**E**ff**ect of Natural Rubber in Polyethylene Composites on Morphology, Mechanical Properties and Biodegradability**

**Elena Mastalygina 1,2,\*, Ivetta Varyan 1,2, Natalya Kolesnikova 2, Maria Isabel Cabrera Gonzalez <sup>3</sup> and Anatoly Popov 1,2**


Received: 28 December 2019; Accepted: 7 February 2020; Published: 13 February 2020

**Abstract:** Compounding natural additives with synthetic polymers allows developing more eco-friendly materials with enhanced biodegradability. The composite films based on low-density polyethylene (PE) with different content of natural rubber (NR) (10–30 wt%) were investigated. The influence of NR content on structural features, water absorption and mechanical properties of the composites were studied. The 70PE/30NR composite is characterized by the uniform distribution and the smallest size of NR domains (45 ± 5 μm). A tensile test was satisfied by the mechanical properties of the biocomposites, caused by elasticity of NR domains. The tensile strength of 70PE/30NR composite film is 5 ± 0.25 MPa. Higher water absorption of PE/NR composites (1.5–3.7 wt%) compared to neat PE facilitates penetrating vital activity products of microorganisms. Mycological test with mold fungi and full-scale soil test detected the composite with 30 wt% of NR as the most biodegradable (mass loss was 7.2 wt% for 90 days). According to infrared spectroscopy and differential scanning calorimetry analysis, NR consumption and PE structural changes in the biocomposites after exposure to soil occurred. The PE/NR composites with enhanced biodegradability as well as satisfied mechanical and technological properties have potential applications in packaging and agricultural films.

**Keywords:** packaging material; bio-based polymer composite; polyethylene; natural rubber; water absorption; mycological test; biodegradability; mechanical properties
