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Fernando Catalina - One of the best experts on this subject based on the ideXlab platform.

  • comparative effect of metal Stearates as pro oxidant additives on bacterial biodegradation of thermal and photo degraded low density polyethylene mulching films
    2013
    Co-Authors: C Abrusci, Irma Marin, Enrique Espi, Teresa Corrales, J L Pablos, Fernando Catalina
    Abstract:

    Abstract The effect of Iron, Cobalt and Manganese Stearates are examined on the post-bacterial photochemical and thermal degradation of polyethylene (LDPE). The activity of Stearates has been evaluated by ATR-FTIR, chemiluminescence and GPC of polyethylenes. A significant increase in carbonyl index for PE containing Stearates was determined by FTIR together with a marked decrease in molecular weight as measured by GPC. All three metal Stearates induced the development of drastic photo- and thermal-degradation processes for polyethylenes containing metal Stearates except in the case of LDPE-Fe film which did not exhibit any significant thermocatalytic effect on degradation. In a second post bacterial study step, a mixture of three Bacillus MIX (Bacillus cereus, Bacillus megaterium and Bacillus subtilis) as well as Brevibacillus borstelensis were tested for biodegradation (90 days at 45 °C) of the highly photo- and thermo-degraded polyethylene films. Biodegraded materials were characterized using different techniques and mineralization was evaluated by carbon dioxide measurement using an indirect impedance technique. The biodegradation of degraded LDPE films by B. borstelensis and the mixture of Bacillus MIX was highly effective following the order LDPE-Co > LDPE-Mn > LDPE-Fe and in the range of 9.0–59.2% of mineralization after only 90 days of bacterial bioassay at 45 °C. The approach studied in this work showed much higher degradable efficacy than that already reported in the literature.

  • photodegradation of polyethylenes comparative effect of fe and ca Stearates as pro oxidant additives
    2010
    Co-Authors: Jesus L Pablos, C Abrusci, Irma Marin, Josefa Lopezmarin, Fernando Catalina, Enrique Espi, Teresa Corrales
    Abstract:

    Abstract The effect of iron and calcium Stearates on the degradation of polyethylene (LDPE and LLDPE), under natural and artificial exposure, has been studied. The activity of Stearates has been evaluated by chemiluminescence and FTIR of polyethylenes. The analysis of the molecular weight changes and content of degradation products identified by GC–MS during ageing process confirmed their pro-degrading activity. Films containing Stearates exhibited lower CL emission, and revealed the higher efficiency of Fe-Stearate compared to Ca-Stearate in decomposing hydroperoxides, leading to higher degradation during processing. The results were confirmed by TGA analysis, where the weight loss onset and T max shifted to lower temperatures in polyethylenes with incorporation of Fe- and Ca-Stearates compared to pure polymers. Polyethylenes were outdoor and accelerated exposed, and CL measured at different period of times. Chemiluminescence temperature-ramping tests under nitrogen showed the formation of a peroxide peak at lower temperature, and a significant increase in carbonyl index for PE containing Stearates was found by FTIR. The results were supported by GC–MS, where the concentration of extracted products identified in the polyethylenes containing Fe-stearate was significant, and a much greater decrease in molecular weight was determined by GPC, which confirmed the development of degradation for polyethylenes with Fe-Stearates in comparison to pure or Ca-stearate polyethylenes.

Timothy P. Carr - One of the best experts on this subject based on the ideXlab platform.

  • phytosterol stearate esters elicit similar responses on plasma lipids and cholesterol absorption but different responses on fecal neutral sterol excretion and hepatic free cholesterol in male syrian hamsters
    2011
    Co-Authors: Jiliang Hang, Patrick H. Dussault, Timothy P. Carr
    Abstract:

    Abstract The dietary impact of specific phytosterols incorporated into phytosterol fatty acid esters has not been elucidated. Therefore, we tested the hypothesis that phytosterol esters containing different sterol moieties (sitosterol, sitostanol, or stigmasterol) but the same fatty acid moiety (stearic acid) produce different effects on cholesterol metabolism. Male Syrian hamsters were fed sitosterol, sitostanol, and stigmasterol stearate esters (25 g/kg diet) in an atherogenic diet containing cholesterol (1.2 g/kg) and coconut oil (80 g/kg). The phytosterol Stearates produced no decrease in cholesterol absorption or plasma non–high-density lipoprotein cholesterol despite a reduction in liver free cholesterol in hamsters fed both sitosterol and sitostanol stearate diets. In addition, sitosterol stearate significantly increased fecal esterified and total neutral sterol excretion. Stigmasterol stearate did not differ from control in neutral sterol excretion, plasma lipids, or hepatic lipid concentration. Sitosterol stearate demonstrated the highest level of net intestinal hydrolysis, whereas sitostanol and stigmasterol stearate equivalently demonstrated the lowest. The cholesterol-lowering effect in liver—but not plasma—and the limited presence of fecal free sterols indicate that intact (unhydrolyzed) phytosterol Stearates may impact cholesterol metabolism by mechanisms unrelated to the role of free phytosterols. The consumption of phytosterol esters at 2.5% of the diet elicited only modest impacts on cholesterol metabolism, although sitosterol stearate had a slightly greater therapeutic impact by lowering liver free cholesterol and increasing esterified and total neutral sterol fecal excretion, possibly due to a greater level of intestinal hydrolysis.

