Heat-Treated Polyurethane Buffer Ring for High Temperature Sealing
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Solution Overview
Problem
The existing rod sealing systems fail to maintain sealability and durability at higher service temperatures (up to 120°C) due to loss of resilience and mechanical strength, particularly in the buffer ring, which is critical for pressure load-buffering and preventing oil leakage.
Innovation Solution
A thermoplastic polyurethane molding product is developed by reacting high molecular weight polycarbonate diol, aromatic diisocyanate, and low molecular weight diol, followed by heat treatment to achieve a glass transition point of ≥ 170°C and an endothermic peak area of ≥ 5 J/g, enhancing heat resistance and compression set characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional thermoplastic polyurethane materials are used in the buffer ring, then the rod sealing system can operate at normal temperatures, but the sealability and durability deteriorate significantly at service temperatures up to 120°C due to loss of resilience
Solution Approach 1:
The patent applies parameter changes by modifying the glass transition point (Tg) of the thermoplastic polyurethane material through controlled heat treatment. By adjusting the heat treatment temperature and duration, the Tg is elevated to a specific range (80°C to 120°C), which fundamentally changes the material's thermal response characteristics. This parameter modification enables the buffer ring to maintain its elastic recovery properties and sealability at service temperatures up to 120°C, resolving the contradiction between operating temperature and sealability.
Solution Approach 2:
The patent employs composite material strategy by creating a thermoplastic polyurethane with a specific molecular structure comprising hard segments and soft segments in controlled ratios. The material is formulated as a composite of polyol components (including polycarbonate diol and polyester diol) and diisocyanate, processed through heat treatment to achieve a composite microstructure with enhanced thermal stability. This composite material approach allows the buffer ring to withstand high temperatures while maintaining the resilience necessary for effective sealing.
2Temperature
If heat-resistant materials are selected for the buffer ring to withstand high temperatures, then temperature resistance improves, but the material's abrasion resistance and follow-up to eccentricity may deteriorate
Solution Approach 1:
The patent applies local quality by creating distinct regions within the thermoplastic polyurethane material with different properties. The heat treatment process creates a differentiated microstructure where the hard segments form rigid, heat-resistant domains while the soft segments maintain flexibility and abrasion resistance. This local differentiation of material properties within the same component allows the buffer ring to simultaneously achieve heat resistance and abrasion resistance, resolving the contradiction between these two requirements.
Solution Approach 2:
The patent resolves the contradiction between heat resistance and abrasion resistance through composite material design. The thermoplastic polyurethane is formulated as a composite of hard segments (providing heat resistance and structural integrity) and soft segments (providing abrasion resistance and elasticity). The controlled heat treatment process optimizes the phase separation and distribution of these segments, creating a composite microstructure where each phase contributes its advantageous properties, enabling the material to withstand both thermal and mechanical wear conditions.
3Reliability
If the buffer ring is designed to provide pressure load-buffering, then the service life of the rod seal is extended, but the buffer ring itself is exposed to high-pressure, high-temperature conditions that accelerate material degradation
Solution Approach 1:
The patent applies preliminary action by subjecting the thermoplastic polyurethane material to controlled heat treatment before the buffer ring is installed and begins service. This pre-conditioning process elevates the glass transition point and stabilizes the material's molecular structure in advance, preparing it to withstand the high-pressure, high-temperature conditions it will encounter during operation. By performing this hardening action beforehand, the buffer ring is pre-equipped with enhanced thermal stability, allowing it to maintain pressure load-buffering effectiveness throughout its service life without premature degradation.
Solution Approach 2:
The patent applies beforehand cushioning by using the heat treatment process to pre-absorb and stabilize the material against future thermal stress. The controlled heat exposure during manufacturing acts as a preliminary cushioning measure, allowing the material to undergo controlled structural changes that prevent more severe degradation during actual service. This pre-cushioning approach ensures the buffer ring can withstand the harsh operating conditions while maintaining its load-buffering function, thereby extending the service life of both the buffer ring and the rod seal it protects.
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 heat-treated thermoplastic polyurethane buffer ring maintains pressure load-buffering effectiveness and reduces resilience loss, improving durability and sealability, even at elevated temperatures, thereby extending the service life of the rod sealing system.
Implementation Method 1
subjecting it to heat treatment at a temperature in the range of 135-170°C for 10-100 hours, such that the glass transition point (Tg) of hard phases becomes ≥ 170°C
Implementation Method 2
subjecting it to heat treatment at a temperature in the range of 135-170°C for 10-100 hours
Implementation Method 3
the endothermic peak area (ΔH) at Tg, measured by DSC, becomes ≥ 5 J/g
Data Source
Figure 1~2
AI summary
In a rod sealing system, which comprises a buffer ring, a rod seal, and a dust seal, provided successively in this order from a fluid hydraulic side toward the outside in an annular clearance between two members in reciprocating motion, the buffer ring is made up of a thermoplastic polyurethane molding product obtained by subjecting a thermoplastic polyurethane molding product prepared by reaction of (A) a high molecular weight polycarbonatediol having a number average molecular weight Mn of 500-6,000, (B) an aromatic diisocyanate, and (C) a low molecular weight diol as a chain elongation agent in an NCO/OH ratio of 0.95-1.20,to heat treatment under conditions that a glass transition point (Tg) of hard phases becomes 170 °C or higher, preferably 170- 230 °C , and an endothermic peak area (ΔH) at Tg becomes 5J/g or more, by differential scanning calorimetry. The buffer ring made up of the thermoplastic polyurethane molding product has a distinguished heat resistance capable of withstanding the service environmental temperature, particularly maximum 120°C, compression set characteristics, follow-up to eccentricity, etc.