The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Kannika Hatthapanit - One of the best experts on this subject based on the ideXlab platform.
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Effect of blend ratio on aging, oil and Ozone Resistance of silica-filled chloroprene rubber/natural rubber (CR/NR) blends
Express Polymer Letters, 2020Co-Authors: Chakrit Sirisinha, Kannika HatthapanitAbstract:The effect of blend ratio on properties of chloroprene rubber/natural rubber (CR/NR) blends was investigated. In addition to the mechanical properties, attention was also given to the Resistance to thermal aging, oil and Ozone of the blends. Silica was selected as a reinforcing filler in this study due to its unique characteristic to interact with CR. The results reveal that, due to the better filler dispersion and the greater crosslink density, the silica-filled CR possesses lower com- pound viscosity and better mechanical properties, compared to the silica-filled NR. The aging properties, oil and Ozone Resistance of the silica-filled CR are also significantly better than those of the silica-filled NR. The mechanical properties and the Resistance to degradation of the silica-filled CR/NR blends are mainly governed by the blend morphology. It is found that good mechanical properties in association with adequately high Resistance to degradation from thermal aging and oil are obtained when CR remains the matrix in the blends. Even though the Ozone cracks are found in all blends, a thorough look at the results reveals that considerable improvement in Ozone Resistance is achieved with increasing CR content.
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effect of blend ratio on aging oil and Ozone Resistance of silica filled chloroprene rubber natural rubber cr nr blends
Express Polymer Letters, 2007Co-Authors: Pongdhorn Saeoui, Chakrit Sirisinha, Kannika HatthapanitAbstract:The effect of blend ratio on properties of chloroprene rubber/natural rubber (CR/NR) blends was investigated. In addition to the mechanical properties, attention was also given to the Resistance to thermal aging, oil and Ozone of the blends. Silica was selected as a reinforcing filler in this study due to its unique characteristic to interact with CR. The results reveal that, due to the better filler dispersion and the greater crosslink density, the silica-filled CR possesses lower com- pound viscosity and better mechanical properties, compared to the silica-filled NR. The aging properties, oil and Ozone Resistance of the silica-filled CR are also significantly better than those of the silica-filled NR. The mechanical properties and the Resistance to degradation of the silica-filled CR/NR blends are mainly governed by the blend morphology. It is found that good mechanical properties in association with adequately high Resistance to degradation from thermal aging and oil are obtained when CR remains the matrix in the blends. Even though the Ozone cracks are found in all blends, a thorough look at the results reveals that considerable improvement in Ozone Resistance is achieved with increasing CR content.
Pongdhorn Saeoui - One of the best experts on this subject based on the ideXlab platform.
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effect of blend ratio on aging oil and Ozone Resistance of silica filled chloroprene rubber natural rubber cr nr blends
Express Polymer Letters, 2007Co-Authors: Pongdhorn Saeoui, Chakrit Sirisinha, Kannika HatthapanitAbstract:The effect of blend ratio on properties of chloroprene rubber/natural rubber (CR/NR) blends was investigated. In addition to the mechanical properties, attention was also given to the Resistance to thermal aging, oil and Ozone of the blends. Silica was selected as a reinforcing filler in this study due to its unique characteristic to interact with CR. The results reveal that, due to the better filler dispersion and the greater crosslink density, the silica-filled CR possesses lower com- pound viscosity and better mechanical properties, compared to the silica-filled NR. The aging properties, oil and Ozone Resistance of the silica-filled CR are also significantly better than those of the silica-filled NR. The mechanical properties and the Resistance to degradation of the silica-filled CR/NR blends are mainly governed by the blend morphology. It is found that good mechanical properties in association with adequately high Resistance to degradation from thermal aging and oil are obtained when CR remains the matrix in the blends. Even though the Ozone cracks are found in all blends, a thorough look at the results reveals that considerable improvement in Ozone Resistance is achieved with increasing CR content.
Chakrit Sirisinha - One of the best experts on this subject based on the ideXlab platform.
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Effect of blend ratio on aging, oil and Ozone Resistance of silica-filled chloroprene rubber/natural rubber (CR/NR) blends
Express Polymer Letters, 2020Co-Authors: Chakrit Sirisinha, Kannika HatthapanitAbstract:The effect of blend ratio on properties of chloroprene rubber/natural rubber (CR/NR) blends was investigated. In addition to the mechanical properties, attention was also given to the Resistance to thermal aging, oil and Ozone of the blends. Silica was selected as a reinforcing filler in this study due to its unique characteristic to interact with CR. The results reveal that, due to the better filler dispersion and the greater crosslink density, the silica-filled CR possesses lower com- pound viscosity and better mechanical properties, compared to the silica-filled NR. The aging properties, oil and Ozone Resistance of the silica-filled CR are also significantly better than those of the silica-filled NR. The mechanical properties and the Resistance to degradation of the silica-filled CR/NR blends are mainly governed by the blend morphology. It is found that good mechanical properties in association with adequately high Resistance to degradation from thermal aging and oil are obtained when CR remains the matrix in the blends. Even though the Ozone cracks are found in all blends, a thorough look at the results reveals that considerable improvement in Ozone Resistance is achieved with increasing CR content.
