Soil Burial Research Articles

Preparation of Rayon Fiber-Reinforced Polypropylene Composites by Extrusion Techniques

Hybrid composites from rayon fibers (∼2–5 cm size) and polypropylene (PP) were fabricated by using an extruder. Fibre content of the composite was varied from 5–30% by weight and physico-mechanical properties of the composites were measured. Surface morphology as observed by SEM showed good interface adhesion between rayon and PP matrix. Furthermore inclusion of rayon (up to 15% fiber inclusion) in the composite increased tensile, bending and hardness properties. As the fiber content in the composite increased more than 15%, physico-mechanical properties decreased due to the decrease of fiber matrix adhesion. The change of tensile properties due to environmental aging was carried out by keeping the composite under soil for 1 month and tensile properties were measured periodically. The aging result suggests that composites retained about 75% of its original tensile and bending strength even after 1 month soil burial. The modified fibers were also used for the study. As such the fibers were treated with vinyl-trimethyoxysilane and methanol solution and irradiated under UV before being used with PP in extruder. The results showed retardation of the physico-mechanical properties for composites obtained from irradiated rayon fibers than the composites fabricated from non irradiated rayon fibers.

Evaluation of Biodegradability of Poly(Butylene succinate-co-butylene Adipate) on the Basis of Copolymer Composition Determined by Thermally Assisted Hydrolysis and Methylation-Gas Chromatography

Biodegradability of poly(butylene succinate-co-butylene adipate) (PBSA) was studied based on its copolymer composition determined by thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) using trace amounts (20 µg) of the film samples. The copolymer compositions of butylene adipate (BA) units gradually decreased with soil burial degradation time, reflecting preferential biodegradation of BA moieties during soil burial due to their lower crystallinity. Furthermore, local differences in biodegradability of a given PBSA film after soil burial were also successfully evaluated.

Performance Evaluation of a Commercial Polyurethane Coating in Marine Environment

A material evaluation study has been carried out to determine corrosion behavior of a commercial polyurethane coating system (Souplethane 5) in the marine environment. The coating system is solvent free, two-component polyurethane protective coating. The performance of the coating on steel and rebar concrete was evaluated by conducting different types of tests which include atmospheric exposure, immersion in 5% sodium chloride solution, exposure to splash zone in seawater, salt fog, sabkha soil burial, and electrochemical tests, which include potentiodynamic polarization and AC impedance measurements. Uncoated, coated, and coated scribed specimens were used in each study. In general, the coating showed good corrosion resistance in marine environment. However, the coated samples, when subjected to break under applied compressive load, showed partial or complete detachment from the substrate, e.g., steel and rebar concrete. This appears to be the major drawback of the coating while applying on steel and concrete structures.

Soil burial degradation of new bio‐based additives. Part I. Rigid poly(vinyl chloride) films

AbstractCommercial sunflower oil was epoxidized, and the epoxidized sunflower oil (ESO) was used as a thermal stabilizer for poly(vinyl chloride) (PVC). Rigid formulations stabilized with ESO as a new stabilizer and epoxidized soybean oil (ESBO) as a commercial stabilizer for comparison were prepared. The aging of the PVC samples was investigated in landfill soil for 24 months. The structure modifications of the polymer were followed by Fourier transform infrared spectroscopy (FTIR). Furthermore, the variations of density and mechanical properties (tensile and Shore D hardness) were considered. The variations of the mass of the samples, the glass transition temperature (Tg), the molar mass distribution, and the weight loss were followed as a function of time of soil burial. The soil burial test showed the loss of additives by migration and biodegradation that led to the modification of density, mechanical properties, molar mass distribution, and weight loss of the PVC samples. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers

Soil Burial of Polyethylene-g-(Maleic Anhydride) Compatibilised LLDPE/Soya Powder Blends

This study examines the production of linear low density polyethylene (LLDPE)/soya powder blends to be used as alternatives to cellulosic material/polyolefin blends. LLDPE was blended with soya powder in a Haake internal mixer by melt mixing. Composition of the soya powder was varied from 5 wt% to 40 wt%. Polyethylene grafted maleic anhydride (PE-g-MA) was used as a compatibiliser. Environmental degradation was evaluated by composting the blends sample into the soil. It was found that for a higher soya powder composition, the degradation rate increased. Blends with compatibiliser degraded at lower rates than the uncompatibilised blends. The carbonyl indices of uncompatibilised blends subjected to the soil burial test were found to be higher than compatibilised blends. The weight loss changes in time data was collected and used to estimate the further changes by curve-fitting method. The complete degradation of the blends can be estimated from the kinetic curve. DSC results indicate that the crystallinity of the blends increased with increasing soya powder content added after composting.

