Abstract
Blending polyolefins with certain types of natural polymers like starch can be beneficial to their biodegradation. The impact of alpha-amylase on the biodegradation of low-density polyethylene (LDPE)-starch blend samples in an aqueous solution was investigated through characterizing their physical, mechanical and chemical properties. Results indicated that the weight and tensile strength of the enzyme treated samples were reduced by 48% and 87% respectively. Moreover, differential scanning calorimetry (DSC) showed an increase in fusion enthalpy of degraded samples which means that the crystallinity has been increased. The biodegradation of LLDPE appeared in Fourier-transform infrared spectroscopy (FT-IR) through the reduction in the intensity of the related peaks. This observation was supported by energy dispersive x-ray spectroscopy (EDXS) analysis where decreasing the percentage of carbon atoms in the treated blend was obtained. Likewise, the gel permeation chromatography (GPC) results pointed to a significant reduction in both the molecular weight and viscosity of LDPE more than 70% and 60% respectively. Furthermore, thermal gravimetric analysis (TGA) affirmed the function of amylase in degradation of the blend. On the basis of the obtained results, it can be claimed that the main backbone of the polymer, as well as the side branches, have been scissored by the enzyme activity. In other words, alpha-amylase has a promiscuous cometabolic effect on biodegradation of LDPE in polymer-starch blends.
Highlights
Polyolefins have been extensively utilized in a wide range of industrial and domestic applications
Differential scanning calorimetry (DSC) was used to measure the enthalpy of fusion, melting extrapolated onset temperature (Teim), melting peak temperature (Tpm) and melting extrapolated end temperature (Tefm) which indicates the degree of crystallinity and molecular weight range of the polymer in the samples
More crystallinity has occurred in samples after biodegradation process which is in agreement with the reported results[15,35]
Summary
Polyolefins have been extensively utilized in a wide range of industrial and domestic applications. The fusion enthalpy of PE-starch blends after treatment with alpha-amylase (Aα) was obtained more than that of the untreated samples (A0).
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