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effect of blend ratio on aging oil and Ozone Resistance of silica filled chloroprene rubber natural rubber cr nr blends
Express Polymer Letters, 2007Co-Authors: Pongdhorn Saeoui, Chakrit Sirisinha, Kannika HatthapanitAbstract:The effect of blend ratio on properties of chloroprene rubber/natural rubber (CR/NR) blends was investigated. In addition to the mechanical properties, attention was also given to the Resistance to thermal aging, oil and Ozone of the blends. Silica was selected as a reinforcing filler in this study due to its unique characteristic to interact with CR. The results reveal that, due to the better filler dispersion and the greater crosslink density, the silica-filled CR possesses lower com- pound viscosity and better mechanical properties, compared to the silica-filled NR. The aging properties, oil and Ozone Resistance of the silica-filled CR are also significantly better than those of the silica-filled NR. The mechanical properties and the Resistance to degradation of the silica-filled CR/NR blends are mainly governed by the blend morphology. It is found that good mechanical properties in association with adequately high Resistance to degradation from thermal aging and oil are obtained when CR remains the matrix in the blends. Even though the Ozone cracks are found in all blends, a thorough look at the results reveals that considerable improvement in Ozone Resistance is achieved with increasing CR content.
A W Davison - One of the best experts on this subject based on the ideXlab platform.
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spatial variation in Ozone Resistance of british populations of plantago major l
New Phytologist, 2006Co-Authors: K Reiling, A W DavisonAbstract:summary The relative Ozone Resistance of samples from 28 British Plantago major L. populations, grown from seed, was measured by exposure to charcoal–filtered air or air containing 70 nl I−1 O3 (7 h d−1) over 2 wk. Mean relative growth rate (R) and the allometric root/shoot coefficient (K) were measured. Ozone Resistance was expressed as Ores=ROzone/Rcontrol× 100. There were substantial differences between the response of the populations to O3, and the degree of Resistance was statistically related to O3 exposure indices and other environmental factors, notably the amount of summer sunshine. This implies that Ozone concentrations in parts of Britain are sufficiently high to promote evolution of Resistance but alternative explanations are also discussed. Overall, it is concluded that although our results tend to support the hypothesis that O3 Resistance in P. major is related primarily to the O3 climate, the question of causation can only be established unequivocally by further experiments. Establishing whether there has been a change in gene frequency needs repeated observation of populations over time. The significance of spatial variation in Ozone Resistance to the critical levels concept is discussed, particularly in relation to exposure indices.
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artificial selection and heritability of Ozone Resistance in two populations of plantago major
New Phytologist, 1997Co-Authors: C P Whitfield, A W Davison, T W AshendenAbstract:summary Geographically separated populations of Plantago major L. differ in Ozone Resistance, and this is correlated with the exposure to Ozone at the location of each population. In addition, two populations of P. major have been demonstrated to show an increase in Ozone Resistance after summers when Ozone concentrations were high. However, if evolution of Ozone Resistance has occurred in the field there must be appropriate heritable genetic variation and this must be demonstrated. In the present study, artificial selection for Ozone Resistance and sensitivity was imposed on a resistant (‘Lullington Heath’) and sensitive (‘Bush’) population of P. major. Artificial selection is an efficient means of demonstrating additive genetic variance for a character. Selection was based on 2 wk growth in Ozone (70 nl O3 1−1for 7 h d−1), and selected lines were tested for Ozone Resistance under both short and long term Ozone exposures. Changes in Ozone Resistance were demonstrated for each population. On the basis of a 2-wk screening test, selection from the initially sensitive Bush population led to a line that was significantly more resistant to Ozone, but it was not possible to select a line with greater sensitivity than the original population. Conversely, selection from the initially resistant Lullington Heath population led to a line with increased sensitivity but not to a line with increased Resistance. Differences in Ozone Resistance between the selected lines were maintained over the long term and were reflected in growth and seed production at the final harvest. Net assimilation rate, stomatal conductance and leaf pigments were measured. In both populations the lines selected for sensitivity showed a greater effect of Ozone on net assimilation rate. Ozone had a minor effect on chlorophyll content in the Lullington Heath sensitive line but tended to increase carotenoid concentrations. However, this effect on carotenoids was not related to Ozone Resistance. The experiment demonstrated that Ozone Resistance in P. major is heritable. The response to selection reported here supports previous evidence from field collections of a rapid evolution of Ozone Resistance.
