Moldable Polyester Composition for Fuel Tanks
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Solution Overview
Problem
Current polyester compositions fail to achieve a combination of low temperature ductility, low permeability, and good chemical resistance, especially when manufactured by blow molding processes, which are more demanding than injection molding, and are often compromised by additives intended to improve one property at the expense of others.
Innovation Solution
A thermoplastic composition comprising 51-90 wt% of a high molecular weight polyester, 10-49 wt% of an acrylonitrile-butadiene-styrene impact modifier, 0-20 wt% of a multifunctional epoxy compound, 0-40 wt% of a filler, 0-2 wt% of a fibrillated fluoropolymer, and 0-5 wt% of a stabilizer, specifically designed to maintain ductility and chemical resistance while minimizing permeability, suitable for both injection and blow molding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rubbery impact modifier or ductile polymer such as polycarbonate is added to improve low temperature ductility, then low temperature ductility is improved, but chemical resistance and low permeability are degraded
Solution Approach 1:
The patent changes the chemical composition parameters by using specific polyester types (PBT, PET, PCTA) with controlled molecular weights and end group contents, combined with precise ratios of impact modifiers and epoxy compounds, to achieve the desired balance between ductility and chemical resistance without relying on traditional rubbery modifiers that compromise chemical resistance
Solution Approach 2:
The patent creates a composite material system combining polyester base resin with specific impact modifiers (ABS or MBS) and epoxy compounds, where the synergistic interaction between components provides both improved low temperature ductility and maintained chemical resistance, rather than using single-component solutions
2Reliability
If polyester composition is optimized for good chemical resistance, particularly to fuels and short chain alcohols, then chemical resistance is improved, but low temperature ductility is worsened
Solution Approach 1:
The patent adjusts composition parameters including polyester molecular weight (20,000-80,000 daltons), carboxylic acid end group content (5-50 meq/Kg), and precise ratios of impact modifiers (10-49 wt%) and epoxy compounds (0-20 wt%) to simultaneously achieve good chemical resistance and low temperature ductility
Solution Approach 2:
The epoxy compound acts as an intermediary that crosslinks the polyester and impact modifier phases, improving the interfacial adhesion and creating a more homogeneous structure that maintains chemical resistance while enhancing low temperature ductility through improved stress distribution
3Adaptability or versatility
If blow molding process is used to manufacture fuel tanks, then fuel tank applications are enabled, but the molten polymer is exposed to air for longer periods which adversely affects composition properties
Solution Approach 1:
The patent incorporates stabilizers and antioxidants into the composition formulation before processing to preemptively protect the polymer from oxidative degradation during the extended air exposure inherent in blow molding processes, ensuring properties are maintained despite the harsher processing conditions
Data Source
AI summary
A thermoplastic composition comprises, based on the total weight of the composition: 51-90 wt% of a polyester, 10-49 wt% of an ABS impact modifier; 0 to 20 wt% of a multifunctional epoxy compound; 0-40 wt% of a filler; 0-2 wt% of a fibrillated fluoropolymer; and from more than 0 to 5 wt% of a stabilizer composition. An article blow molded or injection molded from the composition has a multi-axial impact total energy from 40-100 Joules at -30°C; a ductility of more than 90%, a permeability of more than 0 to less than or equal to 1.5g/m2-day, measured after exposure Fuel C vapor for 20 weeks at 40°C; an MVR of 1-20 cc/10 min; a flexural modulus of greater than 1300 MPa; and retains at least 75% of its initial tensile elongation at break after exposure to Fuel E85 for 28 days at 70°C.