Effect of Diverse Weathering Conditions on the Physicochemical Properties of Biodegradable Plastic Mulches
Hayes, D. G., L. C. Wadsworth, H. Y., Sintim, M. Flury, M. English, S. M. Schaeffer, and A. M. Saxton.  2017.  Polymer Testing, 62: 454-467.

Abstract:
The effect of simulated and agricultural weathering in two diverse US regions: Tennessee (TN) and Washington (WA), on the physicochemical properties of three commercially available biodegradable plastic mulch films (BDMs), and an experimental polylactic acid/polyhydroxyalkanoate (PLA/PHA) mulch was investigated to assess the potential impact of weather on mulch performance in specialty crop production. The tensile strength and thermostability of PLA/PHA increased by weathering, suggesting the formation of cross-links between the polyesters and inorganic filler. The decrease of mechanical properties for the commercially available BDMs differed slightly: simulated weathering > TN > WA. Chemical bonding changes due to photodegradative, hydrolytic, and oxidative reactions followed the order: TN > WA > simulated weathering. The differences reflect the higher moisture and temperature for TN compared to WA, and that simulated weathering did not mimic many secondary environmental factors, since ultraviolet radiation exposure was nearly equal between weathering treatments.