Abstract
Research subject: The need to increase agricultural production in proportion to population growth and water crisis management requires initiatives that can increase the quantity and quality of crops by using soil moisture storage methods while preserving the environment. In this study, the effect of different wt. % of Thermoplastic starch (TPS) with maleic anhydride (MA) as compatibilizer and nanoclay (15A) on gel content and mechanical properties of Polylactic acid (PLA) and blends of  Linear low-density polyethylene/ Low-density polyethylene (LLDPE / LDPE) was evaluated.
Research approach: Here, 0, 10, 20 and 30 wt. % TPS were added to the blends of LLDPE/LDPE (20/80) and also PLA. Independent parameters in the experimental design were wt. % of TPS, basic polymer type that was PLA or TPS and aging test. For dependent parameters were considered gel content, tensile strength, elongation at break and elastic modulus. Experiments were designed in General Full Factorial Design and performed in three replications.
Main results: Gel content in LLDPE/LDPE blends increased with the addition of TPS and decreased for PLA blends. The gel content change range for experimental samples before and after the aging test was between 10 to 21 and 2 to 5 percent, respectively. Tensile strength and elongation at break were reduced by adding TPS in both series of compounds before aging test. But this reducing rate was less in the 20 wt. % of TPS. The values ​​of tensile strength and elongation at break were: 12 to 19 MPa and 50 to 350 percent, respectively. These values changed after the aging test between 7 and 11 MPa and from zero to 5 percent, respectively.
Keywords: biodegradability, low density polyethylene, poly lactic acid, thermoplastic starch.

Accumulation of polyethylene (PE) wastes has become a major environmental problem. The objective of this research was to assess the potential for microbial degradation of sun-treated low-density PE as a natural way to eliminate PE wastes in semi-industrial condition. Low-density polyethylene (LDPE) films were exposed to one month of sun radiation treatment and then cultured with two PE-degrading bacteria (Sphigobacterium moltivorum IRN11 and Delftia tsuruhatensis IRN27) in aerobic bioreactors over 100 days. Weight loss percentage of the PE and the culture pH were measured. Also, Changes in the chemical structure of the LDPE were assessed by FT-IR and surface erosion and microbial layer formation by bacterial activity was observed by Scanning Electron Microscopy. Partial increases in the culture pH were recorded during the incubation period. The weight loss percentage for T-LDPE samples cultured with Sphigobacterium moltivorum IRN11 and Delftia tsuruhatensis IRN27 was 3.31%±0.013 and 3.98%±0.025 in TLDPE samples, respectively, and functional carbonyl-groups in the TLDPE samples decreased significantly due to bacterial hydrolysis. SEM images showed the different microbial layer formation on sun-treated low-density polyethylene (T-LDPE) for both bacteria. Our results suggest that exposure of LDPE to sun radiation had a significant effect on biodegradation of Ld-PE films and that the two bacteria tested were able to enhance the biodegradation the T-LDPE.