Biodegradation of epoxidized sunflower oil (ESO) and epoxidized soya bean oil (ESBO).
Poly(vinyl chloride) (PVC) is an extensively used thermoplastic material because of its valuable properties, such as superior mechanical and physical properties, high chemical and abrasion resistance, and widely utilized in durable applications, e.g. for pipes, window profiles, house siding, wire cable insulation and flooring [4,8].
The poor thermal stability of PVC requires the use of heat stabilisers in the processing of the polymer. Applicable stabilizers are heavy metals and organotin compounds as well as organic co-stabilizers, depending on the desired product properties .
The lead based stabilisers are classified like toxic for the reproduction, harmful, dangerous for the environment (ecotoxic) and presenting a danger of cumulated effects . For that, alternative additives have been proposed such as epoxidized vegetal oils that are of great importance in polymer industry [2,3]. Vegetable oils are renewable raw materials. Their conversion to useful intermediates for polymeric materials is significant because of their low cost, ready availability, and possible biodegradability.
Biodegradation of stabilisers in the soil:
This part describes the validation and application of a simple respirometer system designed to assess mineralization of the stabilizers: ESO and ESBO under defined conditions. The soil used in this study was collected near a landfill.
For biodegradation in soil, there are validity criteria such as [6,7]:
* The release of C[O.sub.2] by the witness soil must be less than 20% of the average value of the C[O.sub.2] produced by the other samples;
* C/N must be included between 10/1 and 40/1;
* Temperature: it is important to be in the usual conditions for the development of the microorganisms in the soil. In our case, the temperature was set at 28[degrees]C;
* Concentration of substrate in the soil: the amount of substrate used should be sufficient for the release of C[O.sub.2]. In practice, a mass greater than 0.5 mg of sample per gram of soil is used;
* Aeration of the medium is necessary since we want to be in aerobic condition. It is done with air devoid of C[O.sub.2]. The ultimate biodegradation is to run the production of C[O.sub.2], that is to say, the mineralization of organic matter.
The rate of biodegradation is calculated according to the following equation:
% biodegradation of substrate = [C[O.sub.2(soil+subtrant)] - C[O.sub.2]]/C[O.sub.2th] x 100 (1)
C[O.sub.2] (soil + substrate) is the cumulative amount of C[O.sub.2] released by the soil-substrate (mg);
C[O.sub.2] (soil) is the average amount of C[O.sub.2] released by the control soil in mg;
C[O.sub.2] th: is the theoretical content of C[O.sub.2] that may be produced by the test material (substrate) in mg. It is calculated according to the following equation :
C[O.sub.2th] = [M.sub.TOT] x [C.sub.TOT] x 44/12 (2)
[M.sub.TOT]: is the mass of total solids of the material test introduced into the composting vessels at the beginning of the essay in grams;
[C.sub.TOT]: is the relative content of total organic carbon of the total solids contained in the test material, in grams per gram of soil;
44 and 12 are the molecular and atomic weights of carbon dioxide and carbon, respectively.
Daily production of C[O.sub.2]:
The curve of the daily production of C[O.sub.2] obtained after incubation is shown in Figure 1. The results show that, in soils containing ESO and ESBO, the respirometric activity pass by three phases. The first one in which there is a release of C[O.sub.2] corresponds to the degradation of the most labile substances. From the ten day, the decay phase of the biological activity begins, due to the decrease of easily metabolized compounds. After the twenty second day, the Mineralization continues, but slowly and it is characterized by a low release of C[O.sub.2] from the biodegradation of the most resistant substance. Globally, it can be noted that the amount of Daily CO2 produced in the soil enriched by ESO is relatively higher compared to the soil enriched by ESBO.
Cumulative production of C[O.sub.2]:
The cumulative production of C[O.sub.2] after incubation is represented in Figure 2. The results showed that the cumulative amount of C[O.sub.2] increased with the time of incubation. The results show that the cumulative amount of C[O.sub.2] is much higher in the case of soil enriched by ESO Compared to the soil enriched by ESBO. This result lead to say that the biodegradation of ESO is more important compared to that of ESBO.
The rate of biodegradation is calculated using the equations 1 and 2. Figure 3 shows the evolution of the biodegradation rate as function of time.
The following various phases were observed in the case of soil enriched by the ESO and ESBO:
The results showed that after the thirty-one day of incubation, the rate of biodegradation of ESO is equal to 10,80%, while the rate mineralization of ESBO is equal to 9.70. The rate of biodegradation is relatively higher in the case of soil containing the ESO compared to the soil containing ESBO, this result leads to say that the epoxidized sunflower oil is relatively more biodegradable compared to the epoxidized soy bean oil.
The tests show that the ESO is more biodegradable than the ESBO. The results showed that after the thirtyone day of incubation, the rate of biodegradation of ESO is equal to 10,80 %, while the rate mineralization of ESBO is equal to 9.70.
 Green book, 2000. Environmental problems of PVC. Commission of the European communities COM 469.
 Lardjane, N., N. Belhaneche-Bensemra and V. Massardier, 2011. Soil Burial Degradation of New Biobased Additives: I/ Rigid Poly (vinyl chloride) Films. Journal of Vinyl and Additive Technology, 17: 98104.
 Lardjane, N., N. Belhaneche-Bensemra and V. Massardier, 2013. Soil Burial Degradation of New Biobased Additives: Part II. Plasticized Poly (vinyl chloride) Films. Journal of Vinyl and Additive Technology, 19: 183-191.
 Mensker, K.C., G.T. Fedoseeva, editors, 1979. The degradation and stabilization of PVC. USSR: Chemistry Press.
 Murphy, J., 2003. Additives for plastics handbook. Second ed.; Elsevier Advanced Technology: Oxford.
 Norme Internationale, ISO/CD 17556, 1999. Determination of ultime aerobic biodegradability in soil by measuring the oxygen demand in a resperometer or amount of carbon dioxid released.
 Norme Internationale ISO 14855, 1999. Evaluation de la biodegradabilite aerobie ultime et de la desintegration des materiaux plastiques dans des conditions controlees de compostage : Methode par analyse du dioxyde de carbone libere.
 Vogl, O., G.C. Berry, 2002. Thermal properties of poly(vinyl chloride)/montmorillonite nanocomposites Editors. Prog Polym Sci., 27: 2133.
N. Lardjane, Y. Medkour, N. Belhaneche-Bensemra
Laboratoire des Sciences et Techniques de l 'Environnement. Departement de Genie de l'Environnement, Ecole Nationals Polytechnique, BP 182 El-Harrach, Alger, Algerie
Address For Correspondence:
N. Lardjane, Laboratoire des Sciences et T echniques de l'Environnement. Departement de Genie de l'Environnement, Ecole Nationale Polytechnique, BP 182 El-Harrach, Alger, Algerie
Received 12 August 2016; Accepted 17 December 2016; Available online 31 December 2016
Caption: Fig. 1: Daily production of C[O.sub.2] as function of time.
Caption: Fig. 2: Cumulative production of C[O.sub.2] as function of time.
Caption: Fig. 3: Biodegradation rate as function of time.