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研究了聚砜改性酚醛树脂玻纤维强模塑料在200℃、230℃,时间为500h的热老化过程中所发生的力学性能变化情况。结果表明,在200℃老化时,经过500h后,材料的力学性能仍很高,其弯曲强度可达1058.35MPa,冲击强度为242.73kJ/m^2,拉伸强度为389.9MPa,压缩强度(平行于纤维方向)为160.33MPa。老化后,虽然力学性能(除弯曲强度外)会有所下降,但仍能满足材料的使用要求。说明此种模塑料能在200℃以下长期使用,是一种有发展前途的耐热塑料。 相似文献
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通过采用聚砜、复合增韧剂对酚醛模塑料的界面进行改性,成功地制得了一种耐油型酚醛模塑料。分别在200℃和170℃的滑油中浸24h和100h,测其力学性能和电绝缘性能,除垂直纤维方向的压缩强度外,各项性能保持率均达95%以上。采用SEM等手段对改性模塑料进行研究和分析,并同国外同类材料进行比较分析,发现聚砜、复合增韧剂改性酚醛模塑料具有优异的力学性能、电绝缘性能和耐滑油性能,是国防用理想材料。 相似文献
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《工程塑料应用》2020,(8)
为提高聚酰亚胺(PI)模塑料的耐高温性能,以2–(4–氨基苯基)–5–氨基苯并噁唑(BOA)和二氨基二苯醚作为混合二胺与均苯四甲酸酐合成聚酰胺酸树脂,随后通过热亚胺化法制备得到不同噁唑单元添加量的PI模塑粉。利用傅立叶变换红外光谱对模塑粉化学结构进行表征,并考察其在氮气和氧气氛围中的热失重行为。通过热模压方法制备得到含苯并噁唑结构的耐高温PI模塑料,对模塑料室温和430℃高温条件下力学性能进行测试,并对其高温性能稳定性和尺寸稳定性进行表征分析。结果表明,通过两步法和热亚胺化法成功将噁唑基团引入到PI结构中;随着BOA引入量的增加,模塑粉耐热氧稳定性显著提升,模塑料室温拉伸性能有所下降,压缩性能提升,但430℃高温下拉伸性能和压缩性能均优于不含BOA的模塑料,且力学性能保持率显著提高;BOA的引入还提高了PI材料高温性能稳定性,显著降低线性热膨胀系数,含苯并噁唑结构的PI模塑料展现出优越的耐高温性。 相似文献
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以玉米秸秆纤维为增强材料,氨基树脂为基体聚合物,制备了玉米秸秆纤维-氨基树脂模塑料。研究了玉米秸秆纤维浆料质量分数对模塑料的弯曲强度和冲击强度的影响。采用电子扫描显微镜(SEM)表征玉米秸秆纤维和氨基树脂的界面结合性能,并利用动态机械热分析(DMA)和热重分析(TG)分析模塑料的动态力学性能和热稳定性。研究表明,当玉米秸秆纤维浆料质量分数为31%时,氨基树脂模塑料的力学性能优异,弯曲强度为60.41 MPa,冲击强度为1.81 kJ/m2,模塑料的储能模量较高,性能较优;玉米秸秆纤维与氨基树脂的相容性稍差;模塑料在68.8~114.3℃时失重率仅为0.5%~2%,在246.0~345.2℃时失重率较高,达到26%,玉米秸秆纤维质量分数对模塑料的热稳定性影响不明显。 相似文献
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李金忠 《合成材料老化与应用》1979,(3)
1、适用范围 1.1 本标准包括通常用于试验工作而箱内容积为0.6米~3(25呎~3)的通用型热空气老化箱的性能要求,它适用于温度范围约从20℃室温到200℃的重力对流老化箱和温度范围约从20℃室温到500℃的强制通风老化箱。注1—所设计的老化箱最高工作温度约为200℃、300℃和500℃,老化箱的热绝缘和成 相似文献
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以硼酸作为高羟甲基低游离酚PF(酚醛树脂)的改性剂,制备相应的BPF(硼改性酚醛树脂)及其模塑料。采用红外光谱(FT-IR)法对BPF的结构进行了表征,并对其凝胶化时间、固化工艺条件、热性能和模塑料的性能等进行了探讨。研究结果表明:当w(B)=9%时,BPF及其模塑料的综合性能相对最好,其固化工艺为160℃/20 min,后处理工艺为"140℃/1 h→160℃/1 h→180℃/2 h";与纯PF模塑料相比,BPF模塑料的马丁耐热温度(196℃)提高了42℃、弯曲强度(111.8 MPa)提高了21.9 MPa且冲击强度(18.50 kJ/m2)也有所提高。 相似文献
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采用一种自制的苯酚甲醛树脂和复合固化体系,以无机玻璃纤维为增强材料,得到一种可注射成型的酚醛模塑料,对其耐高温性能进行了研究。热变形温度及TGA测试表明该材料耐高温性能优异,热变形温度达到272℃;温度在401℃时仅失重5%。 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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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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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
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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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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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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