High-Tg Thermoplastic Polyurethane Formulation for Wider Processing Windows
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Solution Overview
Problem
Current thermoplastic polyurethane (TPU) materials with high hardness and flexural modulus face challenges such as narrow processing windows, thermal instability, and susceptibility to degradation during processing, often requiring high temperatures and additional energy consumption, while also lacking recyclability and using non-sustainable resources.
Innovation Solution
Development of a reactive formulation for TPU materials with a hardblock content of at least 70 wt%, using aromatic dicarboxylic acid based diols with molecular weights under 500 g/mol, and a balanced isocyanate index, resulting in amorphous TPU materials with high glass transition temperatures and improved thermal stability, allowing processing below 250°C and recyclability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high hardblock content TPU materials are used to achieve high hardness and flexural modulus, then mechanical strength is improved, but processing temperature approaches degradation temperature creating a narrow processing window
Solution Approach 1:
The patent changes the chemical composition parameters by using aromatic dicarboxylic acid based diols with specific molecular weights (under 500 g/mol) and controlling the isocyanate index within a balanced range. This compositional parameter change enables the material to achieve high hardness while maintaining a broader processing window by modifying the thermal and mechanical properties of the polyurethane matrix.
Solution Approach 2:
The patent creates a composite polyurethane system combining aromatic dicarboxylic acid based diols with isocyanate compounds and other polyols in specific ratios. This composite formulation achieves synergistic effects where the aromatic diol provides rigidity and high Tg, while the controlled isocyanate content and balanced isocyanate index prevent excessive crosslinking, thereby expanding the processing window.
2Ease of manufacture
If high processing temperatures are used to process high hardness TPU materials, then processability is improved, but thermal degradation occurs
Solution Approach 1:
The patent modifies the thermal stability parameters of the TPU material by incorporating aromatic dicarboxylic acid based diols, which have high glass transition temperatures and enhanced thermal stability. This compositional change raises the degradation temperature of the material, allowing processing at moderate temperatures without thermal degradation.
Solution Approach 2:
The patent uses low molecular weight aromatic dicarboxylic acid based diols (under 500 g/mol) as chain extenders that provide temporary flexibility during processing but contribute to permanent thermal stability in the final product. These short-chain diols act as processing aids that disappear or integrate fully during curing, leaving a thermally stable crosslinked network.
3Strength
If conventional chain extenders are used to make high hardness TPU, then hardness is improved, but melting point becomes too high requiring processing above 220-230°C
Solution Approach 1:
The patent changes the molecular weight and chemical structure parameters of the chain extender by selecting aromatic dicarboxylic acid based diols with molecular weights under 500 g/mol. This parameter change results in lower melting points compared to conventional chain extenders, enabling processing above 220-230°C while maintaining high hardness through the aromatic structure's rigidity.
4Reliability
If extreme drying is performed to avoid side reactions during depolymerization processing, then bubble formation is prevented, but energy consumption and production costs increase
Solution Approach 1:
The patent converts the potential harm of water presence during processing into a benefit by using aromatic dicarboxylic acid based diols that are less sensitive to moisture. The balanced isocyanate index and controlled formulation allow processing without extreme drying, as the aromatic diol system tolerates trace moisture better than conventional systems, reducing energy consumption while preventing bubble formation.
Solution Approach 2:
The patent changes the moisture sensitivity parameter of the polyurethane system by using aromatic dicarboxylic acid based diols with specific molecular weights and controlled isocyanate content. This parameter change reduces the system's sensitivity to moisture, allowing processing at lower energy levels without excessive drying while maintaining product quality and preventing bubble formation.
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 achieves TPU materials with high hardness (>50 Shore D) and flexural modulus (>300 MPa) at room temperature, with glass transition temperatures above room temperature, enabling processing at lower temperatures and facilitating thermal recyclability with minimal degradation.
Implementation Method 1
the mechanism behind it is explained, which is the depolymerization at the processing temperature using an aromatic diol (the term aromatic diol used U.S. Pat. No. 5,574,092A specifically describe an aromatic or heteroaromatic moiety having two OH groups attached directly to the aromatic carbon atoms, resulting in a thermally reversible urethane bond when reacted with an isocyanate)
Implementation Method 2
the mechanism behind it is explained, which is the depolymerization at the processing temperature using an aromatic diol
Implementation Method 3
having a glass transition temperature above room temperature
Data Source
AI summary
A reactive formulation and method for forming a thermoplastic polyurethane (TPU) having a glass transition temperature (Tg) above room temperature, preferably a Tg higher than 40° C., more preferably higher than 55° C., a flexural modulus in the range 300-15000 MPa-(measured according to ISO 178), most preferably in the range 1500-2700 MPa and a tensile strength at break (according to DIN 53504) in the range of 5 up to 150 MPa is disclosed. Said reactive formulation comprising at least an isocyanate composition and an isocyanate-reactive composition comprising at least an aromatic dicarboxylic acid based diol chain extender having a molecular weight<500 g/mol and optionally fillers.Furthermore, a TPU material having a glass transition temperature (Tg)>room temperature and a flexural modulus in the range 300-15000 MPa (measured according to ISO 178) is disclosed which is thermally recyclable and optionally made from a terephthalic acid based polyester diol chain extender made from recycled PET.