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relationships between Ozone Resistance and climate in european populations of plantago major
New Phytologist, 1997Co-Authors: Tom Lyons, Jeremy Barnes, A W DavisonAbstract:summary The relative Ozone Resistance of 20 European and two American populations of Plant ago major was examined, and relationships with climatic factors at the source of the plant material were explored using data provided by participants in the ICP-Crops initiative (International Co-operative Programme to Investigate the Effects of Air Pollutants and Other Stresses on Agricultural and Semi-Natural Vegetation). Plants grown from seed were exposed to either charcoal/Purafil® filtered air (CF < 5 nmol mol−1 O3) or CF + Ozone (70 nmol mol−1 O3 7 h d−1) over a 2-wk period in controlled environment chambers, and effects on mean plant relative growth rate (R) and allometric root/shoot growth (K) determined. Ozone Resistance (R%) was calculated from (R03/RCF) × 100. Populations exhibited contrasting sensitivities to Ozone, without the development of typical visible symptoms of injury. A positive relationship was found between relative Ozone Resistance and descriptors of the Ozone-climate at the site of seed collection for the year of, and the 2 yr before, seed collection. The best predictors of inherent Ozone Resistance were shown to be cumulative Ozone exposure indices calculated according to current United Nations Economic Commission for Europe (UN-ECE) critical level guidelines for the pollutant (i.e. the accumulated hourly average Ozone exposure over a threshold level of 40 nmol mol−1 (AOT40) or 30 nmol mol−1 (AOT30) calculated during daylight hours for the consecutive 3-month period of the year experiencing the highest Ozone concentrations). No relationships were found between Ozone Resistance and climatic factors (temperature, precipitation, sunshine hours, humidity) or the concentrations of other air pollutants (SO2, NO2, NO). These findings support the view that current ambient levels of Ozone in many regions of Europe are high enough to promote evolution of Resistance to the pollutant in native plant populations. The significance of these findings to the debate over the establishment of separate critical levels for the protection of natural and semi-natural vegetation is discussed.
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a rapid change in Ozone Resistance of plantago major after summers with high Ozone concentrations
New Phytologist, 1995Co-Authors: A W Davison, K ReilingAbstract:summary Ozone concentrations in Britain vary greatly from year to year. In the mid-1980s they were relatively low but in 1989 and 1990 the number of hours when concentrations exceeded 60 nl 1−1 was 3–4 times greater than in the preceding 2 yr. Previous experiments suggested that this might have resulted in an increase in Ozone Resistance of Plant ago major L. populations, so a comparison was made of seed-grown plants collected from the same three sites in Derbyshire/South Yorkshire in the 1980s and 1991. Ozone Resistance was measured by exposure to charcoal-filtered air or air containing 70 nl 1−O3 (7 h d−1) and expressed as R%, the mean relative growth rate in Ozone expressed as a% of that in charcoal-filtered air. Ozone Resistance changed significantly in two of the populations (ISP and Totley) between the years 1985 and 1991. There was no significant change in the Resistance of the Scaftworth population between 1988 and 1991 when expressed as R% but there were significant physiological differences between the collections. The changes in R% were accompanied by differences in the response of the stomata to Ozone and in effects on dark respiration, but not in assimilatory capacity. This is the first report of a change in Ozone Resistance in populations over a short period of time. It is not known if the 1 991 plants were the descendants of the 1985/88 plants or whether there had been an invasion by new genotypes from outside the area. The role of other environmental factors in determining Ozone Resistance, and the implications of the data for the definition and mapping of critical levels are both discussed. It is predicted that if the reported changes were caused by Ozone, the region where future changes in Ozone Resistance are most likely to occur is that between the Midlands and the north of England.
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Effects of Ozone on stomatal conductance and photosynthesis in populations of Plantago major L.
New Phytologist, 1995Co-Authors: K Reiling, A W DavisonAbstract:summary British populations of Plantago major L. differ in Ozone Resistance. As stomata regulate Ozone uptake it is possible that some of this variation in Ozone Resistance is the result of differences in stomatal behaviour. This paper reports a comparative study of the effects of Ozone exposure on the stomatal conductance (gs), net CO2 uptake (A) and intercellular CO2 concentration (C1) of 28 populations over a 5 d period under controlled conditions. The Ozone exposure was 70 ml 70 nl1−1 for 7 h d−1 while controls in charcoal filtered air received < 5 ml 1−2. There was no relationship between mean or maximum stomatal conductance in charcoal filtered air and Ozone Resistance. Ozone reduced gs in all populations within hours of the start of fumigation, but particularly so in the more sensitive ones, then over the next 4 d the pattern changed as the effect on the sensitive populations decreased. The effect on the resistant populations remained more constant. Conductance measurements made in the dark period showed that the stomata did not close completely, and that in Ozone fumigated plants gs was on average 75% of that in control plants. Although the resistant populations showed a large reduction in gs, Ozone had no effect on A or C, indicating that closure was not caused by reduced photosynthesis and higher C. It is argued that closure was probably caused by direct effects on the guard cells. In sensitive populations Ozone reduced A to around 50–60% of the controls on day 1 but only to 70–80% of the controls on day 5. The recovery might have been caused by the decreasing effect on gs but as the uptake of Ozone would have increased at the same time it might have been related to acclimation.
