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为了研究聚苯硫醚(PPS)单丝高温环境下的使用性能,选择直径为0.2,0.4,0.6,0.8 mm的大直径PPS单丝,在一定的温度与时间下进行热处理,研究了PPS单丝的结构及热处理条件对其力学性能的影响。结果表明:PPS分子结构中具有耐热的苯环结构,PPS单丝的熔点为282.4℃,在500℃以下无质量损失,在550℃左右质量损失率最大;对于较小直径(0.2 mm)的PPS单丝,当热处理温度低于200℃时,PPS单丝的断裂强度没有变化,在220℃条件下连续使用60 min,PPS单丝断裂强度下降1.4%,但不影响其使用性能;对于较大直径(0.4,0.6,0.8 mm)的PPS单丝,在热处理时间72 h条件下,当热处理温度为220℃时,3种PPS单丝的断裂强度保持率均在90%以上,在热处理温度220℃条件下,当热处理时间低于100 h时,PPS单丝断裂强度无损失,而热处理时间超过100 h后,PPS单丝断裂强度下降明显;较大直径PPS单丝连续使用环境温度应不超过220℃,在220℃条件下连续使用时间应尽量低于100 h。 相似文献
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为了探索湿热处理工艺中并列复合聚酯纤维的性能变化,采用低黏半消光聚对苯二甲酸乙二醇酯(PET)和聚对苯二甲酸丁二醇酯(PBT)为原料,通过50∶50的复合比进行并列复合纺丝,制得并列复合双组分聚酯纤维。将得到的双组分复合纤维进行湿热处理,研究了热处理温度、时间对并列复合双组分聚酯长丝的卷曲性能和力学性能的影响。结果表明:纤维经过湿热处理后,卷曲结构致密,卷曲半径减小;湿热处理时间对长丝的卷曲性能影响较大,卷曲率、卷曲回复率和卷曲弹性率都随时间的延长而增大;在低温下,卷曲率会随着时间的延长而增大,但较高温度下,长时间的处理不利于卷曲弹性率和卷曲回复率的提高;纤维经过湿热处理,断裂强度下降,断裂伸长率随着处理时间的延长呈现不同的变化趋势。 相似文献
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本研究以日本宝理株式会社的聚苯硫醚(PPS)树脂为原料,采用熔融纺丝方法,在我校的LHF j030纺丝一牵伸设备上制得特种工装用PPS长丝。然后取一定长度的PPS长丝,将其进行干热处理和沸水处理,研究了不同热处理条件对其收缩率与断裂强度性能的影响规律。实验结果表明:PPS纤维在175—185℃期间,干热收缩率为2%~6%,在185—190℃期间,随着温度的升高,干热收缩率急剧增加,幅度达10%;经沸水长时间处理PPS纤维的收缩率无明显变化;干热和沸水处理,对PPS纤维的断裂强度基本没有影响。 相似文献
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《合成纤维》2016,(11)
采用静电纺丝方法制备了聚乙烯醇(PVA)纳米纤维,探讨了工艺参数对纳米纤维形貌的影响,并对PVA纳米纤维膜进行热处理,研究了热处理时间与温度对纳米纤维膜力学性能的影响。研究表明:PVA质量分数在6%~10%区间内变化时,可得到直径分布较为均匀的纳米纤维;在其它条件相同时,随纺丝电压的升高,PVA纳米纤维的不匀增大;接收距离的改变对PVA纳米纤维的直径变化影响不大;随PVA质量分数的增加,纳米纤维膜的断裂强度和断裂伸长率逐渐增大;在热处理时间相同时,PVA纳米纤维膜的断裂强度随温度的升高而增大;处理温度相同时,随处理时间的延长,PVA纳米纤维膜的断裂强度变化不大。 相似文献
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《塑料工业》2019,(10)
采用差示扫描量热仪(DSC)研究了不同热处理时间对碳纤维增强聚苯硫醚(CF/PPS)结晶度的影响;利用动态力学分析仪(DMA)研究了不同热处理时间的CF/PPS试样的储能模量、损耗模量以及阻尼因子的变化情况。结果表明,150℃下CF/PPS试样的结晶度随热处理时间的增加(1~3 h)呈先增大后减小的趋势,相对结晶度最大值为65.3%,最小值为53.5%。这样的变化与不同热处理时间条件下PPS分子链活性以及热氧交联反应程度有关,分子链活性与交联程度会影响聚合物的晶核形成与生长,进而影响材料的结晶度;材料结晶度的升高会提高CF/PPS的储能模量,同时降低其损耗模量,且从阻尼因子图谱中可以得到不同结晶度的CF/PPS试样的玻璃化转变温度随结晶度的增大呈下降的趋势。 相似文献
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热处理对PP/纳米SiO2/PA6/POE-g-MAH复合材料力学性能与结晶行为的影响 总被引:1,自引:0,他引:1
研究了不同热处理温度、热处理时间、冷却方式对PP/纳米SiO2/PA6/POE-g-MAH复合材料力学性能与结晶行为的影响.结果表明,随着热处理温度的升高,复合材料的缺口冲击强度直线下降,断裂强度与断裂伸长率显著提高;热处理时间的增加,对复合材料的缺口冲击强度、断裂伸长率和断裂强度影响显著,对拉伸强度影响较小;在复合材料结晶温度以下温度进行热处理,材料的综合力学性能下降,在结晶温度以上的温度进行热处理,采用快速冷却的冷却方式能够显著改善材料的综合力学性能.最佳热处理工艺:热处理温度为140℃,热处理时间为30 min,水冷冷却. 相似文献
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It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples. 相似文献
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J. R. Aldrich S. P. Carroll W. R. Lusby M. J. Thompson J. P. Kochansky R. M. Waters 《Journal of chemical ecology》1990,16(1):199-210
Scentless plant bugs (Heteroptera: Rhopalidae) are so named because adults of the Serinethinae have vestigial metathoracic scent glands. Serinethines are seed predators of Sapindales, especially Sapindaceae that produce toxic cyanolipids. In two serinethine species whose ranges extend into the southern United States,Jadera haematoloma andJ. sanguinolenta, sequestration of host cyanolipids as glucosides renders these gregarious, aposematic insects unpalatable to a variety of predators. The blood glucoside profile and cyanogenesis ofJadera varies depending on the