The aim of this work is to prepare biodegradable blends of low-density polyethylene (LDPE) and starch that can be used for film blowing. In order to increase the compatibility between LDPE and starch, maleic anhydride was used to graft onto the LDPE molecules (LDPE-g-MAH). Mechanical properties together with the soil and enzyme degradation tests of the LDPE/starch and LDPE-g-MAH/starch specimens were studied. After using the proper composition and processing condition, the a f and values of LDPE-g-MAH/starch blown film specimen are significantly higher than those of the LDPE/starch film specimens with the same starch contents. The biodegradation tests showed that most of the starch particles present in LDPE/starch and LDPE-g-MAH/starch specimens can be degraded within 6weeks.
Journal of Polymer EngineeringLDPE-g-MAH; it was 122.2J/m when the concentration of LDPE-g-MAH was 9wt%. Wang, Liu et al. 161 studied the effect of glycerol and LDPE-g-MAH on the properties of LDPE and rice starch blends. As the result, both the tensile strength and the elongation at break followed the order of rice starch/LDPE/glycerol/LDPE-g-MAH blends > rice starch/LDPE/glycerol > LDPE/rice starch blends. The purpose of this study was devoted to prepare the LDPE/biodegradable starch blends by the simple melt blending method, to systematically investigate their structure and properties, and to propose the optimal conditions for application in blowing of plastic bags. In addition, the maleic anhydride grafted LDPE (LDPE-g-MAH) was studied as an alternative to LDPE. The blends obtained at 165°C were characterized by a Fourier transform infrared (FTIR) spectroscopy, a differential scanning calorimetry (DSC), a scanning electron microscopy (SEM) and the Instron mechanical tester. Moreover, the biodegradability of the synthesized hybrids was performed by evaluating weight loss of samples over time in the soil environment and the enzyme environment.
EXPERIMENTAL
MaterialsThe low-density polyethylene (LDPE), which was obtained from Asia Polymer Corp. (Taiwan, ROC), had a melt flow index of 0.5g/10min and a density of 923kg/m 3 . The corn starch, composed of 27% amylose and 73%amylopectin, was received from Sigma Chemical Corp. (Steinheim, Germany). The starch was dried at 105°C for 24 hours to a moisture content of less than 1%, before blending. Maleic anhydride (ΜΑΗ) and dicumyl peroxide (DCP) were commercial products of Aldrich (Milwaukee, WI).Before use, ΜΑΗ was purified by recrystallization from chloroform and DCP was recrystallized twice by dissolving it in absolute methanol, filtering the solution while hot, and chilling in ice water.
Samples Preparation
LDPE-g-MAH copolymerChoosing DCP as an initiator, the graft reaction of ΜΑΗ onto LDPE was 485 Journal of Polymer Engineering 2 week 4 week 5 week 6 weekFig. 14: SEM micrographs of the LDPE-g-MAH/starch (60 wt %) specimens at different exposure times under α-amylase enzyme environment.