The Interdependence of Biodegradability, Morphology and Mechanical Properties in Polyolefin Elastomer/Starch Blends

Hypothesis: Biodegradable polymer blends in comparison to petroleum-based polymers consume less energy in the production process, and do not produce environmental pollution due to their renewable sources. One of these biodegradable blends is polyolefin elastomer/starch (POE/S) blend. In this study, the effect of composition ratio of polyolefin elastomer/starch on properties such as mechanical, morphology, rheology and biodegradability properties of the blend were investigated. Because of non-polar microstructures of POE and polar starch, a polyolefin elastomer/maleic anhydride copolymer (POE-g-MAH) was used to improve their compatibility.
Blends of polyolefin elastomer and starch were prepared in presence of POE-g-MAH as synthetic compatibilizer with a Brabender internal mixer. The concentration of POE-g-MAH was fixed at 10 wt% and the content of starch in both binary and ternary blends was varied between 0 wt% and 55 wt%.
Findings: The results showed changes in the tensile, hardness, SEM micrographs, and void increasing after exposing the blends to fungi for three months at room temperature. To examine the compatibility of the blends, Fourier transform infrared spectroscopy (FTIR) was used. The observations of the scanning electron micrographs of polymer blends showed that by increasing the amount of starch from 15 to 55 wt%, the size of the dispersion phase increased; though it was reduced by adding 10 wt% of POE-g-MAH in the polymer blends. The rheology tests were carried out using rheometrics mechanical spectrometry (RMS) and the results indicated an increase in the complex viscosity, loss modulus and storage modulus after the addition of the compatibilizer into the blend. By adding starch to POE in the blend, the tensile strength and elongation-at-break decreased. The comparison between the blends with and without compatibilizer showed higher tensile strength and elongation-at-break for the blends with compatibilizer. The biodegradation experiments for the blend with 15 wt% of starch showed that the degradation of blend composition was negligible, but with higher starch content, the degradation rate increased and the blend with compatibilizer showed less degradation than the blend without compatibilizer.