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1.
研究了共混温度、３种硫化体系和共混配比对动态硫化ＥＮＲ／ＰＶＣ共混物力学性能的影响。结果表明，共混温度为１５０￣１６０℃，用促进剂ＤＭ／硫磺体系（ＤＭ为０．８￣１份，硫磺为１￣１．２５份），共混配比为３０／７０￣７０／３０时制得的ＥＮＲ／ＰＶＣ共混物具有良好的力学性能。 相似文献
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天然橡胶（NR）具有优异的综合性能而广泛应用于各个领域,但较差的耐热、耐老化性能影响了NR制品的使用寿命。天然橡胶与顺丁橡胶（BR）共混可改善制品的拉伸强度、耐磨性、抗撕裂性能,提高制品的使用寿命和耐低温性能,二者共混常用于轮胎制造。NR与BR共混,二者的相容性对共混物的相结构和性能具有重要影响。本研究利用Material Studio软件构建模型,采用分子动力学（MD）和耗散粒子动力学（DPD）模拟方法在分子尺度和介观尺度上对室温下NR/BR共混的相容性进行探讨。通过MD模拟,确定了NR和BR在模拟过程的最小聚合度均为20;构建10/90、30/70、50/50、70/30、90/10的NR/BR共混物模型,并计算每个NR/BR共混模型的相互作用参数χ,发现在NR/BR共混体系中NR与BR分子间的相互作用参数χNR-BR始终比临界相互作用参数χC小;分析了不同质量比NR/BR共混物分子间的径向分布函数,发现NR与BR分子间的径向分布函数ginter(r)始终高于NR与NR、BR与BR同种分子间的径向分布函数,表明共混物中不同种类分子间（NR与BR）的相互作用比同种类分子间（NR与NR、BR与BR）的相互作用要强;DPD模拟得到不同质量比NR/BR共混物的介观形貌,发现共混物分散相的相畴尺寸会随着分散相含量的增加而增加,但均未出现宏观相分离的情况。上述模拟结果表明,NR和BR在室温下以不同质量比混合时,始终表现出良好的相容性。为验证模拟结论是否准确,制备了NR/BR共混物试样,并采用动态热机械分析仪对样品进行测试,结果证实了NR/BR共混体系的混溶性。模拟结论与实验结果相匹配,证明分子模拟研究和预测共混物相容性是可行的,可为共混实验提供可靠的参考和指导。 相似文献
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紫薯淀粉与卡拉胶共混体系糊化及流变学特性的研究 总被引：1，自引：0，他引：1
为考察亲水性胶体与紫薯淀粉之间互作机理,以紫薯淀粉为原料,加入不同比例的卡拉胶,研究紫薯淀粉/卡拉胶共混体系糊化及流变学特性的影响。布拉邦德黏度曲线表明,与单独紫薯淀粉相比,添加卡拉胶可增加共混体系的峰值黏度、终值黏度、崩解值及回生值;静态流变学特性研究表明,紫薯淀粉/卡拉胶共混体系均属典型的非牛顿流体,具有假塑性流体的特征,添加卡拉胶后,可提高共混体系的增稠性,降低其流动性,有助于提高体系的假塑性与剪切稳定性;动态流变学特性研究表明,紫薯淀粉/卡拉胶共混体系具有更高的储存模量(G′)和损耗模量(G″),表现出较优越的黏弹特性;在剪切结构恢复力试验中,随着卡拉胶的比例增大,共混体系的恢复力增大。这提示卡拉胶的加入,能改善紫薯淀粉的稳定性,对紫薯产品生产具有一定的应用价值。 相似文献
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采用差示扫描量热计,强力试验机,老化烘箱等设备研究环氧化天然胶(ENR)/丁腈胶(NBR)共混物的耐热氧老化稳定性。结果表明:对于50/50比例ENR/NBR共混物,其老化机理属于硬化劣变型,促进剂、防老剂、补强填充剂的种类和用量对共混物的热氧老化稳定性均有较大影响。通过试验所选取的配方可有效地保证ENR/NBR共混物具有良好的耐热氧稳定性,能广泛应用于工业上。 相似文献
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在前一研究工作基础上,我们采用差示量热计与力学—振动光谱等手段,进一步研究了不同橡胶组分对热塑天然橡胶(聚乙烯含量在30％以下)的结构与性能的影响。我们将溶胶—聚乙烯与凝胶—聚乙烯共混物进行了比较,结果证明,两者在结构与性能上的差异并不显著,但纯化胶—聚乙烯与未纯化胶—聚乙烯共混物之间,存在着明显的差异,证明非胶组分对共混物之间有影响。我们的结果还表明,交联剂DCP具有提高共混物宏观应力值及橡胶分子取向程度的作用。此外,本文还讨论了非胶组分及DCP对共混物电的聚乙烯结晶行为的影响。 相似文献
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环氧化天然胶／丁腈胶共混物硫化条件的研究 总被引：1，自引：1，他引：1
采用流变仪、差示扫描量热计、强力试验机等仪器,开展环氧化天然橡胶/丁腈橡胶共混物硫化条件的研究,包括配方的选择、制备工艺、贮存时间等方面,从而确定适宜的硫化条件与工艺,并据以制备出具有一定程度共硫化的硫化胶;与环氧化橡胶、丁腈橡胶、天然橡胶/丁腈胶共混物相比,环氧化橡胶/丁腈橡胶共混物在力学与耐油性能上均有所改善,因此可以在工业上应用。 相似文献
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炭黑品种对NR/ENR共混物减震材料的影响 总被引：1，自引：0，他引：1
研究不同理化性能炭黑品种对天然橡胶/环氧化天然橡胶(NR/ENR)共混物硫化胶的力学性能、压缩疲劳生热性能和减震性能的影响.结果表明,粒子越小、比表面越人、结构性越高的炭黑的补强性较大,力学性能较好;但其压缩疲劳生热较大.动态热机械分析(DMA)的研究结果表明:随着温度的变化,炭黑粒子大小、结构性等对共混物硫化胶的减震性能有较人的影响,在ENR相的Tg2处,粒子较大的炭黑所填充的共混物硫化胶的tanδ较大;在高于Tg2以上的使用温度范围内,粒子较小的炭黑填充的共混物硫化胶的tanδ相对较高,减震性能较好. 相似文献
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Permeability of the preform is one of key factors in design of RTM (Resin Transfer Molding) mold, determination of processing
conditions, and modeling of flow in the mold. According to previous studies, permeability measured in the unsaturated fiber
mats are higher than that in the saturated fiber mats by about 20 % because of the capillary pressure. In this study, permeabilities
of several fiber preforms are measured for both saturated and unsaturated flows. A saturated experiment of radial flow has
been adopted to measure the permeability of anisotropic fiber preforms with high fiber content, i.e., circular braided preforms.
In this method, four pressure transducers are used to measure the pressure distribution. Permeabilities in different directions
are determined and the experimental results show a good agreement with the theory. Since permeability is affected by the capillary
effect, permeability should be measured in the unsaturated condition for the textile composites to be manufactured under lower
