Browse Publications Technical Papers 2000-01-1097
2000-03-06

The Permeation Characterisation of CARILON Polymer by Gravimetric-, Sorption- and a New FID Speciation (SHELL Micro-SHED) Test Methods 2000-01-1097

Evolving emission legislation in both the USA and Europe is requiring the automotive industry to develop novel solutions for their fuel/vapour circuits, yielding significant improvements in evaporative emission behaviour. Thus material structures with excellent barrier properties against various automotive gasoline fuels are receiving a significant amount of attention for this purpose. CARILON® Polymer, an aliphatic polyketone (PK) from SHELL Chemicals1 holds promise as such a barrier construction material. It has excellent barrier properties, chemical resistance and low temperature impact performance, and is a serious contender to help in the manufacturing of a fully design integrated monolithic fuel system, designed to meet the most stringent regulations in this respect.Characterising the permeation behaviour of such good barrier materials via long term, conventional gravimetric laboratory testing, is extremely difficult. To increase our understanding, we have also investigated the permeation behaviour of a matrix of material solutions and standard fuels via other existing (e.g. sorption) and new techniques, in addition to long term gravimetric monitoring of permeation cells. We also developed an analytical equipment set-up and procedures, internally referred to as the “SHELL Micro-SHED”, enabling us to quantitatively determine the total level of permeation of a specific fuel as well the permeation of the majority of the individual components, at two hour intervals. Mini-SHED experiments were carried out of Carilon Polymer injection moulded, welded mini-boxes.The results obtained, combining these techniques, show that the permeability of European legislative fuel for CARILON Polymer at 40°C, is in the order of 25 mg.mm/m2.d. For EVOH (in a multi-layer structure with HDPE) this is in the order of 8 mg.mm/m2.day. Translating these results to a mini-SHED response for a fuel tank with a typical surface area of 1.5 m2, computes to approximately 5 mg/day for a 3 mm thick integrated CARILON Polymer tank and approximately 60-20 mg/day for a 6 mm thick HDPE/EVOH/HDPE closed body tank (EVOH layer 100-300 micron). On this basis, a complete assembled multi-layer actual tank is expected to yield approximately 410-370 mg/day.Sorption experiments demonstrated that CARILON Polymer exhibits Fickean diffusion behaviour. It is estimated that the CARILON Polymer tank will have a time lag > 10 years with CEC reference fuel at a storage temperature of 40°C. The time lag for the HDPE/EVOH/HDPE structure is expected to be primarily determined by leak containment efficiency, thus the beneficial effect of the barrier layer will be overruled in practice.

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