Reactive Polyamideimide Oligomers for Melt Processing
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Solution Overview
Problem
High molecular weight all-aromatic polyamideimides (PAIs) face challenges in melt processing due to high sensitivity to temperature and shear rate, requiring extensive drying and thermal post-treatment for water removal, which limits their use in complex shapes and manufacturing processes like injection molding and 3D printing.
Innovation Solution
Development of reactive polyamideimide oligomers with a number average molecular weight of 1,000 to 10,000 g/mol, formed by step-growth polymerization and cyclodehydration, allowing for chain extension and crosslinking without generating water by-products, enabling easier melt processing and reduced thermal post-treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high molecular weight PAI is used to achieve excellent high temperature strength and chemical resistance, then mechanical properties are improved, but melt viscosity becomes highly sensitive to temperature and shear rate, requiring processing temperatures greater than 600°F (316°C)
Solution Approach 1:
The patent segments the polymer into oligomeric units with controlled molecular weight (1,000-10,000 g/mol) rather than using high molecular weight polymer. This segmentation allows the material to be processed at lower temperatures while maintaining the ability to achieve high strength through subsequent crosslinking of the oligomeric units
Solution Approach 2:
The patent changes the molecular weight parameter from high molecular weight to oligomeric range, and introduces crosslinkable functional groups that enable the material to transition from a low-viscosity state during processing to a high-strength crosslinked network after curing, thereby resolving the contradiction between processability and mechanical properties
2Ease of manufacture
If amic acid groups are present in the polymer backbone to provide flexibility and melt processability, then ease of processing is improved, but the polymer becomes highly moisture sensitive and requires thorough drying before and during melt processing
Solution Approach 1:
The patent extracts the moisture-sensitive amic acid groups from the polymer structure and replaces them with crosslinkable functional groups that do not require strict moisture control. This eliminates the harmful moisture sensitivity while preserving the desired melt processability
Solution Approach 2:
The patent uses oligomeric precursors that are stable and easy to handle, eliminating the need for extensive drying procedures. The crosslinking reaction then creates the final high-performance network, effectively replacing the problematic long-term stable but moisture-sensitive amic acid structure
3Ease of manufacture
If injection molding grade PAI with lower molecular weight is used to improve melt processing, then ease of manufacture is improved, but large amounts of water must be removed from final parts through time-consuming post-cure processes
Solution Approach 1:
The patent converts the potential harm of water generation during curing into a benefit by using crosslinkable functional groups that cure without generating water. This eliminates the time-consuming water removal step while maintaining the advantages of lower molecular weight processing
Solution Approach 2:
The patent changes the curing mechanism from cyclodehydration (which generates water) to crosslinking reactions (which do not generate water). This parameter change in the chemical reaction type eliminates the need for extended post-cure processes while maintaining processability benefits
4Strength
If chain extension is performed to build molecular weight in situ, then mechanical properties are improved, but residence time must be optimized to avoid excessive viscosity increase and flow loss
Solution Approach 1:
The patent performs preliminary action by pre-forming oligomeric units with controlled molecular weight and crosslinkable functional groups before processing. This eliminates the need for in-situ chain extension during processing, thereby avoiding viscosity increase and flow loss while maintaining mechanical properties
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
Enables the production of complex parts with improved mechanical properties, reduced processing time, and elimination of water removal steps, making PAIs suitable for various manufacturing processes including injection molding and 3D printing.
Implementation Method 1
formed by step-growth polymerization and cyclodehydration
Implementation Method 2
amic acid groups convert thermally to imides by cyclodehydration
Data Source
AI summary
Reactive ammonium carboxyl ate salts, polyamide amic acid oligomers, and polyamideimide oligomers are made from at least one aromatic diamine, at least one aromatic di-, tri-, or tetra-functional carboxylic acid or functional equivalent thereof, and at least one crosslinkable monomer or crosslinkable end-capper. The crosslinkable monomer or crosslinkable end-capper is reactive with the at least one aromatic diamine or at least one di-, tri- or tetra-functional aromatic carboxylic acid or functional equivalent thereof and has at least one unreacted functional group capable of chain extension and crosslinking after formation of the reactive polyamideimide oligomer. The reactive polyamide amic acid and polyamideimide oligomers have a number average molecular weight (Mn) of about 1,000 to about 10,000 g/mol, calculated using the Carothers equation. The reactive ammonium carboxyl ate salts, polyamide amic acid oligomers, and polyamideimide oligomers are useful in a wide variety of functional materials, manufacturing methods, and articles.