pressure as in the Vacuum Assisted Resin Transfer Molding (VARTM). 相似文献
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In reproductive swards, stems appear to act as vertical or horizontal barriers to bite formation, influencing instantaneous intake rate (IIR). The hypothesis was tested that the stems’ barrier effect is determined by the physical properties and density of stems. Artificial microswards, consisting of 20‐cm leaves and 15‐cm stems of Panicum maximum, were offered to three steers (362 kg) in a factorial combination of three stem densities (0, 100 and 400 stems m?2) and two levels of stem tensile resistance [low (LTRS) and high tensile‐resisting stems (HTRS)]. LTRS were not a barrier to defoliation and did not affect bite depth and bite mass. HTRS acted as both a horizontal barrier and a vertical barrier depressing bite depth (13·4, 13·6 and 5·1 cm for 0, 100 and 400 stems m?2, respectively), bite area (89·3, 50·8 and 47·6 cm2 for 0, 100 and 400 stems m?2, respectively), bite mass (0·51, 0·29 and 0·11 g for 0, 100 and 400 stems m?2, respectively) and IIR (23·8, 10·5 and 3·6 g sec?2 for 0, 100 and 400 stems m?2, respectively). The results confirmed the importance of the density and physical properties of stems as determinants of the stems’ barrier effect on bite dimensions and IIR. 相似文献
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This work aims to predict the mechanical properties of woven jute/banana hybrid composite. Woven fabrics are arranged in three layers of different sequence. Resin used in this work is Epoxy LY556 with hardener HY951. Composite specimen are prepared by hand-layup techniques. The effect of layering sequence on the mechanical properties namely tensile, flexural and impact was analysed. It is found that the tensile and flexural strength of hybrid composite (Banana/Jute/Banana) is higher than that of individual composites. Similarly, the impact strength of Jute/Banana/Jute hybrid composite is better than other types of composite. It is found that the moisture absorption of woven banana fiber composite is lesser than the hybrid composite. Fractography study of the fractured specimen is carried out using scanning electron microscope to analyse the fracture behaviour of the hybrid composite. 相似文献
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The co-woven-knitted (CWK) fabric and multi-layered biaxial weft-knitted (MBWK) fabric were produced using glass filaments as warp and weft inserted yarns and high tenacity polyester as stitched yarns. Vacuum Assisted Resin Transfer Molding process was used to produce the two composites. Tensile tests were carried out in the course, wale and slanting directions of the composites, respectively. Specific stress-strain curves and failure modes of the two composites were investigated and compared. Results reveal that tensile strengths and elastic moduli of the two composites in the course and wale directions are better than those in the bias direction. All the composite samples fracture in the brittle damage mode. Furthermore, the buckling due to different inserted ways of the warp and weft yarns has a few influences on the tensile properties of the two composites. This research may lay a foundation for the establishment of the process windows for the co-woven-knitted reinforced composites. 相似文献
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The effects of stem density of tropical swards and age of grazing cattle on their foraging behaviour
