Process optimization for sustainable composites from post-consumer PET carpet and recycled PET resin

Abstract

In the United States, over 90 % of discarded carpets end up in landfills, primarily due to the costly and time-consuming process of mechanically separating carpet fibers from their backing. This research uses a novel approach for reusing post-consumer polyethylene terephthalate (PET) by developing recycled composites from post-consumer PET carpet (cPET) and recycled PET (rPET) resin sourced from bottle discards via compression molding. Incorporating whole carpets in the process significantly reduces preprocessing costs and time. A design of experiments approach was employed with variables such as temperature, pressure, dwell time, and composition to optimize mechanical properties. A two-level fractional factorial design for screening followed by a three-level full factorial design was performed to identify suitable processing parameters to achieve better mechanical properties. The optimal molding processing conditions for rPET/cPET (30/70) composites were identified as 270 °C for 250 s under 1 MPa, which yielded a flexural strength of 54.6 ± 6.0 MPa and a flexural modulus of 3180 ± 110 MPa, as verified through reproducibility testing on 10 samples (2 samples each from 5 molding experiments). These enhanced mechanical properties showcase the potential of rPET/cPET composites for structural applications. The composites made up of 30 % recycled PET resin and 70 % post-consumer PET carpet show that a larger fraction of carpet offers a sustainable alternative approach to reduce landfill waste from carpets and develop environmentally friendly materials with good structural integrity.