Studies on the recycling of glycolyzed nylon 66 using novel chain extenders

Nylon 66 (NY66) polymer based products widely used in automotive applications undergo deterioration in their mechanical properties when repeatedly exposed to ethylene glycol (EG) solution. In this study, recycling of glycolyzed NY66 (g-NY66) samples was carried out through melt-compounding with novel isocyanate based chain extenders namely hexamethylene 1,6-dicarbamoyl dicaprolactam (HDC) and tolylene 2,4-dicarbamoyl dicaprolactam (TDC). The recycling efficiency of HDC and TDC on g-NY66 was compared with two commercially available chain extenders 1,1-carbonyl biscaprolactam (CBC) and 1,3-phenylene bis(2-oxazoline) (PBO), and the resultant changes in molecular weight, melt flow, and crystallization behavior in the modified NY66 samples were confirmed from intrinsic viscosity, rheology, and differential scanning calorimetry measurements, respectively. The active ingredients (isocyanate and ɛ-caprolactam) liberated from HDC and TDC during the melt-compounding process reacted efficiently with the end groups of g-NY66 (–OH and –NH 2) resulting in improved molecular weight compared to g-NY66 and the results are reported in detail.