The Use of Natural Rubber as an Initiator of LDPE Biodegradation in Soil

TL;DR

This study shows that adding natural rubber to low-density polyethylene can significantly speed up its biodegradation in soil.

Contribution

The novel finding is that natural rubber forms an interpenetrating structure with LDPE, initiating biodegradation when buried in soil.

Findings

At 50% natural rubber content, LDPE samples lost 70% of their mass after soil exposure.

Natural rubber above 30% concentration forms an interpenetrating structure with LDPE, accelerating biodegradation.

Soil burial caused a significant decrease in LDPE crystallinity and molecular weight.

Abstract

The control of the quantities of multi-tonnage polymers, in particular, making them biodegradable, is an urgent task. This study suggests a new approach in the application of natural rubber (NR) as an initiator of biodegradation of low-density polyethylene (LDPE) in soil. The study examines the structure, properties and rates of biodegradation of thin LDPE films with different content of NR. Such methods as fourier transform infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscope (SEM), atomic force microscopy (AFM), gel-permeation chromatography (GPC), and acoustic microscopy were used for the most complete characterization of NR/LDPE composite systems. It was shown for the first time that at concentrations above 30%, NR is able to form an interpenetrating structure with the LDPE matrix, which has a decisive effect on the initiation of biodegradation during exposure in soil. Thus, the composition with 50% natural rubber exhibits the highest mass loss. The sample with 50% natural rubber content lost 70% of its mass, while the one with 40% NR content lost 38%. Furthermore, after soil burial, a significant decrease in crystallinity was observed: from 39.5% to 31.5% for the 90/10 composition and from 39.1% to 24.2% for the 50/50 composition. The results obtained are confirmed by a noticeable decrease in the molecular weight characteristics of LDPE.

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