Recycling polyethylene from automotive fuel tanks

Abstract

Polyethylene (PE) from postuse automotive fuel tanks is considered a valuable material for mechanical recycling, and we assessed its properties, paying particular attention to transport properties and processability. The characterization included the study of the sorption-desorption isotherms, the rheological analysis of the molten materials and their processability. In particular, we obtained, sorption--desorption isotherms using a model molecule (nheptane) to simulate contact with the fuel. The measurements were carried out on films of PE blend for tanks and separately on the components of the blend. Rotational rheometry was carried out on scraps from used tanks and on virgin material for comparison. We performed some extrusion tests to evaluate the possibility of mechanical recycling of the postuse materials. In particular, we examined the melt-fracture incoming conditions by making use of a twinscrew extruder with a round die. Stress-strain measurements were carried out on films of virgin and used material, obtained with a press on a laboratory scale to evaluate the change of the mechanical properties of a manufacture obtained by reprocessing a polymer aged in contact with a mixture of liquids.

Effects of a mixture of stabilizers on the structure and mechanical properties of polyethylene during reprocessing

“…During processing, polymer materials can be subject to either one or several steps. Thus, it is necessary to evaluate the effects of reprocessing on their structure and their properties 1–8…”

Use of an Alternative Colorant for Polyethylene Fuel Tanks Recycling

“…In this way it was possible to plot the complete isotherm of sorption-desorption, that can give useful information of any hysteretic phenomenon. Figure 1, already shown (7) , reports the sorption-desorption isotherm of nheptane at T=30°C in PE-CB. We observe that the sorption of the hydrocarbon in the blend HDPE-Carbon black is linear with the vapour activity up to a=0.6, and only at higher activities a more than linear sorption, according to the Flory-Huggins sorption behaviour is observed (9) .…”

“…The fuel tanks during all their lifetime are in contact with a liquid mixture of solvents, each of them with a specific interaction with the polymer. In order to simplify the study of the effect of this complex mixture on the tanks, we decided to perform a laboratory simulation using n-heptane as model molecule (7) .…”

“…The aim of the car producers is to reach, as more as possible, 100% recycling, and the concept of the closed loop recycling seems to represent the best solution in this field: the recovered material is reprocessed to produce the same component from which it derives. In a previous work (7) we studied the possibility of recycling polyethylene from automotive fuel tanks of FIAT (Italy) cars. The recycling process of the fuel tanks depends on the possibility of eliminating all the entrapped solvent, due to the prolonged contact with liquid fuel, and on a careful analysis of the rheology of the recycled materials.…”

Recycling Automotive Plastics in China

“…Generally, incomplete degrees of separation of different plastic types mean that products made from such recycled plastics usually have poor performance 5,6 and low added value. Also, the products are usually bulky plastic parts.…”