三维角联锁复合材料弯曲性能的热老化特征

研究了三维角联锁碳纤维复合材料未老化及90℃、110℃、180℃老化16 d的弯曲力学性能。对比三维角联锁复合材料弯曲-挠度曲线、破坏形态及SEM纤维特征,分析老化温度对复合材料弯曲性能的影响。通过环氧树脂DSC分析、红外光谱分析说明老化温度对树脂热学性质、后固化现象及分子结构变化的影响。结果表明:环氧树脂老化过程存在后固化和热降解两种竞争机制,90℃老化16 d的复合材料后固化作用突出,与未老化复合材料相比其弯曲强度增大;110℃老化16 d的复合材料热降解作用占优势,材料起始破坏弯曲强度略有下降;上述两者弯曲模量基本不变,而180℃老化16 d的复合材料热降解剧烈,树脂与纤维之间严重脱粘,材料弯曲强度明显下降,弯曲模量减小。     

玻纤增强环氧树脂复合材料的酸雨循环老化性能与机理

针对潮湿和酸雨多发地域的航空器复合材料老化问题,模拟酸雨和湿热(普通热水)环境,研究了单向玻纤增强环氧树脂复合材料(UGFREC)在酸雨和湿热环境下的吸湿-干燥循环老化行为;分析了不同循环次数下的UGFREC的吸水动力学;采用力学测试装置、热力学分析装置和扫描电镜,分别表征酸雨和湿热循环老化前后UGFREC的弯曲性能、层间剪切性能、冲击强度、动态粘弹性、玻璃化转变温度和冲击破坏形貌;初步给出反映酸雨和湿热循环过程中基体树脂与纤维间的界面应力变化模型。     

TDE-85/AG-80环氧树脂基复合材料微观形貌与力学性能分析

选用两种耐高温多官能团环氧树脂TDE-5和AG-80为基体,T300碳纤维为增强体制备了复合材料单向板,纤维体积含量均为60％。实验测得TDE-85树脂基体复合材料单向板的弯曲模量为74．26GPa,弯曲强度为1061．4MPa,层间剪切强度（ILSS）为54．05MPa;AG-80树脂基体复合材料单向板弯曲模量为55．73GPa,弯曲强度为840．52MPa,层间剪切强度（ILSS）为44．84MPa。前者的弯曲强度、弯曲模量与剪切强度也分别高出后者26．3％、33．2％与20．5％。实验对弯曲试样断口微观形貌的受压部分和受拉部分进行了SEM和高倍数码显微镜观察。结果显示,AG-80树脂基与碳纤维的界面结合情况较差,纤维成束被拔出,纤维表面几乎没有树脂。TDE-85树脂基与碳纤维界面结合情况较好,纤维与树脂结合比较紧密,断面较为平整,只有少量纤维拔出,表面粘附大量树脂。     

碳纤维增强聚醚醚酮复合材料的界面改性

由于其优异的性能。碳纤维(CF)增强聚醚醚酮(PEEK)热塑性复合材料是近年来先进复合材料研发的热点。但因PEEK熔融黏度大、CF丝束密集且具有化学惰性,树脂对纤维丝束浸渍困难和界面相互作用弱阻碍了高性能热塑性复合材料广泛应用,放改进界面性能是研究的重点。本文采用聚醚酰亚胺(PEI)以及聚醚酰亚胺/氧化石墨烯(PEI/GO)对活化后的CF表面进行界面改性处理,再通过模压成型制备CF/PEEK复合材料。结果表明,1 wt%PEI改性剂有效增强了纤维-基体间的相互作用力,0.5 wt%GO的添加使得界面结合性能进一步提升,层间剪切强度(ILSS)提高了68%,弯曲强度、弯曲模量分别提高了54%、68%。复合材料破坏形式由树脂-基体脱黏转变为基体内部断裂。     

不饱和聚酯树脂／大麻纤维复合材料的热氧老化

采用模压工艺制备不饱和聚酯(UP)树脂/大麻纤维复合材料,研究了105℃下热氧老化600h前后复合材料力学性能的变化;采用傅立叶变换红外光谱仪(FTIR)对老化前后复合材料的结构进行对比分析,并通过SEM技术观察复合材料的断面形貌.结果表明,偶联剂KH570处理对复合材料力学性能的总体改善效果最佳.老化600h后,偶联剂处理复合材料具有的最佳力学性能如拉伸强度、拉伸模量、弯曲强度、弯曲模量及冲击强度分别为19.06MPa、5.78GPa、52.988MPa、1.01GPa和3.881kJ/m2.红外分析显示,偶联剂处理得到的复合材料在老化前后的红外图形变化不明显,有些吸收峰甚至得到了加强.SEM结果表明,老化600h后,偶联剂处理的复合材料中纤维仍能较均匀地分散在树脂基体中,两者间的界面粘结良好.     

