Degradation and Nanoplastics Formation due to External Stresses in Semicrystalline Polymers

Recently, it has been reported that semicrystalline polymers such as polyethylene terephthalate (PET) release nanoplastics (with sizes 10 nm – 1 $\mu$m) after a sufficient number of chain scission events have accumulated in the amorphous phase, triggered by hydrolysis or other processes. Due to the stability of crystalline domains, these pollutants tend to persist in the environment with a high potential for bio-accumulation and toxicity. Although the long tie-chains that hold the crystalline lamellae together can be shown to be particularly susceptible to early breakage, the exact mechanisms and the timescales of material failure that lead to nanoplastics formation are unknown. The theory of thermally activated fracture developed by Eyring, Zhurkov, and Peterlin suggests that external stresses on polymers accelerate the rate of bond breaking. Thus, we expect samples under stress to create nanoplastics more readily than unstressed analogs. Here, we describe an experimental setup we designed to incorporate tensile stress (constant load) in PET samples undergoing hydrolysis. We report 1) the change in the induction time for nanoplastics formation, and 2) their resulting number, size and shape distribution as a function of applied stress.