Thermoplastic Elastomer Pipe Seal Compression Molding
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Solution Overview
Problem
Thermoplastic elastomers (TPEs) face challenges in forming strong joints for large diameter pipe seals due to excessive thermoplastic extrusion during thermal welding, leading to substandard seal performance and increased costs compared to thermoset rubber seals, particularly in demanding applications like sewer pipes.
Innovation Solution
A process involving extrusion of thermoplastic material into a continuous profile, followed by compression molding of the leading and trailing ends before significant cooling to form a joint, using suitable thermoplastic materials like dynamically vulcanized TPEs and TPVs, which imparts a predetermined cross-sectional profile and enhances joint strength and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thermal welding process is used to join thermoplastic elastomer ends, then the sealing application can be achieved, but excessive thermoplastic extends causing leaking and substandard seal performance
Solution Approach 1:
The invention changes the temperature parameter by performing compression molding on the extrudate while it is still hot and molten, rather than allowing it to cool first. This parameter change prevents excessive thermoplastic extension and achieves proper joint formation without the defects associated with conventional thermal welding of cooled thermoplastic elastomers.
Solution Approach 2:
The invention performs the compression molding action while the extrudate is still in a molten state, before cooling occurs. This preliminary action ensures that the material remains pliable and forms a proper joint without excessive extension, avoiding the need for subsequent correction or rework.
2Device complexity
If thermoplastic elastomers are used for large diameter pipe seals, then tooling costs can be reduced, but joint strength becomes insufficient due to material behavior during welding
Solution Approach 1:
The invention changes the temperature parameter by performing compression molding on the extrudate while it is still hot and molten, rather than allowing it to cool first. This parameter change prevents excessive thermoplastic extension and achieves proper joint formation without the defects associated with conventional thermal welding of cooled thermoplastic elastomers.
3Ease of operation
If the extrudate is allowed to cool before joining, then handling becomes easier, but the material loses plastic flow capability resulting in poor joint formation
Solution Approach 1:
The invention performs the compression molding action while the extrudate is still in a molten state, before cooling occurs. This preliminary action ensures that the material remains pliable and forms a proper joint without excessive extension, avoiding the need for subsequent correction or rework.
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 method produces annular members with superior joint strength and reduced tooling costs, enabling the use of TPEs for large diameter pipe seals with improved sealing performance and reduced energy expenditure compared to traditional vulcanization processes.
Implementation Method 1
extruding a strip of molten thermoplastic material through an extrusion die wherein the strip has a generally continuous cross-sectional profile
Implementation Method 2
the leading end and the trailing end are joined to form a joint there between by compression molding of the leading and trailing ends at a temperature sufficiently high to allow plastic flow in the area of the joint
Implementation Method 3
at a temperature sufficiently high to allow plastic flow in the area of the joint
Data Source
AI summary
Process for forming an annular member by extruding a thermoplastic profiled strip at an elevated temperature. Prior to cooling the strip, the still-molten ends undergo in-line compression molding to form an annular member having a joint section. The cross-section of the annular member is continuous in the joint section and the remainder of the body. Preferably, the extrudate may contain a thermoplastic elastomer, more preferably a thermoplastic vulcanizate formed by a dynamic vulcanization process. During the extrusion and compression molding processes, the extrudate may be supported on a rotatable turntable, or alternately on a rotatable molding cylinder.