Polybutylene Terephthalate Resin Weld Strength and Flowability
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Solution Overview
Problem
Existing polybutylene terephthalate resin compositions face challenges in achieving high weld strength while maintaining sufficient flowability, which is essential for producing molded products with desired mechanical and heat resistance properties, particularly when incorporating inorganic fillers.
Innovation Solution
A polybutylene terephthalate resin composition with a weight-average molecular weight between 60,000 and 80,000, combined with an inorganic filler and an elastomer, is used to enhance weld strength and flowability, allowing for effective molding and heat shock resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the viscosity upon melting of resin composition is increased to enhance weld strength, then weld strength between molded products is improved, but flowability of the resin composition during molding deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the weight-average molecular weight of polybutylene terephthalate resin within the range of 60,000-80,000. This specific molecular weight range optimizes the balance between weld strength and flowability, resolving the contradiction by adjusting the physical parameter of the resin to achieve both improved welding performance and sufficient moldability.
Solution Approach 2:
The patent employs composite materials by formulating a resin composition that includes polybutylene terephthalate resin combined with specific additives and modifiers. This composite approach allows the material to exhibit both high weld strength and adequate flowability, as the composition works synergistically to balance the contradictory properties of strength and processability.
2Ease of manufacture
If a modified polyester copolymer containing 5 to 30 mol% of a comonomer is used to improve moldability, then flowability is enhanced, but heat resistance of the molded product deteriorates
Solution Approach 1:
The patent resolves this contradiction by changing the parameter from using modified polyester copolymer with comonomer to using unmodified polybutylene terephthalate resin with controlled molecular weight (60,000-80,000). This parameter change maintains heat resistance while achieving sufficient moldability through the optimized molecular weight range, avoiding the heat resistance deterioration associated with comonomer incorporation.
3Strength
If inorganic filler is added to impart mechanical strength, then mechanical properties are improved, but flowability of the resin composition deteriorates
Solution Approach 1:
The patent addresses this contradiction by changing the parameter of the base resin to have a specific weight-average molecular weight range (60,000-80,000). This parameter change compensates for the flowability reduction caused by inorganic filler addition, as the optimized molecular weight provides sufficient melt flow characteristics even with filler present, while maintaining enhanced mechanical strength.
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 composition achieves strong weld strength and excellent flowability, enabling the production of molded products with improved mechanical and heat resistance properties, suitable for applications such as electronic part cases and housings.
Implementation Method 1
a welded body obtained by welding molded products, each being composed of the resin composition, together
Implementation Method 2
welding methods such as a vibration welding method and an ultrasonic welding method
Implementation Method 3
the viscosity upon melting of resin composition may be increased
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
AI summary
To provide a polybutylene terephthalate resin composition offering excellent flowability, wherein the resin composition raises the weld strength and heat shock resistance of a welded body obtained by welding together molded products obtained by molding the polybutylene terephthalate resin composition. [Solution] A polybutylene terephthalate resin composition comprising a polybutylene terephthalate resin (A) having a weight-average molecular weight of 60,000-80,000 inclusive and an inorganic filler (B). Preferably, also included is 5-20 mass parts of an elastomer (C) relative to 100 mass parts of the polybutylene terephthalate resin (A).