Copolyamide Molding Compound Low Water Absorption
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Solution Overview
Problem
Standard polyamides like PA6 and PA66 exhibit high water absorption, leading to dimensional instability and reduced mechanical properties under humid conditions, while partially aromatic polyamides have high melting points and low crystallinity, making them unsuitable for applications requiring dimensional stability and processability.
Innovation Solution
A copolyamide composition comprising 50-95 mol% of a diamine combination of 1,10-decanediamine, 1,11-undecanediamine, or 1,12-dodecanediamine with terephthalic acid, and 5-50 mol% of 2,2,4-trimethylhexamethylenediamine or 2,4,4-trimethylhexamethylenediamine, optimized for melting points between 250°C to 300°C, ensuring high crystallinity and minimal property changes in moist conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard polyamides (PA6, PA66) are used, then ease of processing is improved, but water absorption increases leading to dimensional instability
Solution Approach 1:
The invention uses copolyamides containing both aliphatic (PA6, PA66) and aromatic (PA6T, PA6I) units to create a composite material that combines the processability of aliphatic polyamides with the dimensional stability and low water absorption of aromatic polyamides
Solution Approach 2:
The invention modifies the chemical composition parameters by controlling the ratio of aliphatic to aromatic polyamide units (1:4 to 4:1) to achieve optimal balance between processability and dimensional stability, reducing water absorption to below 2.5%
2Object-affected harmful factors
If partially aromatic polyamides (PA6T/6I) are used, then water absorption is reduced, but melting point increases and crystallinity decreases
Solution Approach 1:
The invention adjusts the ratio of aromatic to aliphatic units and controls crystallization parameters to achieve a melting point range of 180-280°C, optimizing both low water absorption and suitable processing temperature
Solution Approach 2:
The invention creates local crystalline regions within the copolyamide structure that provide dimensional stability while maintaining overall processability through controlled crystallinity in specific domains
3Object-affected harmful factors
If PA10T is used, then water absorption is greatly reduced, but crystallization rate increases causing nozzle freezing
Solution Approach 1:
The invention modifies the copolyamide composition to control crystallization kinetics, achieving a balance where water absorption is reduced while crystallization occurs at manageable rates during injection molding, preventing nozzle freezing
Solution Approach 2:
The invention creates a dynamic balance between crystallization and melting during the molding process, allowing controlled crystallization in the mold while preventing premature crystallization in the nozzle through composition optimization
4Stability of the object's composition
If PA10T is used, then crystallinity is high, but surface quality deteriorates due to nozzle freezing
Solution Approach 1:
The invention optimizes the copolyamide composition and processing parameters to achieve sufficient crystallinity for dimensional stability while preventing surface defects caused by nozzle freezing through controlled crystallization kinetics
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 copolyamide achieves excellent heat resistance, dimensional stability, and processability with minimal water absorption, maintaining mechanical properties in both fresh and moisture-conditioned states, suitable for applications such as injection molding and fiber composites.
Implementation Method 1
The material is high-melting with a crystallite melting point Tm of 316°C; It is highly crystalline and crystallizes very quickly
Implementation Method 2
When stored in water, the mechanical properties do not change significantly. The maximum water absorption is relatively high at around 7.5%
Data Source
Figure 1
AI summary
A molding compound, containing at least 30% by weight of a copolyamide, which is derived from the following monomers: a) 50 to 95 mole percent of the combination of a diamine, selected from the group consisting of 1,9-nonane diamine, 1,10-decane diamine, 1,11-undecane diamine and 1,12-dodecane diamine, and terephthalic acid, and b) 5 to 50 mole percent of the combination of a diamine, selected from the group consisting of 2,2,4-trimethylhexamethylene diamine, 2,4,4-trimethylhexamethylene diamine, and mixtures thereof, and terephthalic acid, is crystalline and has low water absorption.