C Abrusci - One of the best experts on this subject based on the ideXlab platform.

  • comparative effect of metal Stearates as pro oxidant additives on bacterial biodegradation of thermal and photo degraded low density polyethylene mulching films
    2013
    Co-Authors: C Abrusci, Irma Marin, Enrique Espi, Teresa Corrales, J L Pablos, Fernando Catalina
    Abstract:

    Abstract The effect of Iron, Cobalt and Manganese Stearates are examined on the post-bacterial photochemical and thermal degradation of polyethylene (LDPE). The activity of Stearates has been evaluated by ATR-FTIR, chemiluminescence and GPC of polyethylenes. A significant increase in carbonyl index for PE containing Stearates was determined by FTIR together with a marked decrease in molecular weight as measured by GPC. All three metal Stearates induced the development of drastic photo- and thermal-degradation processes for polyethylenes containing metal Stearates except in the case of LDPE-Fe film which did not exhibit any significant thermocatalytic effect on degradation. In a second post bacterial study step, a mixture of three Bacillus MIX (Bacillus cereus, Bacillus megaterium and Bacillus subtilis) as well as Brevibacillus borstelensis were tested for biodegradation (90 days at 45 °C) of the highly photo- and thermo-degraded polyethylene films. Biodegraded materials were characterized using different techniques and mineralization was evaluated by carbon dioxide measurement using an indirect impedance technique. The biodegradation of degraded LDPE films by B. borstelensis and the mixture of Bacillus MIX was highly effective following the order LDPE-Co > LDPE-Mn > LDPE-Fe and in the range of 9.0–59.2% of mineralization after only 90 days of bacterial bioassay at 45 °C. The approach studied in this work showed much higher degradable efficacy than that already reported in the literature.

  • photodegradation of polyethylenes comparative effect of fe and ca Stearates as pro oxidant additives
    2010
    Co-Authors: Jesus L Pablos, C Abrusci, Irma Marin, Josefa Lopezmarin, Fernando Catalina, Enrique Espi, Teresa Corrales
    Abstract:

    Abstract The effect of iron and calcium Stearates on the degradation of polyethylene (LDPE and LLDPE), under natural and artificial exposure, has been studied. The activity of Stearates has been evaluated by chemiluminescence and FTIR of polyethylenes. The analysis of the molecular weight changes and content of degradation products identified by GC–MS during ageing process confirmed their pro-degrading activity. Films containing Stearates exhibited lower CL emission, and revealed the higher efficiency of Fe-Stearate compared to Ca-Stearate in decomposing hydroperoxides, leading to higher degradation during processing. The results were confirmed by TGA analysis, where the weight loss onset and T max shifted to lower temperatures in polyethylenes with incorporation of Fe- and Ca-Stearates compared to pure polymers. Polyethylenes were outdoor and accelerated exposed, and CL measured at different period of times. Chemiluminescence temperature-ramping tests under nitrogen showed the formation of a peroxide peak at lower temperature, and a significant increase in carbonyl index for PE containing Stearates was found by FTIR. The results were supported by GC–MS, where the concentration of extracted products identified in the polyethylenes containing Fe-stearate was significant, and a much greater decrease in molecular weight was determined by GPC, which confirmed the development of degradation for polyethylenes with Fe-Stearates in comparison to pure or Ca-stearate polyethylenes.

Teresa Corrales - One of the best experts on this subject based on the ideXlab platform.

  • comparative effect of metal Stearates as pro oxidant additives on bacterial biodegradation of thermal and photo degraded low density polyethylene mulching films
    2013
    Co-Authors: C Abrusci, Irma Marin, Enrique Espi, Teresa Corrales, J L Pablos, Fernando Catalina
    Abstract:

    Abstract The effect of Iron, Cobalt and Manganese Stearates are examined on the post-bacterial photochemical and thermal degradation of polyethylene (LDPE). The activity of Stearates has been evaluated by ATR-FTIR, chemiluminescence and GPC of polyethylenes. A significant increase in carbonyl index for PE containing Stearates was determined by FTIR together with a marked decrease in molecular weight as measured by GPC. All three metal Stearates induced the development of drastic photo- and thermal-degradation processes for polyethylenes containing metal Stearates except in the case of LDPE-Fe film which did not exhibit any significant thermocatalytic effect on degradation. In a second post bacterial study step, a mixture of three Bacillus MIX (Bacillus cereus, Bacillus megaterium and Bacillus subtilis) as well as Brevibacillus borstelensis were tested for biodegradation (90 days at 45 °C) of the highly photo- and thermo-degraded polyethylene films. Biodegraded materials were characterized using different techniques and mineralization was evaluated by carbon dioxide measurement using an indirect impedance technique. The biodegradation of degraded LDPE films by B. borstelensis and the mixture of Bacillus MIX was highly effective following the order LDPE-Co > LDPE-Mn > LDPE-Fe and in the range of 9.0–59.2% of mineralization after only 90 days of bacterial bioassay at 45 °C. The approach studied in this work showed much higher degradable efficacy than that already reported in the literature.

