Investigation of physical and rheological properties of LDPE / HDPE /thermoplastic starch biodegradable blend films

In this work, low‐density polyethylene/high‐density polyethylene/thermoplastic starch (LDPE/HDPE/TS) films were prepared with different compositions to obtain environmentally friendly materials. LDPE/HDPE/TS blends, at ratios of 95:5:15, 90:10:15, 85:15:15, 85:15:20, 85:15:25, and 85:15:30, were processed into thin films by a single‐step single‐screw extrusion. Fourier transform infrared spectra and scanning electron microscopy (SEM) micrographs confirmed the immiscibility of matrices and TS in the blend. In the SEM images, relatively good surface adhesion between matrix and starch was observed due to the presence of HDPE and glycerol in blends at low TS content. Differential scanning calorimetry analysis depicted an increase in the percentage of crystallinity with increasing HDPE. Starch presence in the blend had a more pronounced effect on the crystallization of HDPE when compared to LDPE with the long chain branching. Water absorption of the samples decreased with increasing HDPE and increased with TS content. The rheological properties of LDPE/HDPE/TS blends were investigated before and after biodegradation. Results were fitted with well‐known rheological models to achieve more valuable data about the effect of the composition as well degradation condition on the blend property. By adding HDPE in the blends, rheological properties close to the neat LDPE were obtained for LDPE/HDPE/TS films in the melt state.