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Oxo-Biodegradable Polymer By Modification Of Polyolefine

Polymers commonly used in large quantities are as packaging materials. The most of the synthetic polymers used as packaging materials derived from the types of polyolefins such as polystyrene and polypropylene, which can not be decomposed by microorganisms that exist in nature, which causes environmental pollution. Several ways have been used to reduce the increase in plastic waste, among others, by hoarding underground or incineration. However, both methods have a negative impact on the environment. The most popular alternative solution to reduce the plastic waste is by recycling. The difficulty is that the plastic mixture must be separated first according to the types of plastics before recycling, and also recycling results of the plastic waste usually have a lower quality than the plastic origin. A modification of non-biodegradable synthetic polymers with a biodegradable polymer producing environmentally friendly polymers is one of the alternative methods to resolve the above problem. At this time it has developed a modification of synthetic polymers that are non biodegradable polymers to become new polymers easily decomposed in nature known as oxobiodegradable polymers. Generally, a biodegradable plastic that can be decomposed by microorganism in nature includes biopolymers such as starch, cellulose, and polyesters, which are designed the breaking polymer chains by microorganisms to produce organic products that do not harm in the environment. While in oxo-biodegradable polymers, polymers with the addition of a pro-oxidant additive are designed the degradation of polymer through oxidationreduction reactions as a result of the influence of heat and UV rays, followed by the biodegra-dation by microorganisms, so that the polymer can be decomposed in nature with more easily, although it still takes time to degrade the polymer completely. Several researchers have developed oxo-biodegradable plastics that are environmentally friendly, with a mix of synthetic polymer with a variety of additives. TDPA (Totally Degradable Plastic Additives) is one of the pro-oxidant additives currently used commercially in the plastics industry, and these additives are still imported from abroad with a relatively high cost. This additive is complex and salts of organic compounds and multivalent transition metals such as Fe, Mn, or Co, which can initiate oxidative degradation to enhance the degradability of polymer, when the polymer is exposed to sunlight and oxygen.

Polypropylene (PP) is one of thermoplastic polymers produced commercially as plastic materials. This polymer resists to humidity and chemical, but it is easily oxidized due to the presence of tersier carbon atom in the backbone chain. Polypropylene is also difficult decomposed by microorganisms in environment.
Based on the above issues, the purpose of this study was to modify polypropylene by adding pro-oxidant additives into the polymer to result the oxo-biodegradable polypropylene, so it can be used in various applications with no cause environmental problems, and also to obtain information on the effect of pro-oksidan additives on the properties of the oxobiodegradable polypropylene, including their biodegra-dability in nature. In particular composition of the pro-oxidant additives in polymers is expected to obtain oxo-biodegradable polymers with better properties. Therefore, in this study was focused on the preparation of the pro-oxidant additive for modifying properties of polypropylene to produce oxo-biodegradable polypropylene.

In this report is presented results of the pro-oxidant additive obtained by double decomposition reaction, the first reaction is saponification between stearic acid and sodium hydroxide in ethanol at 75oC for 4 hours under atmosphere nitrogen to produce sodium stearate, and the second reaction is trans-soponification between sodium stearate obtained in the first reaction and cobalt acetate at 75oC for 3 hours to result cobalt stearate with yield of 58.73%. Cobalt stearate was characterized by analysis functional groups with using FTIR that indicates the presence of absorption peaks at wave number around 1560 cm-1 which is an asymmetric vibrations of –C=O functional group that binds to the cobalt.

Figure 1. Surface morphology of SEM (a) Polypropylene and (b) Oxo-degradable polypropylene with 0.5% cobalt stearate after irradiation with UV for 10 days.

Figure 2. The surface morphology of the oxo-degradable polypropylene with using SEM (a). Before biodegradation,(b). After biodegradation for 30 days.

The addition of cobalt stearate as the oxidant additive in polypropylene at various concentrations, and followed by irradiation with UV light for up to 10 days showed a significant change in the absorption peak intensity at the wave number of 1700-1800 cm-1 which is a carbonyl functional group, and the increase the cobalt stearate concentration added into polypropylene, the absorption peak intensity of the carbonyl group increases. This result indicates that the pro-oxidant additive of cobalt stearate is quite active in oxidizing polymer by irradiation with UV light. Based on the analysis of the mechanical properties, the addition of cobalt stearate in polypropylene followed by irradiation with UV light can decrease the mechanical properties of polypropylene, and the higher concentration of cobalt stearate and the longer time of irradiation with UV light are given in polyproppylene, the stress and elongation of polymers decrease or the polymer films become more rigid. Results of biodegradation by microorganisms from the activated sludge showed that the percentage weight loss of polymers increases with the increasing incubation time and the concentration of cobalt stearate in polypropylene films. These results are supported by analysis the surface property of polymers films with using SEM before and after biodegradation for 30 days indicating the presence of a damage and porous in the surface of oxo-degradation polypropylene films after biodegradation for 30 days. These results indicate that the microorganisms of activated sludge could decompose polypropylene films by the addition of cobalt stearate as pro-oxidant additives in polymers and followed followed by irradiation with UV light.

1. Zufira Putri and I Made Arcana, Biodegradation Test of SPS-LS blends as Polymer Electrolyte Membrane Fuel Cells, The Fourth International Conference on Mathematics and Natural Sciences (ICMNS), ITB-Bandung, AIP Conference Proceedings 1589, 266 (2014)
2. I Made Arcana, Bunbun Bundjali, and Ni Ketut Hariyawati, Preparation of Polymers Electrolyte Membranes for Lithium Battery from Styrofoam Waste, Advanced Materials Research Vols. 875-877 (2014) pp 1529-1533

HEAD OF RESEARCH TEAM : Prof. Dr. I Made Arcana
TEAM MEMBERS : Dr. Bunbun Bundjali, MS; Hariyawati D., SSi., MM.
OFFICIAL ADDRESS : Inorganic and Physical Chemistry Research Groups, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha No. 10 Bandung 40132
EMAIL : arcana[at]