  • photodegradation of polyethylenes comparative effect of fe and ca Stearates as pro oxidant additives
    2010
    Co-Authors: Jesus L Pablos, C Abrusci, Irma Marin, Josefa Lopezmarin, Fernando Catalina, Enrique Espi, Teresa Corrales
    Abstract:

    Abstract The effect of iron and calcium Stearates on the degradation of polyethylene (LDPE and LLDPE), under natural and artificial exposure, has been studied. The activity of Stearates has been evaluated by chemiluminescence and FTIR of polyethylenes. The analysis of the molecular weight changes and content of degradation products identified by GC–MS during ageing process confirmed their pro-degrading activity. Films containing Stearates exhibited lower CL emission, and revealed the higher efficiency of Fe-Stearate compared to Ca-Stearate in decomposing hydroperoxides, leading to higher degradation during processing. The results were confirmed by TGA analysis, where the weight loss onset and T max shifted to lower temperatures in polyethylenes with incorporation of Fe- and Ca-Stearates compared to pure polymers. Polyethylenes were outdoor and accelerated exposed, and CL measured at different period of times. Chemiluminescence temperature-ramping tests under nitrogen showed the formation of a peroxide peak at lower temperature, and a significant increase in carbonyl index for PE containing Stearates was found by FTIR. The results were supported by GC–MS, where the concentration of extracted products identified in the polyethylenes containing Fe-stearate was significant, and a much greater decrease in molecular weight was determined by GPC, which confirmed the development of degradation for polyethylenes with Fe-Stearates in comparison to pure or Ca-stearate polyethylenes.

Chitra Rajagopal - One of the best experts on this subject based on the ideXlab platform.

  • investigating the role of metal oxidation state on the degradation behaviour of ldpe
    2009
    Co-Authors: Prasun Kumar Roy, P Surekha, R Raman, Chitra Rajagopal
    Abstract:

    Abstract Transition metal Stearates have been reported to act as effective pro-oxidants for polyethylene, even at trace concentrations. This study is an attempt to investigate the effect of the oxidation state of a metal on its pro-oxidant nature. Three metal Stearates, namely manganese, iron and cobalt, in their common oxidation states (+2 and +3), were synthesized and their effect on the photo-oxidative and thermo-oxidative degradation of low-density polyethylene (LDPE) films has been investigated. Films of 70 ± 5 μ were prepared by film blowing technique, exposed to xenon arc weatherometer and air oven at 70 °C for extended time periods. The chemical and physical changes induced by this exposure were followed by monitoring the changes in mechanical properties (tensile strength and elongation at break), carbonyl index (CI), molecular weight (viscometry), MFI, density, and thermal properties. The results were analysed to explain the structural and chemical modifications taking place in the polymeric matrix as a result of aging. The studies reveal that the oxidation state of the metal did not affect its ability to initiate and accelerate degradation. The thermo-oxidative degradation in the presence of metal stearate was found to follow the order: cobalt > manganese > iron. However, iron stearate was capable of initiating photo-oxidative degradation to the same extent as cobalt and manganese, in the concentration range investigated. The results indicate that iron is primarily an effective photo-oxidant, while cobalt and manganese can act both as photo-oxidant as well as thermo-oxidant.

  • study on the degradation of low density polyethylene in the presence of cobalt stearate and benzil
    2006
    Co-Authors: Prasun Kumar Roy, P Surekha, R Raman, Chitra Rajagopal, Veena Choudhary
    Abstract:

    Degradable polymers are in great demand for a variety of applications such as packaging, agriculture, and medicine. Polyolefins blended with photodegradants/biodegradants are potential candidates for replacing the nondegradable thermoplastics in areas where litter abatement poses problems. In the present article, the effect of metallic photoinitiators like cobalt stearate and a combination of metallic/nonmetallic photoinitiators, i.e., a mixture of cobalt stearate and benzil, on the photooxidative degradation of low-density polyethylene (LDPE) films have been investigated. Attempts have been made to correlate the results as a function of mixed additives. Films of LDPE containing varying amounts of cobalt stearate and a combination of benzil and cobalt stearate were prepared. The photodegradation of these films has been monitored by various techniques like FTIR spectroscopy, differential thermal analysis, and density and viscosity measurements. Cobalt stearate was highly effective in accelerating the photodegradation of LDPE films at low concentrations. The addition of benzil to cobalt stearate decreased the rate of photodegradation compared to cobalt stearate alone. A retarding effect was observed when benzil alone was added to LDPE. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 236–243, 2006