Management strategies for uncured thermoset and thermoplastic prepreg waste: A Review

The prepregs life-cycle generates a substantial amount of waste, primary in the form of offcuts. The predominant disposal method, landfilling, is both environmentally and economically unsustainable. Despite the existence of thermal, chemical and mechanical recycling methods, the uncured state of the waste allows for direct reformatting into a new material form, constituted by regular prepreg patches, therefore termed ”Prepreg Patch-Based Material” (PPBM). This potentially brings to the advantages of lower environmental burdens and higher properties retention. This review explores the suitability of the PBM format to thermoset and thermoplastics prepreg offcuts (PPOs). Firstly, the technologies for PPBMs production and processing are presented, distinguishing random and engineered formats. Then, the meso-structure of each PBM form is extensively discussed and its link with the resulting material properties is unveiled. A discussion of the stress transfer mechanics in PBMs is provided for both engineered and random systems, highlighting the role of the different variables into play. Subsequently, the review presents the complication of establishing a circular framework using PPOs as secondary raw material, including materials aging, cutting and backing paper removal. The potential environmental benefits are assessed through LCA methodology. Finally, the benefits and limitations of engineered and random PPBMs are critically discussed in comparison to recycled fibers systems, and the main technological gaps for the implementation of reformatting are uncovered.