cyanolipid chemistry of hosts, and adults and larvae fed golden rain tree seeds (Koelreuteria paniculata) excrete the volatile lactone, 4-methyl-2(5H)-furanone, to which they are attracted.Jadera fed balloon vine seeds (Cardiospermum spp.) do not excrete the attractive lactone. Loss of the usual heteropteran defensive glands in serinethines may have coevolved with host specificity on toxic plants, and the orientation ofJadera to a volatile excretory product could be an adaptive response to save time.Mention of a commercial product does not consititute an endorsement by the USDA. 相似文献
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M. S. J. Simmonds W. M. Blaney F. Delle Monache M. Marquina Mac-Quhae G. B. Marini Bettolo 《Journal of chemical ecology》1985,11(12):1593-1599
Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria. 相似文献
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Cheng-Le Zhao Shane Porzio Alan Smith Haiyan Ge H. T. Davis L. E. Scriven 《Journal of Coatings Technology and Research》2006,3(2):109-115
Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively.
There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized.
High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without
the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of
fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to
achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic
SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve
F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender
particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing,
and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing
or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually
preserves suspension stability during freezing.
Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago,
IL. Tied for first place in The John A. Gordon Best Paper Competition. 相似文献
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2008~2009年世界塑料工业进展 总被引:4,自引:1,他引:3
中蓝晨光化工研究院有限公司《塑料工业》编辑部 《塑料工业》2010,38(3)
收集了2008年7月~2009年6月世界塑料工业的相关资料,介绍了2008~2009年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况。按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、环氧树脂、不饱和聚酯树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍。 相似文献
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Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US
In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae
and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted
in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures
(release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species
(Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species
to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were
exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of
separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles
from the southeastern region of the US. 相似文献
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ICP-MS法测定地球化学样品中As、Cr、Ge、V等18种微量痕量元素的研究 总被引:15,自引:0,他引:15
建立了测定地球化学样品中包括As、Cr、Ge、V等18种微量、痕量元素的ICP-MS方法。地化试样用HF-HNO3混酸分解后,以1 1 HNO3溶解干渣。由于制样不使用盐酸,避免了Cl对As、Cr、Ge、V的质谱干扰。用国家一级地球化学标准物质GBW 07309制备溶液优化仪器工作参数,并用于校准。方法测定限(6s)为:0.007~6.4μg/g,精密度(RSD%,n=12)为:29%~9.4%,经过国家一级地球化学标准物质的分析验证,结果与标准值吻合。方法已应用于国土资源调查的试样分析。 相似文献