Structural composites from post-consumer polypropylene carpets and different polyolefin resins

Carpets are heterogenous in nature and challenging to recycle due to their complex structures. Annually, they account for over 3 million tons (approximately 1.2%) of Municipal Solid Waste (MSW) in the U.S., with less than 10% being recycled. Most of this waste ends up in landfills, with no viable solution to prevent it. The most recycled plastic is polyethylene terephthalate (PET), which typically comes from plastic bottles, which are already easily recycled and even circularly used to make new bottles. In contrast, materials like bottle caps and retail bags, typically made of polyolefins, are often mixed with other materials such as labels, ink, and remnant products, which creates challenges for separation and recycling. A circular recycling approach for carpets and mixed polyolefins resins has not been successful. Conventional recycling methods tend to focus on economically viable plastics, such as nylon carpets and partially cleaned plastic bottles. However, these methods often recycle only the carpet tuft and the main body of the bottle, leaving the carpet backing and other components to be discarded in landfills. A more comprehensive solution to these challenges is to use entire carpets, along with bottle waste polyolefins, to produce functional composites. This approach not only maximizes material recovery but also reduces waste sent to landfills.This thesis focuses on a method developed to fabricate recycled composites from whole post-consumer polypropylene carpets combined with different recycled polyolefin resins through compression molding. The mechanical properties of these composites were evaluated using three-point flexural bend and creep compliance tests. The optimization involved careful screening of molding parameters to identify the best temperatures and resin-to-carpet ratios, maximizing mechanical properties while minimizing the use of resins and additives. This sustainable approach not only diverts carpet waste from landfills but also reduces the carbon footprint of plastic materials, offering a practical solution to a growing environmental challenge.