Thermoplastic Starch and Mica Clay Composites as Biodegradable Mulching Films

Abstract

Multifunctional horticultural mulches satisfy different agronomic needs: control weeds and insects, reduction of water evaporation and soil erosion, as well as prevention of soil splashing on fruits and vegetables. In recent years, biodegradable mulches as substitutes of non-degradable materials have gained relevance in accordance with more environmentally friendly policies. Accordingly, mulching films based on composites of thermoplastic starch (TPS) reinforced with mica clay (MC) particles were developed. Obtained films resulted flexible and those containing MC evidenced a reddish coloration attributed to the high iron content in the mineral. The incorporation of MC within TPS significantly reduced the direct transmissivity coefficients in the photosynthetically active radiation region (radiation that employ green plants for photosynthesis), reaching a decrease of ~ 82% for TPS composites with 5% w/w particles. These results are very interesting for mulching since films could prevent the weed growth that competes with the crop. The presence of 5% w/w MC increased 3.9 times the sun protection factor and 1.3 times the UVB protection of TPS films. As it was expected, materials with MC resulted less transparent than films without the particles. Mineral particles could contribute to preserve the TPS films integrity during the crop cycle since adding 1 and 5% w/w MC decreased the materials disintegration after 30 days of composting in ~ 35 and ~ 57%, respectively. Observations from preliminary agronomic assays showed a well-growth seed of arugula, lettuce and pepper when TPS based materials and TPS mica clay composites were used as mulching films.