Influence of antimicrobial finishes on the biodeterioration of cotton and cotton/polyester fabrics: Leaching versus bio-barrier formation

The influence of antimicrobial activity of two contemporary finishes, specifically a dispersion of colloidal silver (Ag) and 3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride (Si-QAC), on the degree of biodeterioration of 100% cotton (CO) fabric and fabric composed of a mixture of cotton and polyester (CO/PET) was studied. Ag was chosen for the leaching agent, while Si-QAC was used as the bio-barrier-forming agent. The biodeterioration of samples finished with different concentrations of Ag and Si-QAC was analysed from a standard soil burial test after 3, 6 and 12 days of exposure to soil microflora. SEM micrographs revealed intensive biodeterioration of the unfinished cellulose fibres, while the highly biologically resistant polyester fibres remained undamaged. A controlled release of Ag successfully inhibited biodeterioration of the cellulose fibres in the CO and CO/PET fabrics when its concentration reached a lethal, biocidal concentration. Contrary to the effects of Ag, the bio-barrier formation of Si-QAC on CO and CO/PET fabrics was insufficient to protect the cellulose fibres during longer periods of soil burial, irrespective of its concentration. Intensive chemical changes to the cellulose were clearly seen from the FT-IR spectra of all of the samples. The resistance of the polyester component to biodeterioration did not provide any significant protection for the cotton component in CO/PET fabric.

An environmentally compatible synthesis of polyesters derived from 5‐(2‐phthalimidoethanesulfonamido) isophthalic acid as a novel diacid monomer

AbstractA biologically active diacid monomer, 5‐(2‐phthalimidoethanesulfonamido) isophthalic acid (6), based on taurine, was easily prepared in three steps. Also a series of novel biologically active polyesters (PE)s were synthesized by the reaction of this monomer with several aromatic diols by step growth polymerization using tosyl chloride (TsCl)/dimethylformamide (DMF)/pyridine (Py) system as a condensing agent. The resulting new polymers were obtained in good to high yields with moderate inherent viscosities. All of the PEs were characterized by FTIR and some of them were also characterized by 1H‐NMR and elemental analyses methods. The thermal stability of PEs was evaluated with thermogravimetric analysis and differential scanning calorimetry techniques under a nitrogen atmosphere and it was found that they have moderate stability. Wheat seedlings were normally grown in the presence of 6 and it's derived PEs in soil. Also the high dehydrogenase activities in treated soils with obtained compounds showed biodegradability of polymers under soil burial in natural environments. It can be concluded that the synthesized compounds derived from taurine are possibly biologically active and environmentally nontoxic for soil microorganisms. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synthesis and characterization of novel biodegradable adsorbents based on carboxy methylchitosan–calixarenes

A novel biodegradable polymer, based on modification of carboxymethyl chitosan with calixarene units, was prepared and characterized by various analysis tools like: FTIR, SEM, XRD, and TGA. The thermal behavior of CMCh was investigated after its modification with the calixarene. Adsorption of various metal ions like: Ni 2+, Co 2+, and Cd 2+ was investigated for both parent CMCh and CMCh–CA. Dye-uptake behavior was also studied for both CMCh and CMCh–CA towards two types of dyes (acidic and cationic dye). The biodegradability of CMCh–CA was investigated under soil burial for weeks, as a possible solution to waste disposal problems through biological means because biodegradation offers an efficient or ‘green’ solution to tackle waste management.

Bio-based plastic a way for reduce municipal solid waste

There are many ways to reduce plastic waste in the environment. Bio-based plastic could be a best solution for sustainable environment. In this article bio-based plastic were prepared. Potato starch and corn starch as a biopolymer blending with polyethylene. Samples buried into soil for eight months and put in aerated sludge tank for 2 month. Weights lose of sampled after removing from degradation environment indicates a biodegradation rate. FTIR spectra before and after exposure to aerated sludge was done, Through FTIR spectroscopy, the biodegradability rate and reduction in some of the existing bonds in polymer before and after placing the samples inside aerated sludge tank is exhibited and the consumption of polymer by microorganisms is also revealed. Compare SEM before and after soil burial confirm biodegradability of compounds in the natural environment because polymer matrix consume by soil microorganisms.

High modulus regenerated cellulose fiber-reinforced cellulose acetate butyrate biocomposites

The properties of composites prepared with a matrix of biodegradable cellulose ester (cellulose acetate butyrate, CAB) and reinforced with regenerated cellulose lyocell fibers (lyocell/CAB) were studied and compared with short flax fiber-reinforced composites (flax/CAB), used as reference. The effect of the lyocell fiber content on the composite properties was also investigated. Tensile properties, dimensional stability, fiber—matrix compatibility, and biodegradability were investigated by tensile testing, water absorption test, scanning electron microscopic analysis, and soil burial test, respectively. From the results, it was shown how the Young’s modulus of lyocell/CAB composites increased from 2 GPa for neat CAB to 4 GPa for a composite with a lyocell fiber content of 34.8% (v/v). Similar trend was obtained for flax/CAB biocomposites which showed higher modulus than lyocell/CAB composites, with values of 5 GPa for a flax/CAB composite with the same composition. Moreover, tensile strength of lyocell/CAB composites with fiber content higher than 16.7% (v/v) resulted in lower values than neat CAB, indicating a high probability of failure cracks on lyocell/CAB composite samples when increasing fiber composition. In addition, compared to neat CAB, elongation at break decreased for all the composites studied. It was also observed that increasing the fiber content, the water absorption of the composites increased compared to neat CAB matrix due to the hydrophilic nature of the lyocell and flax fibers. The biodegradation test showed, after 60 days of soil burial, about 10% and 25% of mass lost for 34.8% (v/v) of lyocell/ CAB and flax/CAB composites, respectively.

Preliminary study on enhanced properties and biological resistance of chemically modified Acacia spp.

A preliminary experimental study was carried out to examine the ability of a chemically modified Acacia spp. to resist biodegradation. The modifications of Acacia mangium and Acacia hybridwere carried out by propionic anhydride and succinic anhydride in the presence of sodium formate as a catalyst. The treated samples were found resistant to microbial attack, while the untreated ones were damaged on 12 months exposure to a soil burial. The appearance grading, mass loss, mechanical properties, and scanning electron microscopy results revealed that chemical modification enhances the resistance of Acacia mangium and Acacia hybrid wood species to biodegradation.

Biodegradation and mildew resistance of naturally colored cottons

Naturally colored cottons contain significantly higher amounts of wax and have a different wax constitution and connectivity with cellulose than conventional cotton. Researchers have proposed that this wax content, together with the natural pigmentation, may serve as a defense against soil-borne pathogens. The purpose of this research is to study the biodegradation and mildew resistance characteristics of naturally colored cotton compared to conventional white and dyed cotton under field soil burial and laboratory mildew culture conditions. Laboratory culture results show that naturally brown and green colored cotton fabrics resist the growth of Aspergillius niger. However, after soil burial, both naturally brown and green cotton specimens showed severe degradation, manifested by significant loss of fabric strength as well as fiber structural damage. This suggests that naturally colored cottons are biodegradable. However, the rate of biodegradation of naturally colored cottons, especially green cotton, is much lower than that of white cotton or conventional dyed cotton.

Isolation and identification of polystyrene biodegrading bacteria from soil

With the increased production of municipal solid waste by the disposal of plastic materials, there is a need to develop new biodegradable materials and biodegrade existing plastic materials in daily use. Polystyrene and expanded polystyrene are commodity plastics that are extensively used in packaging and other applications. Six bacterial isolates were isolated from soil buried expanded polystyrene films showing adherence and growth with the polystyrene as a sole carbon source. Scanning electron microscopy (SEM) of the film surface used for isolation showed extensive microbial growth. The preliminary screening of biodegradation capability was done by Fourier transform infrared (FTIR) spectroscopy for surface chemical changes and high pressure liquid chromatography (HPLC) for analysis of biodegradation products. Bacterial isolates NA26, NB6, NB26 showed the production of biodegradation products in the extracellular media indicating biodegradation process. Key words: Polystyrene, bacteria, biodegradation, soil burial, FTIR.

Degradation of poly(3-hydroxybutyrate- co-3-hydroxyvalerate) by a newly isolated Actinomadura sp. AF-555, from soil

The purpose of this study was to isolate the poly (3-hydroxybutyrate- co-3-hydroxyvalerate) (PHBV) degrading microorganisms from soil, and the analysis of degradation by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. After soil burial for 120 days at 37 °C, a new actinobacterial strain, Actinomadura sp. AF-555, was isolated from the surface of PHBV film, through an enrichment technique. The increase in biomass on the surface of PHBV film pieces and in the medium after culturing in basal salt medium indicated that it utilizes PHBV as a source of carbon and energy. Scanning electron microscopy of PHBV film at the end of incubation showed many changes in surface morphology, such as erosion and extensive roughening of the surface with pit formation, as compared to the untreated plastic pieces. The FTIR spectra of PHBV film showed a decrease in the peak from 1725 cm −1 (untreated plastic film) to 1721 cm −1, and disappearance of a peak present in controls, at 2745 cm −1, indicating the breakdown of ester (>C O) or O–R groups and –C–H bonds, respectively. The intensity of the band at 1185 cm −1, the amorphous state-sensitive band, increased, indicating an increase in 3HV content. It can be concluded that soil contains microorganisms that can potentially be used for biodegradation of plastic wastes.

A Study of Biodegradation Behaviour of Dextrin Grafted Polyethylene by Soil Burial Method

Present studies report the biodegradation of dextrin grafted polyethylene (PE), successfully synthesized by graft co-polymerization method using benzoyl peroxide as the radical initiator. Biodegradable behaviour of the grafted PE was ascertained by soil burial test. Percent weight loss was measured as a function of number of days and it was observed that percent weight loss increased with increasing number of days. To further substantiate the degradation, microanalysis of the soil containing the samples was carried out. An increase in the colonies of microorganisms was observed with increasing number of days. The hydrolysis of the samples taken out from the soil after a specified number of days also corroborated the findings revealing continuous loss of weight. Effect of degradation of the grafted samples on the growth of plants (wheat and soybean) was studied and it was observed that the products of degradation are not harmful to the growth of the plants.

Atmospheric and soil degradation of aliphatic–aromatic polyester films

The degradation of an aliphatic–aromatic biodegradable polyester film was studied under conditions of solar exposure and soil burial in a tropical area. Film samples were evaluated for changes over 40 weeks by visual examination, scanning electronic microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, mechanical properties, molecular weight, gel content, and thermal properties. Photodegradation played a major role in the atmospheric degradation of the film, causing it to lose integrity and mechanical properties after week 8 due to main chain scission and crosslinking. SEM micrographs and FTIR spectra indicated that photodegradation started at the exposed side of the film and propagated through the polymer matrix after week 8. FTIR spectra also indicated that subsequent photooxidation processes took place. The reduction of molecular weight of the soil burial samples was much slower than that of the non-crosslinked portion of solar exposed film samples. The reduction of number average molecular weight of the non-crosslinked solar exposed samples followed a first order reaction, whereas the soil burial samples show a surface erosion biodegradation behavior. The relationship among total solar radiation, gel content and number average molecular weight indicated that an accumulated total solar radiation of 800 MJ/m 2, reached in approximately 7 weeks at the exposure site, is required for PBAT mulch film integrity loss.

Biological mineralization of organic matter in the modern virgin and plowed chernozems, buried chernozems, and fossil chernozems

The phenomenon of mineralization (biological mineralization) of organic matter in chernozems has been studied. A decrease in the content of Corg with time can be considered an index of the organic matter mineralization. It is suggested that the humus horizons of modern chernozems contain the pools of organic matter of different ages: easily decomposable organic matter, labile biologically active humus, stable biologically active humus, and relatively inert humus. The composition and mean residence times of these pools and their contribution to the total organic matter content have been estimated. The particular types of the biological mineralization have been determined on the basis of the comparison between the velocities of mineralization (M) and humification (H) processes: total unidirectional mineralization (M ≫ H), equilibrium mineralization (M ∼ H), nonequilibrium mineralization (M> <H), and zero mineralization. The separation of subtypes is based on data on the relative rates (%) of the organic matter mineralization. On the basis of available experimental data on chernozems buried under kurgans and in loess sediments (with the age of up to 800 ka), the quantitative relationship of the humus content in the buried soils on their age has been found; it has an exponential shape. During the first 100 ka after the soil burial, the soil humus content gradually (with a slowing intensity) decreases from 100–75 to 6.5% of its content in the virgin chernozems. Then, 100–1000 ka after the soil burial, the soil humus content remains approximately constant (6.5% of the initial level, or 0.3% of the soil mass). The rates of mineralization have been estimated. It is shown that the elemental composition (C, H, N, O) of humic acids remains relatively stable for a long time due to the regeneration of the chemical structure of humus (matric restoration of humus). It is suggested that several different forms of humus related to pedogenesis should be distinguished in the biosphere. The renewable humus in the equilibrium state with the environment is typical of the open biospheric (soil) systems. The fossil humus, whose content decreases with time, and whose composition remains stable, is typical of the semiclosed and closed systems. With time, it transforms into residual humus, whose content and composition remain stable. The fossilized organic matter in the fossil soils and sediments of the past geological epochs (Mesozoic and Paleozoic) considerably differs from the renewable, fossil, and residual humus.

Thermal analysis of soil-buried oxo-biodegradable polyethylene based blends

Low-density polyethylene (LDPE) blended with poly(3-hydroxybutyrate) (PHB) and additivated with pro-oxidant were soil buried for 180 days and characterized using thermogravimetry (TG) and differential scanning calorimetry (DSC). TG data showed that both onset and maximum rate degradation temperatures decreased as a function of biodegradation time. Apparent activation energies (Ea) using the Broido integral method decreased with the burial time increasing. PE crystallinity degree values increased in general up to 2 months of biodegradation. At the end of the soil burial (SB) test these values decreased principally for samples that were previously thermo-oxidized in an oven.

Potential Advantages of Poly(Acrylonitrile-Co-Methyl Acrylate)/Sodium Silicate Nanocomposites over P(An-Co-Ma) Copolymer

Poly (acrylonitrile-co-methyl acrylate) copolymer and P(AN-co-MA)/sodium silicate (SS) nanocomposite were synthesized via non-conventional emulsion method using an in situ transition metal complex Co(II)/EDTA and ammonium persulfate (APS) as initiator. The copolymer and nanocomposite so obtained were characterized and the results were compared. UV-visible spectral analysis revealed various interactions between the in situ complex and other reaction components. Infrared and 1H NMR spectra confirmed the formation of the P(AN-co-MA) copolymer and P(AN-co-MA)/SS nanocomposite. Furthermore, as evidenced by transmission electron microscopy (TEM), the composite obtained was found to have nano scale structure. X-ray diffraction (XRD) studies were carried out to analyze the aqueous dispersions of silicate with monomers, initiators, and monomers with initiators. For P(AN-co-MA) copolymer and P(AN-co-MA)/SS nanocomposite, XRD results confirmed that the silicate layers were exfoliated in the copolymer matrix during the polymerization process. An increase in the thermal stability for the nanocomposite was recorded by thermo gravimetric analysis (TGA). In comparison with the P(AN-co-MA) copolymer, the new P(AN-co-MA)/SS nanocomposite was found to show super absorbency and was biodegradable when tested by soil burial, activated sludge and cultured media and further confirmed by scanning electron microscopy (SEM).

Photo- and bio-degradation of poly(ester-urethane)s films based on poly[(R)-3-Hydroxybutyrate] and poly(ε-Caprolactone) blocks

Biodegradable segmented poly(ester-urethane)s derived from telechelic dihydroxy-poly[(R)-3-hydroxybutyrate], acting as hard segments, and poly(e-caprolactone)-diols, acting as soft segments, using 1,6-hexamethylene diisocyanate, as non toxic connecting agent, were synthesized. The copolymers were characterized with regard to their molecular weight by GPC and their main thermal transitions by DSC. These copolymers as well as PHB were exposed to UV-irradiation for different time intervals and the changes in the chemical structure were analyzed by FTIR spectroscopy. Under our experimental conditions, it was found that the increase of irradiation time was accompanied by increase of the proportion of the gel fraction and the decrease of the intrinsic viscosity of the soluble fraction of the investigated copolymers. The biodegradability of PHB and poly(ester-urethane) sample containing ~40 wt% PHB before and after UV-irradiation was investigated under soil burial. The results showed that the photolysis in air prior to biodegradation increased the rate of degradation.