Cross-linked Thermoplastic Polyurea via Diisocyanate Injection Molding
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Solution Overview
Problem
Thermoplastic polyurethanes exhibit poor performance characteristics in abrasion, tensile strength, and compression set compared to thermoset polyurethanes, and current methods for producing thermoset polyurethanes are costly and inefficient due to the need for casting processes.
Innovation Solution
A cross-linked thermoplastic polyurea is created by combining a thermoplastic urethane base material with a monomeric di-isocyanate and a diamine, or hydroquinone, and then processed using injection molding techniques, which includes heating the mixture to 250° F to 550° F and curing at 150° F to 250° F for 2 to 36 hours.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thermoplastic polyurethanes are used to enable injection molding and extrusion, then ease of manufacture and productivity are improved, but abrasion resistance, tensile strength, and compression set performance deteriorate
Solution Approach 1:
The patent changes the molecular structure parameters of thermoplastic polyurethane by introducing cross-linking through diisocyanate and diamine/polyol components. This creates a network structure that improves mechanical properties (tensile strength, abrasion resistance, compression set) while maintaining thermoplastic processability through controlled cross-linking density and reversible bond formation.
Solution Approach 2:
The patent creates a composite material system combining thermoplastic polyurethane base resin with cross-linking agents (diisocyanate and diamine/polyol). The resulting material exhibits properties of both thermoplastic processability and thermoset mechanical performance, effectively merging advantages of both material classes.
2Strength
If thermoset polyurethanes are used to improve abrasion resistance, tensile strength, and compression set, then strength and durability are improved, but ease of manufacture and productivity deteriorate due to casting process requirements
Solution Approach 1:
The patent inverts the conventional approach by making thermoplastic polyurethane cross-linkable rather than making thermoset polyurethane processable by injection molding. The cross-linking occurs after injection molding during a post-curing step, allowing the material to be processed as a thermoplastic and then converted to a thermoset network structure, thereby achieving thermoset performance through thermoplastic processing.
3Reliability
If thermoset polyurethanes are used to achieve good compression set characteristics, then reliability is improved, but device complexity and manufacturing cost increase due to casting processes
Solution Approach 1:
The patent merges the injection molding process with subsequent cross-linking curing in a single manufacturing workflow. The material is injected in thermoplastic form and then cured in-situ or in a separate but integrated step, combining the advantages of injection molding (simplified equipment, higher productivity) with thermoset cross-linking (improved compression set, tensile strength, and abrasion resistance).
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 resulting cross-linked thermoplastic polyurea achieves performance characteristics similar to thermoset polyurethanes, such as improved abrasion, tensile strength, and compression set, while being produced more efficiently and cost-effectively using conventional injection molding techniques.
Implementation Method 1
a monomeric di-isocyanate comprising between 1 to 10% of the mixture on a total weight basis, and a diamine comprising between 1 to 10% of the mixture on a total weight basis
Implementation Method 2
The mixture is then heated to a temperature within the range of 250° F. to 550° F
Implementation Method 3
Post-injection, the material is cured at a temperature between 150° F. to 250° F. for a period of time between 2 and 36 hours
Data Source
AI summary
A cross-linked thermoplastic polyurea is formed by heating a mixture containing a thermoplastic urethane base material, a monomeric and/or polymeric di-isocyanate comprising between 1 to 10% of the total weight of the mixture, and a diamine comprising between 1 to 10% of the total weight of the mixture. A thermoplastic polyurethane may be formed by substituting hydroquinone for the diamine. The mixture is heated to a temperature within the range of 250° F. to 550° F. The heated mixture, which is flowable, is then injected into at least one injection molding device. The mixture is then cured at a temperature between 150° F. to 250° F. for a period of time between 2 and 36 hours. The cross-linked thermoplastic polyurethane/polyurea retains the excellent flowability characteristics of a thermoplastic urethane while the same time exhibits good abrasion, tensile strength, rebound, and compression set characteristics which are similar to those found in thermoset urethanes.