Nanocomposite Films from Car Bumper Waste

A novel method recycles linear low-density polyethylene (LLDPE) with car bumper waste into nanocomposite films.

Car bumpers are typically composed of thermoplastic polyolefin elastomers (TPOs). While front bumpers are usually made of pure TPO, manufacturers often use talc-filled TPO for rear bumpers to lower production costs. Coatings and talc fillers make recycling used plastic bumpers challenging.

You can also read: Boosting Biodegradable Packaging with PLA/Nanoclay/ZnO Films.

Additionally, polyolefins exhibit reduced performance across a variety of properties when recycled. Adding clays to form polymer/clay nanocomposites can improve many such properties.

Recycling to Create Plastic Mulch Films

Recycled polyolefin/clay nanocomposites show promise for applications in plastic mulch films, particularly for fumigation mulch. For instance, these films improve gas-barrier properties, thereby trapping volatile pesticides in the soil. In a recent study, researchers developed a nanocomposite film comprising waste bumpers, compatibilizers, fillers, and virgin LLDPE. Furthermore, they enhanced these films with nanoclay fillers compatibilized with polyethylene grafted maleic anhydride (PE-g-MEH). Ultimately, this study intended to develop a cost-effective method for producing plastic mulch films while, in tandem, creating a new recycling pathway for discarded car bumpers.

Analyzing Waste Bumpers

Researchers used Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and thermogravimetric analysis (TGA) to characterize the waste bumpers. The composition of the bumpers included polypropylene, polypropylene-based elastomer, polyethylene, acrylic paint, and talc. Using TGA, researchers analyzed the thermal stability and compositional characteristics of the waste material. Results indicated that the material contained 5% CaCO, 9% talc residue, and 84% organic polypropylene.

Adding Nanoclay to Influence Crystallinity

The nanoclay content of the polymer matrix has a significant effect on composite mechanical properties.

With 3 wt% nanoclay, Blend D exhibited the highest percent crystallinity of the samples. This is due to the combined nucleation effects of Pe-g-MAH (9 wt%) and the nanoclay. At 5 wt% nanoclay, the crystallinity decreased significantly due to an intercalated structure as opposed to an exfoliated structure.

Researchers evaluated the tensile strength, tear resistance, and impact strength of each blend. They found that tensile strength increases with the addition of nanoclay before falling at 3 wt%. At 3 wt% nanoclay, the tensile strength improved by about 23% due to a reinforcement effect from the clay’s dispersion.

Barrier Properties

Characterizing the material’s permeability to oxygen is the determining factor of whether it is usable in barrier film applications. Results of permeability characterization showed an improvement of 7.7% with 1 wt% nanoclay and 28% with 5 wt%. The clay layers create a twisted diffusion pathway, delaying diffusion of gas and water vapor.