PET-PBT Polyester Composition Crystallization Control
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Solution Overview
Problem
Compositions of polybutylene terephthalate (PBT) and polyethylene terephthalate (PET) used in injection molding require high mold temperatures to achieve adequate crystallization, leading to increased technical requirements and longer cycle times, while the addition of nucleating agents to enhance crystallization can negatively impact mechanical properties and stability.
Innovation Solution
The use of PET and PBT compositions with a sodium or potassium content of 1 to 10,000 ppm, preferably 3 to 5000 ppm, in a ratio of 5:1 to 0.2:1, particularly 1.5:1 to 0.8:1, where PET is recycled from bottles and treated with alkali metal hydroxides to optimize crystallization behavior without additional auxiliaries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high mold temperatures are used to achieve adequate crystallization of PET, then crystallization is improved, but cycle times increase and technical requirements increase
Solution Approach 1:
The invention changes the chemical composition parameters of the polyester blend by incorporating PBT in specific ratios (5:1 to 0.2:1, preferably 2.2:1 to 0.5:1, particularly preferably 1.5:1 to 0.8:1) and controlling sodium/potassium content (1 to 10,000 ppm, preferably 3 to 5,000 ppm, particularly preferably 7 to 1,000 ppm). This compositional parameter change enables adequate crystallization at lower mold temperatures, directly resolving the contradiction between crystallization quality and cycle time
Solution Approach 2:
The invention uses a composite material system combining PBT and PET in specific ratios. PBT serves as a nucleating agent and crystallization promoter within the composite, enabling the blend to achieve adequate crystallization at lower mold temperatures than pure PET, thus reducing cycle times while maintaining crystallization quality
2Manufacturing precision
If nucleating agents are added to increase crystallization rate, then crystallization is improved, but mechanical properties and stability deteriorate
Solution Approach 1:
The invention enables the polyester composition to self-nucleate and self-regulate crystallization through its own compositional characteristics. The PBT component and controlled alkali metal content (1 to 10,000 ppm, preferably 3 to 5,000 ppm, particularly preferably 7 to 1,000 ppm) provide inherent nucleation capability without requiring external nucleating agents, thus maintaining mechanical properties and stability while achieving improved crystallization rate
Solution Approach 2:
The PBT-PET composite system inherently provides nucleation functionality through the PBT component, eliminating the need for separate nucleating agent additives. This composite approach achieves enhanced crystallization rate while preserving mechanical properties and compositional stability, as the nucleation effect arises from the blend composition itself rather than from added auxiliaries
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
This approach optimizes crystallization and processing behavior, reducing cycle times and allowing lower mold temperatures, while maintaining the mechanical properties and stability of the compositions.
Implementation Method 1
The overall crystallization rate of polyesters can be increased by using various nucleation additives... the PET has a sodium content and/or potassium content, preferably a sodium content, of from 1 to 10 000 ppm
Data Source
AI summary
The invention relates to compositions based on polyethylene terephthalate and polybutylene terephthalate with optimized crystallization behavior and consequently with optimized processing behavior in the injection molding process, and also to products to be produced therefrom, in particular with optimized crystallinity.