Thermoplastic Elastomer Block Copolymer Inner Liner for Tire Gastightness
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Solution Overview
Problem
Conventional pneumatic tires with butyl rubber inner layers face issues with hysteresis losses, adhesion problems, and limited heat resistance, leading to increased rolling resistance and fuel consumption, as well as material creep and tearing during high-speed tests.
Innovation Solution
A thermoplastic elastomer block copolymer is used as a gastight inner layer, comprising an elastomeric block with a glass transition temperature of less than -20°C and thermoplastic blocks derived from polymerizable monomers and random copolymers of α-methylstyrene and β-pinene, enhancing adhesion and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If butyl rubber is used as the gastight inner layer, then gastightness is improved, but hysteresis losses increase leading to higher rolling resistance
Solution Approach 1:
The patent changes the chemical composition parameters of the elastomer layer by using a specific block copolymer structure with controlled ratios of butadiene (40-70 wt%), styrene (15-30 wt%), and polyisobutylene (10-30 wt%). This parameter optimization maintains gastightness while reducing hysteresis losses compared to conventional butyl rubber
Solution Approach 2:
The invention creates a composite elastomeric system by combining multiple polymer components (polybutadiene, polystyrene, and polyisobutylene) into a block copolymer structure. This composite approach leverages the low hysteresis of polybutadiene while incorporating polyisobutylene to maintain gastightness properties
2Loss of energy
If thermoplastic elastomers are used to reduce hysteresis, then rolling resistance improves, but adhesion to carcass ply deteriorates
Solution Approach 1:
The patent applies local quality by creating distinct blocks within the copolymer structure: polybutadiene blocks provide low hysteresis for reduced rolling resistance, while polystyrene blocks provide adhesion to the carcass ply. Each block performs its specific function locally within the overall elastomer structure
Solution Approach 2:
The elastomer is segmented into distinct functional blocks: polybutadiene segments for low rolling resistance, polystyrene segments for adhesion, and polyisobutylene segments for gastightness. This segmentation allows each component to optimize its specific function without compromising others
3Strength
If conventional elastomers are used, then adhesion is maintained, but heat resistance is limited causing material creep at high temperatures
Solution Approach 1:
The patent changes the thermal parameters of the elastomer by incorporating high glass transition temperature polystyrene blocks (Tg ≈ 100°C) and controlling the molecular weight and crosslinking density. This enables the material to maintain adhesion while resisting heat-induced creep at temperatures up to 80-100°C
4Ease of manufacture
If thermoplastic elastomers are used, then processing ease improves, but material integrity deteriorates during hot curing due to tearing
Solution Approach 1:
The patent applies local quality by concentrating thermoplastic characteristics in specific polyisobutylene blocks that facilitate processing, while maintaining crosslinkable polybutadiene and polystyrene blocks that provide structural integrity during hot curing. This localized functional distribution resolves the contradiction between ease of manufacture and material strength
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 block copolymer layer provides improved gastightness, adhesion, and heat resistance, reducing hysteresis losses and material creep, while allowing for safe demolding and maintaining tire integrity under hot conditions.
Implementation Method 1
an elastomeric block comprising at least units derived from isobutylene, and having a glass transition temperature of less than or equal to −20° C.
Implementation Method 2
the absence of double bonds in the thermoplastic elastomer makes it relatively insensitive to co-vulcanization with the carcass ply during curing
Data Source
AI summary
A pneumatic object is provided with an elastomer layer which is gastight to inflation gases, said elastomer layer comprising, as predominant elastomer, a thermoplastic elastomer in the form of a block copolymer which comprises: (a) an elastomeric block comprising at least units derived from isobutylene, and having a glass transition temperature of less than or equal to −20° C., and (b) one or more thermoplastic blocks, the thermoplastic block(s) each comprising at least one first block consisting of units derived from at least one polymerizable monomer and at least one second block, said second block(s) being a random copolymer consisting of units derived from α-methylstyrene and of units derived from β-pinene. A process for rendering a pneumatic object gastight to inflation gases is also disclosed.