Synthesis and Deblocking Investigations of Phenol Blocked Aliphatic Isocyanates and Their Application in the Development of Epoxy-Polyurethane Films

Phenol blocked hexamethylenediisocyanate adducts and polyisocyanates were synthesized and their structure was validated by FTIR, 1H & 13C NMR spectroscopy, TGA, DSC and CO2 evolution techniques were used to evaluate the deblocking temperature of blocked isocyanates. Gel time studies of blocked isocyanates with terathane polyol and solubility study of blocked isocyanates with different polyols were conducted to demonstrate the structure-property correlation. Epoxy-polyurethane films were produced utilizing the blocked isocyanates reported in this work with epoxy resin and their structure was verified by ATR Spectroscopy. TGA, DSC, shore A hardness, tensile strength and flexural strength analysis were used to investigate the thermal and mechanical characteristics of these films. The findings of deblocking temperature and gel time revealed that unsubstituted phenol blocked isocyanates and polyisocyanates deblock at lower temperatures and cure for a shorter time period than substituted phenol blocked isocyanates. Thermal and mechanical characteristics of epoxy-polyurethane films based on blocked polyisocyanates are satisfactory.

Isolation, characterization and optimization of bacterial isolate SARR1 for biodegradation of pretreated low density polyethylene

Accumulation of low-density polyethylene (LDPE) has caused a threat to the environment because of its stable and inert nature as it cannot be degraded easily by microorganisms. Its lightweight, low cost, strength, durability, and its various other applications, have led to the wide usage of the polymer, which is exerting a negative effect on both marine and land biota. The development of an eco-friendly or a promising strategy is needed to reduce LDPE waste from both land and water. In the present study, observations have been made to isolate highly efficient LDPE degrading bacteria. The response surface methodology (RSM) was used to predict the best optimization of media for the degradation of LDPE by isolate SARR1. The isolate SARR1 was selected through primary screening by weight loss method and secondary screening using CO2 evolution test, TTC and MATH Test. The isolate SARR1 showed 6.30 ± 0.25 g/L CO2 evolution. The microbial adhesion hydrophobicity (MATH) was observed during log phase (100 to 56.89 ± 0.97 %) and stationary phase (100 to 82.92 ± 1.24 %). An isolate SARR1 converted the TTC into red coloured insoluble triphenyl formazan (TPF) after incubation of 7 days. The isolated bacteria SARR1 showed 38.3 ± 1.27 % biodegradation efficiency in the pretreated LDPE strips at 37 °C and pH 7.0 under optimized conditions within 30 days of incubation. This bioremediation and biodegradation approach is eco-friendly and safe for the environment. The results of treatment with isolate SARR1 had a potential hope to degrade LDPE at higher rate than natural degradation.

Effect of Cover Crop Type and Application Rate on Soil Nitrogen Mineralization and Availability in Organic Rice Production

In drill-seeded, delay-flooded organic rice production, reliable predictions of N supply from cover crop (CC) residues to subsequent rice are still a challenge. An incubation was conducted to determine the effects of CC types (clover, ryegrass, clover and ryegrass mixtures, and fallow), residue application rates (0, 0.6, 1.2, 1.8, and 2.4%) and incubation time on soil CO2 evolution and N mineralization and availability. The cumulative CO2 evolution linearly increased with increasing residue rate. Compared to the control, adding CCs residue significantly increased the cumulative CO2 emission, which was greatest in soils with clover or mixtures of clover and ryegrass, followed by fallow, and lowest in soils with ryegrass. The modeling results indicated clover had the greatest initial C and N mineralization rates and the shortest half-lives. A temporary decrease in soil mineral N caused by immobilization occurred at the initial incubation stage in all treatments. However, the trend reversed progressively, with the clover treatment requiring the shortest time to meet the crossover point. The results suggested clover was the optimal CC type, 0.6% was the optimal residue rate, and a minimum of 27 days between CC termination and rice planting was required to maximize mineral N supply for organic rice.

