Thermoplastic Elastomer Underlayer for Retreadable Radial Tires
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Solution Overview
Problem
The existing materials used in tire treads make the detreading and retreading process complex and expensive, leading to the rarity of retreaded passenger vehicle tires, as the stripping operation is inefficient.
Innovation Solution
A radial tire with a thermoplastic elastomer underlayer, comprising a block copolymer with a specific composition and molecular structure, facilitates easy separation of the worn tread from the tire structure by heating, allowing for efficient detreading and retreading by fusion with a new tread layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional materials are used in the tread layer, then the tire structure maintains good adhesion and strength, but the detreading operation becomes complex and expensive
Solution Approach 1:
The tread assembly is segmented into two distinct layers: a traditional elastomeric tread layer for road contact and a thermoplastic underlayer for bonding to the carcass. This segmentation allows the tread to be separated during detreading while the underlayer remains on the carcass, simplifying the detreading process without compromising the bond strength during normal use.
Solution Approach 2:
The underlayer uses thermoplastic materials whose physical properties change with temperature. At processing temperatures, the thermoplastic becomes soft and adhesive, creating strong bonding between the tread and carcass. During detreading, heating the thermoplastic causes it to soften and release the tread, enabling easy separation without damaging the carcass.
2Duration of action of moving object
If the entire tire is replaced instead of retreading, then tire life is extended, but material waste increases and environmental impact worsens
Solution Approach 1:
The invention enables recovery and reuse of the tire carcass by facilitating efficient detreading. The thermoplastic underlayer acts as a reusable bonding agent that can be heated to release the worn tread and then reactivated to bond a new tread, allowing the valuable carcass structure to be recovered and reused multiple times rather than discarded with the worn tread.
Solution Approach 2:
The thermoplastic underlayer undergoes phase transitions between solid and molten states through temperature control. During retreading, the thermoplastic is heated to its melting point to release the old tread and then cooled to bond the new tread, enabling repeated cycles of tread replacement while preserving the carcass and reducing material waste.
3Ease of operation
If a thermoplastic underlayer is introduced to facilitate detreading, then the stripping operation is simplified, but the device complexity increases due to multi-layer construction
Solution Approach 1:
The thermoplastic underlayer merges multiple functions into a single component: it provides bonding between the tread and carcass during normal use, acts as a release layer during detreading when heated, and serves as a primer for the new tread application. This consolidation simplifies the overall retreading process despite the additional layer.
Solution Approach 2:
The thermoplastic underlayer performs multiple functions throughout the tire lifecycle: initial bonding during manufacturing, heat-responsive release during detreading, and adhesion promotion during retreading. This multi-functionality justifies the additional layer by eliminating the need for separate bonding agents and simplifying the detreading operation.
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
This solution simplifies the detreading process, extends tire life, reduces material waste, and enables cost-effective and environmentally friendly retreading, as the tire carcass can be reused indefinitely.
Implementation Method 1
heating the separation of the worn tread from the rest of the structure of the tire
Implementation Method 2
apply a sufficient temperature and pressure to the interface to achieve the fusion of the two thermoplastic layers
Data Source
Figure 1
Figure 2
AI summary
The present invention concerns a radial tyre (1) for a motor vehicle, comprising a crown (2) comprising a tread (3) provided with at least one radially external portion (3a) intended to enter into contact with the road; two inextensible beads (4), two sidewalls (5) linking the beads (4) to the tread (3), a carcass reinforcement (6) passing into the two sidewalls (5) and anchored in the beads (4); a crown reinforcement or belt (7) disposed circumferentially between the radially external portion (3a) of the tread (3) and the carcass reinforcement (6); a radially internal elastomer layer (8), called "sub-layer", different in composition to the composition of the radially external portion (3a) of the tread, said sub-layer itself being disposed circumferentially between the radially external portion (3a) of the tread (3) and the carcass reinforcement (6); characterised in that said sub-layer comprises at least one thermoplastic elastomer, said thermoplastic elastomer being a block copolymer comprising at least one elastomer block and at least one thermoplastic block, the total amount of thermoplastic elastomer being comprised in a range varying from 65 to 100 pce (parts by weight per hundred parts of elastomer) and characterised in that said sub-layer has a ratio of elastic modulus at 200°C and at 60°C different to that of the adjacent layers, such that the following equation is satisfied with each of the adjacent layers: