Characterization of polystyrene and polyacrylic based polymeric materials exposed to oxidative degradation

The characterization of oxidative degraded polystyrene-based resin (R1) and polyacrylic based resin (R2) resins in H2O2 and HClO4 degradation medium were made based on the kinetics and thermodynamic data obtained for the ion-isotopic exchange reactions using such resins. For the reactions performed by using resins degraded in H2O2 medium, the reaction rate (k) values obtained for the fresh R1 (0.315 min–1) and R2 (0.187 min–1) resins decreases to 0.300 and 0.155 min–1 respectively for the resins degraded in 20% H2O2 medium, which further decreases to 0.289 and 0.142 min–1 respectively for the resins degraded in 30% H2O2 medium. A similar trend in the results were observed for the reactions performed by using the above resins degraded in HClO4 medium. The higher values of k (min–1) and low values of various thermodynamic parameters for the ion-isotopic exchange reactions performed by using fresh and degraded polystyrene-based resin R1 resins suggests superior degradation stability as compared to polyacrylic based R2 resin.

Application Potential Analysis of Enhanced Oil Recovery by Biopolymer-Producing Bacteria and Biosurfactant-Producing Bacteria Compound Flooding

To study the feasibility of polymer-producing bacteria Enterobacter cloacae (E. cloacae) FY-07 and surfactant-producing bacteria Pseudomonas aeruginosa WJ-1 combined profile control and flooding, the compatibility of FY-07 and WJ-1 was evaluated using laboratory experiments. The results showed that the growth and metabolism of WJ-1 was not significantly affected by the FY-07 in the degradation medium, and the surface tension of fermentation broth was reduced from 70 mN/m to 30 mN/m. FY-07 enhanced the degradation of WJ-1, increasing the ratio of C14- to C15+ from 0.37 to 0.67. The core-flooding experiments indicated the oil recovery of 17.4% when both FY-07 and WJ-1 were injected into the system, as against to 10.4% and 7.9% for FY-07 and WJ-1, respectively, when injected alone. The results demonstrate a good compatibility between the FY-07 and WJ-1 strains and highlight the application potential of stain FY-07 and strain WJ-1 compound flooding for enhancing the oil recovery in heterogeneous reservoirs.

One Year Evaluation of Material Properties Changes of Polylactide Parts in Various Hydrolytic Degradation Conditions

Biodegradable biocompatible materials are widely used in medical applications. Determining the possibility of using biodegradable materials depends on determining the changes in their parameters over time due to degradation. The current scientific research on biodegradable materials has presented results based on research methods characterized by the different geometry and cross-section size of the specimen, type of degradation medium, or different pH value of the medium or maximum degradation time. This paper presents the results of a one-year study on the influence of the type of degradation medium on the changes in mechanical behavior and the uptake of the degradation medium by biodegradable specimens with large cross-sections. In addition, a prototype of a test stand was created, which allowed for the specimens to be stored vertically to ensure regular medium exposure and eliminate the interaction of the surface of the tested specimens with the sides of the container. The obtained results allowed the statistical significance of differences in the mechanical parameters determined in the uniaxial tensile test after 2, 4, 6, 12, 26, 39, and 52 weeks of degradation to be indicated depending on the type of degradation medium. It was proven that the changes in mechanical behavior depend on the percentage change in the mass of the specimens during degradation. The percentage change in mass depends on the type of degradation medium. Based on the results of this research, it was noted that in long-term degradation above 12 weeks, buffered sodium chloride solution is the optimal choice for the degradation medium. However, distilled water or physiological saline solution can be used as an alternative during the degradation period for up to 12 weeks.

Researches of liquid contaminants influence on change of hardness of agricultural tyre tread

Tyres represent the only element which connects a vehicle with a roadway and they are one of the most important parts of the vehicle. Investigated samples from chosen agricultural tyres were placed into a degradation medium. Degradation media were chosen on the basis of their supposed application; the second criterion of the choice was operating liquids used in machines. A primary aim was defining a change of hardness of these samples; the second-rate aim was observing changes of a tyre weight. The aim of the research is an evaluation of the hardness change in surface layers of a tread depending on specific degradation environments to which the tyre is potentially exposed. The highest influence on the hardness was proved in the case of diesel oil and engine oil. Any essential influence of NPK fertilizer solution was not proved. The effect of water and a solution of NaCl on the hardness change was minimal.

Degradation medium of agrocomplex – adhesive bonded joints interaction

Research of degradation medium occurring in agrocomplex at the current interaction with bonded joints strength and lifetime is desired owing to the possibilities of bonding applications in this dynamically developing field. The bonding technology is used in construction of machines, lines and devices of agriculture, forestry and food industry. Among the perspectives of bonding technologies the adhesive bonding can be considered thanks to its predominant pluses. At the bonding technology or more precisely adhesive bonding technology application the limits must be characterized, which occur in the process of application in the concrete medium. On the basis of characteristics and analyses the countermeasures eliminating the negative factors can be taken. Published results set themselves the goal to know degradation processes taking place in bonded joints contemporarily with taking account of adhesive/adherend interaction with accent on application in agriculture. Experimentally found results confirm the presumption of a significant portion of the adhesive layer on the adhesive bond strength decrease in the practice due to the degradation processes.

Studies on the transformation of selected polychlorinated biphenyl congeners by Pseudomonas strain LB 400

Resting cells of Pseudomonas strain LB400 are known to transform polychlorinated biphenyls (PCBs) when the cells are previously grown on biphenyl. In this study, PCB transformation was also observed in resting cells grown on other substrates such as glucose and glycerol. The presence of PCB congeners in the growth medium increased the lag phase for the growth of cells on a biphenyl substrate but not on a glycerol substrate. Supplementation of the degradation medium with biphenyl dramatically decreased the rate of PCB congener transformation, while the presence of glycerol or glucose had little or no effect on PCB transformation rates. Removal rates with biphenyl-grown cells in the standard degradation medium for 2,4,2′,4′-tetrachlorobiphenyl, 2,4,5,2′,5′-pentachlorobiphenyl, and 2,3-dichlorobiphenyl were 1.06, 1.66, and 224 μmol/(L∙h), respectively. Relative rates of transformation of 2,3-dichlorobiphenyl by biphenyl-, glucose-, and glycerol-grown cells were 100:36:36 and were similar to the relative rates of transformation of 2,4,5,2′,5′-pentachlorobiphenyl (100:33:42). The presence of PCBs adversely affected cell viability of biphenyl-grown cells over a 48-h incubation period and may explain the decline observed in PCB conversion capacity over the same incubation period. A major objective of this study was to investigate the significance of using biphenyl as the carbon source for growth of Pseudomonas strain LB400 cells capable of PCB transformation. Our findings indicate that, whereas higher rates of transformation of PCBs are observed with biphenyl-grown cells, cells grown on other carbon sources retain PCB-transforming enzymes. In addition, it has been demonstrated that biphenyl inhibits transformation of PCBs by the organism, whereas glycerol or glucose does not.Key words: Pseudomonas strain LB400, polychlorinated biphenyls, degradation, biphenyl.