Microbial Degradation of Plastic in Aqueous Solutions Demonstrated by CO2 Evolution and Quantification

The environmental accumulation of plastics worldwide is a consequence of the durability of the material. Alternative polymers, marketed as biodegradable, present a potential solution to mitigate their ecological damage. However, understanding of biodegradability has been hindered by a lack of reproducible testing methods. We developed a novel method to evaluate the biodegradability of plastic samples based on the monitoring of bacterial respiration in aqueous media via the quantification of CO2 produced, where the only carbon source available is from the polymer. Rhodococcus rhodochrous and Alcanivorax borkumensis were used as model organisms for soil and marine systems, respectively. Our results demonstrate that this approach is reproducible and can be used with a variety of plastics, allowing comparison of the relative biodegradability of the different materials. In the case of low-density polyethylene, the study demonstrated a clear correlation between the molecular weight of the sample and CO2 released, taken as a measure of biodegradability.

Soy Flour Substitution in Polymeric Methylene Diphenyl Diisocyanate Resin for Composite Panel Applications

Partial substitution of polymeric methylene diphenyl diisocyanate (pMDI) resin by 10 to 15 percent soy flour for the manufacture of strand board improves board properties while decreasing cost. For particleboard and medium-density fiberboard the soy-substituted resin performs as well as the control pMDI. The reaction of soy flour with pMDI occurs over several hours as tracked by CO2 evolution. The soy-amended resin must be used within about 30 minutes of formulation. Uniform mixing of soy flour with pMDI is critical because unreacted soy flour tends to retain water, which degrades the wet properties of the board. The soy flour increases the tack of pMDI resin, which increases the surface coverage and the relative bonded area at the glue line.

Dung decomposition of cattle grazing from mixed pastures of Signalgrass (Brachiaria decumbens Stapf.) and tree legumes

The mineralization rate of ruminant manure may influence the fertilization management of pastures. This study aimed to evaluate feces decomposition of heifers grazing signalgrass (Brachiaria decumbens Stapf.) fertilized or not with N, or intercropped with legumes in the dry forest region. Two experiments were conducted; the first one was a CRD that evaluated the evolution of CO2 from a mixture of soil and feces (10:1) during 22 days of incubation in a hermetically sealed bucket with a solution of NaOH 0.5 mol L-1. The second one was a RCBD that evaluated the in situ decomposition of feces in nylon bags in time periods 4, 8, 16, 32, 64, 128 and 256 days after incubation above ground. The single negative exponential mathematical model was adequate (P ≤ 0.0001) to quantify the CO2 evolution of the mixture of soil and feces, indicating that 78% of CO2 was released at the beginning of the incubation, especially for the feces collected in the signalgrass pastures intercropped with Gliricidia sepium (Jacq.) Kunth ex Walp. (gliricídia). After the first 5 days, CO2 evolution was more stable. Remaining biomass in the litterbag along decomposition fitted the single negative exponential model (P < 0.001). Greater relative decomposition rate (k) of bovine fecal biomass occurred for the N-fertilized signalgrass treatment (k = 0.0031 g g-1 day-1) and a lesser rate for the treatment intercropped with Mimosa caesalpiniifolia Benth. (sabiá) (k = 0.0018 g g-1 day-1). Nitrogen fertilization in signalgrass pasture favored the decomposition of bovine feces at the end of 256 days of incubation.

Release of Nitrogen and CO2 evolution from Manures and Fertilizers applied in Soil: An incubation study

Carbon and nitrogen mineralization and urease activity were evaluated under wet and dry climate with input of manures and fertilizers. Results indicates that release of NH4+ and NO3N and CO2 evolution was maximum during 7 to 21 days after incubation (DAI) with recommended dose of fertilizer and decreased later on. Release of N and C took place after 21 DAI where manures applied either with neem cake or fertilizers. The evolution of CO2C and total nitrogen were significantly higher in poultry manure combined with neem cake and FYM as compared to vermicompost along with neem cake. The NH4+N released during the entire incubation period were higher than NO3N. Combination of neem cake, poultry manure and FYM had higher enzyme activity than other treatments. Application of commercial fertilizers registered significantly higher CO2C fluxes upto 35 DAI compared to manures and control. Overall effect of manures applied with neem cake or their combination proved better in the treatments for release of nitrogen. Correlation study between CO2C flux, total N and urease activity showed that a positive relationship (p<0.05) with each others.