A. A. Popov - One of the best experts on this subject based on the ideXlab platform.
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Ozone Resistance of vulcanized NBR-PVC blends
Polymer science. Series A Chemistry physics, 2020Co-Authors: N. M. Livanova, A. A. Popov, S. G. Karpova, T. A. Bogaevskaya, M. P. FarmakovskayaAbstract:A relationship between structure and Ozone Resistance of the vulcanized 70: 30 blends of butadiene-acrylonitrile rubbers (NBR) and poly(vinyl chloride) (PVC) was studied. The samples were prepared from NBR of the SKN-18, SKN-26, and SKN-40 grades and PVC (obtained by emulsion or suspension polymerization) by methods of high- and low-temperature blending followed by treatment in a thermostat. The properties of blends (including homogeneity, interphase layer structure, and Ozone Resistance) were studied by methods of stress relaxation, EPR, and IR spectroscopy. A mechanism of the Ozone-protective action of thermoplast (PVC) in the blends with NBR is considered for the systems possessing various degrees of homogeneity.
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Ozone Resistance of butadiene-acrylonitrile rubber and ethylene-propylene terpolymer covulcanizates
Polymer science. Series A Chemistry physics, 2020Co-Authors: N. M. Livanova, A. A. Popov, S. G. Karpova, V. A. Shershnev, V. B. IvashkinAbstract:The Ozone Resistance, surface layer structure, and composition of covulcanizates of butadiene-acrylonitrile rubbers containing different amounts of acrylonitrile units with ethylene-propylene terpolymers (EPDM) were studied using the stress relaxation and ESR and FMIR IR spectroscopy techniques. The Ozone Resistance of the materials was shown to depend on the compatibility of the components, the development of the interphase layer that determines the degree of covulcanization of the rubbers, and the EPDM network density.
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Ozone Resistance of 1,4-cis-polyisoprene covulcanizates with ethylene-propylene-diene elastomers with different compositions and Mooney viscosities
Polymer science. Series A Chemistry physics, 2020Co-Authors: N. M. Livanova, A. A. Popov, V. A. Shershnev, V. D. YulovskayaAbstract:The effects of the content of ethylene, propylene, and diene units in ethylene-propylene-diene terpolymers (EPDMs) with varying Mooney viscosity on Ozone Resistance and the amount of chemical crosslinks and physical junctions in covulcanizates of these terpolymers with 1,4-cis-polyisoprene were investigated. It was shown that the Ozone Resistance of the examined covulcanizates depends not only on the composition of EPDM rubbers but also on their Mooney viscosity.
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Structure of ethylene-propylene-diene elastomers and properties of their covulcanizates with cis-1,4-poly(isoprene)
Polymer science. Series A Chemistry physics, 2020Co-Authors: N. M. Livanova, A. A. Popov, V. A. Shershnev, V. D. YulovskayaAbstract:The effects of the amount of ethylene, propylene, and diene units in ethylene-propylene terpolymer rubbers on the Ozone Resistance, mechanical properties, and swelling of these elastomers with cis-1,4-poly(isoprene) were studied. Covulcanizates with the maximum content of ethylene units exhibited the highest Ozone Resistance. An explanation of the experimental findings was given.
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Free Volume and the Rates of the Ozone Degradation of Vulcanizates’ Statistical and Block Nitrile–Butadiene Rubbers
Russian Journal of Physical Chemistry B, 2020Co-Authors: N. M. Livanova, A. A. PopovAbstract:The correlation between the rate of Ozone destruction of vulcanizates of statistical and block nitrile-butadiene rubbers (NBRs) with the proportion of free volume in the defects of the structure and the total free volume of copolymers is established. It is shown that the rate of Ozone destruction of vulcanizates is determined by the absorption capacity of the copolymers. The amount of Ozone absorbed depends on the content and distribution of acrylonitrile units and the isomerism of the butadiene component. Statistical copolymers are characterized by a higher sorption capacity in relation to Ozone and low Ozone Resistance in comparison with the block copolymers.
