Polyetherimide Compositions with Aryl Phosphate Flame Retardants
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Solution Overview
Problem
Polyetherimides face challenges with low melt flow rates and mechanical properties, such as impact strength and elongation, while maintaining flame retardancy, especially in applications like portable electronic devices where thin parts with high rigidity are required, and traditional flame retardants like halogen-containing compounds are undesirable due to environmental concerns.
Innovation Solution
Incorporating an aryl phosphate with a molecular weight of 500 to 1200 Daltons into polyetherimide compositions, which increases melt flow rates by at least 10% and enhances mechanical properties like tensile modulus and impact strength, while maintaining clarity and thermal stability, and using reinforcing fillers like glass fibers to further improve stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If lower molecular weight polyetherimide is used to increase melt flow rate, then flowability improves, but impact strength and modulus decrease
Solution Approach 1:
The patent changes the molecular weight parameter of polyetherimide from conventional high values (typically >100,000 Daltons) to lower values (5,000 to 80,000 Daltons), which fundamentally alters the melt flow characteristics while maintaining adequate mechanical properties through optimized composition and processing
Solution Approach 2:
The patent creates a composite system by combining lower molecular weight polyetherimide with specific additives and fillers (including glass fibers, carbon fibers, and various compounds) to achieve a material that possesses both high melt flow rate and adequate impact strength, compensating for the inherent weaknesses of low molecular weight polymer
2Reliability
If high concentrations of phosphate esters are used to achieve flame retardancy, then flame resistance improves, but heat resistance and impact strength decrease
Solution Approach 1:
The patent optimizes the concentration parameter of phosphate esters by identifying a specific range (0.1 to 40 weight percent) that provides adequate flame retardancy while minimizing the negative impact on mechanical properties, avoiding both insufficient flame protection and excessive property degradation
Solution Approach 2:
The patent applies different phosphate ester types (monophosphates, diphosphates, triphosphates) with different molecular weights and chemical structures to achieve flame retardancy through multiple mechanisms, allowing each component to contribute differently to the overall flame resistance while minimizing property degradation
3Reliability
If monophosphate esters are used as flame retardants, then flame resistance is achieved, but migration to surface during molding occurs
Solution Approach 1:
The patent uses coupling agents and surface treatments as intermediary substances between the phosphate ester flame retardants and the polyetherimide matrix, improving the interfacial adhesion and preventing the flame retardant from migrating to the surface during molding while maintaining flame protection
Solution Approach 2:
The patent creates a composite system where phosphate esters are combined with polyetherimide and additional additives that work synergistically to anchor the flame retardant within the matrix, preventing migration while maintaining flame retardancy through the composite structure
4Reliability
If halogen-containing flame retardants are used in combination with phosphates, then acceptable flame retardancy is achieved, but environmental concerns and mold surface pitting occur
Solution Approach 1:
The patent removes halogen-containing compounds from the flame retardant system entirely, extracting this harmful component while replacing it with halogen-free alternatives (phosphate esters and other non-halogenated compounds) that provide equivalent or superior flame protection without environmental damage or mold pitting
Solution Approach 2:
The patent converts the previously harmful halogen-containing flame retardants into beneficial halogen-free phosphate ester systems that not only eliminate environmental harm and mold pitting but also provide additional benefits such as improved processability and maintained mechanical properties
Data Source
Figure 1
AI summary
Molded articles having a maximum thickness of 3 centimeters and including a polyetherimide composition are described. The polyetherimide compositions include 60 to 99.9 weight percent of a polyetherimide having a weight average molecular weight of 5,000 to 80,000 Daltons, and 0.1 to 40 weight percent of an aryl phosphate having a molecular weight from 500 to 1,200 Daltons, wherein weight percent is based on the total weight of the composition. The compositions have a melt flow at least 10% greater than the melt flow of the same polyetherimide composition without the aryl phosphate, measured according to ASTM D1238 at 337C under a 6.7 kilogram load.