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Arunjunai Raj Mahendran Nicolai Aust Klaus Lederer 《Polymer-Plastics Technology and Engineering》2013,52(11):1142-1146
The partial degradation of high-density polyethylene was done in an internal mixer for different residence time. The oxidative thermomechanical degradation resulted in the formation of carbonyl groups in the polymer. The carbonyl index values estimated from the FTIR studies indicate the increase of carbonyl groups without any induction time. The common phenomenon during oxidative degradation of polyethylene is the increase in trans-vinylene groups and decrease in vinyl groups and these phenomena are observed in the current investigation. Owing to the chain scission occurring during the mixing at processing temperature, the change in morphology was studied by the amount of crystallinity estimated through DSC. The variation in the molar mass of the material was followed by SEC method. 相似文献
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测定了橡胶籽油的物化性能及组成. 加入6种抗氧化剂,采用Rancimat法研究了其添加量及复配、温度、0#柴油添加量、金属铜、铁等对橡胶籽油生物柴油氧化稳定性能的影响. 结果表明,橡胶籽油所制生物柴油不饱和脂肪酸含量达82.1%,诱导期为0.81 h,达不到国家标准(6 h). 6种抗氧化剂在添加量为4000′10-6(w)时对橡胶籽油生物柴油的氧化稳定性能均有提升,其中TBHQ效果最好,使其氧化稳定性诱导期达13.09 h,6种抗氧化剂的抗氧化效果为TBHQ>BHT>D-TBHQ>OG>PG>BHA. PG与其他抗氧化剂复配后效果较好,而TBHQ与其他抗氧化剂复配后效果降低. 温度和0#轻柴油添加量对橡胶籽油生物柴油的氧化稳定性能影响很大,随温度升高,诱导期明显缩短,而随0#柴油添加量增大,诱导期增加,添加量较大时诱导期增幅很大. 铁、铜对其氧化稳定性能也有一定影响. 相似文献
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The effect ot two antioxidants, IPPD and DENA, on the aging properties of TMTD-vulcanized natural rubber was studied by DSC. In the case of IPPD, the results were compared with mechanical measurements. The DSC measurements were carried out on specimens taken at different depths from cylindrical samples. The decrease in oxidative induction time was less pronounced for IPPD than for DENA at the edge of the samples. In the interior, the opposite behaviour was observed. 相似文献
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An oxidative aging-viscoelastic constitutive model was established to study the coupled heterogeneous oxidation and viscoelastic performance of rubber during aging process. The basic elasticity and viscoelasticity of rubber materials were comparatively considered as the function of ongoing aging. The dynamic compression process of natural rubber at different aging times was analyzed by the finite element method. And then the effects of oxygen uptake, diffusion, and oxidative reactions on the dynamic viscoelasticity of rubber were analyzed. The permeability of the oxygen in natural rubber was determined by means of molecular dynamics simulation. The results reveal that the heterogeneous degradation caused by diffusion-limited oxidation can lead to a complex stress distribution in the natural rubber specimen under dynamic loading condition; the relaxation time and the energy dissipation of the rubber specimen also increased after aging. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47452 相似文献
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The thermal stability of a series of organotellurium compounds was determined by thermogravimetric analysis and the stabilizing capacity of the most heat-resistant compounds assessed in natural rubber, polyethylene, and polypropylene by measurement of the oxidative induction time (OIT). The most active compounds, bis[4-(dimethylamino)phenyl]telluride ( 5 ) and bis[2,6-dimethyl-4-(dimethylamino)phenyl]telluride ( 10 ) stabilized natural rubber considerably at the 1% level and even more so at the 2% level. A similar stabilizing effect of compound 5 was found in polyethylene and polypropylene at the 0.1% level. © 1996 John Wiley & Sons, Inc. 相似文献
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Nadja M. Simkovsky Alfred Ecker 《European Journal of Lipid Science and Technology》1998,100(12):534-538
Influence of light and contents of tocopherols on the oxidative stability of fatty acid methyl esters The oxidative stability of different plant oil based fatty acid methyl esters can be estimated by determining the induction period with the active oxygen method. Measuring the volatile and oil soluble acids for a long period preceding the induction period shows that the values are approaching a certain limit. Even if the esters do not differ dramatically in the composition of fatty acids it is a fact that the different production processes influence the amount of tocopherols significantly. The exclusion of light is more crucial than the exclusion of air when storing plant oil based fatty acid esters. 相似文献
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硅烷偶联剂在粘土胶中的抗热氧老化作用 总被引:2,自引:0,他引:2
本文主要讨论了硅烷偶联剂的抗热氧老化作用通过采用天然橡胶塑性保护率的测定方法、橡胶热空气老化试验方法、扫描电子显微镜分析等,对硅烷偶联剂对粘土胶性能的影响进行了探讨,研究结果表明硅烷偶联剂不仅可以大大提高材料的强度,而且有明显的抗热氧老化效果。 相似文献
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Effect of non‐rubber components on vulcanization kinetics of natural rubber was studied with the use of a Rheometer MDR‐2000. The results show that the rate constants of induction period and curing period of natural rubber (NR) are greater than that of natural rubber extracted with acetone (NRE), and the activation energies of induction period and curing period of NR are lower than that of NRE. The activation energy of induction period of NR is reduced by16.9% and the activation energy of curing period of NR is reduced by 3.2% compared to the activation energies of NRE. The time tdis of NR is shorter than that of NRE at the same temperature. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
