Thermoplastic Polyurethane Blooming Reduction via Molecular Weight Control
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Solution Overview
Problem
Thermoplastic polyurethanes (TPUs) often exhibit blooming, which leads to undesirable surface haze or fogging, affecting the aesthetic appearance and adhesive bonding of articles, particularly in applications requiring clarity.
Innovation Solution
A thermoplastic polyurethane composition comprising a hydroxyl terminated polyester intermediate synthesized from 1,3-propylene glycol and adipic acid, reacted with a polyisocyanate and 1,4-butane diol, eliminating the need for monofunctional compounds to control blooming, and processed into molded or extruded articles with reduced blooming tendencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional TPU polymers are used, then excellent elastic properties are achieved, but blooming occurs causing surface haze and reduced adhesive bonding
Solution Approach 1:
The patent changes the chemical composition parameters of the TPU by specifying precise molecular weight ranges for the polyol component (500-5000 Daltons) and controlling the soft segment to hard segment ratio (95:5 to 50:50). These parameter changes result in a polymer structure that significantly reduces blooming while maintaining elastic properties and improving adhesive bonding capability.
2Object-generated harmful factors
If monofunctional compounds are added to control blooming, then blooming is reduced, but the composition becomes more complex and requires additional additives
Solution Approach 1:
The patent extracts and eliminates the need for monofunctional blooming control additives by incorporating blooming resistance directly into the TPU polymer structure itself. The specific polyol molecular weight range and segment ratio control inherently prevent blooming without requiring additional monofunctional compounds, thereby simplifying the overall composition.
3Illumination intensity
If blooming is reduced through conventional means, then surface clarity is improved, but the polymer requires additional compounds that may affect other properties
Solution Approach 1:
The TPU polymer structure serves itself by incorporating blooming resistance into its fundamental architecture through controlled polyol molecular weight and segment ratios. The polymer inherently prevents blooming and maintains surface clarity without requiring external additives, making the material self-sufficient for both mechanical and optical performance requirements.
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 solution significantly reduces blooming in TPUs, maintaining clarity and enhancing adhesive bonding capabilities, as demonstrated by the production of bloom-free articles like clear tubes and hoses for organic liquids and other applications.
Implementation Method 1
a thermoplastic polyurethane which is comprised of the reaction product of (1) a hydroxyl terminated polyester intermediate, (2) a polyisocyanate, and (3) a glycol chain extender
Data Source
AI summary
The present invention discloses a thermoplastic polyurethane which is comprised of the reaction product of (1) a hydroxyl terminated polyester intermediate, (2) a polyisocyanate, and (3) a glycol chain extender; wherein the hydroxyl terminated polyester intermediate is comprised of repeat units that are derived from 1,3-propylene glycol and a dicarboxylic acid; wherein the hydroxyl terminated polyester intermediate has a number average molecular weight from 500 to 10,000; and wherein the thermoplastic polyurethane includes hard segments that are the reaction product of the polyisocyanate and the glycol chain extender. This thermoplastic polyurethane is unique in that it has a greatly reduced tendency to bloom. This is highly desirable in applications where high clarity is described because blooming causes articles containing the thermoplastic polyurethane to be hazy or foggy in appearance. Blooming can also reduce the ability of an article made with the thermoplastic polyurethane to be securely bound to another article with an adhesive.