Radiation, thermo-oxidative and storage induced changes in microstructure, crystallinity and dielectric properties of (un)oriented isotactic polypropylene

Bacterial cellulose (BC) is a new kind of cellulose with great potential in enhancing preparation of isotactic Polypropylene (iPP) composites, which have been found with excellent performance. However, the interface compatibility between BC and iPP is poor. In this study, iPP/BC composites were prepared by solution mixing. Esterification modified BC (CO) and Maleic anhydride grafted polypropylene (MAPP) added as a compatibilizer was both used to improve the interfacial compatibility of the iPP/BC composites. The rheology and isothermal crystallization behavior of the composites was tested and discussed. The result shows that the complex viscosity and storage modulus of the composite significantly increase in the rule iPP, iPP/BC2, iPP/CO2, and M-iPP/BC3, which indicates that the compatibility of the composite increases as this rule. According to the isothermal crystallization kinetics result, the crystal growth mode of iPP was not affected by the addition of BC and the interfacial compatibility. The spherulite growth rate of the iPP/BC composite increases with increasing crystallization temperature. Especially, the value decreases as the same rule with the complex viscosity and storage modulus of the composite at the same isothermal crystallization temperature. These results suggest that the interface compatibility of iPP/BC composites is greatly improved and the interface compatibility of the M-iPP/BC3 is better than the iPP/CO2.

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Effect of pH, temperature, amount of litter and storage density on ammonia emissions from stable manure

The Journal of Agricultural Science ◽

10.1017/s0021859600078722 ◽

1996 ◽

Vol 127 (4) ◽

pp. 501-509 ◽

Cited By ~ 59

Author(s):

T. Dewes

Keyword(s):

Laboratory Tests ◽

Ammonia Emission ◽

Ammonia Emissions ◽

Ph Values ◽

Degrading Bacteria ◽

Proteolytic Bacteria ◽

Stable Manure ◽

Induced Changes ◽

Two Peaks ◽

And Storage

SUMMARYIn laboratory tests using stable manure consisting of wheat straw and slurry, ammonia emission was found to have two peaks corresponding to the population dynamics of proteolytic bacteria and amino acid-degrading bacteria respectively. Cumulative ammonia emissions over 14 days were 0·8–23·2% of the initial total nitrogen (Nt) and were both abiotically and biotically induced. Changes in pH had the most significant effect on the abiotically induced ammonia emissions. After 14 days of decomposition, at pH values of 6·0 and 7·5, abiotically induced emissions remained close to the limit of detectability, whereas at pH 9·0 as much as 9·8% of the initial Nt was lost. An increase in storage pressure from 0 to 400 and 800 kp/m2 generally decreased the biotic emissions to 9·6, 2·8 and 2·3%; while increasing the amounts of litter (2·5, 5·0 and 15·0 kg straw/LAU per day) led to a decline not only in the biotic (17·1, 12·8, 3·5%) but also in the abiotic emissions (6·1, 5·5, 1·6%). Varying the temperature (20, 30 and 40 °C) resulted in biotically induced emissions of 7·9, 11·7 and 11·6%, respectively, and abiotically induced emissions of 1·1, 1·4 and 2·2% of the initial Nt. At temperatures of 30 and 40 °C, the amount of microbially digested sources of carbon available was obviously sufficient to permit almost total reincorporation of NH4+ from 4 days onwards.

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Discussion of Papers Presented at the Symposlum: Time-Induced Changes in the Dielectric Properties of Ice Ih

The Journal of Physical Chemistry ◽

10.1021/j100244a608 ◽

1983 ◽

Vol 87 (21) ◽

pp. 4330-4330

Author(s):

P Camp

Keyword(s):

Dielectric Properties ◽

Induced Changes

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Properties of isotactic polypropylene irradiated in various atmospheres

Hemijska industrija ◽

10.2298/hemind091221029m ◽

2010 ◽

Vol 64 (3) ◽

pp. 201-208 ◽

Cited By ~ 1

Author(s):

Dejan Milicevic ◽

Edin Suljovrujic

Keyword(s):

