Polyketone-UHMWPE Seal Compound for Weld Line Strength
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Solution Overview
Problem
Aliphatic polyketones, despite their excellent mechanical and tribological properties, face challenges in injection molding due to poor weld line strength, making them unsuitable for rotationally symmetrical seals like rod and piston seals, which require high extrusion resistance and tribological performance comparable to PTFE-based materials.
Innovation Solution
A polyketone compound comprising 85.0 to 99.5 wt % aliphatic polyketone and 0.5 to 15.0 wt % ultra-high molecular weight polyethylene, which improves weld line strength and maintains tribological properties, allowing for cost-effective injection molding of seals with enhanced extrusion resistance and frictional performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PTFE is added to polyketone to improve tribological properties, then friction and wear resistance improve, but weld line strength deteriorates
Solution Approach 1:
The patent changes the chemical composition parameter by replacing PTFE with ultra-high molecular weight polyethylene (UHMWPE). This substitution maintains the tribological benefits while eliminating the weld line strength problem, as UHMWPE does not exhibit the same detrimental effects on weld line formation as PTFE does in polyketone compounds.
Solution Approach 2:
The patent creates a composite material system consisting of polyketone blended with ultra-high molecular weight polyethylene. This composite achieves the desired tribological performance through the polyethylene component while the polyketone matrix provides the necessary mechanical properties and weld line strength, resolving the contradiction between friction resistance and weldability.
2Productivity
If polyketone is used for injection molding, then manufacturing efficiency improves, but weld line strength deteriorates
Solution Approach 1:
The patent modifies the material composition parameter by incorporating ultra-high molecular weight polyethylene into the polyketone compound. This change enables the material to be processed by injection molding while preventing weld line failure, as the polyethylene component improves the overall processability and weld line formation without sacrificing the inherent injection molding efficiency of polyketone.
3Force
If PTFE-modified polyketone is used for seals, then extrusion resistance improves, but weld line strength deteriorates
Solution Approach 1:
The patent changes the compositional parameter by substituting PTFE with ultra-high molecular weight polyethylene in the seal material. This substitution maintains the extrusion resistance required for seal applications while eliminating the weld line strength deterioration, allowing seals to be successfully manufactured by injection molding with proper weld line formation.
Solution Approach 2:
The patent develops a composite seal material combining polyketone with ultra-high molecular weight polyethylene. The polyketone phase provides the necessary extrusion resistance and mechanical strength for seal applications, while the polyethylene phase ensures good weld line strength and processability, resolving the contradiction between extrusion performance and weldability.
Data Source
AI summary
An aliphatic polyketone compound including 85.0 to 99.5 wt % aliphatic polyketone and 0.5 to 15.0 wt % ultra-high molecular weight polyethylene. An aliphatic polyketone compound described where the ultra-high molecular weight polyethylene is 2.0 to 8.0 wt %. An aliphatic polyketone compound where the ultra-high molecular weight polyethylene has a molecular weight greater than 1.0 million g/mol.