Research subject: Increasing plastic wastes of the packaging industry and concerns about their environmental problems, have attracted many researchers to use biopolymers. Therefore, the preparation of cheap biodegradable films with desirable properties for using in the packaging industry can be an attractive challenge.
Research approach: In this study, poly (lactic acid) (PLA) based ternary blends were prepared by experimental design (mixture method). For this purpose, thermoplastic starch (TPS) was first prepared using 28 wt% sorbitol and 14 wt% glycerol. Then, PLA / PCL (poly (caprolactone), PCL) / TPS ternary blends at different concentrations were prepared using the melt mixing method. Morphological, physical (tensile, water vapor permeability), biodegradability, and rheological tests were also carried out. Finally, the optimum sample was determined using Minitab software.
Main results: Scanning electron microscope (SEM) images revealed incompatibility and phase separation in the blends. Moreover, with increasing PCL and TPS contents, flexibility enhanced due to the plasticization effect of PCL and mechanical properties declined, respectively. The permeability test results showed that the samples containing less TPS due to its hydrophilic nature and more PCL leads to increase the crystallinity of the matrix, had lower water vapor permeability. The effect of TPS on the biodegradability test was also well established. In this way, the sample containing 35 wt% TPS loses about 50% of its weight within 14 weeks. Finally, the sample with 50/25/25 (PLA / PCL / TPS) composition was selected as the optimum sample by Minitab software. The results showed that the formulated films in this study have the potential to be used in biodegradable packaging materials with good mechanical and barrier properties.

Aims: The study of the behavior of active suspended fluid introduced a new topic for a wide range of applications such as reactors, microfluidic pumps, cultivating surfaces and antibacterial surfaces. The motility of bacterial suspension has generated a shear force (Hydrodynamic interaction) across the cells, which has an effect on the fluid viscosity. In this study, shear rheometer was used to evaluate the viscosity behavior of Escherichia coli (E. coli) in a water/polymer environment as a function of bacteria concentration and shear rate.
Materials and Methods: In the experimental study, the activity of E. coli was evaluated by choosing the constant concentration (0.01g/ml) and molecular weight of polyvinylpyrrolidone (360KDa). Also, the surface tensions of E. coli, Acetobacter xylinum, and S. aureus solutions were calculated using Wilhelmy test.
Findings: Activity of E. coli suspension results the lower viscosity comparing with the bacteria-free solution. The relative viscosities of the solutions were analyzed in a wide range of shear rates and bacterial concentrations. At a low shear rate up to1S^-1, the relative viscosity was found to be less than a unit value (Less than water). Also, due to the collective motility break up to smaller parts at high shear rates, the viscosity increased. The critical volume fraction was defined in determined bacterial concentration (0.8v/v) to analyze the collective movement of bacteria. The interfacial tension was reduced by bacteria presence of three different stain types that confirmed the effect of bacteria activity on the flow behavior.
Conclusion: The activity of E. coli bacteria makes it easy for fluid to flow at low shear rates. The viscosity reduction of active particle has a potential to demonstrate a variety of novel applications when a reduced energy level is needed.