Investigation of material degradation during multiple recycling loops of a glass fiber reinforced polypropylene compound to evaluate life cycle analysis based on mechanical properties

Abstract

In order to reduce the global warming potential of their vehicles, automotive manufacturers are increasingly striving to use recyclates. However, recyclates often have weaker mechanical properties than comparable virgin polymers. Structurally, the weaker material properties can be compensated by an additional material effort. In semi-structural components of the vehicle interior, the bending stiffness is particularly important, which can be increased by a higher wall thickness to compensate for poorer mechanical properties, leading to higher component weights. The question is to what extent recyclates with poorer mechanical properties than virgin polymer result in CO₂-reductions in the overall life cycle.

In this work, long glass fiber reinforced polypropylene is recycled several times and the mechanical properties are determined. An LCA is carried out, based on bending stiffness as a functional unit to compare the advantages of recyclates with the disadvantages of higher component weights.

It turns out that in a vehicle with combustion engine only the first recycling loop results in a smaller GWP than the virgin polymer. For a vehicle with electric drive, this is the case for the second recycling loop.