Laser Transmissive Polyester Composition for Welding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Polybutylene terephthalate (PBT) exhibits low laser transparency due to high crystalline phases, which limits its application in laser transmission welding, and attempts to improve transparency through blending or adding aromatic sodium salts compromise mechanical and thermal properties.
Innovation Solution
A laser transmissive composition comprising a polyester compound, a non-aromatic organic nucleating agent, a chain extender or branching agent with multiple reactive groups, heat stabilizers, process stabilizers, lubricants, and further additives, which synergistically enhances laser transparency and mechanical properties while maintaining processability and preventing excessive crosslinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PBT is used to form the laser transparent polymer layer, then mechanical strength is improved, but laser transmission is reduced due to high crystalline phases
Solution Approach 1:
The patent changes the chemical structure parameter of the polyester by using non-cyclic aliphatic dicarboxylic acids with specific carbon chain lengths (C4-C12) instead of conventional aromatic dicarboxylic acids. This structural modification reduces crystalline phase formation while maintaining mechanical strength, thereby improving laser transmission without sacrificing mechanical properties.
Solution Approach 2:
The patent creates a composite polyester material by combining non-cyclic aliphatic dicarboxylic acid units with aromatic dicarboxylic acid units in specific ratios (30-70 wt% aliphatic content). This composite structure achieves a balance between crystalline phase reduction (for laser transmission) and mechanical strength maintenance.
2Strength
If glass fiber is added to increase the strength of the material, then mechanical strength is improved, but laser transmission is reduced further
Solution Approach 1:
The patent modifies the base polyester composition to have inherently better laser transmission properties through the non-cyclic aliphatic structure, which allows the material to tolerate the addition of glass fibers (0-40 wt%) without severe degradation of laser transmission. The improved base polymer matrix maintains adequate laser transmission even with filler addition while preserving the strength enhancement from glass fibers.
3Illumination intensity
If aromatic sodium salt is added to reduce the size of the crystalline phase, then laser transparency is improved, but mechanical properties and thermal properties are compromised
Solution Approach 1:
The patent fundamentally changes the approach from adding nucleating agents to modify crystalline structure, to selecting monomers that inherently produce favorable crystalline characteristics. The non-cyclic aliphatic dicarboxylic acid structure creates a polyester with reduced crystalline phase formation tendency, improving laser transparency without the mechanical property degradation associated with aromatic sodium salt additives.
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 significantly improves laser transparency and mechanical properties, maintaining stable melt viscosity and resistance to environmental exposure, making it suitable for laser transmission welding applications without degrading other polymer properties.
Implementation Method 1
a non-aromatic organic nucleating agent
Implementation Method 2
a high-power laser—with wavelengths in the range of, for example, 900 to 1200 nm—that passes through a laser transparent layer of polymer to a laser absorbent layer of polymer which absorbs the energy from the laser, causing it to heat up
Implementation Method 3
The crystalline phases of the polymer exhibit a different refractive index than the amorphous regions, causing the laser to be scattered as it passes through the polymer
Data Source
AI summary
Embodiments of the present disclosure include laser transmissive compositions and related methods. The laser transmissive compositions may include one or more of the following components: (a) a polyester compound; (b) a filler; (c) a non-aromatic organic nucleating agent; (d) at least one of a chain extender and a branching agent, wherein the chain extender/branching agent includes two or more reactive groups attached thereto; (e) at least one heat stabilizer; (f) at least one process stabilizer; (g) at least one lubricant; and (h) one or more further additives.