The effects of stem density of tropical swards and age of cattle on their foraging behaviour were evaluated using artificial microswards, consisting of leaves of 20 cm in height and high tensile‐resisting stems of 25 cm in height of Panicum maximum. The treatments consisted of a factorial combination of four stem densities of swards (0, 100, 200 and 400 stems m?2) and two ages of cattle (1‐ and 3‐year‐old steers). There was a significant interaction between stem density of sward and age of cattle for bite area (BA), bite mass (BM) and instantaneous intake rate (IIR). Stem density had a significant negative effect on these variables describing ingestive behaviour which was particularly strong for older steers. In leaf‐only swards, mature cattle achieved a much greater BA (106·5 vs. 57·9 cm2), BM (0·88 vs. 0·47 g DM) and IIR (46·9 vs. 17·2 g DM min?1) than did young cattle. However, these variables were very similar across ages of cattle at the highest stem density of sward. These results show the importance of the high tensile‐resisting stems as deterrents of the grazing process in tropical pastures, particularly in older cattle. 相似文献
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The objective of this investigation was to evaluate some of the physical and mechanical properties of resin-treated plywood type panels manufactured from bamboo strips (Gigantochloa scortechinii). Experimental plybamboo samples were made from low molecular weight phenol formaldehyde (LMwPF) treated bamboo strips. They were exposed to outdoor condition ranging from 1 to 12 months. Modulus of elasticity (MOE), modulus of rupture (MOR), compression strength, and surface roughness of treated and untreated samples were evaluated. Resin impregnated samples had the highest bending and compression strength properties. While the untreated samples failed after 3-month of outdoor exposure. Treated specimens exposed for 12-month had the MOE, MOR, and compression strength values of 14,253 N/mm2, 101.3 N/mm2, and 34.63 N/mm2, respectively. Surface quality of both treated and untreated samples was adversely influenced as the function of outdoor exposure time, based on numerical values obtained from a stylus type equipment. Overall properties of treated samples tested in work resulted in higher values than those of untreated samples. It appears that resin impregnation could be considered as an alternative method to enhance the characteristics of plybamboo exposed to environmental conditions as can be concluded from the results of this study. 相似文献
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Fadhel Jaâfar Mohamed Ali Lassoued Mahdi Sahnoun Souad Sfar Morched Cheikhrouhou 《Fibers and Polymers》2012,13(3):346-351
The medical uses of textile fibers and fabric forms keep on growing. Today, the knits can be used in the medical field. The
aim of this present work was to prepare compressive knits, impregnated by ethylcellulose (EC) microcapsules, for the burnt
skin. Ethylcellulose microcapsules containing jojoba oil were prepared via the phase separation method. Jojoba oil was chosen
because it plays an essential role in skin hydration and avoids the sebum accumulation. Ethylcellulose microcapsules obtained
were grafted on two different compressive knit surfaces by impregnation, using the Acrylic Resin (AR) as binder. The prepared
microcapsules were analyzed by Scanning Electron Microscopy (SEM). The stability of the microcapsules, the efficiency of the
microencapsulation method and the jojoba oil content determination were also investigated. This method of application improved
the fabric surface and permitted in maximum the preserving of initial characteristics of knit, such as touch, flexibility
and lightness. 相似文献
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《Industrial Crops and Products》2005,21(2):155-163