碳纤维/聚三唑树脂复合材料的湿热老化行为

本文研究了碳纤维/聚三唑树脂复合材料(T700/PTA)在80℃、相对湿度98%条件下的湿热老化行为。分别采用静态力学性能测试、吸湿称重、动态热机械分析、扫描电子显微镜观察等手段考察了复合材料在湿热条件下的力学性能变化、吸湿特性和形貌变化;利用半经验数学模型对复合材料进行强度拟合和寿命预测。结果表明,复合材料的弯曲强度、层间剪切强度受湿热影响显著,尤其在老化初期;复合材料吸湿第一阶段符合Fick扩散定律,扩散系数D=1.129×10-6mm2/s;吸湿后试样的动态热机械分析谱图上出现两个转变,干燥后次级转变消失;湿热老化后,纤维与树脂基体之间的界面作用减弱;利用数学模型预测复合材料弯曲强度保留率为50%时的老化寿命为33600h,T700/PTA复合材料具有优良的耐湿热老化性能。     

碳纤维湿法缠绕用高模量高韧性环氧树脂基体

设计了一系列针对碳纤维湿法缠绕的环氧树脂基体,测试了树脂浇注体及其复合材料的力学性能和热机械性能,研究了树脂基体对碳纤维复合材料界面性能的影响.试验结果表明,对韧性树脂体系,树脂基体的模量是发挥纤维强度的关键因素,模量的提升将大幅提高复合材料的综合性能.经复配和优化的树脂体系兼具高模量和高韧性,其T700碳纤维复合材料NOL环拉伸强度达到2480MPa,T800碳纤维复合材料NOL环拉伸强度达到2780MPa,玻璃化温度(Tg)超过200℃,具有优异的界面性能和耐热性能.     

PBO/T700层间混杂复合材料弯曲及压缩性能研究

研究了PBO纤维与T700碳纤维层间混杂复合材料的弯曲性能和压缩性能。利用材料万能试验机研究了混杂复合材料的弯曲强度和弯曲模量、压缩强度和压缩模量随混杂比的变化情况,同时对混杂复合材料的弯曲破坏和压缩破坏模式进行了研究。研究结果表明,混杂工艺能够使PBO纤维复合材料的弯曲强度从542MPa增大到1120MPa,压缩强度从233.2MPa增大到702MPa;PBO纤维复合材料和T700碳纤维复合材料弯曲和压缩试样的破坏模式分别表现为典型的韧性破坏和脆性破坏,PBO/T700层间混杂复合材料的弯曲和压缩破坏模式随着混杂比增大,逐渐从韧性破坏转变为脆性破坏。     

树脂对碳纤维/玻璃纤维层间混杂复合材料湿态弯曲特性影响

为了探究树脂基体对相同铺层方式下碳纤维/玻璃纤维层间混杂复合材料(碳/玻体积混杂比为1.86/1)干态、湿态(100℃水煮2 h)弯曲特性的影响,首先对环氧树脂和乙烯基树脂浇铸体试样分别开展了耐水性加速老化试验,并对两种树脂浇铸体试样在每个老化试验周期下分别开展剩余弯曲特性试验;然后对碳/玻层间混杂复合材料开展干、湿态弯曲试验。结果表明,无论是在常规试验(未经过老化)还是在各个老化试验周期,两种树脂浇铸体试样弯曲应力–位移曲线变化规律基本一致,但总体而言,环氧树脂浇铸体试样常规弯曲强度和各个阶段老化后弯曲强度均优于乙烯基树脂浇铸体试样;相同试验状态下,两种树脂基混杂复合材料试样湿态弯曲强度和弯曲弹性模量均较干态试样产生不同程度的降低,但环氧树脂基混杂复合材料试样在干、湿态环境下的弯曲性能均优于乙烯基树脂基混杂复合材料试样。     

碳纤维、Kevlar—49在树脂中浸润性的研究

碳纤维和Kevlar—49是新型的增强材料,随着科学技术的发展,宇航空间不断开拓,这两种纤维的应用愈来愈广泛。复合材料的横向强度、横向模量及剪切强度取决于界面粘接性能,纤维在树脂中的浸润性又直接影响着界面粘接性能。为了使碳纤维及Kevlar—49复合材料具有优异的粘接性能,必须对纤维的浸润性及其影响因素进行研究。 目前,我国用于结构复合材料的碳纤维有中、高强型,其中以中强型为主,高模量碳纤维也开始使用。本文主要研究中强型碳纤维(吉林炭素厂产品)、日本T—200A碳纤维及     

Sapindaceae,cyanolipids, and bugs

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.     

Insect antifeedant properties of anthranoids from the genusVismia

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.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

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.     

2008～2009年世界塑料工业进展

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。     

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.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

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.