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초록

A selective, solvent-based method was developed for the recovery of polyamide 6 (PA6) and polyamide 66 (PA66) from glass fiber-reinforced composites and post-consumer automotive waste. Formic acid was identified as a suitable dissolution solvent because of its high solvency for PA6 and PA66 at room temperature, whereas methanol served as an effective antisolvent for polymer precipitation. Process conditions such as the dissolution time, polymer concentration, and temperature were optimized to achieve high recovery efficiency. The polymer recovery yield exceeded 95% for the virgin composites and reached 98.9% for the waste-derived samples under the optimal conditions. Compared to the virgin composites, the thermal decomposition and melting temperature of the recovered polymers changed minimally, whereas the crystallinity increased slightly owing to filler removal. The molecular weight and polydispersity were maintained within the commercial range, indicating negligible degradation. The structural integrity of the polymer backbone was confirmed, and only trace amounts of the filler remained in the recovered products. This approach offers a scalable and low-energy strategy for recycling high-purity, engineered polyamides from complex waste streams.

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