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Isothermal differential thermal analysis (DTA) is well known for measuring thermal stability of polyolefins by determining the oxidative induction time at elevated temperatures. Oxidative induction time, measured up to 7,000 hours and over a temperature range from 240°C to 120°C, has been used to study the stability of polybutene-1 and crosslinked polyethylene in the melt state. The Arrhenius plots of DTA results show that straight line extrapolation from high to low temperatures is not possible. Thermoanalytically measured oxidation induction times and mechanical failure in oven aging experiments agree for polybutene and crosslinked polyethylene, Measurements of molecular weight and of mechanical properties of polybutene-1 during the induction period of oven aging experiments at low temperatures revealed that molecular weight and tensile properties are not sensitive indicators for the beginning of aging. The state of deterioration can be estimated easier by measurement of residual lifetime in the isothermal DTA experiment. Diffusion processes of stabilizers in polyolefins, as well as the consumption of stabilizer at elevated temperatures, especially during the induction period also was observed by DTA. Finally the extraction of stabilizer by hot water was measured by isothermal DTA. 相似文献
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The shear deformation which a rubber compound undergoes when passing through a mill nip was calculated. For this purpose the pressure distribution was measured using a strain gauge mounted in the table of a RAPRA micro-mill. The method has been applied to black-loaded master batches of natural rubber and styrene-butadiene rubber, where the shear deformation was estimated as a function of the mill nip opening. Furthermore, the physical properties of a latex-mixed powder vulcanizate was measured as a function of the estimated shear deformation. 相似文献
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In this work, the wet natural rubber granules were dried by hot air and by microwave at 115°C, respectively; the morphological structures of dried natural rubber granules were studied by using a scanning electronic microscope, whereas the thermal oxidative properties of dried natural rubber granules were investigated by comparison of variation in properties before and after aging, and the changes in the thermal oxidative decompose temperatures. The results showed that it needed 13.47 min for microwave drying and 210.00 min for hot air drying to reduce the moisture content of wet natural rubber to the required value. The granules of natural rubber dried by microwave were of rough surfaces and the cutting traces produced during the processing of wet natural rubber remained on the natural rubber surface; whereas, the natural rubber granules dried by hot air were of smooth surfaces, and the cutting traces produced during the processing of wet granules disappeared. The thermal oxidative resistance of vulcanized natural rubber dried by microwave improved significantly. The initial plasticity (P0), plasticity retention index, and thermo‐oxidative decomposition temperature of natural rubber dried by microwave were higher than those of natural rubber dried by hot air. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
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在管式炉中对废轮胎橡胶粉进行了有氧再生,并考察了气氛、再生温度和再生时间对废轮胎橡胶粉有氧再生过程的影响。结果表明,有氧条件下橡胶粉的质量损失和溶胶质量分数均随温度升高而增大,溶胶中合成胶分子链之间易发生二次重组再交联反应,天然橡胶分子链则主要发生断裂。240 ℃下橡胶粉在有氧条件下再生10 min时,溶胶质量分数达55.9%。橡胶主链和交联键断裂主要发生了氧化反应,生成含羰基和亚砜基的化合物,同时伴有水和二氧化碳等生成,说明橡胶粉中的橡胶分子链有效断链。 相似文献
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酸凝固天然橡胶和微生物凝固天然橡胶硫化特性研究 总被引:5,自引:1,他引:4
采用硫化仪分析2种天然橡胶的硫化过程,探讨了炭黑和硫化温度对硫化诱导期、正硫化时间和最大转矩的影响。研究结果发现:微生物凝固胶和酸凝固胶的硫化诱导期和正硫化时间随硫化温度的上升显著下降,且都能很好符合阿仑尼乌斯方程;胶样的最大转矩与硫化温度呈很好的线性关系,且随着硫化温度的升高,逐渐降低;当采用纯胶配方时,微生物凝固胶的MH0显著高于酸凝固胶,而加入炭黑后.2种胶样的MH0均显著提高。但微生物凝固胶的MH0稍低于酸凝固胶。 相似文献
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M. G. Wyzgoski 《应用聚合物科学杂志》1981,26(5):1689-1704
Injection-molded tensile bars of unstabilized polypropylene were oven aged at 90°C. After an induction period, tensile elongation decreased catastrophically. During the induction period no evidence of oxidation was observed by infrared reflectance; however, a definite surface etching was noted by electron microscopy. Differential scanning calorimetry measurements indicated that, for samples aged beyond the induction time, oxidative degradation caused a decrease in the melting temperature of polypropylene. Toluene immersion was used to remove selectively material from the surface of tensile bars aged for various times. Using this technique, changes in melting behavior were observed for partially aged polypropylene even prior to the catastrophic decrease in tensile elongation. Similarly, oxidation products and a reduction in molecular weight were detected for the dissolved surface layer during the apparent induction time. Results indicate that molecular weight measurement is the most sensitive indicator of oxidative degradation during the induction period. 相似文献
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《塑料、橡胶和复合材料》2013,42(8):334-339
AbstractThermal–oxidative degradation behaviours of raw natural rubber (NR) have been investigated by using thermogravimetry analysis in inert and oxidative atmospheres and the plasticity retention index (PRI). The activation energy Ea, was calculated using Horowitz–Metzger and Coats–Redfern methods and compared with PRI. The Ea values obtained by each method were in good agreement with each other. The June samples are the least stable rubbers among the studied ones, whereas February samples exhibited the highest values of activation energy, therefore in agreement with the PRI behaviour, which indicates that the thermo-oxidative stability of the June samples are the poorest during the thermo-oxidative degradation reaction. Natural rubber is a product of biological origin, and thus these variations in the values of thermal behaviour and PRI might be related to the genetic differences and alterations of climatic conditions that act directly on the synthesis of non-rubber constituents, which are generally reflected in latex and rubber properties. 相似文献
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