Study On The Processing And Properties Of A New Liner Material For Fuel Tanks In Natural Gas Vehicles

With the popularization and application of compressed natural gasvehicles (CNG vehicles), the requirement of its fuel tank materials is rising.In this study, a linear low density polyethylene grafted with maleicanhydride (LLDPE-g-MAH) is processed by the rotational moldingmethod and the injection molding method. LLDPE-g-MAH is aged inanaerobic thermal environments under the reference of the workingconditions of fuel tank liners in CNG vehicles. Combined with static loadtensile test and dynamic fatigue test and other methods, the researches onthe water resistance, the thermal stability and mechanical properties areused to examine LLDPE-g-MAH as a new liner material and to explore itsphysical properties. The results show that LLDPE-g-MAH is suitable forinjection molding and rotational molding process. The yield stress ofinjection molded LLDPE-g-MAH is9.9MPa, with the tensile strength of13MPa, the elongation of446.7%and the Young’s modulus of about248MPa. There is no significant change in tensile properties afteranaerobic thermal aging or after107times200N-20N asymmetric cyclicstress mechanical aging. The yield stress of rotational moldedLLDPE-g-MAH is17MPa, with the tensile strength of5.4MPa, theelongation of71%and the Young’s modulus of about457MPa, and afteranaerobic thermal aging the tensile properties are reduced. For alternatingbending fatigue tests, the fracture doesn’t occur in injection moldedLLDPE-g-MAH at10Hz,2.72%cyclic strain. For tensile fatigue tests(R=0.1), the endurance limit of unaged injection molded LLDPE-g-MAH is about210N at10Hz, and thermal effects are not significant on fatiguebehavior. A micro-defects accumulated fatigue kinetic model isinvestigated to fit the S-N curve of injection molded LLDPE-g-MAH intensile fatigue tests. It is stable and better than other pure mathematicalmodels to predict the failure life which has a decreasing trend under anincreasing stress.