Laser Weldable Thermoplastic Compositions for NIR Transmission
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Solution Overview
Problem
Crystalline and glass-filled thermoplastic materials pose challenges for near-infrared (NIR) laser welding due to low NIR transmission and scattering effects, limiting weld strength and assembly speed.
Innovation Solution
A thermoplastic composition combining crystalline or semi-crystalline polyester with amorphous poly(ester-carbonate) and glass fibers, optimized for high NIR transmission and thermal properties, allowing for efficient laser welding with improved weld strength and reduced surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If crystalline or glass-filled thermoplastic materials are used, then mechanical strength and structural properties are improved, but NIR transmission is reduced and scattering effects increase, limiting weld strength and assembly speed
Solution Approach 1:
The patent applies composite materials by combining crystalline polyester (PBT or PET) with amorphous poly(ester-carbonate) and glass fibers in specific proportions. This composite structure allows the material to simultaneously achieve high mechanical strength from the crystalline phase and high NIR transmission from the amorphous phase, resolving the contradiction between strength and laser transmission
Solution Approach 2:
The patent changes the compositional parameters by precisely controlling the weight percentages of each component (crystalline polyester 45-86%, amorphous poly(ester-carbonate) 9-25%, glass fiber 5-30%). By adjusting these parameters, the material achieves optimal balance between mechanical properties and NIR transmission characteristics
2Stability of the object's composition
If crystalline materials with fillers are used, then structural integrity is improved, but laser energy dispersion increases and adhesion at the interface is reduced
Solution Approach 1:
The composite structure combines crystalline polyester for structural integrity with amorphous poly(ester-carbonate) that maintains laser energy transmission. The amorphous phase prevents excessive scattering of laser energy while the crystalline phase provides structural stability, ensuring both integrity and reliable weld adhesion
Solution Approach 2:
The patent creates local quality differentiation within the material: the crystalline regions provide structural integrity while the amorphous regions facilitate laser energy transmission. This local differentiation allows different parts of the material to fulfill different functions simultaneously
3Volume of moving object
If upper layer thickness is increased, then structural coverage is improved, but scattering effects are enhanced and laser welding becomes restricted or impossible
Solution Approach 1:
The composite material allows increased layer thickness while maintaining laser transmission because the amorphous poly(ester-carbonate) phase has superior NIR transmission properties. This enables thicker layers to be welded effectively without sacrificing welding speed or structural coverage
4Productivity
If welding speed is increased, then assembly cycle time is reduced, but sufficient laser energy at the interface cannot be achieved with crystalline materials
Solution Approach 1:
The composite structure with amorphous poly(ester-carbonate) enables high welding speeds while maintaining sufficient laser energy at the interface. The amorphous phase transmits laser energy more effectively than pure crystalline materials, allowing faster scan speeds without compromising weld quality
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 high NIR transmission and weld strength, enabling faster welding speeds and maintaining excellent thermal properties, such as a Vicat softening temperature of at least 170°C, while minimizing surface roughness for better contact during joining.
Implementation Method 1
one of the polymer articles to be at least partially transparent to laser light... The laser passes through the first laser transparent layer and is absorbed by the second polymer layer
Implementation Method 2
the other to absorb a significant amount of the laser light... the laser passes through the first laser transparent layer and is absorbed by the second polymer layer, generating heat in the exposed area
Implementation Method 3
Scattering effects are greatly enhanced when fillers such as glass fibers are present
Data Source
AI summary
A laser weldable composition comprises a combination of: (a) from more than 45 to less than 94 weight percent of a crystalline or semicrystalline thermoplastic polyester component selected from poly (butylene terephthalate), poly (ethylene terephthalate), poly (butylene terephthalate) copolymers poly (ethylene terephthalate) copolymers, and combinations thereof; (b) from greater than 6 to less than 25 weight percent of an amorphous thermoplastic poly(ester) copolymer, poly (ester- carbonate), or combination thereof; (c) optionally, from 1 to 30 weight percent of a filler; and (d) optionally, from 0.01 to 5 weight percent of an antioxidant, mold release agent, colorant stabilizer, or a combination thereof; wherein an article having a 2mm thickness and molde from the composition has (i) a near infrared transmission at 960 nanometers of greater than 30 percent and(ii) a Vicat softening temperature of at least 170°C.