Low Temperature ◽

Ir Spectroscopy ◽

Gamma Irradiation ◽

Isotactic Polypropylene ◽

Oxidative Degradation ◽

Gel Point ◽

Dielectric Losses ◽

Dielectric Relaxations ◽

Radiation Induced ◽

Induced Changes

In this paper, changes in structure and physical properties of stabilized isotactic polypropylene (iPP) were created by gamma irradiation, up to a dose of 700 kGy, in different media: air, deionized distilled (DD) water and acetylene. Two main effects occur when polyolefins, such as iPP, are subjected to ionizing radiation: crosslinking and scission of macromolecules. The domination of one or the other of these competitive processes is determined by both the structural peculiarities of the polymers and the experimental irradiation conditions. Gel and infrared (IR) spectroscopy measurements were used to determine the changes in the degree of network formation and oxidative degradation, respectively. Sol-gel analysis was studied in detail using the Charlesby-Pinner (C-P) equation. The radiation-induced changes in the structure and evolution of oxygen-containing species were also studied through dielectric loss (tan ?) analysis in a wide temperature and/or frequency range. Evolution of low temperature dielectric relaxations with gamma irradiation was investigated. The results showed that degradation was the major reaction in the initial step of irradiation, no matter what the atmosphere was. The C-P equation seemed applicable when stabilized iPP was irradiated within a certain dose range in various atmospheres. The iPP irradiated in acetylene/air had the lowest/highest values for oxidation level, dielectric losses, Dg and G(s)/G(x) values. The calculated Dg values are 1.5 and 5 times larger for the irradiation in DD water and air than for the acetylene. Furthermore, our data confirm that oxidation strongly affects the gel point but has a much lower effect on the G(S)/G(X) ratio. In the case of dielectric relaxation measurements, the connection between the oxidative degradation and dielectric properties is well established and is in good agreement with IR spectroscopy measurements. The amount of carbonyl, hydroperoxide and other polar groups is much higher for the irradiation in air than in other media, leading to higher dielectric losses. Disappearance of low temperature (? and ?) relaxations with gamma radiation confirmed great sensitivity of iPP structure to radiation-induced changes. Complete ?vanishing? of the ? relaxation in iPP samples irradiated in air is connected with a large radiation-induced oxidative degradation in this medium. Similar crosslinking, oxidation and dielectric behaviour was observed for the samples irradiated in water and acetylene, indicating DD water as a good crosslinking medium.

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Microflora of Austrian Natural-Set Yogurt

Journal of Food Protection ◽

10.4315/0362-028x-53.6.478 ◽

1990 ◽

Vol 53 (6) ◽

pp. 478-480 ◽

Cited By ~ 19

Author(s):

HARALD ROHM ◽

FRIEDA LECHNER ◽

MARIETTA LEHNER

Keyword(s):

Storage Temperature ◽

Debaryomyces Hansenii ◽

Streptococcus Thermophilus ◽

Lactobacillus Bulgaricus ◽

Rhodotorula Mucilaginosa ◽

Pichia Guilliermondii ◽

Ferment Lactose ◽

Induced Changes ◽

Trichosporon Beigelii ◽

And Storage

Randomly selected Austrian natural-set yogurts were examined for storage-induced changes in the populations of viable yogurt starter organisms and microbial contaminants. Typically, numbers of Streptococcus thermophilus and Lactobacillus bulgaricus remained above 108 cfu/g in yogurt stored at 10°C until the sell-by-date (15–20 d after manufacture). Both elevated storage temperature and storage periods markedly reduced the survival of yogurt starter bacteria. Depending on the sample origin, the yeast populations increased from less than 10/g to above 106/g when yogurts were stored at 10°C until the sell-by-date. The isolated yeasts were identified as Candida inconspicua, C. intermedia, C. parapsilosis, C. rugosa, C. tropicalis, C. zeylanoides, Debaryomyces hansenii, Metschnikowia reukauffii, Pichia guilliermondii, Rhodotorula mucilaginosa, Torulaspora delbrueckii, Trichosporon beigelii, and Yarrowia lipolytica. While a few out of 233 isolates were found to assimilate lactose, none were able to ferment lactose.

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