TPU Coated Pipe Liner Resists Steam Curing Blow Through
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Solution Overview
Problem
Existing thermoplastic polyurethane (TPU) materials used in cured-in-place pipe liners are not suitable for use with epoxy resin and steam curing, as they can blow through due to the exothermic reaction and high temperatures, leading to holes in the liner, and lack compatibility with other curing methods like hot water.
Innovation Solution
Development of a new TPU polymer made from a hydroxyl terminated polyester intermediate, glycol chain extender, and diisocyanate, with specific molecular weight and acid number characteristics, that can withstand the heat and steam used in epoxy resin curing, and also be compatible with hot water, preventing 'blow through' and ensuring liner integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermoplastic polyurethane (TPU) is used to coat the fabric in cured in place liners, then the liner has good abrasion resistance, tear resistance and elastic properties, but the TPU blows through the fabric during epoxy resin/amine curative exothermic reaction and steam curing, forming holes in the liner
Solution Approach 1:
The patent changes the chemical composition parameters of the TPU polymer by specifying particular molecular weight ranges (5,000-500,000), acid number ranges (1-20), and formulation ratios of polyol to diisocyanate (10:1 to 1:10). These parameter adjustments modify the TPU's thermal stability and chemical resistance, enabling it to withstand the exothermic reaction temperatures and steam curing conditions without degrading or blowing through the fabric substrate.
Solution Approach 2:
The patent creates a composite material system consisting of TPU-coated fabric saturated with epoxy resin/amine curative. The TPU coating forms a protective composite layer that combines the mechanical properties of polyurethane with the thermal and chemical stability required for high-temperature curing processes. This composite structure prevents the fabric from degrading during the exothermic reaction and steam curing while maintaining the liner's mechanical integrity.
2Productivity
If steam is used to cure the epoxy resin and press the liner against the inside of the pipe, then the curing process is faster and steam is faster to evacuate than hot water, but the heat from the exothermic reaction and steam causes prior art TPU to blow through the fabric
Solution Approach 1:
The patent modifies the TPU's thermal parameters through controlled synthesis, achieving a material that can withstand the high temperatures of steam curing (typically 100°C or higher) and the exothermic reaction (which can reach 150-200°C). The specific molecular weight and acid number ranges specified ensure the TPU maintains its structural integrity at these elevated temperatures, preventing blow-through while allowing the rapid steam curing process to proceed.
3Quantity of substance
If the TPU coating is made thinner to allow better resin saturation of the fabric, then the resin can penetrate the fabric more effectively, but the TPU becomes more susceptible to blowing through during high temperature curing
Solution Approach 1:
The patent changes the TPU's molecular parameters (molecular weight 5,000-500,000, acid number 1-20) to achieve optimal balance between coating thickness and thermal resistance. These parameter adjustments allow the TPU to maintain sufficient thickness for protection while enabling adequate resin penetration, as the modified TPU structure provides both permeability to the resin and resistance to thermal degradation.
Solution Approach 2:
The patent creates a optimized composite structure where the TPU coating, fabric substrate, and epoxy resin work together as an integrated system. The TPU coating provides a controlled barrier that allows resin saturation while preventing blow-through during curing. The composite material properties emerge from the interaction between the modified TPU and the fabric-resin system, achieving both resin penetration and thermal protection.
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 new TPU polymer maintains structural integrity during curing with steam or hot water, allowing for efficient and reliable installation of epoxy-based cured-in-place liners without forming holes, and is compatible with various thermoset resins, enhancing the durability and longevity of the liners.
Implementation Method 1
The epoxy/ amine reaction is exothermic and the heat from this reaction and the steam will cause prior art TPU to blow through the fabric containing the epoxy resin and form holes in the liner
Implementation Method 2
The TPU used in this invention has sufficient heat resistance to be able to withstand the epoxy resin/amine curative exotherm as well as the steam temperature used in installation of the liner
Data Source
AI summary
A liner for repairing damaged pipes, such as underground sewer or gas pipes is disclosed. The liner comprises a TPU coating on a fibrous mat of non-woven fabric. The TPU coating is a high heat resistance polyester TPU which allows an epoxy resin/amine to be saturated in the non-woven fabric and the cure initiated by the use of steam or hot water. The cured epoxy resin coverts the liner from a flexible state to a rigid state as the liner is cured in place inside the liner. The TPU containing liner may also be used with thermoset resins other than epoxy resins, such as polyester resins and vinyl ester resins.