PCT Polymer LED Reflectors with Viscosity Stabilizers
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Solution Overview
Problem
Existing LED reflector materials face challenges with thermal aging, yellowing, and fluctuating viscosity during injection molding, which affect their reflectance and mechanical strength, particularly in high-temperature applications and complex geometries.
Innovation Solution
A polymer composition comprising poly(1,4-cyclohexanedimethanol terephthalate) (PCT) with a white pigment and reactive viscosity stabilizers like phenoxy resin or non-aromatic epoxy resin, which maintains stable viscosity and prevents yellowing, ensuring high reflectance and mechanical integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If conventional polymer resin is used for LED reflector, then the reflector can be molded, but the resin yellows during thermal aging and loses reflectance
Solution Approach 1:
The patent changes the chemical composition parameters of the polymer resin by incorporating specific additives including hindered amine light stabilizers (HALS), phosphite antioxidants, and UV absorbers. These compositional parameter changes enable the resin to maintain its reflectance properties (>90% at 460 nm) and whiteness index (>70) after thermal aging at 200°C for 4 hours, resolving the yellowing issue while preserving optical performance.
Solution Approach 2:
The patent creates a composite polymer material system that combines PCT polymer with multiple functional additives: reactive viscosity stabilizers (phenoxy resin or non-aromatic epoxy resin), white pigments (titanium dioxide), and thermal/oxidative stabilizers. This composite formulation achieves both processability and thermal aging resistance while maintaining high reflectance, solving the contradiction between durability and optical performance.
2Ease of manufacture
If polymer resin is heated for injection molding, then the resin flows into mold, but viscosity fluctuates during processing
Solution Approach 1:
The patent introduces reactive viscosity stabilizers (phenoxy resin or non-aromatic epoxy resin) as intermediary substances that mediate between the polymer chains during heating. These stabilizers prevent excessive viscosity fluctuations by controlling polymer chain interactions at elevated temperatures, enabling stable injection molding process while maintaining good melt flow into complex geometries.
Solution Approach 2:
The patent optimizes the molecular weight and composition parameters of the PCT polymer to achieve a balance between melt flow and viscosity stability. The specific polymer formulation with controlled inherent viscosity (0.3-1.5) provides sufficient flow into complex LED geometries while resisting excessive thinning during processing, resolving the contradiction between ease of manufacture and composition stability.
3Power
If LED operates at high temperature, then the LED produces light, but the reflector material degrades and loses mechanical strength
Solution Approach 1:
The patent incorporates thermal and oxidative stabilizers (hindered amine light stabilizers, phosphite antioxidants) in advance into the polymer formulation before the LED operates. These stabilizers provide beforehand cushioning protection against thermal degradation and oxidation that would otherwise occur during high-temperature LED operation, preserving both mechanical strength and optical properties throughout the LED's operational life.
Solution Approach 2:
The patent develops a composite polymer material system that combines PCT with multiple stabilizing agents and functional additives. This composite formulation provides thermal stability, oxidative resistance, and mechanical strength retention at elevated temperatures, enabling the reflector to withstand high-temperature LED operation without degradation while maintaining its structural and optical functions.
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 polymer composition achieves initial reflectance of over 90% at 460 nm and maintains a whiteness index above 70 after thermal aging, providing excellent melt flow properties and mechanical strength, suitable for complex LED geometries and high-temperature use.
Implementation Method 1
the polymer resin should reflect a significant amount of light in the visible light region and particularly should reflect a significant percentage of light in the blue light wavelength range
Implementation Method 2
The polymer composition comprises poly(1,4-cyclohexanedimethanol terephthalate) (PCT) with a white pigment
Implementation Method 3
reactive viscosity stabilizers like phenoxy resin or non-aromatic epoxy resin, which maintains stable viscosity
Implementation Method 4
maintains a whiteness index above 70 after thermal aging
Implementation Method 5
suitable for complex LED geometries and high-temperature use
Data Source
AI summary
Polymer compositions are described containing a poly(1,4-cyclohexanedimethanol terephthalate) polymer in combination with a white pigment and optionally one or more reinforcing fillers. In accordance with the present disclosure, the composition also contains one or more reactive viscosity stabilizers. In order to prevent against yellowing, the composition is free of various aromatic epoxy resins, such as novolac epoxy resins. The polymer composition has excellent reflectance properties making the composition well suited for producing reflectors for light sources, such as LED assemblies.