaneously.
3Strength
If inner liner thickness is reduced to improve flexibility, then fatigue resistance improves, but gas barrier property deteriorates
Solution Approach 1:
The invention uses a composite of thin EVOH layer and rubber layer where the EVOH provides exceptional gas barrier properties even at reduced thickness, while the rubber layer provides flexibility and fatigue resistance. This composite structure maintains gas barrier performance while improving flexibility compared to conventional thick rubber liners.
Data Source
Figure 1
Figure 2
Figure 3(a)~3(d)
AI summary
To provide a multilayer structure having high gas barrier property and crack resistance as well as excellent fatigue resistance, an inner liner for a pneumatic tire using such a multilayer structure, and a pneumatic tire comprising the inner liner. According to the present invention, in a multilayer structure 1 including a barrier layer 2 and an elastomer layer 3, a proportion of a thickness of the elastomer layer 3 in the multilayer structure ((U1+U2+...+Un)/T) is 60% or more.