Liquid Crystalline Polyester Composition for High Heat Deflection Temperature
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Solution Overview
Problem
The relationship between composition and melting temperature of thermotropic liquid crystalline polyesters (TLCPs) derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, and hydroquinone is not well established, limiting their high heat deflection temperature (HDT) and processibility for applications in electrical and electronics industries, as well as modification of conventional polymers.
Innovation Solution
A series of TLCPs with specific mole percent ranges of repeat units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, and hydroquinone are synthesized, establishing a correlation between composition and melting point, allowing for the design of polyesters with desired melting temperatures and HDTs through a 3-dimensional plot of melting point vs. polymer composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the melting temperature of TLCP is increased to ensure high HDT, then heat deflection temperature is improved, but processibility deteriorates
Solution Approach 1:
The patent applies parameter changes by systematically varying the compositional parameters (mole percentages) of repeat units derived from HBA, HNA, TA, and HQ to achieve the desired balance between melting temperature and processibility. By changing the chemical composition parameters within specific ranges, the patent optimizes both HDT and processibility simultaneously
Solution Approach 2:
The patent creates a composite polyester structure by combining four different repeat units (A, B, C, and D) derived from different monomers. This composite approach allows the material to exhibit both high heat resistance and good processibility that cannot be achieved with single-component polyesters
2Ease of manufacture
If the melting temperature of TLCP is decreased to improve processibility, then processibility is improved, but heat deflection temperature deteriorates
Solution Approach 1:
The patent uses parameter changes by adjusting the compositional ratios within defined ranges to achieve optimal processibility while maintaining sufficient HDT. The specific mole percent ranges for each repeat unit are determined to balance these conflicting requirements
3Temperature
If the composition of TLCP is optimized for high HDT, then heat deflection temperature is improved, but melting temperature becomes too high for melt mixing with conventional polymers
Solution Approach 1:
The patent applies local quality by creating regions of different compositional characteristics within the polyester structure. By controlling the distribution and ratios of specific repeat units, the material achieves high HDT in certain aspects while maintaining lower melting points in other aspects, enabling compatibility with conventional polymers for melt mixing applications
Data Source
AI summary
The present invention provides a class of thermotropic liquid crystalline polyesters (TLCPs) and molding compositions comprising the polyesters and glass fiber. The TLCPs consist essentially of repeat units derived from p-hydroxybenzoic acid (HBA), 6-hydroxy-2-naphthoic acid (HNA), terephthalic acid (TA), and hydroquinone (HQ), and the mole percent of HBA, HNA, TA and HQ is 34-72%, 12-26%, 4-21% and 4-21%, respectively. The TLCPs have a melting temperature equal to or below 355° C., an inherent viscosity of 4.0-10.0 dL/g and a Heat Deflection Temperature (HDT) in the range of 260-285° C. when compounded with 30% by weight glass fiber. The optimum compositions, selected from the above-mentioned compositional ranges exhibit a relatively low melting temperature and a relatively high HDT. Specified compositions, selected from the above-mentioned compositional ranges have low melting point, which are useful to blend with conventional polymers such as poly (ethylene terephthalate) and nylon etc.