Multilayer Tire Inner Liner Resolving Gas Barrier and Crack Resistance Trade-off
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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 thinness, with ethylene-vinyl alcohol copolymer (EVOH) liners offering improved internal pressure retention but prone to cracking under deformation due to high elastic modulus.
Innovation Solution
A multilayer structure comprising a barrier layer with 50% or less elongation at break and an elastomer layer with 100% or more elongation at break, alternately laminated to disperse stress and enhance flexibility, using polymers like ethylene-vinyl alcohol copolymer and polyurethane-based thermoplastic elastomers, with each layer thickness optimized to improve 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 crack resistance deteriorates due to high elastic modulus
Solution Approach 1:
The invention uses a composite material structure consisting of an EVOH layer (providing gas barrier property) and a rubber layer (providing crack resistance). The EVOH content is controlled at 20-80 mass% to balance gas barrier performance and flexibility. This composite approach allows the inner liner to maintain high internal pressure retention while resisting cracks during tire deformation.
Solution Approach 2:
The invention changes the compositional parameters of the inner liner by controlling the EVOH content within 20-80 mass% and adjusting the molecular weight, gel fraction, and vinyl alcohol content of EVOH. These parameter adjustments optimize both the gas barrier property and the crack resistance, 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 gas barrier property deteriorates requiring increased thickness
Solution Approach 1:
The invention creates a composite inner liner where EVOH (20-80 mass%) provides superior gas barrier properties compared to conventional butyl rubber, while the rubber component maintains crack resistance. This composite structure achieves both high gas barrier property and flexibility without requiring increased thickness.
Solution Approach 2:
The invention applies different materials with different properties in specific proportions within the same inner liner structure. The EVOH phase provides localized gas barrier function while the rubber phase provides localized flexibility and crack resistance, achieving overall optimization of both properties.
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 multilayer structure achieves high gas barrier properties and excellent fatigue resistance, allowing for reduced thickness and improved durability of the inner liner, maintaining internal pressure retention and flexibility during tire deformation.
Implementation Method 1
polymer material having 50 % or less elongation at break... ensuring high gas barrier property
Implementation Method 2
elastomer layer with 100 % or more elongation at break... stress applied to the multilayer structure may be efficiently dispersed
Implementation Method 3
plastic deformation amount of the multilayer structure at the time of 100 % strain input is greater than a deformation amount at a pseudo tolerance point... achieving excellent fatigue resistance
Data Source
Figure 1
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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 the multilayer structure, and a pneumatic tire comprising the inner liner. According to the present invention, the multilayer structure includes a barrier layer 2 made of polymer material with 50% or less elongation at break conforming to JIS K 7113 at 20 °C and 65 %RH and an elastomer layer 3 made of polymer material with 100% or more elongation at break conforming to JIS K 7113 at 20 °C and 65 %RH, wherein a plastic deformation amount at the time of 100% strain input is larger than a deformation amount at a tolerance point.