Grindelia chiloensis (Asteraceae) is a shrub native to the Patagonia and Monte regions of Argentina, presently under investigation as a resin crop. The rate of production of diterpene resin–acids is, in part, determined by environmental conditions and can be manipulated changing water, nitrogen, and radiation availability. Although the theory predicts that resin content should increase with low temperature, this response has not been tested, yet. The objective of this work was to test whether the response of resin production to temperature predicted by the Growth-Differentiation-Balance Hypothesis (GDBH) is found in G. chiloensis. Cloned plants of G. chiloensis were grown in greenhouses under different temperature regimes. Structural and functional characters were measured. Leaf resin and stem total non-structural carbohydrate content (TNC) were higher in plants grown at sub-optimal temperature (low temperature) for growth, whereas assimilation rate was not affected, in accordance with predictions. Under low temperature, specific leaf weight (SLW) and leaf–stem ratio were higher due to reductions in leaf expansion and stem growth, whereas individual leaf mass was not affected. Resin composition was slightly affected by temperature, suggesting that it is under strong genetic control. The stimulant effect of restrictive environmental conditions (low temperature in our study) required to compensate for the short growing season found in cooler environments such as Patagonia, appears insufficient to compensate for the reductions in aboveground biomass, thus resulting in lower resin production per plant. 相似文献
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田间低钾胁迫条件下水稻对钾的吸收和利用效率 总被引：11，自引：0，他引：11
通过田间试验,研究了在不同程度低钾胁迫条件下,杂交稻和常规稻在不同生育阶段对钾的吸收、分配和利用效率。在连续8季施氮、磷肥而不施钾肥的严重低钾胁迫条件下,施用钾肥使稻谷产量、水稻钾吸收总量显著增加而钾利用效率显著降低,同时表现出明显的耕作历史同施用钾肥间的交互作用。从幼穗分化期到抽穗期,水稻钾的积累量约占总积累量的一半以上,为水稻积累钾的关键时期。水稻对钾肥反应存在明显的品种间差异,在供钾充足条件下,杂交稻协优46的钾吸收量显著大于常规稻秀水11,但其钾利用效率却显著低于秀水11,表现出对钾的奢侈性吸收;在缺K条件下,杂交稻的钾吸收量低于常规稻,其钾利用效率与常规稻无明显差异。运用混合型离子交换树脂球测试法,可以了解淹水条件下土壤中生物有效性钾的动态变化特征,原地埋置7 d的树脂球的钾吸附量同水稻地上部分钾吸收量呈显著正相关。 相似文献
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The extraction of induced oleoresin from Pinus elliottii through bark streaking supplies products to the food, pharmaceutical and chemical industries. Resin flow is a typical defense response in conifers and is controled by various environmental factors. Although many studies have focused on oleoresin production in temperate forests, particularly in response to bark beetle attacks, relatively little is known about the physiological regulation of sustainable resin exudation in subtropical planted forests, in which commercial exploitation of this product is favored by the absence of significant pest insect populations. Therefore, the annual oleoresin yield of approximately 2660, 28-year-old trees from different sites was monitored for two consecutive years in southern Brazil. Plain wounding and wounding followed by application of a commercial resin stimulant paste containing the ethylene precursor 2-chloroethylphosphonic acid (CEPA) were used as reference treatments. Different concentrations of auxin, paraquat, yeast extract, and salicylic acid (isolated or in combination with CEPA) were also tested. Higher resin yields were associated with spring and summer, whereas winter had lower but significant yields. Auxin and salicylic acid stimulated the production of oleoresin relative to commercial paste in at least one concentration. Replacement of CEPA with auxin or salicylic acid yielded equivalent oleoresin production, indicating a comparable or complementary effect of these molecules in the process, as well as having implications for new stimulant paste formulations. 相似文献