Supermarket plastic bags biotreatment in soil

Abstract

The plastic, since its invention by Alexander Parkes in 1862, has been very used to decrease commercial costs and feed consumerist tendency of modern society. Nowadays, the damages caused by plastic discard in environmental have reached large proportions. In the specific case of the supermarket bags, the raw material is the plastic film, produced from high and how density polyethylene (HDPE and LDPE, respectively). In Brazil, are produced 210 thousand ton/year of plastic film, representing 9,7% of at all country production. Plastic bags have left in the landfill obstruct the water flow, delaying the biodeterioration of biodegradable materials. Plastics have kept in the environmental during a long time, causing visual pollution and in some cases chemical pollution. Some alternatives are now motivated to minimize environmental impact due plastic bags discard. Oxybiodegradable plastics use is a possible way to decrease the degradation time of plastic materials in the environmental. Oxybiodegradable bags of supermarket have a short period of biodegradation, about 1 to 6 years, a time very short considering that usual synthetic plastics take about 200 years to biodegrade. Its degradation can be caused by light, heat and stress that influence the degradation rate. Plastic oxybiodegradation occurs in two steps: (1) the plastic is converted to molecular fragments by the O2 reaction, and (2) oxidated molecules are biodegradated, this is, converted to CO2, H2O and biomass by microorganisms. In polymers biodegradation two basic mechanisms are involved: biological hidrolysis and biological oxidation, depends on the polymer nature and the environmental conditions. The filler added to the oxybiodegradable bags processing has the function of beginning the polymer degradation in the O2 presence. The polymers used in market plastic bags are, basically: high density polyethylene (HDPE) and low density (LDPE). The first ones is the fourth thermoplastic soldier in the world and the second more recycled. This polymer has high strength to the impact, even in low temperatures, and good resistance to the chemical solvents. Its melting point its about 128-135ºC.LDPE is a thermoplastic with branch chains, which influence the crystallization degree and transition temperatures. This material has good properties: toughness, high resistance to the impact, high flexibility, besides of the good electric properties. Its application is significant as a feeding package, package of pharmaceutical and hospital products, toys, pipes, hoses and plasticized films. This project intends to analyse different supermarket bags (with oxybiodegradable filler and without) in relation to biodegradation in soil, using measurements of weight, infrared (FTIR), scan electronic microscopy (SEM) and contact angle. (AU)